Single-Atom Catalysts for Photocatalytic Reactions - ACS Sustainable

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Single-Atom Catalysts for Photocatalytic Reactions Qiushi Wang, Dafeng Zhang, Yong Chen, Wen-Fu Fu, and Xiao-Jun Lv ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b06273 • Publication Date (Web): 04 Mar 2019 Downloaded from http://pubs.acs.org on March 6, 2019

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ACS Sustainable Chemistry & Engineering

Single-Atom Catalysts for Photocatalytic Reactions Qiushi Wang,†, § Dafeng Zhang, †, ‡Yong Chen, † Wen-Fu Fu† and Xiao-Jun Lv*, † † Key

Laboratory of Photochemical Conversion and Optoelectronic Materials & CAS-HKU Joint

Laboratory on New Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China ‡

Department of Energy and Chemical Engineering, College of Chemistry and Chemical

Engineering, Henan Polytechnic University, Jiaozuo 454003, P. R. China § University

of Chinese Academy of Sciences, Beijing 100049, P. R. China

Email: [email protected] KEYWORDS. Single atom catalysts, Synthesis, Photocatalytic reaction, High active, Maximum atomic utilization Mailing address：29 Zhongguancun East Road, Haidian District, Beijing, 100190, China

ABSTRACT. Hydrogen and other renewable resources derived by sunlight have attracted great attention to sustainable development. But the photochemical performance of diverse systems is restricted because of the poor efficiency of photon absorption, easy recombination of photogenerated electron–hole pairs, and slowly transfer of charge carriers. Single-atom catalysts (SACs), in which isolated atoms are supported on the supports without forming nanoparticles, have received increasing interests in photocatalysis due to the high catalytic activity, selectivity,

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stability , and 100% atom utilization. In this review, we highlight and introduce recent advances in the preparation method of SACs and concrete examples of single-atom photocatalysts used for the hydrogen evolution from water, overall water splitting, CO2 and N2 reduction reaction. At last, we discuss the underlying mechanisms for photocatalytic performance of single atoms catalysts and the prospects for the development of SACs.

INTRODUCTION Traditional heterogeneous catalysts containing a broad size distribution of metal particles, has been extensively applied in energy conversion,1-4 chemical production,5,

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and vehicular exhaust

purification.7 However, the utilization efficiency and selectivity of these metal nanoparticles are very low owing to only a small fraction with a suitable size distribution can serve as catalytic active species, much more other-size particles are not useful or generate undesired secondary reactions. Single-atom catalysts (SACs), comprising individually supported metal atoms and supports show unusual potential for the reasonable use of metal resources and the maximum atom-utilization efficiency, the unique electronic structure and unsaturated coordination environments of the active centers guarantee the high activity in a variety of reactions.8-11 In 2011, Zhang et al.12 successfully fabricated and observed the single Pt atoms on FeOx support with Pt-O-Fe architecture which shows high catalytic activity and stability in CO oxidation reaction. SACs have attracted much attention and rapidly developing as a new frontier in catalysis science due to their some unique superiority.13, 14 In the last few years, numerous single-atom catalysts were synthesized and studied in various applications. The isolated atoms should be anchored on supports against aggregation due to the increasing surface free energy as the size of particles decrease to single atoms. The different types


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of supports, such as metal oxides, metals, two-dimension layer structure materials, and porous metal-organic frameworks (MOFs) nanomaterials, have a clearly effect on performance of SACs because of the metalsupport interactions that chemical bonding between metal and support.15-17 For metal oxides support, single metal atoms can be anchored by metal-oxygen-cation-(support), or occupy the sites of the cations in supports,18-21 such as Pt1/FeOx,12 Au/Fe3O4,20 Pd/Al2O3.21 This metal-O-support structures keep the stability of single atom catalysts in diverse catalytic reactions.20, 22, 23 The location of single atoms on metal support is correlated with the chemical potential of the metal support element.24 For 2D layered materials, the single atoms were embedded into the defects of supports,25-28 or bonded with in-plane N atoms of the graphitic carbon nitride (g-C3N4) framework,29 or replace in-plane Mo atoms as dopant.30 The unsaturated single atoms can also be incorporate into the MOFs matrix by coordination reaction, the porous structure of MOFs can provide larger surface area.31-33 SACs have shown unexpected performance in various reactions, such as CO oxidation,12, 34-36 hydrogenation reaction,37-39 water−gas shift (WGS),40-43 electrochemical reaction including synthesis of H2O2,44, 45 water splitting,46-49 carbon dioxide reduction,50-52 and photocatalysis.29, 31, 53-55

The photocatalytic reaction driven by solar energy as alternative strategy has shown great

potential for resolving the increasing energy and environmental questions. However, most semiconductor photocatalysts exhibit unsatisfactory photochemical properties because of poor efficiency of photon absorption, easy recombination of photogenerated electron–hole pairs as well as slowly transfer of charge carrier.56, 57 In addition, the dimension of metal cocatalysts has a great influence on the activity and selectivity for photocatalysis. In 2014, Yang’s group55 for the first time fabricated single metal atoms (Pt, Pd, Rh, and Ru) anchored on TiO2 for photocatalytic H2


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evolution and the catalysts displayed higher photocatalytic activity than the metal clusters loaded on TiO2, this work opens a door for SACs in photocatalytic field. There are some reviews summarize the progresses of SACs in many fields,6, 13, 14, 58-60 but rarely involved the studies of photocatalysis. For photocatalytic reactions, the introduction of SACs can effectively improve the capacity of light absorption, charge transfer, and electron conductivity, meanwhile, anchored single-atom catalysts on the supports exhibit remarkable stability and longlife, which have been verified in many photocatalytic reactions.32, 54, 61, 62 The implantation of single atoms can clearly modify the electron and energy band structure of the supports, which lead to the enhancement of light absorption, the separation and transfer of photocarriers, increase the density of mobile charge carriers round the Fermi level consequently realize the overall water splitting.63 Furthermore, the synergistic effect of unsaturated single atoms and supports contribute to adsorption and activation of reactants.33, 64 Importantly, much more works have demonstrated that SACs can provide much more uniform active sites and typical advantages of 100% atom utilization.32, 33, 54, 61 These advantages of SACs contribute to the increase of activity and selectivity for photocatalytic reactions compared to nanoparticles and heterogeneous catalysts. Thus, SACs possess the merits of high activity, selectively, and stability in photocatalysis. In this review, we introduce recent researches in synthetic strategies for SACs and we primary focus on the great potential for the photocatalytic reaction application of SACs in key clean energy conversion reactions, including hydrogen evolution from water, overall water splitting, CO2, and N2 reduction reaction and other organic degradation. It is worth noting that the excellent photocatalytic performance of SACs is well correlated with the unique electronic and structural properties of SACs. In the end, the major challenges and opportunities for further research and application on SACs are proposed.


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Synthesis of SACs Efficiently anchoring isolated single atoms on support surfaces is the key task in the synthesis of high active SACs. However, it is one great challenge that prevent single atoms from aggregation in the process of preparation and catalysis. In recent years, excitingly, several strategies have been put forward to resolve this issue. Atomic layer deposition (ALD) method ALD method, a sophisticated technology which controls the scale of catalysts in nanometer and sub-nanometer by simply altering the deposition cycles. It has been demonstrated that ALD can also be used to control the deposition of SACs.65, 66 Sun’s group 67 adopted the ALD method to prepare isolated single Pt atoms supported on graphene nanosheets (GNS). In the ALD process of Pt/GNS (Figure 1a), the graphene is alternately exposed to Pt precursor vapors and purity O2. Under a self-limiting growth feature, it was achieved the precise deposition of single atoms in an atom layer-by-layer pattern. The Pt/GNS catalyst performed an excellent catalytic activity in methanol oxidation reaction, the current density of Pt/GNS is much higher than commercial Pt/C (Figure 1b). The remarkable performance is caused by the single Pt atoms nature of low coordination and unsaturated 5d orbitals which is demonstrated using X-ray absorption fine structure (XAFS) (Figure 1c, 1d). They also fabricated Pt single-atom catalysts which supported by nitrogen-doped graphene and play an active role in hydrogen evolution reaction.46


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Figure 1. Synthesis of SACs by ALD method. (a) Mechanism illustration of fabricate single Pt atoms on graphene nanosheets. (b) CVs of methanol oxidation on samples. (c) The Pt L3 edge Xray absorption near-edge structure (XANES) spectra of samples and inset is the magnification spectra. (d) The K3-weighted Fourier transform spectra from extended X-ray absorption fine structure (EXAFS) of samples. Reproduced with permission from ref 67. Copyright 2013 Springer Nature. Wet-chemical routes In wet-chemical routes, the precursor materials consist of single atom species, metal atoms can be dispersed on the supports by means of a chemical reaction. A number of studies proposed that supports could offer anchoring sites for single atoms because of the existence of surface defects. Thus, single atom species are prevented from aggregating because of the metalsupport


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interactions. Among the promising routes, co-precipitation method is favored for fabrication of SACs by virtue of its convenient and low-coat, in which the precursor mixture solution containing the catalyst species forms a precipitate at a certain temperature and pH value. For instance, Zhang and co-workers12 first successfully synthesized the Pt1/FeOx catalyst by co-precipitation method and post-treatment procedure. It clearly shows only 0.17 wt% Pt species dispersed on FeOx support by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and the positions of Fe atoms occupied exactly by the Pt atoms (Figure 2a, 2b). The Pt1/FeOx exhibits outstanding stability and unexpected activity for carbon monoxide oxidation as well as preferential oxidation of carbon monoxide in the atmosphere of hydrogen. However, the loading of SACs prepared by the co-precipitation method is generally low. As shown in Figure 2c and 2d, as the content of Pt in Pt/FeOx enhanced to 2.5 wt%, Pt clusters could be observed. They using aberrationcorrected STEM (AC-STEM) reported that the existence of isolated Pt single atoms is related to the post-treatment process. Pt single atoms can be observed after calcination process at 600 oC for 5 hours. Nevertheless, reduction treatment at 200 oC for 30 minutes can cause the growth of subnano clusters and nanoparticles, which is possibly the result of the surface chemistry and/or structure changes of FeOx.68 Afterwards, they prepared Ir single atoms catalyst with iron oxide support (Ir1/FeOx) with the same method which is identified to be much more active for WGS.40 In the co-precipitation method, both the pH and temperature have a significant effect on the preparation. In addition, wet impregnation method, as one of widely employed approaches in the fabrication of conventional catalysts, has received extensive attention for the preparation of SACs because of easy operation and no special equipment required. Pt single-atom catalysts dispersed on different supports have been synthesized by operated in chloroplatinic acid aqueous solution.36, 69, 70


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Figure 2. (a, b) HAADF-STEM images of 0.17 wt% Pt, Pt single atoms (white circles) are supported on FeOx (a) and the Fe atoms are occupied by Pt atoms (b). (c, d) HAADF-STEM images of 2.5 wt% Pt, different size of Pt species are shown that include single atoms (white circles), 2D Pt rafts (black circles), and 3D Pt clusters (white squares). Reproduced with permission from ref 12. Copyright 2011 Springer Nature. Photochemical approach Photochemical approach is a mild and cost-effective preparation method based on UV irradiation which avoids single atoms agglomeration to nanoparticles comparing to conventional calcination method. Zheng’s group71 developed a room-temperature photochemical route to synthesize an extraordinarily stable Pd1/TiO2 with the Pd loading up to 1.5%. Diverse characterization analysis


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demonstrated that Pd atoms uniformly dispersed on two-atom-thick TiO2 nanosheets which modified by ethylene glycolate (EG). The Pd1/TiO2 displayed high stability as well as catalytic activity in hydrogenation. A key factor of synthesized Pd1/TiO2 catalyst is the formation of EG radicals which promoted the removal of Cl ligands in PdCl2, consequently, single Pd atoms steadily anchored on TiO2 nanosheets by forming more Pd-O bonds after UV treatment. Atom trapping strategy The generally preparation of single-atom catalysts can be achieved by the limited metal content and operating temperatures.72 However, there is still a challenge that Pt species tend to aggregate into large particles in industrially drastic reaction conditions such as oxidizing CO, NO, and hydrocarbons, which lead to catalytic activity decrease, and this process called Ostwald ripening.73, 74

Although it can be thermodynamically stabilize single Pt atoms by the introduction of ligands

or strong metalsupport interactions.75, 76 The Pt single-atom catalysts will still tend to aggregate more or less under aging treatment at elevated temperatures in air. Therefore, exploit thermally stable SACs is critical for industrial applications. Datye et al.77 discovered that PdO exhibits the ability of trap mobile PtO2 to form Pt−Pd alloys by physical vapor deposition in air. Thus, the sintering of Pt is clearly restrained. Inspired by this phenomenon, they for the first time achieved effective trapping of the Pt species by CeO2 to synthesize single-atom catalyst.78 As shown in Figure 3a, Pt/La-Al2O3 catalyst and ceria undergo aging at 800 oC in flowing air, the


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Figure 3. Synthesis of SACs by atom trapping strategy. (a) Schematic of Pt nanoparticle sintering and Pt atoms trapping by ceria. (b, c) AC-STEM images of 1 wt% Pt atoms on ceria nanorod (b) and polyhedral ceria (c). (d) Mechanism illustration of the fabrication of copper SACs from bulk copper. Reproduced with permission from refs 78 and 81. Copyright 2016 American Association for the Advancement of Science and 2018 Springer Nature.


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emitted PtO2 vapor located at the surface of ceria in the form of Pt2+. The isolated single Pt atoms dispersed on both ceria nanorod and polyhedral ceria which are revealed in AC-STEM images (Figure 3b, 3c), in contrast Pt will be sintered if there is no CeO2 support. Using atom trapping strategy, a series of thermal stable single atoms (Pd,79 Au,79 Ni80) catalysts have been prepared from metal nanoparticles. Interestingly, Wu and co-worker81 directly synthesized SACs by using the inexpensive and easily available bulk metal materials. As shown in Figure 3d, copper atoms are emitted out from copper foam and transfered to defects of the N-doped carbon support under NH3 atmosphere (Cu-SAs/N-C). Photocatalytic Applications of SACs Photocatalysis is viewed as potential strategy to resolve energy and environmental questions.82 However, Developing high-activity, durable, and economical photocatalysts remains a great challenge for the application of photochemical energy conversion technology. The effective photocatalysts are still the key heart for increase the photocatalytic conversion efficiency. Recently, many advanced single-atom photocatalysts have been developed with excellent activity, selectivity, and stability. Next, we will introduce and summarize the photocatalytic applications of SACs in key energy conversion reactions including HER, overall water splitting, CO2 reduction reaction, and N2 reduction reaction, which demonstrate the great potential of SACs for achieving highly efficient and selective photocatalytic processes. Moreover, the influences of the structure of SACs to the catalytic performance will be discussed. Photocatalytic H2 evolution Hydrogen is a useful and environment friendly energy that replaces fossil fuels if hydrogen is produced by water electrolysis or photocatalytic water splitting. In 1972, Fujishima was firstly


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realize water splitting in a photoelectrochemical cell using TiO2.83 Anatase TiO2 has been widely employed in photocatalytic processes because of its merits of photo-chemical stability, nontoxicity, and unique electronic band structure.84,

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In addition, as a typical noble metal,

platinum has been became a favorable cocatalyst in photocatalytic H2 production by virtue of its high redox potential and high work function.86 Luo et al.87 synthesized the Pt1/TiO2-A as photocatalyst in H2 evolution by photochemical approach (Figure 4a). Characterization results responded that single Pt atoms evenly embedded on the surface of nanosized anatase TiO2 and single Pt atoms only present in (101) facets. The H2 evolution has achieved up to 84.5 μmol h1 when the loading of Pt atoms is 0.6 wt%, and this optimal Pt1/TiO2-A still keeps an excellent stability and photocatalytic activity performance after 20 cycles (Figure 4b). The experimental results reveal that the important reason for the remarkable photocatalytic activity of Pt1/TiO2-A is that single Pt atoms selectively precipitate on specific crystal faces of TiO2. In order to further enhance the carrier transportation and charge surface transfer, Zhao et al.61 adopted 1D TiO2 nanobelts as photosensitizer, and cocatalyst is Co single atoms coordinated with graphene by N dopant (Co-NG), which can notably enhance photocatalytic H2 production performance (Figure 4c). The hydrogen production rate of 3.5 wt% Co-NG/TiO2 is significantly higher than that of 3.5 wt% NG/TiO2 and TiO2 nanobelts by 2.6 and 31.2 times respectively (Figure 4d). The outstanding synergetic effect between single Co atoms and NG plays a role in photoexcited electrons rapid transfer, which effectively decreased the rate of carrier recombination, simultaneously prolonged carrier lifespan, and eventually enhanced the H+ reduction reaction. Single Co atoms inserted in N-doped graphene as cocatalyst onto CdS also displays highly effective and long life for photocatalytic H2 evolution.88 Under the same conditions, 0.25 wt% Co-NG/CdS has a greater H2


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evolution rate (1382 μmol h1) than traditional Pt-NPs/CdS photocatalyst (1077 μmol h1), and the quantum efficiency can reach up to 50.5% at 420 nm irradiation.

Figure 4. (a) Illustration of photocatalytic hydrogen production in Pt1/TiO2-A. (b) Corresponding H2 production rate of samples. (c) Schematic diagram of carrier transport and hydrogen evolution in the Co-NG/TiO2. (d) Photocatalytic hydrogen production assessment with samples. Reproduced with permission from refs 87 and 61. Copyright 2017 Elsevier and 2018 American Chemical Society. 2D layered g-C3N4 is considered as the most stable carbon nitrides under ambient conditions, and it became a popular photocatalyst for H2 production owing to its appropriate conduction and valence band positions.89-91 It has been studied that the N/C-coordinating framework provides occasion to the intercalation of exotic species, indicating g-CN has the potential to anchor single atoms worked for photocatalysis.92 Xie et al.54 reported Pt single atoms dispersed on 2D g-C3N4


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(Pt-CN) which sever as cocatalyst to improve photocatalytic H2 evolution. The excellent stability of Pt-CN is caused by the form of Pt-N/C bonds that promote single Pt atoms to stabilize on the top of the C3N4 network. Characterization results manifested that the increase of both charge separation and photogenerated electron–hole pairs transfer are attributed to the introduction of single Pt atoms. Thus, the Pt-CN showed higher catalytic activity in photocatalytic hydrogen production than Pt NPs and bare g-C3N4. MOFs, a newly-developing porous materials, have potential to stabilize single atoms during catalytic reactions due to their unique structures. Jiang’s group31 realized to stabilize single Pt atoms by aluminum-based porphyrinic MOF (Al-TCPP) for photocatalytic hydrogen production irradiated by simulated sunlight. The successful introduction of single Pt atoms is originated from the strong interaction between Pt and pyrrolic N atoms (Figure 5). Consequently, the single Pt atoms hosted by MOF provide fast channel for electron transfer and have an effect on optimizing the hydrogen binding energy, which issue in salient increase activity of H2 evolution with turnover frequency of 35 h−1, approximately higher than Al-TCPP-Pt NPs by 30 times. Porphyrin units in MOFs possess square-planar four pyrrolic N sites, generally benefiting an intercalation of single atoms. Recently, zirconium-porphyrinic MOF hollow nanotubes have been successfully fabricated to immobilize numerous noble-metal single atoms, the Ir/Pt-zirconium-porphyrinic MOF displayed excellent catalytic performances for the photocatalytic H2 production under simulated sunlight.32


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Figure 5. Schematic diagram of the preparation and photocatalytic H2 evolution in Al-TCPP-Pt. Reproduced with permission from ref 31. Copyright 2018 Wiley-VCH. Photocatalytic overall water splitting A feasible path to enhance the quantum efficiency of photocatalytic overall water splitting is construct photocatalysts which offer rich photon absorption, efficient photogenerated electron– hole pairs separation and rapid transportation.93 Wei and co-workers53 developed single-Co containing catalyst, in which individual Co atoms anchored on phosphorus-doped graphitic carbon nitrides (PCN) catalyst (named Co1-phosphide/PCN) for overall water splitting in the absence of sacrificial reagents. As shown in Figure 6a, the photogenerated electron–hole pairs are efficiently dissociated, and transmitted to g-C3N4 and Co1-phosphide that act as the reactive centers of H2 evolution and O2 evolution, respectively. Spectra measurements powerfully demonstrated the


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accelerated electron–hole separation. The molar ratio of gas evolution was constant in 2:1 (H2 : O2) and remained its previous photocatalytic activity after continuous 24 h reaction (Figure 6b). Moreover, the atomically dispersed Co1-phosphide/PCN obtained significant improvement for H2 evolution up to 410.3 μmol h 1 g1 by light irradiation (Figure 6c). The outstanding photocatalytic activity of Co1-phosphide/PCN can be attributed to the following three factors: firstly, the observed of mid-gap state extends the light absorption range and becomes separation site to provisionally capture photoexcited electrons moving from the conduction band (Figure 6d). Secondly, the P dopant accelerated the electric conductivity. Thirdly, the steady Co single atoms boost the adsorption and activation of H2O molecules benefitting to oxygen evolution.

Figure 6. (a) Illustration of the Co1-phosphide/PCN for photocatalytic overall water splitting. (b) Under simulated light (λ > 300 nm), the gases production rates of hydrogen and oxygen from water splitting in the Co1-phosphide/PCN. (c) The rates of hydrogen evolution with samples. (d) Diagram illustration of the electronic band structure for Co1-phosphide/PCN photocatalyst. Reproduced with permission from ref 53. Copyright 2017 Wiley-VCH.


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According to the considerations of designing excellent SACs by adjust the band energy levels and optimize the electronic structure, Liu’s group63 reported atomic +2 valence Pt dispersed on gC3N4 (PtII-C3N4) via robust Pt-N bond to realize photocatalytic overall water splitting. The implanted Pt single atoms enhance the light absorption, improve the separation and transfer of photogenerated charges, promote the valence band maximum positively shift, increase the density of carriers in the round of the Fermi level, which are the reason of realize water oxidation at N sites and H2 evolution at Pt single sites. Photocatalytic carbon dioxide reduction The photocatalysis of reducing carbon dioxide into hydrocarbon fuels is critical for controlling the concentration of CO2 in the atmosphere and alleviating energy crisis. Nevertheless, CO2 is chemically stable, CO2 reduction is a scientifically challenging work which lacks suitable catalysts and energy input.94 Du et al.95 achieved the calculations of efficiently photocatalytic CO2 reduction in Pd and Pt single atoms deposited on g-C3N4 (Pd/g-C3N4 and Pt/g-C3N4, respectively), via density functional theory (DFT). The single atoms (Pd and Pt) were stably anchored into the cavity of g-C3N4 as active sites, and the excellent catalytic activities owing to the strong interaction between the adjacent N and the single metal atoms. Meanwhile, graphitic carbon nitride provides the hydrogen source for CO2 hydrogenation and expands absorption range from visible to infrared light. The evaluation of reaction pathways demonstrated that the Pd/g-C3N4 tend to produce HCOOH for photocatalytic CO2 reduction, while the conversion of carbon dioxide on the Pt/gC3N4 preferred to CH4.


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Figure 7. (a) Diagram of the MOF-525-Co and the incorporation of single Co atom. (b, c) The production of CO (b) and CH4 (c) over time in samples (MOF-525-Co: green, MOF-525-Zn: orange, MOF-525: purple, H6TCPP ligand: pink). Reproduced with permission from ref 33. Copyright 2017 Wiley-VCH. Recently, MOFs with uniquely 3D network structure and adsorption of CO2 capability, has been used as superior photocatalysts for CO2 reduction.96, 97 Co-based materials are considered to be one of most promising catalysts for CO2 reduction according to previous studies.98, 99 Ye and her colleagues33 synthesized MOF-525-Co catalyst, consisting of porphyrin-based MOFs and implanted Co single atoms active sites, which exhibits superior efficiency and stability in CO2 capture and conversion under visible light irradiation (Figure 7a). The incorporated Co single atoms sever as active centers to enhance the ability of capture CO2, and facilitate simultaneously the migration of photogenerated exciton to prolong the lifetime of electrons, that will be in favor


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of CO2 conversion. As shown in Figure 7b and 7c, the MOF-525-Co photocatalyst shows an obvious increase in the rate of both CO evolution and CH4 evolution compared to other samples. The special performance of single Co atom in term of photocatalytic CO2 conversion is demonstrated in the Co1-G nanosheets.62 Atomic Co uniformly dispersed on partially oxidized graphene, where O atoms and C atoms contained in graphene layer provide coordination to Co center. XANES spectra reveals that the electronic structure of single Co atom is between CoO and Co foil, the positive charge nature of Co atom origin from the metalsupport interactions (Figure 8a). In case of [Ru(bpy)3]Cl2 as the light absorber and triethanolamine (TEOA) as the sacrificial agent, the Co1-G photocatalyst exhibits an excellent turnover number (TON) and turnover frequency (TOF) of maximum CO production reaching up to 678 and 3.77 min1, which are higher than other heterogeneous photocatalysts for CO2 reduction reported to date (Figure 8b). The keys of Co1-G photocatalyst with outstanding catalytic activity and robustness are attributed to complete utilization of single Co atoms active sites, at the same time，the graphene support also promote the transfer of excited electron coming from [Ru(bpy)3]3+ to the single Co atoms to achieve CO2 reduction (Figure 8c, 8d).


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Figure 8. (a) The XANES spectra at Co K-edge of Co1–G, Co foil, and CoO. (b) The TONs for CO2 reduction with Co1–G, G, CoCl2, CoCl2 + G, and CoCl2 + GO as photocatalysts under visiblelight irradiation. (c) Schematic illustration of the transportation of electron between [Ru(bpy)3]Cl2 and Co1–G. (d) Schematic diagram of the photocatalytic CO2 reduction of on Co1–G photocatalyst. Reproduced with permission from ref 62. Copyright 2018 Wiley-VCH. Existing studies have shown that, Cu species such as Cu clusters,100, 101 Cu ions,102 and Cu oxide,103-105 supported on TiO2 catalysts are contributed to increase the catalytic activity and selectivity for carbon dioxide conversion. Further studies found that the surface engineering techniques of TiO2 support also play a vital role in solar-driven CO2 reduction, for example, the


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existence of oxygen vacancies (Ov) dramatically influence the size of supported species, CO2 adsorption and activity.106-109 The size of Cu species on TiO2 support has a clear effect on the production selectivity. Experimental and DFT’s studies demonstrated this conclusion that isolated Rh active sites on TiO2 performed high selectivity for CO2 reduction.110, 111 Based on previous research, Deskins et al.112 investigated the synergistic effect between defects, photogenerated electrons, and SACs for carbon dioxide conversion using both DFT and experiment techniques. Figure 9a shows that the Cu single atom in or near the Ov is negatively charged. And the existing of both Cu single atoms and Ov facilitate the selective adsorption of bent CO2 and reduce the reaction energies of bent CO2 dissociation (CO2* → CO* + O*). XPS results further revealed the important influence of Ov on the valence state of copper, such as, only the presence of Cu+ on Cu/Ov/TiO2, while both Cu2+ and Cu+ on Cu/TiO2. Fourier transform infrared (FTIR) spectroscopy detected a peak at 1638 cm1 represented the absorption of bent CO2 on TiO2 surface with Ov under light irradiation. And the peak located at 2111cm1 is the absorption peak of CO molecule produced by photoinduced CO2 dissociation (Figure 9b). In addition, they modeled Pt/Ov/TiO2 take part in CO2 dissociation and summarized the possible reaction pathways in Figure 9c, which provide theoretical guidance for catalysts construction in the future.


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Figure 9. (a) View of single Cu atom adsorbed on TiO2 (101) surfaces. (b) FTIR spectra of different catalysts after photocatalytic CO2 reduction for one hour. (c) Summary of possible CO2 dissociation pathways as calculated by DFT. Reproduced with permission from ref 112. Copyright 2018 American Chemical Society. Photocatalytic nitrogen reduction Nitrogen is the most abundant gas of the atmosphere, but the utilization of N2 is limited because of extremely steady N≡N covalent triple bond.113 It could be achieved for nitrogen fixation relying on nitrogenases in nature, while it depends on Haber-Bosch process to produce NH3 in the industry with an operation needs huge energy input and produces a large number of greenhouse gases.114, 115

Thus, it is desirable to develop inexpensive catalysts that are applied to nitrogen reduction

reaction (NRR) under ambient conditions. Although, it was discovered that Fe-doped TiO2 achieved NH3 synthesis from N2 under UV-light irradiation in 1977,116 there are still various catalysts studied for NRR in order to improve the reaction rate, increase the production selectivity,


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and reduce energy consumption.117 As shown in Figure 10a, Xie et al.118 reported Cu SACs for photoinduced NRR which single Cu atoms incorporated into the defects of carbon nitride nanosheets (Cu-CN). Experimental results demonstrate that isolated valence electrons yielded by single Cu atoms can readily convert to free electrons under light irradiation, and facilitate the generation of NH3 with a rate of 186 μmol g−1 h−1 under ambient conditions (Figure 10b). The quantum efficiency is 1.01% at 420 nm monochromatic light.

Figure 10. (a) Structure diagram of the Cu-CN photocatalyst. (b) The evolution rate of NH3 by pCN, Cu-CN under different atmospheres. (c) Photoluminescene spectra of Cu-CN compared to pCN. (d) Photocurrent performance of samples. Reproduced with permission from ref 118. Copyright 2018 Springer.


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The single Cu atoms effectively suppress the recombination of photogenerated excitons and promote the efficient separation of the photoexcited electron–hole pairs (Figure 10c, 10d). So far, many metal catalysts have been observed to carry on NRR by photocatalytic or electrocatalytic,119-123 whereas metal-free catalysts rarely reported. Based on the concept of electron “acceptance-donation”, Wang and co-wokers124 designed a metal-free single atom photocatalyst consist of boron single-atom decorated on g-C3N4 (B/g-C3N4) for NRR by visible light. The incorporation of B atom obviously enhance the light absorption and stability. Firstprinciples calculations investigated that B/g-C3N4 photocatalyst efficiently reduce N2 into NH3 by the enzymatic mechanism with an onset potential as low as 0.20 V. thus, the as-designed B/g-C3N4 will be a candidate for further experiments. Photocatalytic other reactions NO contamination derived from industrial and vehicular gaseous emission is one of the main gases that cause photochemical smog.125 The treatment of NO will have an important impact on health and sustainable development. Wang’s group126 achieved the synthesis of the single Pt atoms embedding into graphitic carbon nitride nanosheets (Pt-SA-CN) by Pt-N coordination bonds. The Pt-SA-CN exhibits highly activity in solar-driven NO oxidation to NO3. Pratsinis et al.127 fabricated single Pd atoms cocatalyst on TiO2. Experimental results revealed that single Pd atoms exhibited high nitrate poisoning resistance and selectivity for NO oxidation under artificial solar light. Besides, in the field of water treatment removing completely the residual organic contaminants is still a great challenge with conventional techniques.128, 129 In contrast, photocatalytic remediation of water resident contaminants is considered as an effective method. Hence, many single metal


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atoms supported on CN have been synthesized and used as photocatalytic degradation reductions.130-132 These investigations suggested that single-atom photocatalysts will be one of the most promising catalysts for environmental remediation in future. Summary and Prospect It has shown that SACs possess greatly potential on photocatalysis and hold great promise in term of solar energy conversion and storage. Very recently, some innovative preparation methods, advanced characterization technologies, and theoretical modeling have been founded and contributed to deeply understand the nature of single-atom catalysts to achieve the fabrication and adjustment of high efficient single-atom photocatalysts. In this review, we summarize and classify some advanced preparing methods and photocatalytic performances of SACs, probing the importance of the alteration of supports for the loading of single atoms, including the coordination sites, defects, vacancies, and heteroatom doping on dispersion and separation of the single metal atoms. Therefore, the choice and pretreatment of the support is necessary and crucial before its using. Besides, the stability of single metal atoms can be enhanced through metalsupport interactions (MSIs) or strong interactions between single atom and neighboring coordination atoms. We hope to realize the gold of increasing the number of active sites and enhancing the reactivity of the active sites simultaneously. At present, only few semiconductor like TiO2, g-C3N4 have been used as the support, other semiconductor system should be further developed. We highlight some concrete applications of SACs in the field of photocatalysis. SACs show an attractive performance with high catalytic activity, selectivity, and maximum atomic utilization because of their low-coordination status, quantum size effect, and MSIs, etc. Therefore, singleatom photocatalysts have proven to be active in some typical catalysis such as the hydrogen


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evolution from water, overall water splitting, CO2 and N2 reduction reaction. In addition, singleatom catalysts are considered as a transition state between homogeneous and heterogeneous catalysts owing to the single active sites on supports surface. This feature provides some unique advantages compared to the nanocluster, nanoparticle, and bulk catalysts: (i) a remarkable catalytic activity due to unsaturated coordination sites; (ii) reducing the amount of catalysts because of the high atomic utilization; and (iii) the single active sites facilitating the study of catalytic mechanisms. The research of relationship between structure and photocatalytic mechanism will help us illuminate the optimized design of photocatalysts for the high-efficiency photochemical energy conversion process. Although SACs have demonstrated excellent performance in photocatalysis, some great challenges still remain in SACs, including: (i) effectively improving the metal loading content of SACs; (ii)controllable, simple synthesis of SACs with large-scale single atoms; (iii) in-depth study of the strong interactions between single atoms and supports in SACs; (iv) rational construct of single active sites for optimizing and improving the catalytic properties of SACs, and expanding much more photocatalytic system and application is also highly desirable. Furthermore, developing advanced characterization techniques are extremely vital to enable the identification of single atoms and the research of photocatalytic mechanisms including in situ STM, in situ STEM, and in situ XAFS. Single-atom catalysts have opened up a new pathway for the design and application of catalysts. It is believed that we can design specific SACs for the targeted reactions and achieve the atomic-economic green catalytic process in the near future. AUTHOR INFORMATION Corresponding Authors


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* Xiao-Jun Lv. E-mail: [email protected] ORCID Xiao-Jun lv: 0000-0002-8040-881X Dafeng Zhang: 0000-0002-2124-3867 Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was financially supported by the NSFC (Grant No. 21477136), Beijing Natural Science Foundation (2182077). We are also thankful for the financial support by the Strategic Priority Research Program of the Chinese Academy of Sciences, Grant No. XDB17030300. REFERENCES (1) Zhu, C.; Du, D.; Eychmüller, A.; Lin, Y. Engineering Ordered and Nonordered Porous Noble Metal Nanostructures: Synthesis, Assembly, and Their Applications in Electrochemistry. Chem. Rev. 2015, 115, 8896−8943, DOI 10.1021/acs.chemrev.5b00255. (2) Liu, X.; Iocozzia, J.; Wang, Y.; Cui, X.; Chen, Y.; Zhao, S.; Li, Z.; Lin, Z. Noble Metal– Metal Oxide Nanohybrids with Tailored Nanostructures for Efficient Solar Energy Conversion, Photocatalysis and Environmental Remediation. Energy Environ. Sci. 2017, 10, 402−434, DOI 10.1039/C6EE02265K. (3) Cai, P.; Li, Y.; Wang, G.; Wen, Z. Alkaline-Acid Zn-H2O Fuel Cell for the Simultaneous Generation of Hydrogen and Electricity. Angew. Chem. Int. Ed. 2018, 57, 3910−3915, DOI 10.1002/anie.201712765.


27


Page 28 of 51

(4) Li, Z.; Liu, H.; Liu, Y.; He, P.; Li, J. A Room-Temperature Ionic-Liquid-Templated ProtonConducting Gelatinous Electrolyte. J. Phys. Chem.: B 2004, 108, 17512−17518, DOI 10.1021/jp047252x. (5) Fürstner, A. Gold and Platinum Catalysis-a Convenient Tool for Generating Molecular Complexity. Chem. Soc. Rev. 2009, 38, 3208−3221, DOI 10.1039/b816696j. (6) Zheng, N.; Zhang, T. Preface: Single-Atom Catalysts as a New Generation of Heterogeneous Catalysts. Natl. Sci. Rev. 2018, 5, 625−625, DOI 10.1093/nsr/nwy095. (7) Zhang, S.; Nguyen, L.; Liang, J.-X.; Shan, J.; Liu, J.; Frenkel, A. I.; Patlolla, A.; Huang, W.; Li, J.; Tao, F. Catalysis on Singly Dispersed Bimetallic Sites. Nat. Commun. 2015, 6, 7938, DOI 10.1038/ncomms8938. (8) Herzing, A. A.; Kiely, C. J.; Carley, A. F.; Landon, P.; Hutchings, G. J. Identification of Active Gold Nanoclusters on Iron Oxide Supports for CO Oxidation. Science 2008, 321, 1331−1335, DOI 10.1126/science.1185200. (9) Lei, Y.; Mehmood, F.; Lee, S.; Greeley, J.; Lee, B.; Seifert, S.; Winans, R. E.; Elam, J. W.; Meyer, R. J.; Redfern, P. C. Increased Silver Activity for Direct Propylene Epoxidation via Subnanometer Size Effects. Science 2010, 328, 224−228, DOI 10.1126/science.1185200. (10) Qiao, B.; Liu, L.; Zhang, J.; Deng, Y. Preparation of Highly Effective Ferric Hydroxide Supported Noble Metal Catalysts for CO Oxidations: From Gold to Palladium. J. Catal. 2009, 261, 241−244, DOI 10.1016/j.jcat.2008.11.012.


28

Page 29 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(11) Kaden, W. E.; Wu, T.; Kunkel, W. A.; Anderson, S. L. Electronic Structure Controls Reactivity of Size-Selected Pd Clusters Adsorbed on TiO2 Surfaces. Science 2009, 326, 826−829, DOI 10.1126/science.1180297. (12) Qiao, B.; Wang, A.; Yang, X.; Allard, L. F.; Jiang, Z.; Cui, Y.; Liu, J.; Li, J.; Zhang, T. Single-Atom Catalysis of CO Oxidation Using Pt1/FeOx. Nat. Chem. 2011, 3, 634−641, DOI 10.1038/nchem.1095. (13) Liu, J. Catalysis by Supported Single Metal Atoms. ACS Catal. 2017, 7, 34−59, DOI 10.1021/acscatal.6b01534. (14) Yang, X.-F.; Wang, A.; Qiao, B.; Li, J.; Liu, J.; Zhang, T. Single-Atom Catalysts: A New Frontier in Heterogeneous Catalysis. Accounts Chem. Res. 2013, 46, 1740−1748, DOI 10.1021/ar300361m. (15) Haruta, M. Size-and Support-Dependency in the Catalysis of Gold. Catal. Today 1997, 36, 153−166, DOI 10.1016/S0920-5861(96)00208-8. (16) Yoon, B.; Häkkinen, H.; Landman, U.; Wörz, A. S.; Antonietti, J.-M.; Abbet, S.; Judai, K.; Heiz, U. Charging Effects on Bonding and Catalyzed Oxidation of CO on Au8 Clusters on MgO. Science 2005, 307, 403−407, DOI 10.1126/science.1104168. (17) Tauster, S.; Fung, S.; Baker, R.; Horsley, J. Strong Interactions in Supported-Metal Catalysts. Science 1981, 211, 1121−1125, DOI 10.1126/science.211.4487.1121. (18) Wang, S.; Borisevich, A. Y.; Rashkeev, S. N.; Glazoff, M. V.; Sohlberg, K.; Pennycook, S. J.; Pantelides, S. T. Dopants Adsorbed as Single Atoms Prevent Degradation of Catalysts. Nat. mater. 2004, 3, 143−146, DOI 10.1038/nmat1077.


29


Page 30 of 51

(19) Ghosh, T. K.; Nair, N. N. Rh1/γ-Al2O3 Single-Atom Catalysis of O2 Activation and CO Oxidation: Mechanism, Effects of Hydration, Oxidation State, and Cluster Size. ChemCatChem 2013, 5, 1811−1821, DOI 10.1002/cctc.201200799. (20) Rim, K. T.; Eom, D.; Liu, L.; Stolyarova, E.; Raitano, J. M.; Chan, S.-W.; FlytzaniStephanopoulos, M.; Flynn, G. W. Charging and Chemical Reactivity of Gold Nanoparticles and Adatoms on the (111) Surface of Single-Crystal Magnetite: A Scanning Tunneling Microscopy/Spectroscopy Study. J. Phys. Chem. C 2009, 113, 10198−10205, DOI 10.1021/jp8112599. (21) Hackett, S. F.; Brydson, R. M.; Gass, M. H.; Harvey, I.; Newman, A. D.; Wilson, K.; Lee, A. F. High-Activity, Single-Site Mesoporous Pd/Al2O3 Catalysts for Selective Aerobic Oxidation of Allylic Alcohols. Angew. Chem. Int. Ed. 2007, 46, 8593−8596, DOI 10.1002/anie.200702534. (22) Fu, Q.; Saltsburg, H.; Flytzani-Stephanopoulos, M. Active Nonmetallic Au and Pt Species on

Ceria-Based

Water-Gas

Shift

Catalysts.

Science

2003,

301,

935−938,

DOI

10.1126/science.1085721. (23) Novotný, Z.; Argentero, G.; Wang, Z.; Schmid, M.; Diebold, U.; Parkinson, G. S. Ordered Array of Single Adatoms with Remarkable Thermal Stability: Au/Fe3O4(001). Phys. Rev. Lett. 2012, 108, 216103, DOI 10.1103/PhysRevLett.108.216103. (24) Zhang, H.; Watanabe, T.; Okumura, M.; Haruta, M.; Toshima, N. Catalytically Highly Active Top Gold Atom on Palladium Nanocluster. Nat. mater. 2012, 11, 49−52, DOI 10.1038/nmat3143.


30

Page 31 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(25) Wang, Y.; Zhang, W.; Deng, D.; Bao, X. Two-Dimensional Materials Confining Single Atoms for Catalysis. Chin. J. Catal. 2017, 38, 1443-1453, DOI 10.1016/S1872-2067(17)62839-0. (26) Tang, Y.; Yang, Z.; Dai, X. A Theoretical Simulation on the Catalytic Oxidation of CO on Pt/Graphene. Phys. Chem. Chem.Phys. 2012, 14, 16566−16572, DOI 10.1039/C2CP41441D. (27) Wang, H.; Feng, Q.; Cheng, Y.; Yao, Y.; Wang, Q.; Li, K.; Schwingenschlögl, U.; Zhang, X. X.; Yang, W. Atomic Bonding between Metal and Graphene. J. Phys. Chem. C 2013, 117, 4632−4638, DOI 10.1021/jp311658m. (28) Ta, H. Q.; Zhao, L.; Yin, W.; Pohl, D.; Rellinghaus, B.; Gemming, T.; Trzebicka, B.; Palisaitis, J.; Jing, G.; Persson, P. O. Single Cr Atom Catalytic Growth of Graphene. Nano Res. 2018, 11, 2405−2411, DOI 10.1007/s12274-017-1861-3. (29) Cao, Y.; Wang, D.; Lin, Y.; Liu, W.; Cao, L.; Liu, X.; Zhang, W.; Mou, X.; Fang, S.; Shen, X. Single Pt Atom with Highly Vacant d-Orbital for Accelerating Photocatalytic H2 Evolution. ACS Appl. Energy Mater. 2018, 1, 6082−6088, DOI 10.1021/acsaem.8b01143. (30) Deng, J.; Li, H.; Xiao, J.; Tu, Y.; Deng, D.; Yang, H.; Tian, H.; Li, J.; Ren, P.; Bao, X. Triggering the Electrocatalytic Hydrogen Evolution Activity of the Inert Two-Dimensional MoS2 Surface Via Single-Atom Metal Doping. Energy Environ. Sci. 2015, 8, 1594−1601, DOI 10.1039/C5EE00751H. (31) Fang, X.; Shang, Q.; Wang, Y.; Jiao, L.; Yao, T.; Li, Y.; Zhang, Q.; Luo, Y.; Jiang, H. L. Single Pt Atoms Confined into a Metal-Organic Framework for Efficient Photocatalysis. Adv. Mater. 2018, 30. 1705112, DOI 10.1002/adma.201705112.


31


Page 32 of 51

(32) He, T.; Chen, S.; Ni, B.; Gong, Y.; Wu, Z.; Song, L.; Gu, L.; Hu, W.; Wang, X. ZirconiumPorphyrin-Based Metal-Organic Framework Hollow Nanotubes for Immobilization of NobleMetal Single Atoms. Angew. Chem. Int. Ed. 2018, 57, 3493−3498, DOI 10.1002/anie.201800817. (33) Zhang, H.; Wei, J.; Dong, J.; Liu, G.; Shi, L.; An, P.; Zhao, G.; Kong, J.; Wang, X.; Meng, X.; Zhang, J.; Ye, J. Efficient Visible-Light-Driven Carbon Dioxide Reduction by a Single-Atom Implanted Metal-Organic Framework. Angew. Chem. Int. Ed. 2016, 55, 14310−14314, DOI 10.1002/anie.201608597. (34) Qiao, B.; Liang, J.-X.; Wang, A.; Xu, C.-Q.; Li, J.; Zhang, T.; Liu, J. J. Ultrastable SingleAtom Gold Catalysts with Strong Covalent MetalSupport Interaction (CMSI). Nano Res. 2015, 8, 2913−2924, DOI 10.1007/s12274-015-0796-9. (35) Qiao, B.; Liu, J.; Wang, Y.-G.; Lin, Q.; Liu, X.; Wang, A.; Li, J.; Zhang, T.; Liu, J. Highly Efficient Catalysis of Preferential Oxidation of CO in H2-Rich Stream by Gold Single-Atom Catalysts. ACS Catalysis 2015, 5, 6249−6254, DOI 10.1021/acscatal.5b01114. (36) Moses-DeBusk, M.; Yoon, M.; Allard, L. F.; Mullins, D. R.; Wu, Z.; Yang, X.; Veith, G.; Stocks, G. M.; Narula, C. K. CO Oxidation on Supported Single Pt Atoms: Experimental and ab Initio Density Functional Studies of CO Interaction with Pt Atom on θ-Al2O3(010) Surface. J. Am. Chem. Soc. 2013, 135, 12634−12645, DOI 10.1021/ja401847c. (37) Zhang, X.; Shi, H.; Xu, B. Q. Catalysis by Gold: Isolated Surface Au3+ Ions Are Active Sites for Selective Hydrogenation of 1, 3-Butadiene over Au/ZrO2 Catalysts. Angew. Chem. Int. Ed. 2005, 44, 7132−7135, DOI 10.1002/anie.200502101.


32

Page 33 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(38) Wei, H.; Liu, X.; Wang, A.; Zhang, L.; Qiao, B.; Yang, X.; Huang, Y.; Miao, S.; Liu, J.; Zhang, T. FeOx-Supported Platinum Single-Atom and Pseudo-Single-Atom Catalysts for Chemoselective Hydrogenation of Functionalized Nitroarenes. Nat. Commun. 2014, 5, 5634, DOI 10.1038/ncomms6634. (39) Peng, Y.; Geng, Z.; Zhao, S.; Wang, L.; Li, H.; Wang, X.; Zheng, X.; Zhu, J.; Li, Z.; Si, R. Pt Single Atoms Embedded in the Surface of Ni Nanocrystals as Highly Active Catalysts for Selective Hydrogenation of Nitro Compounds. Nano Lett. 2018, 18, 3785−3791, DOI 10.1021/acs.nanolett.8b01059. (40) Lin, J.; Wang, A.; Qiao, B.; Liu, X.; Yang, X.; Wang, X.; Liang, J.; Li, J.; Liu, J.; Zhang, T. Remarkable Performance of Ir1/FeOx Single-Atom Catalyst in Water Gas Shift Reaction. J. Am. Chem. Soc. 2013, 135, 15314−15317, DOI 10.1021/ja408574m. (41) Yang, M.; Allard, L. F.; Flytzani-Stephanopoulos, M. Atomically Dispersed Au–(OH)x Species Bound on Titania Catalyze the Low-Temperature Water-Gas Shift Reaction. J. Am. Chem. Soc. 2013, 135, 3768−3771, DOI 10.1021/ja312646d. (42) Yang, M.; Li, S.; Wang, Y.; Herron, J. A.; Xu, Y.; Allard, L. F.; Lee, S.; Huang, J.; Mavrikakis, M.; Flytzani-Stephanopoulos, M. Catalytically Active Au-O(OH)X-Species Stabilized by Alkali Ions on Zeolites and Mesoporous Oxides. Science 2014, 346, 1498−1501, DOI 10.1126/science.1260526. (43) Cheng, N.; Stambula, S.; Wang, D.; Banis, M. N.; Liu, J.; Riese, A.; Xiao, B.; Li, R.; Sham, T.-K.; Liu, L.-M. Platinum Single-Atom and Cluster Catalysis of the Hydrogen Evolution Reaction. Nat. Commun. 2016, 7, 13638, DOI 10.1038/ncomms13638.


33


Page 34 of 51

(44) Jirkovský, J. S.; Panas, I.; Ahlberg, E.; Halasa, M.; Romani, S.; Schiffrin, D. J. Single Atom Hot-Spots at Au–Pd Nanoalloys for Electrocatalytic H2O2 Production. J. Am. Chem. Soc. 2011, 133, 19432−19441, DOI 10.1021/ja206477z. (45) Choi, C. H.; Kim, M.; Kwon, H. C.; Cho, S. J.; Yun, S.; Kim, H.-T.; Mayrhofer, K. J.; Kim, H.; Choi, M. Tuning Selectivity of Electrochemical Reactions by Atomically Dispersed Platinum Catalyst. Nat. Commun. 2016, 7, 10922, DOI 10.1038/ncomms10922. (46) Cheng, N.; Stambula, S.; Wang, D.; Banis, M. N.; Liu, J.; Riese, A.; Xiao, B.; Li, R.; Sham, T. K.; Liu, L. M.; Botton, G. A.; Sun, X. Platinum Single-Atom and Cluster Catalysis of the Hydrogen Evolution Reaction. Nat. Commun. 2016, 7, 13638, DOI 10.1038/ncomms13638. (47) Fei, H.; Dong, J.; Arellano-Jiménez, M. J.; Ye, G.; Dong Kim, N.; Samuel, E. L. G.; Peng, Z.; Zhu, Z.; Qin, F.; Bao, J.; Yacaman, M. J.; Ajayan, P. M.; Chen, D.; Tour, J. M. Atomic Cobalt on Nitrogen-Doped Graphene for Hydrogen Generation. Nat. Commun. 2015, 6, 8668, DOI 10.1038/ncomms9668. (48) Zhang, L.; Han, L.; Liu, H.; Liu, X.; Luo, J. Potential-Cycling Synthesis of Single Platinum Atoms for Efficient Hydrogen Evolution in Neutral Media. Angew. Chem. Int. Ed. 2017, 56, 13694−13698, DOI 10.1002/anie.201706921. (49) Yin, X.-P.; Wang, H.-J.; Tang, S.-F.; Lu, X.-L.; Shu, M.; Si, R.; Lu, T.-B. Engineering the Coordination Environment of Single-Atom Pt Anchored on Graphdiyne for Optimizing Electrocatalytic Hydrogen Evolution. Angew. Chem. Int. Ed 2018, 57, 9382−9386, DOI 10.1002/anie.201804817.


34

Page 35 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(50) Jiang, K.; Siahrostami, S.; Zheng, T.; Hu, Y.; Hwang, S.; Stavitski, E.; Peng, Y.; Dynes, J.; Gangisetty, M.; Su, D. Isolated Ni Single Atoms in Graphene Nanosheets for High-Performance CO2 Reduction. Energy Environ. Sci. 2018, 11, 893−903, DOI 10.1039/C7EE03245E. (51) Back, S.; Lim, J.; Kim, N.-Y.; Kim, Y.-H.; Jung, Y. Single-Atom Catalysts for CO2 Electroreduction with Significant Activity and Selectivity Improvements. Chem. Sci. 2017, 8, 1090−1096, DOI 10.1039/c6sc03911a. (52) Back, S.; Jung, Y. TiC- and TiN-Supported Single-Atom Catalysts for Dramatic Improvements in CO2 Electrochemical Reduction to CH4. ACS Energy Lett. 2017, 2, 969−975, DOI 10.1021/acsenergylett.7b00152. (53) Liu, W.; Cao, L.; Cheng, W.; Cao, Y.; Liu, X.; Zhang, W.; Mou, X.; Jin, L.; Zheng, X.; Che, W.; Liu, Q.; Yao, T.; Wei, S. Single-Site Active Cobalt-Based Photocatalyst with a Long Carrier Lifetime for Spontaneous Overall Water Splitting. Angew. Chem. Int. Ed. 2017, 56, 9312−9317, DOI 10.1002/anie.201704358. (54) Li, X.; Bi, W.; Zhang, L.; Tao, S.; Chu, W.; Zhang, Q.; Luo, Y.; Wu, C.; Xie, Y. SingleAtom Pt as Co-Catalyst for Enhanced Photocatalytic H2 Evolution. Adv. Mater. 2016, 28, 2427−2431, DOI 10.1002/adma.201505281. (55) Xing, J.; Chen, J. F.; Li, Y. H.; Yuan, W. T.; Zhou, Y.; Zheng, L. R.; Wang, H. F.; Hu, P.; Wang, Y.; Zhao, H. J.; Wang, Y.; Yang, H. G. Stable Isolated Metal Atoms as Active Sites for Photocatalytic Hydrogen Evolution. Chem. 2014, 20, 2138−2144, DOI 10.1002/chem.201303366.


35


Page 36 of 51

(56) Liu, C.; Zhang, Y.; Dong, F.; Reshak, A.; Ye, L.; Pinna, N.; Zeng, C.; Zhang, T.; Huang, H. Chlorine Intercalation in Graphitic Carbon Nitride for Efficient Photocatalysis. Appl. Catal., B 2017, 203, 465−474, DOI 10.1016/j.apcatb.2016.10.002. (57) Yang, Y.; Guo, Y.; Liu, F.; Yuan, X.; Guo, Y.; Zhang, S.; Guo, W.; Huo, M. Preparation and Enhanced Visible-Light Photocatalytic Activity of Silver Deposited Graphitic Carbon Nitride Plasmonic Photocatalyst. Appl. Catal., B 2013, 142, 828−837, DOI 10.1016/j.apcatb.2013.06.026. (58) Chen, Y.; Huang, Z.; Ma, Z.; Chen, J.; Tang, X. Fabrication, Characterization, and Stability of Supported Single-Atom Catalysts. Catal. Sci. Technol. 2017, 7, 4250−4258, DOI 10.1039/C7CY00723J. (59) Zhu, C.; Fu, S.; Shi, Q.; Du, D.; Lin, Y. Single-Atom Electrocatalysts. Angew. Chem. Int. Ed. 2017, 56, 13944−13960, DOI 10.1002/anie.201703864. (60) Chen, Y.; Ji, S.; Chen, C.; Peng, Q.; Wang, D.; Li, Y. Single-Atom Catalysts: Synthetic Strategies

and

Electrochemical

Applications.

Joule

2018,

2,

1242−1264,

DOI

10.1016/j.joule.2018.06.019. (61) Yi, L.; Lan, F.; Li, J.; Zhao, C. Efficient Noble-Metal-Free Co-NG/TiO2 Photocatalyst for H2 Evolution: Synergistic Effect between Single-Atom Co and N-Doped Graphene for Enhanced Photocatalytic

Activity.

ACS

Sustain.

Chem.

Eng.

2018,

6,

12766−12775,

DOI

10.1021/acssuschemeng.8b02001. (62) Gao, C.; Chen, S.; Wang, Y.; Wang, J.; Zheng, X.; Zhu, J.; Song, L.; Zhang, W.; Xiong, Y. Heterogeneous Single-Atom Catalyst for Visible-Light-Driven High-Turnover CO2 Reduction: The Role of Electron Transfer. Adv. Mater. 2018, 30, 1704624, DOI 10.1002/adma.201704624.


36

Page 37 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(63) Su, H.; Che, W.; Tang, F.; Cheng, W.; Zhao, X.; Zhang, H.; Liu, Q. Valence Band Engineering Via Ptii Single-Atom Confinement Realizing Photocatalytic Water Splitting. J. Phys. Chem. C 2018, 122, 21108−21114, DOI 10.1021/acs.jpcc.8b03383. (64) Long, R.; Li, Y.; Liu, Y.; Chen, S.; Zheng, X.; Gao, C.; He, C.; Chen, N.; Qi, Z.; Song, L.; Jiang, J.; Zhu, J.; Xiong, Y. Isolation of Cu Atoms in Pd Lattice: Forming Highly Selective Sites for Photocatalytic Conversion of CO2 to CH4. J. Am. Chem. Soc. 2017, 139, 4486−4492, DOI 10.1021/jacs.7b00452. (65) King, J. S.; Wittstock, A.; Biener, J.; Kucheyev, S. O.; Wang, Y. M.; Baumann, T. F.; Giri, S. K.; Hamza, A. V.; Baeumer, M.; Bent, S. F. Ultralow Loading Pt Nanocatalysts Prepared by Atomic Layer Deposition on Carbon Aerogels. Nano Lett. 2008, 8, 2405−2409, DOI 10.1021/nl801299z. (66) Liu, C.; Wang, C. C.; Kei, C. C.; Hsueh, Y. C.; Perng, T. P. Atomic Layer Deposition of Platinum Nanoparticles on Carbon Nanotubes for Application in Proton-Exchange Membrane Fuel Cells. Small 2009, 5, 1535−1538, DOI 10.1002/smll.200900278. (67) Sun, S.; Zhang, G.; Gauquelin, N.; Chen, N.; Zhou, J.; Yang, S.; Chen, W.; Meng, X.; Geng, D.; Banis, M. N.; Li, R.; Ye, S.; Knights, S.; Botton, G. A.; Sham, T.-K.; Sun, X. SingleAtom Catalysis Using Pt/Graphene Achieved through Atomic Layer Deposition. Sci. Rep. 2013, 3, 1775, DOI 10.1038/srep01775. (68) Qiao, B.; Wang, A.; Zhang, T.; Liu, J. Aberration-Corrected Stem Study of Atomically Dispersed Pti/FeOx Catalyst with High Loading of Pt. Microsc. Microanal. 2015, 21, 1733−1734, DOI 10.1017/S1431927615009447.


37


Page 38 of 51

(69) Kamai, R.; Kamiya, K.; Hashimoto, K.; Nakanishi, S. Oxygen-Tolerant Electrodes with Platinum-Loaded Covalent Triazine Frameworks for the Hydrogen Oxidation Reaction. Angew. Chem. Int. Ed. 2016, 55, 13184−13188, DOI 10.1002/anie.201607741. (70) Lin, L.; Zhou, W.; Gao, R.; Yao, S.; Zhang, X.; Xu, W.; Zheng, S.; Jiang, Z.; Yu, Q.; Li, Y. W.; Shi, C.; Wen, X. D.; Ma, D. Low-Temperature Hydrogen Production from Water and Methanol Using Pt/α-MoC Catalysts. Nature 2017, 544, 80−83, DOI 10.1038/nature21672. (71) Liu, P.; Zhao, Y.; Qin, R.; Mo, S.; Chen, G.; Gu, L.; Chevrier, D. M.; Zhang, P.; Guo, Q.; Zang, D. Photochemical Route for Synthesizing Atomically Dispersed Palladium Catalysts. Science 2016, 352, 797−800, DOI 10.1126/science.aaf5251. (72) Zhang, Z.; Zhu, Y.; Asakura, H.; Zhang, B.; Zhang, J.; Zhou, M.; Han, Y.; Tanaka, T.; Wang, A.; Zhang, T.; Yan, N. Thermally Stable Single Atom Pt/m-Al2O3 for Selective Hydrogenation and CO Oxidation. Nat. Commun. 2017, 8, 16100, DOI 10.1038/ncomms16100. (73) Graham, G. W.; Jen, H. W.; Ezekoye, O.; Kudla, R. J.; Chun, W.; Pan, X. Q.; McCabe, R. W. Effect of Alloy Composition on Dispersion Stability and Catalytic Activity for NO Oxidation over Alumina-Supported Pt–Pd Catalysts. Catal. Lett. 2007, 116, 1−8, DOI 10.1007/s10562-0079124-7. (74) Wiebenga, M. H.; Kim, C. H.; Schmieg, S. J.; Oh, S. H.; Brown, D. B.; Kim, D. H.; Lee, J.-H.; Peden, C. H. F. Deactivation Mechanisms of Pt/Pd-Based Diesel Oxidation Catalysts. Catal. Today 2012, 184, 197−204, DOI 10.1016/j.cattod.2011.11.014.


38

Page 39 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(75) Nagai, Y.; Hirabayashi, T.; Dohmae, K.; Takagi, N.; Minami, T.; Shinjoh, H.; Matsumoto, S. Sintering Inhibition Mechanism of Platinum Supported on Ceria-Based Oxide and Pt-Oxide– Support Interaction. J. Catal. 2006, 242, 103−109, DOI 10.1016/j.jcat.2006.06.002. (76) Li, G.; Jin, R. Atomically Precise Gold Nanoclusters as New Model Catalysts. Accounts Chem. Res. 2013, 46, 1749−1758, DOI 10.1021/ar300213z. (77) Carrillo, C.; Johns, T. R.; Xiong, H.; DeLaRiva, A.; Challa, S. R.; Goeke, R. S.; Artyushkova, K.; Li, W.; Kim, C. H.; Datye, A. K. Trapping of Mobile Pt Species by PdO Nanoparticles under Oxidizing Conditions. J. Phys. Chem. Lett. 2014, 5, 2089−2093, DOI 10.1021/jz5009483. (78) Jones, J.; Xiong, H.; DeLaRiva, A. T.; Peterson, E. J.; Pham, H.; Challa, S. R.; Qi, G.; Oh, S.; Wiebenga, M. H.; Hernández, X. I. P. Thermally Stable Single-Atom Platinum-on-Ceria Catalysts Via Atom Trapping. Science 2016, 353, 150−154, DOI 10.1126/science.aaf8800. (79) Wei, S.; Li, A.; Liu, J. C.; Li, Z.; Chen, W.; Gong, Y.; Zhang, Q.; Cheong, W. C.; Wang, Y.; Zheng, L.; Xiao, H.; Chen, C.; Wang, D.; Peng, Q.; Gu, L.; Han, X.; Li, J.; Li, Y. Direct Observation of Noble Metal Nanoparticles Transforming to Thermally Stable Single Atoms. Nat. Nanotechnol. 2018, 13, 856−861, DOI 10.1038/s41565-018-0197-9. (80) Yang, J.; Qiu, Z.; Zhao, C.; Wei, W.; Chen, W.; Li, Z.; Qu, Y.; Dong, J.; Luo, J.; Li, Z.; Wu, Y. In Situ Thermal Atomization to Convert Supported Nickel Nanoparticles into SurfaceBound Nickel Single-Atom Catalysts. Angew. Chem. Int. Ed. 2018, 57, 14095−14100, DOI 10.1002/anie.201808049.


39


Page 40 of 51

(81) Qu, Y.; Li, Z.; Chen, W.; Lin, Y.; Yuan, T.; Yang, Z.; Zhao, C.; Wang, J.; Zhao, C.; Wang, X.; Zhou, F.; Zhuang, Z.; Wu, Y.; Li, Y. Direct Transformation of Bulk Copper into Copper Single Sites via Emitting and Trapping of Atoms. Nat. Catal. 2018, 1, 781−786, DOI 10.1038/s41929018-0146-x. (82) Xie, G.; Zhang, K.; Guo, B.; Liu, Q.; Fang, L.; Gong, J. R. Graphene-Based Materials for Hydrogen Generation from Light-Driven Water Splitting. Adv. Mater. 2013, 25, 3820−3839, DOI 10.1002/adma.201301207. (83) Fujishima, A.; Honda, K. Electrochemical Photolysis of Water at a Semiconductor Electrode. Nature 1972, 238, 37−38, DOI 10.1038/238037a0. (84) Bourikas, K.; Kordulis, C.; Lycourghiotis, A. Titanium Dioxide (Anatase and Rutile): Surface Chemistry, Liquid-Solid Interface Chemistry, and Scientific Synthesis of Supported Catalysts. Chem. Rev. 2014, 114, 9754−9823, DOI 10.1021/cr300230q. (85) Henderson, M. A. A Surface Science Perspective on TiO2 Photocatalysis. Surf. Sci. Rep. 2011, 66, 185−297, DOI 10.1016/j.surfrep.2011.01.001. (86) Wang, Y.; Wang, Y.; Xu, R. Photochemical Deposition of Pt on CdS for H2 Evolution from Water: Markedly Enhanced Activity by Controlling Pt Reduction Environment. J. Phys. Chem. C 2013, 117, 783−790, DOI 10.1021/jp309603c. (87) Sui, Y.; Liu, S.; Li, T.; Liu, Q.; Jiang, T.; Guo, Y.; Luo, J.-L. Atomically Dispersed Pt on Specific TiO2 Facets for Photocatalytic H2 Evolution. J. Catal. 2017, 353, 250−255, DOI 10.1016/j.jcat.2017.07.024.


40

Page 41 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(88) Zhao, Q.; Yao, W.; Huang, C.; Wu, Q.; Xu, Q. Effective and Durable Co Single Atomic Cocatalysts for Photocatalytic Hydrogen Production. ACS Appl. Mater. Interfaces 2017, 9, 42734−42741, DOI 10.1021/acsami.7b13566. (89) Wang, X.; Maeda, K.; Thomas, A.; Takanabe, K.; Xin, G.; Carlsson, J. M.; Domen, K.; Antonietti, M. A Metal-Free Polymeric Photocatalyst for Hydrogen Production from Water under Visible Light. Nat. Mater. 2009, 8, 76−80, DOI 10.1038/nmat2317. (90) Liu, J.; Liu, Y.; Liu, N.; Han, Y.; Zhang, X.; Huang, H.; Lifshitz, Y.; Lee, S.-T.; Zhong, J.; Kang, Z. Metal-Free Efficient Photocatalyst for Stable Visible Water Splitting via a Two-Electron Pathway. Science 2015, 347, 970−974, DOI 10.1126/science.aaa3145. (91) Zhang, Y.; Liu, J.; Wu, G.; Chen, W. Porous Graphitic Carbon Nitride Synthesized via Direct Polymerization of Urea for Efficient Sunlight-Driven Photocatalytic Hydrogen Production. Nanoscale 2012, 4, 5300−5303, DOI 10.1039/c2nr30948c. (92) Wang, X.; Chen, X.; Thomas, A.; Fu, X.; Antonietti, M. Metal-Containing Carbon Nitride Compounds: A New Functional Organic-Metal Hybrid Material. Adv. Mater. 2009, 21, 1609−1612, DOI 10.1002/adma.200802627. (93) Ran, J.; Zhang, J.; Yu, J.; Jaroniec, M.; Qiao, S. Z. Earth-Abundant Cocatalysts for Semiconductor-Based Photocatalytic Water Splitting. Chem. Soc. Rev. 2014, 43, 7787−7812, DOI 10.1039/c3cs60425j. (94) Benson, E. E.; Kubiak, C. P.; Sathrum, A. J.; Smieja, J. M. Electrocatalytic and Homogeneous Approaches to Conversion of CO2 to Liquid Fuels. Chem. Soc. Rev. 2009, 38, 89−99, DOI 10.1039/b804323j.


41


Page 42 of 51

(95) Gao, G.; Jiao, Y.; Waclawik, E. R.; Du, A. Single Atom (Pd/Pt) Supported on Graphitic Carbon Nitride as an Efficient Photocatalyst for Visible-Light Reduction of Carbon Dioxide. J. Am. Chem. Soc. 2016, 138, 6292−6297, DOI 10.1021/jacs.6b02692. (96) Wang, C.; Xie, Z.; deKrafft, K. E.; Lin, W. Doping Metal-Organic Frameworks for Water Oxidation, Carbon Dioxide Reduction, and Organic Photocatalysis. J. Am. Chem. Soc. 2011, 133, 13445−13454, DOI 10.1021/ja203564w. (97) Fu, Y.; Sun, D.; Chen, Y.; Huang, R.; Ding, Z.; Fu, X.; Li, Z. An Amine-Functionalized Titanium Metal-Organic Framework Photocatalyst with Visible-Light-Induced Activity for CO2 Reduction. Angew. Chem. Int. Ed. 2012, 51, 3364−3367, DOI 10.1002/anie.201108357. (98) Guo, Z.; Cheng, S.; Cometto, C.; Anxolabehere-Mallart, E.; Ng, S. M.; Ko, C. C.; Liu, G.; Chen, L.; Robert, M.; Lau, T. C. Highly Efficient and Selective Photocatalytic CO2 Reduction by Iron and Cobalt Quaterpyridine Complexes. J. Am. Chem. Soc. 2016, 138, 9413−9416, DOI 10.1021/jacs.6b06002. (99) Gao, S.; Lin, Y.; Jiao, X.; Sun, Y.; Luo, Q.; Zhang, W.; Li, D.; Yang, J.; Xie, Y. Partially Oxidized Atomic Cobalt Layers for Carbon Dioxide Electroreduction to Liquid Fuel. Nature 2016, 529, 68−71, DOI 10.1038/nature16455. (100) Liu, C.; Yang, B.; Tyo, E.; Seifert, S.; DeBartolo, J.; von Issendorff, B.; Zapol, P.; Vajda, S.; Curtiss, L. A. Carbon Dioxide Conversion to Methanol over Size-Selected Cu4 Clusters at Low Pressures. J. Am. Chem. Soc. 2015, 137, 8676−8679, DOI 10.1021/jacs.5b03668.


42

Page 43 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(101) Yang, Y.; Evans, J.; Rodriguez, J. A.; White, M. G.; Liu, P. Fundamental Studies of Methanol Synthesis from CO2 Hydrogenation on Cu(111), Cu Clusters, and Cu/ZnO(000ī). Phys. Chem. Chem. Phys. 2010, 12, 9909−9917, DOI 10.1039/c001484b. (102) Yan, Y.; Yu, Y.; Huang, S.; Yang, Y.; Yang, X.; Yin, S.; Cao, Y. Adjustment and Matching of Energy Band of TiO2-Based Photocatalysts by Metal Ions (Pd, Cu, Mn) for Photoreduction of CO2 into CH4. J. Phys. Chem. C 2017, 121, 1089−1098, DOI 10.1021/acs.jpcc.6b07180. (103) In, S. I.; Vaughn, D. D., 2nd; Schaak, R. E. Hybrid CuO-TiO2-xNx Hollow Nanocubes for Photocatalytic Conversion of CO2 into Methane under Solar Irradiation. Angew. Chem. Int. Ed. 2012, 51, 3915−3918, DOI 10.1002/anie.201108936. (104) Nasution, H.; Purnama, E.; Kosela, S.; Gunlazuardi, J. Photocatalytic Reduction of CO2 on Copper-Doped Titania Catalysts Prepared by Improved-Impregnation Method. Catal. Commun. 2005, 6, 313−319, DOI 10.1016/j.catcom.2005.01.011. (105) Li, Y.; Wang, W.-N.; Zhan, Z.; Woo, M.-H.; Wu, C.-Y.; Biswas, P. Photocatalytic Reduction of CO2 with H2O on Mesoporous Silica Supported Cu/TiO2 Catalysts. Appl. Catal., B 2010, 100, 386−392, DOI 10.1016/j.apcatb.2010.08.015. (106) Gong, X.-Q.; Selloni, A.; Dulub, O.; Jacobson, P.; Diebold, U. Small Au and Pt Clusters at the Anatase TiO2(101) Surface: Behavior at Terraces, Steps, and Surface Oxygen Vacancies. J. Am. Chem. Soc. 2008, 130, 370−381, DOI 10.1021/ja0773148.


43


Page 44 of 51

(107) Liu, L.; Zhao, H.; Andino, J. M.; Li, Y. Photocatalytic CO2 Reduction with H2O on TiO2 Nanocrystals: Comparison of Anatase, Rutile, and Brookite Polymorphs and Exploration of Surface Chemistry. ACS Catal. 2012, 2, 1817−1828, DOI 10.1021/cs300273q. (108) Ji, Y.; Luo, Y. New Mechanism for Photocatalytic Reduction of CO2 on the Anatase TiO2(101) Surface: The Essential Role of Oxygen Vacancy. J. Am. Chem. Soc. 2016, 138, 15896−15902, DOI 10.1021/jacs.6b05695. (109) Rodriguez, M. M.; Peng, X.; Liu, L.; Li, Y.; Andino, J. M. A Density Functional Theory and Experimental Study of CO2 Interaction with Brookite TiO2. J. Phys. Chem. C 2012, 116, 19755−19764, DOI 10.1021/jp302342t. (110) Matsubu, J. C.; Yang, V. N.; Christopher, P. Isolated Metal Active Site Concentration and Stability Control Catalytic CO2 Reduction Selectivity. J. Am. Chem. Soc. 2015, 137, 3076−3084, DOI 10.1021/ja5128133. (111) Ma, S.; Song, W.; Liu, B.; Zheng, H.; Deng, J.; Zhong, W.; Liu, J.; Gong, X.-Q.; Zhao, Z. Elucidation of the High CO2 Reduction Selectivity of Isolated Rh Supported on TiO2: A DFT Study. Catal. Sci. Technol. 2016, 6, 6128−6136, DOI 10.1039/C5CY02158H. (112) Chen, J.; Iyemperumal, S. K.; Fenton, T.; Carl, A.; Grimm, R.; Li, G.; Deskins, N. A. Synergy between Defects, Photoexcited Electrons, and Supported Single Atom Catalysts for CO2 Reduction. ACS Catal. 2018, 8, 10464−10478, DOI 10.1021/acscatal.8b02372. (113) Légaré, M.-A.; Bélanger-Chabot, G.; Dewhurst, R. D.; Welz, E.; Krummenacher, I.; Engels, B.; Braunschweig, H. Nitrogen Fixation and Reduction at Boron. Science 2018, 359, 896−900, DOI 10.1126/science.aaq1684.


44

Page 45 of 51 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(114) Hoffman, B. M.; Lukoyanov, D.; Yang, Z. Y.; Dean, D. R.; Seefeldt, L. C. Mechanism of Nitrogen Fixation by Nitrogenase: The Next Stage. Chem. Rev. 2014, 114, 4041−4062, DOI 10.1021/cr400641x. (115) Rafiqul, I.; Weber, C.; Lehmann, B.; Voss, A. Energy Efficiency Improvements in Ammonia Production—Perspectives and Uncertainties. Energy 2005, 30, 2487−2504, DOI 10.1016/j.energy.2004.12.004. (116) Schrauzer, G.; Guth, T. Photolysis of Water and Photoreduction of Nitrogen on Titanium Dioxide. J. Am. Chem. Soc. 1977, 99, 7189−7193, DOI 10.1021/ja00464a015. (117) Seh, Z. W.; Kibsgaard, J.; Dickens, C. F.; Chorkendorff, I.; Nørskov, J. K.; Jaramillo, T. F. Combining Theory and Experiment in Electrocatalysis: Insights into Materials Design. Science 2017, 355, eaad4998, DOI 10.1126/science.aad4998. (118) Huang, P.; Liu, W.; He, Z.; Xiao, C.; Yao, T.; Zou, Y.; Wang, C.; Qi, Z.; Tong, W.; Pan, B. Single Atom Accelerates Ammonia Photosynthesis. Sci. Chi. Chem. 2018, 61, 1187−1196, DOI 10.1007/s11426-018-9273-1. (119) Li, H.; Shang, J.; Ai, Z.; Zhang, L. Efficient Visible Light Nitrogen Fixation with Biobr Nanosheets of Oxygen Vacancies on the Exposed {001} Facets. J. Am. Chem. Soc. 2015, 137, 6393−6399, DOI 10.1021/jacs.5b03105. (120) Zhao, Y.; Zhao, Y.; Waterhouse, G. I. N.; Zheng, L.; Cao, X.; Teng, F.; Wu, L. Z.; Tung, C. H.; O'Hare, D.; Zhang, T. Layered-Double-Hydroxide Nanosheets as Efficient Visible-LightDriven Photocatalysts for Dinitrogen Fixation. Adv. Mater. 2017, 29. 1703828, DOI 10.1002/adma.201703828.


45


Page 46 of 51

(121) Shi, M. M.; Bao, D.; Wulan, B. R.; Li, Y. H.; Zhang, Y. F.; Yan, J. M.; Jiang, Q. Au SubNanoclusters on TiO2 toward Highly Efficient and Selective Electrocatalyst for N2 Conversion to NH3 at Ambient Conditions. Adv. Mater. 2017, 29. 1606550, DOI 10.1002/adma.201606550. (122) Zhang, L.; Ji, X.; Ren, X.; Ma, Y.; Shi, X.; Tian, Z.; Asiri, A. M.; Chen, L.; Tang, B.; Sun, X. Electrochemical Ammonia Synthesis via Nitrogen Reduction Reaction on a MoS2 Catalyst: Theoretical and Experimental Studies. Adv. Mater. 2018, 30, 1800191, DOI 10.1002/adma.201800191. (123) Geng, Z.; Liu, Y.; Kong, X.; Li, P.; Li, K.; Liu, Z.; Du, J.; Shu, M.; Si, R.; Zeng, J. Achieving a Record-High Yield Rate of 120.9 μgNH3 mgcat.1 h1 for N2 Electrochemical Reduction over Ru Single-Atom Catalysts. Adv. Mater. 2018, 30, 1803498, DOI 10.1002/adma.201803498. (124) Ling, C.; Niu, X.; Li, Q.; Du, A.; Wang, J. Metal-Free Single Atom Catalyst for N2 Fixation Driven by Visible Light. J. Am. Chem. Soc. 2018, 140, 14161−14168, DOI 10.1021/jacs.8b07472. (125) Chao, C. Y. Comparison between Indoor and Outdoor Air Contaminant Levels in Residential Buildings from Passive Sampler Study. Build. Environ. 2001, 36, 999−1007, DOI 10.1016/S0360-1323(00)00057-3. (126) Ou, M.; Wan, S.; Zhong, Q.; Zhang, S.; Wang, Y. Single Pt Atoms Deposition on g-C3N4 Nanosheets for Photocatalytic H2 Evolution or NO Oxidation under Visible Light. Int. J. Hydrogen Energ. 2017, 42, 27043−27054, DOI 10.1016/j.ijhydene.2017.09.047. (127) Fujiwara, K.; Pratsinis, S. E. Single Pd Atoms on TiO2 Dominate Photocatalytic NOx Removal. Appl. Catal., B 2018, 226, 127−134, DOI 10.1016/j.apcatb.2017.12.042.


46

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(128) Yang, X.; Flowers, R. C.; Weinberg, H. S.; Singer, P. C. Occurrence and Removal of Pharmaceuticals and Personal Care Products (PPCPs) in an Advanced Wastewater Reclamation Plant. Water Res. 2011, 45, 5218−5228, DOI 10.1016/j.watres.2011.07.026. (129) Fan, Y.; Ji, Y.; Kong, D.; Lu, J.; Zhou, Q. Kinetic and Mechanistic Investigations of the Degradation of Sulfamethazine in Heat-Activated Persulfate Oxidation Process. J. Hazard. Mater. 2015, 300, 39−47, DOI 10.1016/j.jhazmat.2015.06.058. (130) Wang, Y.; Zhao, X.; Cao, D.; Wang, Y.; Zhu, Y. Peroxymonosulfate Enhanced Visible Light Photocatalytic Degradation Bisphenol a by Single-Atom Dispersed Ag Mesoporous g-C3N4 Hybrid. Appl. Catal., B 2017, 211, 79−88, DOI 10.1016/j.apcatb.2017.03.079. (131) Wang, F.; Wang, Y.; Feng, Y.; Zeng, Y.; Xie, Z.; Zhang, Q.; Su, Y.; Chen, P.; Liu, Y.; Yao, K. Novel Ternary Photocatalyst of Single Atom-Dispersed Silver and Carbon Quantum Dots Co-Loaded with Ultrathin g-C3N4 for Broad Spectrum Photocatalytic Degradation of Naproxen. Appl. Catal., B 2018, 221, 510−520, DOI 10.1016/j.apcatb.2017.09.055. (132) Wang, F.; Wang, Y.; Li, Y.; Cui, X.; Zhang, Q.; Xie, Z.; Liu, H.; Feng, Y.; Lv, W.; Liu, G. The Facile Synthesis of a Single Atom-Dispersed Silver-Modified Ultrathin g-C3N4 Hybrid for the

Enhanced

Visible-Light

Photocatalytic

Degradation

of

Sulfamethazine

with

Peroxymonosulfate. Dalton T. 2018, 47, 6924−6933, DOI 10.1039/C8DT00919H.


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Table of Content

Single-atom catalysts for photocatalytic energy conversion. Single-atom catalysts have attracted increasing interests in photocatalytic reaction because of their high catalytic activity, stability, selectivity, and 100% atom utilization.


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Qiushi Wang is currently a master student under the supervision of Prof. Xiaojun Lv at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. She obtained a B.S. degree in the college of science from Northeastern University in 2017. Her study interesting is the preparation of catalysts for photocatalytic and electrocatalytic water splitting, CO2 and N2 reduction reaction.

Dafeng Zhang is currently an associate professor in the Department of Energy and Chemical Engineering, Henan Polytechnic University. He received his Ph.D. degree in materials physical chemistry from Beihang University under the supervision of Prof. Peng Diao (2010). He worked as a postdoctoral research associate with Prof. Wenfu Fu and Xiao-Jun Lv at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences (2017). His research interests include


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the design and synthesis of nanomaterials and exploration of their applications in electrochemical catalysis.

Yong Chen studied at the Technical Institute of Physics and Chemistry (TIPC), Chinese Academy of Sciences, where he worked with Prof. Wen-Fu Fu for his PhD (completed in 2007). From 2007 to 2011, he carried out postdoctoral research with Prof. Chi-Ming Che at The University of Hong Kong, and he subsequently joined the faculty at TIPC. His research interests include the photophysics and photochemistry of transition metal complexes and photocatalytic solar energy conversion.


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Wen-Fu Fu received his Ph.D. from University of Erlangen‐Nuremberg, Germany in 1997. From 1998–2000, he carried out postdoctoral research with Prof. Chi‐Ming Che at The University of Hong Kong. Now he is a Professor at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. His research interests include synthesis, characterization, and exploring optical properties of metal complexes, solar energy storage, photocatalytic water splitting and CO2 reduction.

Xiao-Jun Lv is an associate professor at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. He obtained his BS and PhD degree in Material Physics and Chemistry in 2001 and 2007 at Beihang University under the supervision of Prof. Qi Zhang. He then worked as a postdoctoral researcher associate with Prof. Jinghong Li and Prof. Jin Z. Zhang at Tsinghua University. During 2015-2016, he visited Prof. Heinz Frei's laboratory in the Lawrence Berkeley National Lab of United States. His current scientific interests focus on catalyst nanomaterials for energy conversion.


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Single-Atom Catalysts for Photocatalytic Reactions - ACS Sustainable

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