Remarkable Enhancement in Solar Oxygen ... - ACS Publications

Apr 12, 2019 - Herein, we report the fabrication of a novel g-C3N4/MoS2/Ag3PO4 ternary composite and its application in photocatalytic oxygen evolutio...
0 downloads 0 Views 1MB Size
Subscriber access provided by CAL STATE UNIV BAKERSFIELD

Article

Remarkable Enhancement in Solar Oxygen Evolution from MoSe2/Ag3PO4 Heterojunction Photocatalyst via in situ Constructing Interfacial Contact Dongsheng Li, Huaichong Wang, Hua Tang, Xiaofei Yang, and Qinqin Liu ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.9b00252 • Publication Date (Web): 12 Apr 2019 Downloaded from http://pubs.acs.org on April 15, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34 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

ACS Sustainable Chemistry & Engineering

Remarkable Enhancement in Solar Oxygen Evolution from MoSe2/Ag3PO4 Heterojunction Photocatalyst via in situ Constructing Interfacial Contact Dongsheng Li,† Huaichong Wang,† Hua Tang,*,† Xiaofei Yang,†,§ Qinqin Liu *,†

† School

of Materials Science and Engineering, Jiangsu University, Zhenjiang, 212013,

P. R. China. E-mail: [email protected]; [email protected] §

College of Science & Institute of Materials Physics and Chemistry, Nanjing Forestry

University, Nanjing 210037, P. R. China

1

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

ABSTRACT: To explore low-cost and earth-abundant co-catalysts is important for developing efficient photocatalytic system for water splitting. Herein, we report a hybrid photocatalyst consisting of Ag3PO4 nanoparticles in-situ grown on the surface of two dimensional MoSe2 nanoarchitectures acting as a noble-metal-free co-catalyst for photocatalytic oxygen evolution under LED-light irradiation. The MoSe2/Ag3PO4 heterojunctions exhibited an obviously enhanced activity for photocatalytic O2 generation compared with pure Ag3PO4 or the physical mixed samples with the same component, and the MoSe2/Ag3PO4 composite with optimal ratio of co-catalysts demonstrated the highest O2 evolution rate of 182 µmolL-1g-1h-1. The highly photocatalytic performance could be mainly ascribed to the formation of close and large contact interface between MoSe2 and Ag3PO4 via in-situ preparation method, leading to ultrafast interfacial charge migration and highly efficient charge separation. More importantly, introduction of MoSe2 co-catalyst not only could promote light harvesting and provide more active adsorption sites, but also prevent the photocorrosion of the Ag3PO4 during the photocatalytic reaction. This work may open up new insights for the introduction of a noble-metal-free MoSe2 as an effective co-catalyst for solar energy conversion to achieve O2 generation.

Keywords: MoSe2, Ag3PO4, heterojunction, photocatalytic oxygen evolution, co-catalyst

2

ACS Paragon Plus Environment

Page 2 of 34

Page 3 of 34 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

ACS Sustainable Chemistry & Engineering

INTRODUCTION The photocatalytic production of hydrogen and oxygen is one of the important strategies to resolve the current global energy and environmental problems.1-10 Photocatalytic water splitting process consists of two half-reactions, one is the water reduction to produce hydrogen and the other is oxygen evolution from water oxidation, and the water oxidation is harder to realize due to a higher energy barrier needed to be overcome.11-13 Compared with the numerous semiconductors can act for hydrogen production photocatalysts,14-17 only a few photocatalysts including Ag3PO4,18 BiVO4,19 WO3,20 etc. demonstrated the ability for water splitting to produce oxygen, however, the moderate water oxidation capacities over bare photocatalyst due to the intrinsic property associated with band gaps and band edge positions are far from the requirements for practical application.21-23 Recently, Ag3PO4 has proven to be an excellent visible light-active photocatalyst due to its high photocatalytic activity toward water splitting and photodegradation of organic contaminants.24,25 Nevertheless, the inherently photocorrsion under light irradiation and soluble problem in aqueous solution, as well as fast recombination of photogenerated charges of pristine Ag3PO4 greatly restrict photocatalytic activity.26 Therefore, it is still a big challenge for exploring effective methods to enhance the stability and activity of the Ag3PO4 photocatalyst. Among diverse techniques, modifying Ag3PO4 by loading co-catalysts has been considered as an interesting and efficient strategy to accelerate the separation of photo-generated charge carriers and 3

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Page 4 of 34

provide more active sites.27-33 Tang et al. found that loading Co3O4 as co-catalysts modified Ag3PO4 for the achievement of enhanced photocatalytic activity and stability.34 Song and co-workers adopted three-dimensional hollow carbon graphene as a noble-metal free co-catalyst to accelerate the electron transfer of Ag3PO4.35 Guo et al. proved that SrTiO3 co-catalysts could boost the electron transfer of Ag3PO4 and enhanced O2 evolution.36 Although Ag3PO4-based photocatalysts incorporated with certain cocatalysts have been reported and the coupling of the co-catalysts have been confirmed to increase the photocatalytic performance, the efficiency of photocatalytic oxygen generation from water splitting on Ag3PO4 still deserves further studies. Recently, transition metal dichalcogenides (TMDs), especially MoS2, have gained interest as cocatalysts for photocatalytic application because of its good surface adsorption ability and proper electronic properties.37-41 In contrast with MoS2, MoSe2 as an important member of TMDs has a more metallic in nature and higher electrical conductivity, which exhibits remarkable electrocatalytic HER activity. However, there are only a few researches on MoSe2 cocatalyst

in photocatalytic

water splitting system.42,43 Recently, Zeng et al.44, Chen et al.43, Xu et al.45 reported that photocatalytic H2 activity can be greatly increased by coupling MoSe2 and other semiconductor. Inspired by these findings, we propose that the metallic MoSe2 owning excellent conductivity and generous active sites may be utilized as a cocatalyst for photocatalytic O2 generation. Herein, we report a highly efficient photocatalytic O2-evolution system 4

ACS Paragon Plus Environment

Page 5 of 34 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

ACS Sustainable Chemistry & Engineering

employing two dimensional MoSe2 as a co-catalyst. In this study, MoSe2/Ag3PO4 heterojunction photocatalyst were for the first time synthesized by a solution phase approach. The photocatalytic O2-production activities and stabilities over the MoSe2/Ag3PO4 composite photocatalysts were also evaluated. The structure characteristics and electrochemical characterizations were presented to reveal the improved photocatalytic O2 evolution activity over MoSe2/Ag3PO4 heterojunction composites. A possible mechanism of photocatalytic enhancement is presented. This study can provide a novel strategy for the development of Ag3PO4-based photocatalysts for energy production.

EXPERIMENTAL SECTION Synthesis of the Ag3PO4/MoSe2 composites The two dimensional MoSe2 were prepared using a hydrothermal method based on our previous report.46 The MoSe2/Ag3PO4 (named as MoSe2/AP) samples were synthesized via in-situ formation of Ag3PO4 on the as-prepared MoSe2 samples. Typically, flower-like MoSe2 with different mass (10mg, 20mg, 50mg, and 100mg), named as 2wt.% MoSe2/AP, 4wt.% MoSe2/AP, 10wt.% MoSe2/AP and 20wt.% MoSe2/AP, respectively, were ultrasonic dispersed in 100 mL distilled water. After that, AgNO3 solution (20 mL, 1.8 mmol/L) was dropped into the MoSe2 suspension under magnetic stirring for 12 h. Next, Na3PO4·12H2O solution (20 mL,1.8 mmol/L) was added into the above mixed solution and then stirred for another 4 h. Finally, the 5

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

obtained samples were centrifuged, washed and dried in vacuum at 60℃ for 24 h. Pure Ag3PO4 was synthesized using the same procedure. The schematic illustration for the preparation of MoSe2/AP was shown in Figure 1. The experimental details for the characterization, and photocatalytic oxygen evolution measurement of the samples are presented in the Supporting Information.

Figure 1. Schematic illustration of the synthesis of MoSe2/AP composites

RESULTS AND DISCUSSION Phase composition and crystal structure of the MoSe2/AP hybrids with different ratios are investigated by XRD and pristine Ag3PO4 and MoSe2 are shown for comparison (Figure 2). Pure Ag3PO4 exhibits obvious diffraction peaks located at 20.88°, 29.70°, 33.29°, 36.59°, 42.49°, 47.79°, 52.70°, 55.02°, 57.28°, 61.64°, 65.84°, 6

ACS Paragon Plus Environment

Page 6 of 34

Page 7 of 34 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

ACS Sustainable Chemistry & Engineering

69.9°, 71.90° and 73.87°, which is corresponding to the body-centered cubic structure (JCPDS No. 06-0505).47,48 For pure MoSe2, the peaks at 13.69°, 27.64°,31.42°, 37.88° and 55.92° are corresponded to the (002), (004), (100), (103) and (110) crystal planes, respectively, confirming the existence of the hexagonal system of MoSe2 (JCPDS No. 29-0914).46 However, the MoSe2/AP hybrids exhibit similar XRD pattern with pure Ag3PO4 (Figure 2), and no noticeable diffraction peaks of MoSe2 can be observed, which is ascribed to low concentration and low crystallization degree of MoSe2.

Figure 2. XRD patterns of (a) Ag3PO4, MoSe2 and 4wt.% MoSe2/AP composite (b) MoSe2/AP composites with different content.

The FE-SEM images of MoSe2, Ag3PO4 and 4 wt% MoSe2/AP composite. As shown in Figure 3a and Figure 3b, pure MoSe2 possessed the flower-like structures assembled by thin sheets, while Ag3PO4 presents an irregular polyhedron morphology with the size of 50-200 nm. A typical SEM image of the MoSe2/AP composite was seen from Figure 3c and Figure 3d. It can be clearly observed that Ag3PO4 nanoparticles are anchored on the MoSe2 sheets with a tightly contact between Ag3PO4 and MoSe2. It is noted that the particle size of the Ag3PO4 in composite is 7

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

reduced to 20 ~ 30 nm due to the space-confined effect of MoSe2 hierarchical corrugations. The TEM images (Figure S1) demonstrate a intimate integration between the Ag3PO4 nanoparticles and the MoSe2 sheets, indicating the formation of heterojunction via the in-situ deposition of Ag3PO4 on the MoSe2 nanosheets. EDS mapping confirmed the uniform distribution of the chemical element, including Ag (yellow), O (blue), P (green), Mo (red) and Se (purple), in the 4wt.% MoSe2/AP composite, as shown in Figure 3e. This indicates that the elements of Ag, O, P, Mo and Se are evenly distributed on substrate, demonstrating the MoSe2/AP composite was successfully synthesized.

8

ACS Paragon Plus Environment

Page 8 of 34

Page 9 of 34 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

ACS Sustainable Chemistry & Engineering

Figure 3. SEM images of (a) MoSe2, (b) Ag3PO4, (c, d) 4wt.% MoSe2/AP composite, and (e) element mapping images of Ag, O, P, Mo and Se.

9

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Figure 4. (a) survey spectrum and high resolution XPS spectra of (b) Ag 3d, (c) P 2p, (d) O 1s (e) Mo 3d and (f) Se 3d of 4wt.% MoSe2/AP composite.

XPS results was used to further investigation of the chemical compositions and bonding configuration of the 4wt.% MoSe2/AP, as shown in Figure 4a. It could be easily found the presence of Ag, O, P, Mo and Se. The Ag 3d XPS spectrum (Figure 10

ACS Paragon Plus Environment

Page 10 of 34

Page 11 of 34 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

ACS Sustainable Chemistry & Engineering

4b) reveals two characteristic peaks at binding energies of 367.8 and 373.8 eV corresponding to the Ag 3d5/2 and Ag 3d3/2 orbitals, respectively. 49The peak of P 2p at 132.6 eV (Figure 4c), O 1s at 530 and 532.2 eV (Figure 4d) were due to the P5+ and O2- in PO43-, respectively.50 Fig. 4e and 4f show the high resolution XPS spectra of Mo 3d and Se 3d of the 4wt.% MoSe2/AP. Two peaks of Mo 3d around at 233.2 eV and 236.4 eV can be assigned to Mo 3d3/2 and Mo 3d5/2.51 The spectrum of Se 3d displays the doublet at 55.1 eV, and 55.7 eV, which is attributed to Se 3d3/2and Se 3d1/2,52 further elucidating the successful hybridization of MoSe2 and Ag3PO4.

Figure 5. (a) Oxygen evolution and (b) Oxygen evolution rate on different photocatalysts, (c) Oxygen evolution of physical mixture samples, and (d) the cycling 11

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

runs of photocatalytic O2 evolution over 4wt.% MoSe2/AP composite (a: Ag3PO4, b: 2 wt.% MoSe2/AP, c: 4 wt.% MoSe2/AP, d: 10 wt.% MoSe2/AP and e: 20 wt.% MoSe2/AP).

The photocatalytic performances of MoSe2/AP composites were characterized by oxygen evolution from water splitting under LED-irradiation. Bare Ag3PO4 shows a low photocatalytic activity (56 µmolL-1g-1h-1) due to its rapid recombination of photogenerated charges (Fig.5a and b). The MoSe2 loading can enhance the photocatalytic O2 evolution. The highest photocatalytic O2 evolution rate is achieved in 4wt.% MoSe2/AP, whose O2 evolution rate of 182 µmolL-1g-1h-1 is approximately 3.25 times as much as pure Ag3PO4. However, further increasing the MoSe2 loading would lead to a decrease in photocatalytic performance (i.e. 10 and 20 wt.%). For comparison, photocatalytic oxygen evolution performance of samples synthesized by the physical mixtures with different mass ratios are shown in Figure 5c. It can be observed that the oxygen generation rate increased slightly in physical mixtures, and 10wt.% MoSe2/AP achieved the highest oxygen evolution rate (66 µmolL-1g-1h-1). It can be found that the MoSe2 has not played the role of enhancing the photocatalytic performance of Ag3PO4, supposing that the poor contact of Ag3PO4 and MoSe2 through simply physical mixing is not conducive to the transmission of electrons and leads to the poor activity. These results indicate that the amount of MoSe2 co-catalysts and interface contact between the co-catalyst and 12

ACS Paragon Plus Environment

Page 12 of 34

Page 13 of 34 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

ACS Sustainable Chemistry & Engineering

semiconductor both play pivotal roles in the performance enhancement of Ag3PO4. A detailed comparison between as-obtained sample in this study and related catalysts in literatures, was shown in Table S1, indicating that as-prepared MoSe2/AP in this study showed a stronger catalytic property for photocatalytic O2 generation. Furthermore, the effects of catalyst dosage on photocatalytic oxygen evolution performance are further studied and the results are present in Figure S2. Photocatalytic efficiency increased with the catalyst loading was increased up to 1g, and then start to decrease with more dosage of catalyst. Possibly, excess catalyst dosage leaded to a decreased light penetration through the solution due to the increased opacity of the suspension.53 Besides excellent photocatalytic oxygen evolution performance, the recycling test was performed with 4wt.% MoSe2/AP sample. It can be seen that the photocatalytic performance of 4wt.% MoSe2/AP displays a significant oxygen evolution results than pure Ag3PO4 after four cycling runs (Fig.5d). It can be noted that the oxygen-evolution rate of 4wt.% MoSe2/AP after four cycles still produces 2.5 times as much as pure Ag3PO4, suggesting that the MoSe2 co-catalyst is beneficial to raise the photocatalytic performance as well as to enhance the stability of Ag3PO4.

13

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Figure 6. XRD patterns of 4wt.% MoSe2/AP composite before and after photocatalytic reaction.

The recycled 4wt.% MoSe2/AP powders were collected and characterized by XRD, as shown in Figure 6. It can be found that four new peaks located at 38.12°, 44.28°, 64.43° and 77.47° corresponding to (111), (200), (220) and (311) plane of metallic Ag were detected after photocatalytic reaction. The formation of the Ag nanoparticles was supposed to that the Ag+ ions from AgNO3 aqueous solution would be deoxidized to metallic Ag on the surface of MoSe2 sheets by the photogenerated electrons under the irradiation, which can inhibit the release of Ag+ ions from Ag3PO4 and enhance the stability of Ag3PO4.

14

ACS Paragon Plus Environment

Page 14 of 34

Page 15 of 34 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

ACS Sustainable Chemistry & Engineering

Figure 7. (a) UV-vis DRS, (b) PL spectra, (c) Electrochemical impedance spectroscopy and (d) Transient photocurrent response of Ag3PO4 and 4wt.% MoSe2/AP. The absorption spectra of Ag3PO4, MoSe2 and 4wt.% MoSe2/AP composite are shown in Figure 7a. The Ag3PO4 possesses a good visible light absorption, and shows a fundamental absorption edge at about 520 nm54, while MoSe2 shows broad absorption from 200 nm to 800 nm. In contrast to pure Ag3PO4, the 4wt.% MoSe2/AP hybrid exhibits significantly enhanced intensity at wider wavelength range from 500 nm to 800 nm. Photocurrent response, EIS spectra, PL spectra and time-resolved PL spectra were utilized to study the photo-induced charges generation.29,55-57 Figure 7b shows the comparison of PL intensity of 4wt.% MoSe2/AP and Ag3PO4. Pristine Ag3PO4 exhibits a strong emission peak at approximately 550 nm, but the 4wt.% 15

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

MoSe2/Ag3PO4 sample shows a remarkably decrease in PL intensity, indicating that the recombination process of photogenerated carriers in Ag3PO4 is prohibited by the introduction of the MoSe2 cocatalyst.58-61 Based on the time-resolved fluorescence spectra (see Figure S4), the average radiative lifetimes for Ag3PO4 and MoSe2/AP are 0.22 and 0.17 ns, respectively. The obvious quenching and lifetime reduction in PL spectra implies the fast charge carrier transfer from Ag3PO4 to MoSe2.58,59,62 The smaller radius of Nyquist arc (Figure 7c) and significantly enhanced photocurrent (Figure 7d) also confirm the improved charge transfer efficiency of the MoSe2/AP 63-66.

Figure 8. ESR spectra of radical adducts trapped by DMPO in methanol (a) and aqueous (b) dispersions of Ag3PO4 and 4 wt.% MoSe2/AP (c) DMPO-O2•− and (d) DMPO-•OH of 4

wt.% MoSe2/AP under visible light irradiation

16

ACS Paragon Plus Environment

Page 16 of 34

Page 17 of 34 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

ACS Sustainable Chemistry & Engineering

The enhancement mechanism of photocatalytic water oxidation was further studied by electron spin resonance (ESR) characterization, as shown in Figure 8a and Figure 8b. When exposed to visible light irradiation, typical characteristic peaks of hydroxyl radical (DMPO-•OH) and superoxide radical (DMPO-O2•−) were observed for Ag3PO4 and MoSe2/AP.67 Moreover, the signal intensity for DMPO-•OH and DMPO-O2•− radical of 4wt.% MoSe2/AP is stronger than that of pristine Ag3PO4, demonstrating that more •OH and O2•− radicals were generated over 4wt.% MoSe2/AP composite. The concentration of DMPO-•OH and DMPO-O2•− adducts increased with the prolong of the irradiation time (Figure 8c and Figure 8d). In contrast, no obvious radical signals were detected in the dark, indicated the necessity of light illumination.68 It can be concluded that the •OH and O2•− radicals play the major role of the oxygen generation.

Figure 9. Schematic illustration of the photocatalytic mechanism of MoSe2/AP composite photocatalyst under visible light irradiation 17

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Based on the above results and analysis, the enhancement mechanism of the photocatalytic oxygen generation of the MoSe2/AP hybrid is proposed (Figure 9). When the composite is exposed by visible light, the electrons of Ag3PO4 are excited to the conduction band and leave holes at the valance band. The photoexcited electrons migrate to the metallic MoSe2 due to the intimate contract between Ag3PO4 and MoSe2. In the meantime, the Ag+ ions from AgNO3 aqueous solution are reduced to metallic Ag by the electrons accumulated on the MoSe2. Therefore, the MoSe2 nanosheets and the in-situ formed Ag nanoparticles both can act as co-catalysts to construct a bridge for faster electron transport to improve the separation efficiency of photogenerated carries and photocatalytic activity. Therefore, the holes left in the Ag3PO4 with superior oxidation can react with H2O to generate O2, resulting in the enhancement of photocatalytic performance of the MoSe2/AP.

CONCLUSIONS Herein, MoSe2 was utilized as a non-metalic co-catalyst into a photocatalytic water splitting system for oxygen evolution reaction. The MoSe2/AP heterojunction photocatalyst were firstly fabricated by through a simple in-situ deposition method. The as-synthesized samples showed improved photocatalytic oxygen-evolution performance than that of Ag3PO4, and the optimal ration sample, 4 wt.% MoSe2/AP, demonstrates 3.25 times oxygen-evolving rate higher than that of Ag3PO4 or the 18

ACS Paragon Plus Environment

Page 18 of 34

Page 19 of 34 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

ACS Sustainable Chemistry & Engineering

MoSe2/AP samples prepared by physical mixing. The enhancement reason was studied by the PL, time-resolved PL, EIS, photocurrent and ESR, and it was supposed that the MoSe2 co-catalyst can inhibit the agglomeration of Ag3PO4 nanoparticles and provide more active sites to promote the separation and transfer of photogenerated charges. The tight contact between Ag3PO4 and MoSe2, as well as MoSe2 nanosheets and the in-situ formed Ag nanoparticles in photocatalyst system as dual electron co-catalysts to construct a bridge for faster electron transport facilitate the separation of photogenerated carries and improvement of the photocatalytic oxygen evolution. This work provides useful guidance for developing a noble-metal free co-catalyst system for O2 producing photocatalyst.

ASSOCIATED CONTENT Supporting Information Characterization details, Photocatalytic oxygen evolution The Supporting Information is available free of charge on the ACS Publications website

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. [email protected] Notes 19

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

The authors declare no competing financial interest ACKNOWLEDGEMENTS This work was partially supported by the National Natural Science Foundation of China (51672113), X. Yang acknowledges the financial support from Start-up Fund for High-Level Talents, Nanjing Forestry University, Natural Science Foundation of Jiangsu Province (BK20171299). H. Tang thanks the Education Department of Jiangsu Province for funding through QingLan Project.

REFERENCES (1) Qiao, M.; Liu, J.; Wang, Y.; Li, Y. F.; Chen, Z. F. PdSeO3 monolayer: promising inorganic 2D photocatalyst for direct overall water splitting without using sacrificial reagents and cocatalysts. J. Am. Chem. Soc. 2018, 140, 12256-12262, DOI: 10.1021/jacs.8b07855. (2) Volokh, M.; Peng, G.; Barrio, J.; Shalom, M. Carbon nitride materials for water splitting photoelectrochemical cells. Angew. Chem., Int. Ed. 2018, DOI: 10.1002/anie.201806514. (3) Meng, A. Y.; Wu, S.; Cheng, B.; Yu, J. G.; Xu, J. S. Hierarchical TiO2/Ni(OH)2 composite fibers with enhanced photocatalytic CO2 reduction performance. J. Mater. Chem. A. 2018, 6, 4729-4736, DOI: 10.1039/C7TA10073F. (4) Barrio, J.; Lin, L. H.; Wang, X. C.; Shalom, M. Design of a unique energy-band 20

ACS Paragon Plus Environment

Page 20 of 34

Page 21 of 34 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

ACS Sustainable Chemistry & Engineering

structure and morphology in a carbon nitride photocatalyst for improved charge separation and hydrogen production. ACS Sustainable Chem. Eng. 2018, 6, 519-530, DOI: 10.1021/acssuschemeng.7b02807. (5) Low, J. X.; Zhang, L. Y.; Tong, T.; Shen, B. J.; Yu, J. G. TiO2/MXene Ti3C2 composite with excellent photocatalytic CO2 reduction activity. J. Catal. 2018, 361, 255-266, DOI: 10.1016/j.jcat.2018.03.009. (6) Ao, Y. H.; Wang, K. D.; Wang, P. F.; Wang, C.; Hou, J. Synthesis of novel 2D-2D p-n heterojunction BiOBr/La2Ti2O7 composite photocatalyst with enhanced photocatalytic performance under both UV and visible light irradiation. Appl. Catal., B 2016, 194, 157-168, DOI: 10.1016/j.apcatb.2016.04.050. (7) Wang, P. F.; Wu, T. F.; Wang, C.; Hou, J.; Qian, J.; Ao, Y. H. Combining heterojunction engineering with surface cocatalyst modification to synergistically enhance the photocatalytic hydrogen evolution performance of cadmium sulfide nanorods.

ACS

Sustainable

Chem.

Eng.

2017,

5,

7670-7677,

DOI:

10.1021/acssuschemeng.7b01043. (8) Wang, X. F.; Cheng, J. J.; Yu, H. G.; Yu, J. G. A facile hydrothermal synthesis of carbon dots modified g-C3N4 for enhanced photocatalytic H2-evolution performance. Dalton Trans. 2017, 46, 6417-6424, DOI: 10.1039/c7dt00773f. (9) Wang, K.; Li, Q.; Liu, B. S.; Cheng, B.; Ho, W. K.; Yu, J. G. Sulfur-doped g-C3N4 with enhanced photocatalytic CO2-reduction performance. Appl. Catal., B 2015, 176-177, 44-52, DOI: 10.1016/j.apcatb.2015.03.045. 21

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

(10) Huang, H. W.; Xiao, K.; Tian, N.; Dong, F.; Zhang, T. R.; Du, X.; Zhang, Y. H. Template-free precursor-surface-etching route to porous, thin g-C3N4 nanosheets for enhancing photocatalytic reduction and oxidation activity. J. Mater. Chem. A. 2017, 5, 17452-17463, DOI: 10.1039/c7ta04639a. (11) Wei, R. B.; Kuang, P. Y.; Cheng, H.; Chen, Y. B.; Long, J. Y.; Zhang, M. Y.; Liu, Z. Q. Plasmon-enhanced photoelectrochemical water splitting on gold nanoparticle decorated ZnO/CdS nanotube arrays. ACS Sustainable Chem. Eng. 2017, 5, 4249-4257, DOI: 10.1021/acssuschemeng.7b00242. (12) Liu, Q. Q.; Shen, J. Y.; Yang, X. F.; Zhang, T. R.; Tang, H. 3D reduced graphene oxide aerogel-mediated Z-scheme photocatalytic system for highly efficient solar-driven water oxidation and removal of antibiotics. Appl. Catal., B 2018, 232, 562-573, DOI: 10.1016/j.apcatb.2018.03.100. (13) Zhou, T. H.; Wang, D. P.; Goh, S. C. K.; Hong, J. D.; Han, J. Y.; Mao, J. G.; Xu, R. Bio-inspired organic cobalt(II) phosphonates toward water oxidation. Energy Environ. Sci. 2015, 8, 526-534, DOI: 10.1039/c4ee03234a. (14) Wei, R. B.; Huang, Z. L.; Gu, G. H.; Wang, Z.; Zeng, L. X.; Chen, Y. B.; Liu, Z. Q. Dual-cocatalysts decorated rimous CdS spheres advancing highly-efficient visible-light photocatalytic hydrogen production. Appl. Catal., B 2018, 231, 101-107, DOI: 10.1016/j.apcatb.2018.03.014. (15) Xia, P. F.; Zhu, B. C.; Cheng, B.; Yu, J. G.; Xu, J. S. 2D/2D g-C3N4/MnO2 nanocomposite as a direct Z-scheme photocatalyst for enhanced photocatalytic 22

ACS Paragon Plus Environment

Page 22 of 34

Page 23 of 34 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

ACS Sustainable Chemistry & Engineering

activity.

ACS

Sustainable

Chem.

Eng.

2018,

6,

965-973,

DOI:

10.1021/acssuschemeng.7b03289. (16) Ma, Y. J.; Bian, Y.; Liu, Y.; Zhu, A. Q.; Wu, H.; Cui, H.; Chu, D. W.; Pan, J. Construction of Z-scheme system for enhanced photocatalytic H2 evolution based on CdS quantum Dots/CeO2 nanorods heterojunction. ACS Sustainable Chem. Eng. 2018, 6, 2552-2562, DOI: 10.1021/acssuschemeng.7b04049. (17) Xu, F. Y.; Zhang, L. Y.; Cheng, B.; Yu, J. G. Direct Z-scheme TiO2/NiS core–shell hybrid nanofibers with enhanced photocatalytic H2-production activity. ACS

Sustainable

Chem.

Eng.

2018,

6,

12291-12298,

DOI:

10.1021/acssuschemeng.8b02710. (18) Liu, W.; Shen, J.; Yang, X. F.; Liu, Q. Q.; Tang, H. Dual Z-scheme g-C3N4/Ag3PO4/Ag2MoO4 ternary composite photocatalyst for solar oxygen evolution from

water

splitting.

Appl.

Surf.

Sci.

2018,

456,

369-378,

DOI:

10.1016/j.apsusc.2018.06.156. (19) Pan, Q. G.; Zhang, C.; Xiong, Y. J.; Mi, Q. X.; Li, D. D.; Zou, L. L.; Huang, Q. H.; Zou, Z. Q.; Yang, H. Boosting charge separation and transfer by plasmon-enhanced

MoS2/BiVO4

p-n

heterojunction

composite

for

efficient

photoelectrochemical water splitting. ACS Sustainable Chem. Eng. 2018, 6, 6378-6387, DOI: 10.1021/acssuschemeng.8b00170. (20) Wang, Y. T.; Cai, J. M.; Wu, M. Q.; Chen, J. H.; Zhao, W. Y.; Tian, Y.; Ding, T.; Zhang, J.; Jiang, Z.; Li, X. G. Rational construction of oxygen vacancies onto 23

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Page 24 of 34

tungsten trioxide to improve visible light photocatalytic water oxidation reaction. Appl. Catal., B 2018, 239, 398-407, DOI: 10.1016/j.apcatb.2018.08.029. (21) Liu, Q. Q.; Liu, Y. D.; Yin, Y. D. Optical tuning by the self-assembly and disassembly of chain-like plasmonic superstructures. Natl. Sci. Rev. 2018, 5, 128-130, DOI: 10.1093/nsr/nwx067. (22) Tang, H.; Chang, S. F.; Jiang, L. Y.; Tang, G. G.; Liang, W. Novel spindle-shaped nanoporous TiO2 coupled graphitic g-C3N4 nanosheets with enhanced visible-light photocatalytic activity. Ceram. Int. 2016, 42, 18443-18452, DOI: 10.1016/j.ceramint.2016.08.179. (23) Tian, L.; Yang, X. F.; Cui, X. K.; Liu, Q. Q.; Tang, H. Fabrication of dual direct Z-scheme g-C3N4/MoS2/Ag3PO4 photocatalyst and its oxygen evolution performance. Appl. Surf. Sci. 2019, 463, 9-17, DOI: 10.1016/j.apsusc.2018.08.209. (24) Tang, H.; Fu, Y. H.; Chang, S. F.; Xie, S. Y.; Tang, G. G. Construction of Ag3PO4/Ag2MoO4 Z-scheme heterogeneous photocatalyst for the remediation of organic

pollutants.

Chinese.

J.

Catal.

2017,

38,

337-347,

DOI:

10.1016/S1872-2067(16)62570-6. (25) Cui, X. K.; Yang, X. F.; Xian, X. Z.; Tian, L.; Tang, H.; Liu, Q. Q. Insights Into highly improved solar-driven photocatalytic oxygen evolution over integrated Ag3PO4/MoS2

heterostructures.

Front.

Chem.

2018,

6,

8,

DOI:

10.3389/fchem.2018.00123. (26) Wang, P.; Xu, S. Q.; Xia, Y.; Wang, X. F.; Yu, H. G.; Yu, J. G. Synergistic effect 24

ACS Paragon Plus Environment

Page 25 of 34 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

ACS Sustainable Chemistry & Engineering

of CoPi-hole and Cu(II)-electron cocatalysts for enhanced photocatalytic activity and photoinduced stability of Ag3PO4. Phys. Chem. Chem. Phys. 2017, 19, 10309-10316, DOI: 10.1039/c7cp01043e. (27) Yu, H. G.; Cao, G. Q.; Chen, F.; Wang, X. F.; Yu, J. G.; Lei, M. Enhanced photocatalytic performance of Ag3PO4 by simutaneous loading of Ag nanoparticles and

Fe(III)

cocatalyst.

Appl.

Catal.,

B

2014,

160,

658-665,

DOI:

10.1016/j.apcatb.2014.06.015. (28) Zhou, T. H.; Du, Y. H.; Wang, D. P.; Yin, S. M.; Tu, W. G.; Chen, Z.; Borgna, A.; Xu, R. Phosphonate-based metal–organic framework derived Co–P–C hybrid as an efficient electrocatalyst for oxygen evolution reaction. ACS Catal. 2017, 7, 6000-6007, DOI: 10.1021/acscatal.7b00937. (29) Shen, R. C.; Xie, J.; Zhang, H. D.; Zhang, A. P.; Chen, X. B.; Li, X. Enhanced solar fuel H2 generation over g-C3N4 nanosheet photocatalysts by the synergetic effect of noble metal-free Co2P cocatalyst and the environmental phosphorylation strategy. ACS

Sustainable

Chem.

Eng.

2018,

6,

816-826,

DOI:

10.1021/acssuschemeng.7b03169. (30) Cai, T.; Wang, L. L.; Liu, Y. T.; Zhang, S. Q.; Dong, W. Y.; Chen, H.; Yi, X. Y.; Yuan, J. L.; Xia, X. N.; Liu, C. B.; Luo, S. L. Ag3PO4/Ti3C2 MXene interface materials as a schottky catalyst with enhanced photocatalytic activities and anti-photocorrosion performance. Appl. Catal., B 2018, 239, 545-554, DOI: 10.1016/j.apcatb.2018.08.053. 25

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Page 26 of 34

(31) Wan, J.; Du, X.; Liu, E. Z.; Hu, Y.; Fan, J.; Hu, X. Y. Z-scheme visible-light-driven Ag3PO4 nanoparticle@MoS2 quantum dot/few-layered MoS2 nanosheet heterostructures with high efficiency and stability for photocatalytic selective oxidation. J. Catal. 2017, 345, 281-294, DOI: 10.1016/j.jcat.2016.11.013. (32) Men, Y. L.; You, Y.; Pan, Y. X.; Gao, H. C.; Xia, Y.; Cheng, D. G.; Song, J.; Cui, D. X.; Wu, N.; Li, Y. T.; Xin, S.; Goodenough, J. B. Selective CO evolution from photoreduction of CO2 on a metal-carbide-based composite catalyst. J. Am. Chem. Soc. 2018, 140, 13071-13077, DOI: 10.1021/jacs.8b08552. (33) Zeng, D. Q.; Zhou, T.; Ong, W. J.; Wu, M. D.; Duan, X. G.; Xu, W. J.; Chen, Y. Z.; Zhu, Y.-A.; Peng, D. L. Sub-5 nm ultra-fine FeP nanodots as efficient co-catalysts modified porous g-C3N4 for precious-metal-free photocatalytic hydrogen evolution under visible light. ACS Appl. Mater. Interfaces 2019, 11, 5651-5660, DOI: 10.1021/acsami.8b20958. (34) Tang, C. N.; Liu, E. Z.; Wan, J.; Hu, X. Y.; Fan, J. Co3O4 nanoparticles decorated Ag3PO4 tetrapods as an efficient visible-light-driven heterojunction photocatalyst.

Appl.

Catal.,

B

2016,

181,

707-715,

DOI:

10.1016/j.apcatb.2015.08.045. (35) Song, S. Q.; Meng, A. Y.; Jiang, S. J.; Cheng, B. Three-dimensional hollow graphene efficiently promotes electron transfer of Ag3PO4 for photocatalytically eliminating

phenol.

Appl.

Surf.

Sci.

2018,

10.1016/j.apsusc.2018.02.102. 26

ACS Paragon Plus Environment

442,

224-231,

DOI:

Page 27 of 34 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

ACS Sustainable Chemistry & Engineering

(36) Guan, X. J.; Guo, L. J. Cocatalytic effect of SrTiO3 on Ag3PO4 toward enhanced photocatalytic

water

oxidation.

ACS

Catal.

2014,

4,

3020-3026,

DOI:

10.1021/cs5005079. (37) Fu, Y. H.; Liang, W.; Guo, J. Q.; Tang, H.; Liu, S. S. MoS2 quantum dots decorated g-C3N4/Ag heterostructures for enhanced visible light photocatalytic activity. Appl. Surf. Sci. 2018, 430, 234-242, DOI: 10.1016/j.apsusc.2017.08.042. (38) Xu, F. Y.; Zhu, B. C.; Cheng, B.; Yu, J. G.; Xu, J. S. 1D/2D TiO2/MoS2 hybrid nanostructures for enhanced photocatalytic CO2 reduction. Adv. Optical Mater. 2018, 6, 8, DOI: 10.1002/adom.201800911. (39) Yang, J.; Zhu, J. X.; Xu, J. S.; Zhang, C.; Liu, T. MoSe2 nanosheet array with layered MoS2 heterostructures for superior hydrogen evolution and lithium storage performance.

ACS

Appl.

Mater.

Interfaces

2017,

9,

44550-44559,

DOI:

10.1021/acsami.7b15854. (40) Kong, Z. Z.; Chen, X. Z.; Ong, W. J.; Zhao, X. J.; Li, N. Atomic-level insight into the mechanism of 0D/2D black phosphorus quantum dot/graphitic carbon nitride (BPQD/GCN) metal-free heterojunction for photocatalysis. Appl. Surf. Sci. 2019, 463, 1148-1153, DOI: 10.1016/j.apsusc.2018.09.026. (41) Zeng, D. Q.; Ong, W. J.; Chen, Y. Z.; Tee, S. Y.; Chua, C. S.; Peng, D. L.; Han, M. Y. Co2P nanorods as an efficient cocatalyst decorated porous g-C3N4 nanosheets for photocatalytic hydrogen production under visible light irradiation. Part. Part. Syst. Charact 2018, 35, 1700251, DOI: 10.1002/ppsc.201700251. 27

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

(42) Li, N.; Wu, J. J.; Lu, Y. T.; Zhao, Z. J.; Zhang, H. C.; Li, X. T.; Zheng, Y. Z.; Tao, X. Stable multiphasic 1T/2H MoSe2 nanosheets integrated with 1D sulfide semiconductor for drastically enhanced visible-light photocatalytic hydrogen evolution. Appl. Catal., B 2018, 238, 27-37, DOI: 10.1016/j.apcatb.2018.07.002. (43) Zeng, D. Q.; Xiao, L.; Ong, W. J.; Wu, P. Y.; Zheng, H. F.; Chen, Y. Z.; Peng, D. L. Hierarchical ZnIn2S4/MoSe2 nanoarchitectures for efficient noble-metal-free photocatalytic hydrogen evolution under visible light. ChemSusChem. 2017, 10, 4624-4631, DOI: 10.1002/cssc.201701345. (44) Zeng, D. Q.; Wu, P. Y.; Ong, W. J.; Tang, B. S.; Wu, M. D.; Zheng, H. F.; Chen, Y. Z.; Peng, D. L. Construction of network-like and flower-like 2H-MoSe2 nanostructures coupled with porous g-C3N4 for noble-metal-free photocatalytic H2 evolution under visible light. Appl. Catal., B 2018, 233, 26-34, DOI: 10.1016/j.apcatb.2018.03.102. (45) Yi, J. J.; Li, H. P.; Gong, Y. J.; She, X. J.; Song, Y. H.; Xu, Y. G.; Deng, J. J.; Yuan, S. Q.; Xu, H.; Li, H. M. Phase and interlayer effect of transition metal dichalcogenide cocatalyst toward photocatalytic hydrogen evolution: The case of MoSe2. Appl. Catal., B 2019, 243, 330-336, DOI: 10.1016/j.apcatb.2018.10.054. (46) Tang, H.; Huang, H.; Wang, X. S.; Wu, K. Q.; Tang, G. G.; Li, C. S. Hydrothermal synthesis of 3D hierarchical flower-like MoSe2 microspheres and their adsorption performances for methyl orange. Appl. Surf. Sci. 2016, 379, 296-303, DOI: 10.1016/j.apsusc.2016.04.086. 28

ACS Paragon Plus Environment

Page 28 of 34

Page 29 of 34 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

ACS Sustainable Chemistry & Engineering

(47) Yang, X. F.; Tang, H.; Xu, J. S.; Antonietti, M.; Shalom, M. Silver phosphate/graphitic carbon nitride as an efficient photocatalytic tandem system for oxygen

evolution.

ChemSusChem.

2015,

8,

1350-1358,

DOI:

10.1002/cssc.201403168. (48) Yang, X. F.; Chen, Z. P.; Xu, J. S.; Tang, H.; Chen, K. M.; Jiang, Y. Tuning the morphology of g-C3N4 for improvement of Z-scheme photocatalytic water oxidation. ACS Appl. Mater. Interfaces 2015, 7, 15285-15293, DOI: 10.1021/acsami.5b02649. (49) Tian, L.; Xian, X. Z.; Cui, X. K.; Tang, H.; Yang, X. F. Fabrication of modified g-C3N4 nanorod/Ag3PO4 nanocomposites for solar-driven photocatalytic oxygen evolution from water splitting. Appl. Surf. Sci. 2018, 430, 301-308, DOI: 10.1016/j.apsusc.2017.07.185. (50) Cui, X. K.; Tian, L.; Xian, X. Z.; Tang, H.; Yang, X. F. Solar photocatalytic water oxidation over Ag3PO4/g-C3N4 composite materials mediated by metallic Ag and

graphene.

Appl.

Surf.

Sci.

2018,

430,

108-115,

DOI:

10.1016/j.apsusc.2017.07.290. (51) Yin, Y.; Zhang, Y. M.; Gao, T. L.; Yao, T.; Zhang, X. H.; Han, J. C.; Wang, X. J.; Zhang, Z. H.; Xu, P.; Zhang, P.; Cao, X. Z.; Song, B.; Jin, S. Synergistic phase and disorder engineering in 1T-MoSe2 nanosheets for enhanced hydrogen-evolution reaction. Adv. Mater. 2017, 29, 8, DOI: 10.1002/adma.201700311. (52) Jiang, Q. Q.; Lu, Y. F.; Huang, Z. X.; Hu, J. C. Facile solvent-thermal synthesis of ultrathin MoSe2 nanosheets for hydrogen evolution and organic dyes adsorption. 29

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Page 30 of 34

Appl. Surf. Sci. 2017, 402, 277-285, DOI: 10.1016/j.apsusc.2017.01.049. (53) Vaiano, V.; Iervolino, G.; Sannino, D.; Murcia, J. J.; Hidalgo, M. C.; Ciambelli, P.; Navio, J. A. Photocatalytic removal of patent blue V dye on Au-TiO2 and Pt-TiO2 catalysts. Appl. Catal., B 2016, 188, 134-146, DOI: 10.1016/j.apcatb.2016.02.001. (54) Yu, H. G.; Chen, W. Y.; Wang, X. F.; Xu, Y.; Yu, J. G. Enhanced photocatalytic activity and photoinduced stability of Ag-based photocatalysts: The synergistic action of amorphous-Ti(IV) and Fe(III) cocatalysts. Appl. Catal., B 2016, 187, 163-170, DOI: 10.1016/j.apcatb.2016.01.011. (55) Shen, R. C.; Xie, J.; Lu, X. Y.; Chen, X. B.; Li, X. Bifunctional Cu3P decorated g-C3N4 nanosheets as a highly active and robust visible-light photocatalyst for H2 production.

ACS

Sustainable

Chem.

Eng.

2018,

6,

4026-4036,

DOI:

10.1021/acssuschemeng.7b04403. (56) Xu, Q. L.; Zhang, L. Y.; Yu, J. G.; Wageh, S.; Al-Ghamdi, A. A.; Jaroniec, M. Direct Z-scheme photocatalysts: Principles, synthesis, and applications. Mater. Today. 2018, 21, 1042-1063, DOI: 10.1016/j.mattod.2018.04.008. (57) Liu, M. J.; Xia, P. F.; Zhang, L. Y.; Cheng, B.; Yu, J. G. Enhanced photocatalytic H2-production activity of g-C3N4 nanosheets via optimal photodeposition of Pt as cocatalyst.

ACS

Sustainable

Chem.

Eng.

2018,

6,

10472-10480,

DOI:

10.1021/acssuschemeng.8b01835. (58) He, K. L.; Xie, J.; Liu, Z. Q.; Li, N.; Chen, X. B.; Hu, J.; Li, X. Multi-functional Ni3C cocatalyst/g-C3N4 nanoheterojunctions for robust photocatalytic H2 evolution 30

ACS Paragon Plus Environment

Page 31 of 34 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

ACS Sustainable Chemistry & Engineering

under

visible

light.

J.

Mater.

Chem.

A.

2018,

6,

13110-13122,

DOI:

10.1039/c8ta03048k. (59) Yu, H. J.; Li, J. Y.; Zhang, Y. H.; Yang, S. Q.; Han, K. L.; Dong, F.; Ma, T. Y.; Huang, H. W. Three-in-one oxygen vacancy: whole visible-spectrum absorption, efficient charge separation and surface site activation for robust CO2 photoreduction. Angew. Chem., Int. Ed. 2019, 0, DOI: doi:10.1002/anie.201813967. (60) Peng, W. C.; Wang, X.; Li, X. Y. The synergetic effect of MoS2 and graphene on Ag3PO4 for its ultra-enhanced photocatalytic activity in phenol degradation under visible light. Nanoscale 2014, 6, 8311-8317, DOI: 10.1039/c4nr01654h. (61) Li, C. J.; Zhang, P.; Lv, R.; Lu, J. W.; Wang, T.; Wang, S. P.; Wang, H. F.; Gong, J. L. Selective deposition of Ag3PO4 on Monoclinic BiVO4(040) for Highly Efficient Photocatalysis. Small 2013, 9, 3951-3956, DOI: 10.1002/smll.201301276. (62) Zhang, G. G.; Li, G. S.; Lan, Z. A.; Lin, L. H.; Savateev, A.; Heil, T.; Zafeiratos, S.; Wang, X. C.; Antonietti, M. Optimizing optical absorption, exciton dissociation, and charge transfer of a polymeric carbon nitride with ultrahigh solar hydrogen production activity. Angew. Chem., Int. Ed. 2017, 56, 13445-13449, DOI: 10.1002/anie.201706870. (63) Si, H. Y.; Mao, C. J.; Zhou, J. Y.; Rong, X. F.; Deng, Q. X.; Chen, S. L.; Zhao, J. J.; Sun, X. G.; Shen, Y.; Feng, W. J.; Gao, P.; Zhang, J. Z-scheme Ag3PO4/graphdiyne/g-C3N4 composites: Enhanced photocatalytic O2 generation benefiting from dual roles of graphdiyne. Carbon 2018, 132, 598-605, DOI: 31

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Page 32 of 34

10.1016/j.carbon.2018.02.107. (64) Tan, P. F.; Liu, Y.; Zhu, A. Q.; Zeng, W. X.; Cui, H.; Pan, J. Rational design of Z-scheme system based on 3D hierarchical CdS supported 0D Co9S8 nanoparticles for superior photocatalytic H2 generation. ACS Sustainable Chem. Eng. 2018, 6, 10385-10394, DOI: 10.1021/acssuschemeng.8b01751. (65) Fu, J. W.; Bie, C. B.; Cheng, B.; Jiang, C. J.; Yu, J. G. Hollow CoSx polyhedrons act as high-efficiency cocatalyst for enhancing the photocatalytic hydrogen generation of

g-C3N4.

ACS

Sustainable

Chem.

Eng.

2018,

6,

2767-2779,

DOI:

10.1021/acssuschemeng.7b04461. (66) Wen, J. Q.; Xie, J.; Yang, Z. H.; Shen, R. C.; Li, H. Y.; Luo, X. Y.; Chen, X. B.; Li, X. Fabricating the robust g-C3N4 nanosheets/carbons/NiS multiple heterojunctions for enhanced photocatalytic H2 generation: an insight into the trifunctional roles of nanocarbons.

ACS

Sustainable

Chem.

Eng.

2017,

5,

2224-2236,

DOI:

10.1021/acssuschemeng.6b02490. (67) Fu, J. W.; Xu, Q. L.; Low, J. X.; Jiang, C. J.; Yu, J. G. Ultrathin 2D/2D WO3/g-C3N4 step-scheme H2 production photocatalyst. Appl. Catal., B 2019, 243, 556-565, DOI: 10.1016/j.apcatb.2018.11.011. (68) Yang, X. F.; Tian, L.; Zhao, X. L.; Tang, H.; Liu, Q. Q.; Li, G. S. Interfacial optimization

of

g-C3N4-based

Z-scheme

heterojunction

toward

synergistic

enhancement of solar-driven photocatalytic oxygen evolution. Appl. Catal., B 2019, 244, 240-249, DOI: 10.1016/j.apcatb.2018.11.056. 32

ACS Paragon Plus Environment

Page 33 of 34

ACS Sustainable Chemistry & Engineering

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 33

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

Table of Content

Constructing MoSe2/AP heterojunctions consisting of Ag3PO4 nanoparticles in-situ grown on the surface of two dimensional MoSe2 nanoarchitectures provides useful guidance for developing a noble-metal free photocatalytic system for O2 generation photocatalyst.

34

ACS Paragon Plus Environment

Page 34 of 34