Achieving high efficient catalysts for hydrogen evolution reaction by

Subscriber access provided by Iowa State University | Library

Article

Achieving high efficient catalysts for hydrogen evolution reaction by electronic state modification of platinum on versatile Ti3C2Tx (MXene) Youyou Yuan, Haisheng Li, Ligang Wang, Lei Zhang, Dier Shi, Yuexian Hong, and Junliang Sun ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b06045 • Publication Date (Web): 13 Jan 2019 Downloaded from http://pubs.acs.org on January 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 25 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

Achieving high efficient catalysts for hydrogen evolution reaction by electronic state modification of platinum on versatile Ti3C2Tx (MXene)

Youyou Yuan †, Haisheng Li †, Ligang Wang †, Lei Zhang †, Dier Shi †, Yuexian Hong † and Junliang Sun †,*

†

College of chemistry and molecular engineer, Peking University, 5 Yiheyuan Road,

Beijing 100871, P. R. China * Corresponding Author, Email: [email protected] (Junliang Sun)

ABSTRACT: Platinum (Pt)-based catalysts are considered as the most effective electrocatalysts for the hydrogen evolution reaction (HER). Due to the high cost, it is essential to improve the mass activity and durability of platinum by studying the relationship between Pt and the supports. Herein, a series of modified Ti3C2Tx-based (T= O, OH, F) supports are synthesized and Pt was loaded by the wet-impregnation and photo-induced reduction method. This is the first report that Pt-based MXenes have been used to promote HER efficiency with promising performance. The obtained catalyst achieves an overpotential of 55 mV at a current density of 10 mA cm-2. The overpotential mainly relies on the electronic state of Pt, which in turn is influenced by the surface terminals (Ti-OH or Ti-O) of the modified Ti3C2Tx. The enhanced charge transfer between O terminals and Pt accelerates the HER kinetics, hence, the overall catalytic performance.

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

Keywords: MXene, catalysts, hydrogen evolution reaction, platinum, terminals modification

INTRODUCTION Hydrogen energy is one of the promising energy source, which can be produced in a sustainable manner but its enormous quantities are locked in water, hydrocarbons, and other organic matter.1 Pt-based materials, as the most efficient catalysts, can release hydrogen from water via the hydrogen evolution reaction (HER).2-4 However, practical applications are hindered due to its high cost and limited availability. Decreasing the amount of Pt and improving the activity of catalysts can overcome this situation. Tuning the surface structure and the electronic state of Pt are two viable protocols.5-6 The surface structure is influenced by the morphologies and sizes of Pt NPs which can lead to different electrochemical performance.7-10 The modulation of the electronic structure of Pt with enhanced metal-support interaction has been achieved by loading Pt dimers or single atom on individual supports.3-4,

11-14

Therefore, appropriate supports with

sufficient active sites for Pt loading can not only improve the efficiency of catalysts but also their stability. Ti3C2Tx with high conductivity and versatility can serve such a role.15 Although Ti3C2Tx-based hybrid materials have been widely studied in energy storage, water splitting, water purification and electromagnetic interface,16-18 the applications of hybrid material Ti3C2Tx-Pt for HER have not yet been reported, especially the detailed interactions between Pt and Ti3C2Tx.19 So far, only few MXene materials have been reported in HER experiments except Mo2CTx and Ti2CTx.20-21 Most of the studies are focused on the theoretical calculations of MXene which indicate that 2


Page 2 of 25

Page 3 of 25 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 terminal groups especially oxygen terminals play an active role in HER application.22-26 To our knowledge, the HER process contains two steps under acidic conditions: the first step is the absorption of H+ cations onto the catalyst surface (Volmer reaction: H3O+ + e- → H*+ H2O), the second step is the production of H2 which follows two possible reaction pathways (Heyrovsky reaction: H* + H3O+ + e- → H2+ H2O, Tafel reaction: H* + H* → H2).27 The modulation of the electronic state of the active sites on MXenes can accelerate the above reaction steps or even change the HER mechanism preference in the theoretical simulations. Gao et al. showed that MXenes terminated with a mixture of oxygen and hydroxyl groups are conductive, allowing high charge transfer kinetics by promoting hydrogen release during HER.25 Zhang et al. also found that addition of transition metal atoms on the MXene surface is predicted to optimize the Gibbs free energy of hydrogen adsorption and reduce H2 production activation barrier due to the modulated electronic interaction.23, 28 So, we deduced that MXenes with proper terminal groups can also provide electron transfer to Pt, accelerating the reaction step in HER with improved activity, which is needed to be verified through experiments. Herein, Ti3C2Tx was selected as the conductive support, and Pt nanoparticles (NPs) were then deposited on the modified Ti3C2Tx-based materials for HER via wetimpregnation method, followed by reduction with NaBH4. To elucidate different catalytic performance, we used the X-ray photoelectron spectroscopy (XPS) to investigate the interactions between the electronic state of Pt and the terminals of different supports. Meanwhile, another two promising catalysts were also synthesized 3



by a simple photo-induced method. As compared to the wet-impregnation method, the photo-induced method was found to be a more efficient way to deposit Pt NPs, resulting in a more uniform distribution on supports and lower HER overpotential.

EXPERIMENTAL SECTION Materials synthesis Materials preparation: All chemicals and materials were used without further purification. Ti3AlC2 was purchased from Beijing Lianli Technology Co.Ltd. Synthesis of Ti3C2Tx: 2.0 g Ti3AlC2 powders were immersed slowly in a high-density polyethylene beaker containing a 60 ml concentrated aqueous HF (40%) at room temperature (RT).29 Then the suspension was stirred at a speed of 600 rpm for 24h at RT. After that, the concentrated suspension was diluted with fresh deionized water several times and centrifuged at a speed of 6000 rpm for 6 min until the pH value of the solution was higher than 5. Finally, the washed powder was vacuum filtered and dried in vacuum at RT for 12h to be used later. Ti3C2Tx-400, K-Ti3C2Tx and K-Ti3C2Tx-400 were synthesized by the previously reported method.30 Synthesis of D-Ti3C2Tx: 1.32 g LiF and 20 ml 6 M HCl were mixed in a polyethylene beaker and stirred to get a clear solution. Then 1 g ball-milled Ti3AlC2 (LiF: Ti3AlC2=10:1, molar ratio) was added slowly into the solution and stirred at 35 ˚C for 24 h. The etched Ti3C2Tx powder was washed with deionized water and then centrifuged at 3500 rpm until the pH of the supernatant was above 5. The suspension was treated by hand-shaking for 5 min at RT and then centrifuged at 3500 rpm for 2 4


Page 4 of 25

Page 5 of 25 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


min to obtain the supernatant of delaminated Ti3C2Tx (D-Ti3C2Tx). The supernatant was centrifuged at 2000 rpm for 1 h and the dark-green supernatant was collected for full delamination. The D-Ti3C2Tx was stored by purging Argon gas for 0.5 h at 4 ˚C in the refrigerator. Synthesis of TBA-Ti3C2Tx: 0.2 g Ti3C2Tx was dispersed into 0.8 g tetrabutylammonium hydroxide (TBAOH, 25wt% in water) with an additional 20 ml of deionized water. The solution was sonicated for 10 min before stirring for 4 days at 40˚C (the optimized time can decrease to 4h, Figure S11). The obtained suspension was washed with deionized water several times and the TBA-Ti3C2Tx was filtered by vacuum filtration. The powder was dried in a vacuum drying oven at RT for 12 h. Synthesis of Ti3C2Tx-Pt: In this part, wet-impregnation and photo-induced reduction methods are tried to deposit platinum on the above supports to design a good catalyst for HER test. In the wet-impregnation method, the supports used for platinum loading include Ti3C2Tx, Ti3C2Tx-400, K-Ti3C2Tx, K-Ti3C2Tx-400, D-Ti3C2Tx (2-3 mg ml-1) and TBA-Ti3C2Tx. As for the photo-induced reduction method, D-Ti3C2Tx and TBATi3C2Tx were used as supports owing to its good transparency of the solution when the supports were dispersed into the deionized water. The raw materials used as platinum precursors include Pt (NH3)4Cl2·H2O and H2PtCl6·6H2O. Wet-impregnation method: 0.05 g of supports were dispersed into 20 ml deionized water and sonicated for 10 min. 0.01 M Pt (NH3)4Cl2·H2O was used in this method. Then the different loadings of the platinum (256 µl, 512 µl, 1.28 ml, 2.56 ml, and 5.12 ml) were added to the suspension and stirred for 4h or more time. The samples obtained 5



here are named as support-Pt, such as TBA-Ti3C2Tx-Pt, followed by the reduction with NaBH4 and H2. In reduction with NaBH4, 0.1 M NaBH4 was added to reduce Pt2+ to Pt0 and a large amount of gas was produced. Then the mixture was stirred for another 4 h (the time is optimized) and washed with deionized water to remove the unreacted platinum source and NaBH4. The mixture was vacuum filtered to get the powder. The powder was dried in the vacuum oven for 12h at RT. When H2 was used as the reductant, the powder was calcined in the 10% H2/Ar atmosphere at 673K for 4h to reduce the higher valence Pt. The catalysts synthesized with NaBH4 and H2 reduction are labelled as support-Pt-n and support-Pt-n-400, where n indicates the weight percentage of added Pt seeds. Photo-induced reduction method: 30 µl 0.1 M H2PtCl6·6H2O was diluted into 3 ml DTi3C2Tx suspension, then the mixture was sonicated for 10 mins and was frozen quickly using liquid nitrogen. The ice was irradiated by UV lamp for 1 h. Meanwhile, the environment was kept at -10˚C to avoid the melting of ice. The power density of the UV light near the ice was measured (17.8 mW/cm2) using a radiometer. After UV irradiation, the iced mixture was freeze-dried to get the powder for HER test. Materials characterization The PXRD pattern was acquired on a Rigaku Dmax/2400 X-ray diffractometer operating at 40 KV and 100 mA with Cu Kα radiation (λ=1.5406Å). X-ray photoelectron spectroscopy analyses (XPS) were carried out on an Axis Ultra system with monochromatic Al Kα radiation (hν=1486.6 eV), binding energy was referenced to the C 1s peak of (C-C, C-H) bond, which was set at 284.8 eV. The morphologies and 6


Page 6 of 25

Page 7 of 25 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


structures of the supports were examined by SEM (Hitachi S-4800). The highresolution transmission electron microscopy (HRTEM, JEOL and JEM-2100) and HAADF-STEM images were collected on Tecnai F30 with a voltage of 300 KV. The Ar adsorption-desorption isotherms were obtained by a Micromeritics ASAP2020 device at 77 K. Before measurement, the samples were degassed at 473 K for 10 h. AFM data was measured by SPI3800 with a contact mode.

Electrochemical tests A three-electrode system was used for electrochemical measurements on CHI660E with a glassy carbon (0.0785 cm2) electrode as the working electrode. Ag/AgCl electrode (3.5 M KCl) and a graphite rod were used as the reference and counter electrode, respectively. The potential presented in this study was referred with respect to reversible hydrogen electrode (RHE) by the equation E (RHE) = E (Ag/AgCl) + 0.059 pH+0.20. The potential of Ag/AgCl electrode was also calibrated through experiment. The calibration was performed in the high purity hydrogen saturated 0.5 M H2SO4 electrolyte with the Pt wire as the working electrode and counter electrode. CVs were run at a scan rate of 5 mV/s, and the average of the two potentials at which the current crossed zero was taken to be the thermodynamic potential for the hydrogen electrode reactions (Figure S12). The catalysts dispersions were prepared by mixing 3 mg of catalyst in a 1 ml aqueous solutions containing 950 µl of ethanol and 50 µl of 0.5 wt% Nafion solution, followed by ultrasonication for 30 min. Then, the working electrode was fabricated by transferring 10 µl of the aqueous catalyst dispersion onto the glassy carbon electrode. 7



A significant number of bubbles were formed in the testing process, which influenced the polarization curves collected at a low potential. The performance was tested in 0.5 M H2SO4 solution. The i-t cycle tests (4 times) were conducted at an overpotential of 70 mV with a carbon paper (1 cm2, 0.75 cm2, 0.15 cm2). After one cycle, the bubbles were removed from the surface of carbon paper and another polarization curve was observed following the i-t test.

RESULTS AND DISCUSSION Synthesis and characterization of Ti3C2Tx-based supports Different supports with various terminals and interlayer voids were synthesized. Firstly, Ti3C2Tx was synthesized as previously reported.15, 31 Using 40 wt% HF as the etching reagent, the Al layers in the Ti3AlC2 were selectively etched to get the layered Ti3C2Tx with a loosely packed accordion-like structure (Figure S1 in the Supporting Information, SI). The Ti3C2Tx layer with a significant amount of terminal F groups is negatively charged and the H+ exists in the interlayer for charge balance. When Ti3C2Tx was treated with alkaline solutions, such as KOH (1.8 M) and tetrabutylammonium hydroxide (TBAOH, 0.04 M), the cations K+ and TBA+ intercalated into the interlayers of Ti3C2Tx by replacing the H+ to obtain another two supports with the name of KTi3C2Tx and TBA-Ti3C2Tx, respectively. The X-ray diffraction (XRD) was carried out to understand the change of the structure. Figure 1a showed that the (002) peak of Ti3C2Tx at 2 theta=8.7˚ has been shifted to 7.0˚ for K-Ti3C2Tx and 6.4˚ for TBA-Ti3C2Tx. The radius of TBA+ is larger as compared with K+ and H+, the (002) peak shifts to a much lower angle. In a concentrated TBAOH aqueous solutions (1.0 M), it can even 8


Page 8 of 25

Page 9 of 25 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


move to 5.6˚ indicating more TBA+ intercalated into the layers (Figure S2). For clarity, the samples obtained in 1.0 M and 0.04 M TBAOH aqueous solutions are labelled as TBA-Ti3C2Tx-c and TBA-Ti3C2Tx respectively. It is well known that faster charge transfer kinetics can be achieved by reducing Ti3C2Tx layers.32 Ti3C2Tx was then delaminated to a few layers or even monolayer via the minimum intensive layer delamination (MILD) method, the product is labelled as D-Ti3C2Tx.29 A decrease in the number of layers from 10-12 of Ti3C2Tx to 2-3 in D-Ti3C2Tx resulted in reduced peak intensity of (002) peak (Figure S3).

Figure 1. XRD characterization and synthesis procedure of the supports and catalysts. (a) XRD patterns of Ti3C2Tx-based supports. (b) XRD patterns of TBA-Ti3C2Tx-Pt with different weight percentage by reduction with NaBH4. (c) Schematics of the preparation process of TBA-Ti3C2Tx-Pt-n (In all the Figures, Ti3C2Tx was abbreviated to TC). 9



Scanning electronic microscopy (SEM) and transmission electron microscopy (TEM) are used to study the morphologies and microstructures of the above supports. Flower-like thin-sheets of TBA-Ti3C2Tx were observed in Figure 2a. The sheet was about 50 nm wide and 6.2 nm thin shown in Figure 2c, consistent with the 5 to 6 layers in high resolution-TEM (HRTEM) studies (Figure 2b). However, no change was observed in the morphology of TBA-Ti3C2Tx-c as compared to that of Ti3C2Tx (Figure S4). The difference in morphologies of the TBA-Ti3C2Tx and TBA-Ti3C2Tx-c may be attributed to the water content with the former allows more water intercalated into the layers. The presence of the water reduced the electrostatic interaction between the layers. Therefore, TBA-Ti3C2Tx was easy to be exfoliated to thinner nanosheets with shear force via stirring and was selected as one of the supports.33 So as D-Ti3C2Tx, which can be obtained with only 2-3 layers sheets as mentioned before. However, the small interlayer space in K-Ti3C2Tx makes it hard to delaminate into thin nanosheets as compared to TBA-Ti3C2Tx (Figure S5).34 The Brunner-Emmet-Teller (BET) analysis also reflected different morphologies of these supports. The specific surface area of TBA-Ti3C2Tx and D-Ti3C2Tx are 46.8 m2 g-1 and 130 m2 g-1, respectively (Figure 2c), which is much higher than that of K-Ti3C2Tx with a value of 10.0 m2 g-1.30 A higher surface area can provide more Ti–OH and Ti–O terminals. These terminals can interact with the active sites on the support and improve HER performance, which will be discussed later.

10


Page 10 of 25

Page 11 of 25 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 2. Morphological and surface characterization of the supports. (a) SEM and (b) TEM of TBA-Ti3C2Tx. (c) AFM results of TBA-Ti3C2Tx indicating 4-6 layers of TBATi3C2Tx. (d) The Ar adsorption and desorption isothermal plots (black: Ti3C2Tx, red: TBA-Ti3C2Tx, blue: K-Ti3C2Tx-400, purple: TBA-Ti3C2Tx, yellow: D-Ti3C2Tx)

Synthesis and characterization of Ti3C2Tx-Pt-based catalysts The Pt precursors were loaded onto the modified supports accordingly. TBATi3C2Tx was taken as an example to describe the synthesis procedure in the following paragraph. More detailed information can refer to the Experimental Section. Figure 1c illustrates the preparation procedure for TBA-Ti3C2Tx-Pt by using the wetimpregnation method. The zeta potential of the TBA-Ti3C2Tx suspension is -36 mV at 11



pH=8 due to the negatively charged layers. When the positively charged Pt(NH3)42+ was added into the above suspension, they interacted via the electrostatic force to ensure the uniform distribution of Pt on the supports before reduction, as confirmed by the element mapping in Figure 3. Then, two common reductants, H2 and NaBH4, were used to reduce Pt2+ to Pt0 (Figure S6). The catalysts obtained after H2 reduction at 400˚C are not ideal for HER applications due to the partial damage to the Ti-C layers of the supports (Figure S8g). NaBH4 was chosen to be the suitable reductant which imparts no damage to the supports with a relatively convenient operation (Figure 3a and 3b). In this work, all catalysts mentioned later were reduced with NaBH4 if not specified. The samples with different Pt loading on TBA-Ti3C2Tx were labelled as TBA-Ti3C2Tx-Pt-n (where n= 1, 2, 5, 10, 20, indicating the weight percentage based on the initial Pt seed amount and the final Pt content determined by ICP-OES is listed in Table S1) and their XRD patterns were shown in Figure 1b. When the added amount of Pt(NH3)42+ is lower than 5 wt%, the metallic Pt peaks were absent because of a low loading amount (< 1wt%), while for the samples with 10 wt% and 20 wt% Pt loading which have the final content of about 1 wt%, the peaks at 39.3˚, 45.7˚ and 66.43˚ were observed indicating the growing up of Pt NPs loaded on supports. When D-Ti3C2Tx was used as the support, the XRD pattern also showed the peaks of Pt and the support which is similar to that of TBA-Ti3C2Tx (Figure 1b). The morphologies of TBA-Ti3C2Tx-Pt-20 and D-Ti3C2TxPt-20 (figure 3e and 3f) both revealed that certain amounts of Pt were deposited on the supports randomly, and the uniform distribution of Pt nanoparticles with a size of 2 nm can also be observed in TEM images (Figure 3g). The plane of Pt NPs was identified 12


Page 12 of 25

Page 13 of 25 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


to (111) shown in Figure 3h. Such 2 nm sized Pt NPs are identified as more efficient active sites as compared to other Pt NPs for HER in water splitting.35 In addition to the wet-impregnation method mentioned above, the photo-induced reduction method was also tried with D-Ti3C2Tx due to its high transparency.36 As compared to the atomic layer deposition and other multi-step methods, this method is economical and time efficient.3-4, 13 The D-Ti3C2Tx-Pt-UV-5 was synthesized simply from a mixture of DTi3C2Tx suspension and 0.1 M H2PtCl6 solution irradiated under the ultraviolet (UV) light. After UV irradiation, the mixture was freeze-dried instead of filtration or centrifugation to obtain the powder product because of its ultralow concentration (2-3 mg ml-1). The XRD pattern of D-Ti3C2Tx-Pt-UV-5 was similar to the support, and no Pt peaks were observed. However, the unreacted Pt source was observed in the XRD pattern which may be some unknown phase similar to K2PtCl4 (Figure S7). Its effects on HER were not discussed in this report due to the complex reaction process during UV irradiation and would be explored in the future. The Pt NPs were 1 to 2 nm similar to that of TBA-Ti3C2Tx-Pt-20 and no aggregation was found in SEM (Figure 3d and Figure S4), which indicates the photo-induced method being a promising way for transparent supports to fabricate a catalyst with uniform active sites.

13



Figure 3. Morphological characterization of the catalysts. (a, b) HRTEM of TBATi3C2Tx-Pt-20 indicating the intactness of TBA-Ti3C2Tx after Pt loading. (c, d) the size comparison of the Pt NPs synthesized by wet-impregnation and photo-induced method. SEM images of (e) TBA-Ti3C2Tx-Pt-20, (f) D-Ti3C2Tx-Pt-20. (g) HAADF-STEM of TBA-Ti3C2Tx-Pt-20, the yellow circles indicate the Pt nanoclusters around 2 nm. (h) Lattice fringe of Pt NPs on TBA-Ti3C2Tx. (i, j, k, l) The mapping results of TBATi3C2Tx-Pt-20 before reduction.

HER performance of Ti3C2Tx-Pt-based catalyst The synthesized catalyst was deposited on a glassy carbon electrode (0.07 cm2) in 0.5 M H2SO4 solution to evaluate HER performance with a typical three-electrode system. The overpotential (η) obtained from the linear sweep voltammetry (LSV) curves at a current density (J) of 10 mA cm-2 was used as one criterion. Among all the 14


Page 14 of 25

Page 15 of 25 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


catalysts, TBA-Ti3C2Tx-Pt-20 and D-Ti3C2Tx-Pt-20 stand out with a respective overpotential of 55 mV and 70 mV (Figure 4a), while the other Pt-based MXene catalysts have the overpotential above 400 mV, which is close to that of Ti3C2Tx itself. The Pt content of these hybrid catalysts are around 1.0 wt% determined by ICP-OES, and the main difference is the terminals of the supports. So the surface terminals and the electronic state of Pt NPs in the hybrid catalysts were further studied by XPS to explore the intrinsic reason for the difference in HER performance. All catalysts showed two distinct peaks at 531.2 eV and 532.2 eV indicating the Ti-O group and the Ti-OH group, respectively (Figure 4c).37 The peak indicating some absorbed water was also observed at 533.6 eV.38 It is worth to mention that the peak intensity of Ti-O was observed to be the highest for TBA-Ti3C2Tx-Pt-20, and D-Ti3C2Tx-Pt-20 contained the largest amount of Ti-OH terminals among all these catalysts. The increased Ti-OH and Ti-O terminals of the catalysts may affect the electronic state of Pt to improve HER performance. Thus, the electronic states of the Pt loaded on different supports were further studied. The XPS spectra of Pt on different catalysts showed the binding energy of Pt 4f7/2 and 4f5/2 at nearly 71.0 eV and 74.4 eV with slight deviations around 0.2 eV. The position of Pt 4f7/2 moved to lower binding energy with the sequence of TBATi3C2Tx < D-Ti3C2Tx < K-Ti3C2Tx < Ti3C2Tx, which is as same as the trend of HER performance. The XPS analysis of O and Pt showed that more Ti-O and Ti-OH bonds are available on the supports, more negative the binding energy of Pt is. So we speculated that the charge transfer between the terminals and Pt may be responsible for this phenomenon. For the study of the charge transfer, Nayak et.al reported that few15



layer Ti3C2Tx exhibits fast electron transfer kinetics compared to multi-layer Ti3C2Tx.32 In our work, the layer number for both TBA-Ti3C2Tx and D-Ti3C2Tx are below 5 and the faster electron transfer from the support to Pt induced the negative binding energy of Pt for a better HER performance. Compared to TBA-Ti3C2Tx-Pt-20 and D-Ti3C2TxPt-20, the Pt NPs on Ti3C2Tx-400 were relative positively charged indicated by the higher binding energy in Figure 4d. When analysing the surface of Ti3C2Tx-400-Pt-20 (here the support was pre-treated in Ar at 400 ˚C), it was found that less Ti-F groups on the Ti3C2Tx-400 support compared to Ti3C2Tx without pre-treatment and the content of Ti-O was lower than the other two materials (Figure S8c and Figure 4c). Overall, Both TBA-Ti3C2Tx-Pt-20 and the D-Ti3C2Tx-Pt-20 have enough available Ti-O and Ti-OH to interact with Pt, accelerating electron transfer, thereby changing the electronic states of Pt with low binding energy. Moreover, the positively charged Pt in 20 wt% Pt/C compared to our catalysts verified the strong interactions between Pt and our supports again. It is possible that the negatively charged Pt could influence the sorption of H+ to form absorbed H (Had), hence change the Volmer step and improve the HER performance.4, 39-40 For further understanding the kinetics of HER process, the Tafel plots were calculated from LSV curves to confirm the efficiency of charge transfer (Figure 4b). The Tafel slope (b) of both Ti3C2Tx-400-Pt-20 and K-Ti3C2Tx-Pt-20-200 were over 200 mV dec-1 indicating Volmer step (H2O + e- → Had + OH-) as the rate-determining step.41 While the values of TBA-Ti3C2Tx-Pt-20 and D-Ti3C2Tx-Pt-20 are both near 70 mV dec1

which are much smaller than that of other catalysts. That is to say, the Volmer step 16


Page 16 of 25

Page 17 of 25 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


was accelerated indeed because the accelerated adsorption of H+ on more negatively charged Pt NPs. Our observations are in concordance with theoretical calculations that Ti-O terminals acting as the active sites gain more electrons, the absorption energy of H* will decrease.25 This is also implied by electrochemical impedance spectroscopy (EIS, Figure S9), in which the semicircle diameter of TBA-Ti3C2Tx-Pt-20 is much smaller than that of others because of the lower contact and charge transfer resistance in TBA-Ti3C2Tx-Pt-20 consisting of strong interactions between conductive TBATi3C2Tx and Pt NPs. While compared to the commercial Pt/C, the Tafel slope of TBATi3C2Tx-Pt-20 or D-Ti3C2Tx-Pt-20 is high because of the low loading (1 wt% and 0.76 wt%). Their reaction follows the Volmer-Heyrovsky process, and the rate-limiting step is the desorption of Had. It can be concluded that the surface modification of the support with enhanced charge transfer accelerates the HER reaction kinetics. The process of Volmer steps was accelerated and the rate-limiting step changed from the first step (H+ →Had) to the second step (2Had →H2) in the HER.

17



Figure 4. Electrochemical characterization and XPS results of the catalysts. (a) Polarization curves of Pt deposited on the supports in 0.5M H2SO4. (b) Tafel curves of all Pt-based MXene catalysts. (c) O 1s XPS spectra and (d) Pt 4f spectra of D-Ti3C2TxPt-20, TBA-Ti3C2Tx-Pt-20, K-TC-Pt-20-200, TC-400-Pt-20 and 20 wt% Pt/C.

The stability of the TBA-Ti3C2Tx-Pt-20 catalyst during repeated cycles in 0.5 M H2SO4 was also evaluated. The current density versus time (i-t) curve was acquired further on CHI660E with the catalyst coated on a carbon paper with an area of 0.15 cm2. The overpotential of 70 mV was applied to achieve a current density of 10 mA cm-2. A tiny decay of the current density is observed as the bubbles generated from the surface of the carbon paper were difficult to be removed quickly (Figure 5a). However, the current density and the overpotential can both be reset to the original values after refreshing the electrode (Figure S10). This infers that the decrease in current density was mainly caused by the generated bubbles. Some aggregations of Pt NPs during long18


Page 18 of 25

Page 19 of 25 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


time stability tests may also result in decreased current density (Figure S14), while the repetitive LSV curves of 1000 cycles showed that TBA-Ti3C2Tx-Pt-20 still maintained a good cyclic stability with only 10 mV increase of the overpotential, which revealed that Pt NPs aggregations had little influence on the decrease in current density (Figure 5b). The loading amount of Pt is also optimized for obtaining low cost and high efficient catalysts. In our work, when 5, 10 and 20 wt% Pt were initially added onto TBA-Ti3C2Tx (the actual final Pt loading is 0.8, 1.0 and 1.2 wt%, respectively), an overpotential was acquired as 125, 60 and 55 mV, respectively (Figure 5c). While the HER performance of TBA-Ti3C2Tx-Pt with a loading of 0.4 wt% (the added amount of 1 wt% and 2 wt%) is not ideal due to the low content with the high overpotential over 200 mV, which indicates that more Pt nanoparticles provide more interactions with the supports for enhanced HER performance. The samples synthesized by the photoinduced reduction method, which are labelled as D-Ti3C2Tx-Pt–UV-5 and TBATi3C2Tx-Pt-UV-5 exhibited an overpotential of 83 mV and 115 mV, respectively (Figure 5d). Their superior HER performance compared to TBA-Ti3C2Tx-Pt-5 is ascribed to the uniform distribution of Pt NPs described before. Therefore the photoinduced reduction method can provide a feasible way to synthesize new catalysts with good transparency and uniform active sites for HER.

19



Figure 5. Optimization and stability tests of TBA-Ti3C2Tx-Pt-n. (a) Current density versus time (i-t) curve for HER of TBA-Ti3C2Tx-20 at η=70 mV for 20 h. (b) Polarization curves of TBA-Ti3C2Tx-20 obtained for 1000 cycles. (c) Comparison of the overpotential in HER test with different contents of Pt on TBA-Ti3C2Tx. (d) Polarization curve for HER tests of TBA-Ti3C2Tx-Pt-UV-5 and D-Ti3C2Tx-Pt-UV-5.

CONCLUSION A series of Ti3C2Tx-based supports modified with various terminals (e.g. Ti-F, TiO and Ti-OH) were synthesized by the wet-impregnation method and photo-induced method. The photo-induced reduction method shows more advantage for transparent catalysts with uniform active sites. Among all of the Pt-based MXene catalysts synthesized by the wet-impregnation method, TBA-Ti3C2Tx-Pt-20 and D-Ti3C2Tx-Pt20 exhibited the best catalytical performance with an overpotential of 55 mV and 70 20


Page 20 of 25

Page 21 of 25 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


mV for HER with 1.20 wt% and 0.76 wt% loading, respectively. The XPS and BET analysis revealed that more Ti-OH and Ti-O terminals accessible can enhance the interactions between supports and Pt, which in turn accelerates the Volmer step, resulting in outstanding HER performance. Tuning the supports by surface modification can effectively modulate the electronic state of the active sites, thus offering a promising strategy to design excellent catalysts for electrochemical reactions.

SUPPORTING INFORMATION Characterization data is available at http://pubs.acs.org. Physical characterizations, electrochemical characterizations of the materials and supplementary table are supplied as Supporting Information.

ACKNOWLEDGEMENTS This work was financially supported by the National Basic Research Program and the National Natural Science Foundation of China (No 21621061, 2013CB933402, 21471009, 21527803, 2016YFA0301004). We also thank Sinopec for financial support.

REFERENCES 1. Turner, J. A., Sustainable Hydrogen Production. Science 2004, 305 (5686), 972-974, DOI 10.1126/science.1103197. 2. Yang, S.; Kim, J.; Tak, Y. J.; Soon, A.; Lee, H., Single-Atom Catalyst of Platinum Supported on Titanium Nitride for Selective Electrochemical Reactions. Angew. Chem. Int. Ed. 2016, 55 (6), 2058-2062, DOI 10.1002/anie.201509241. 3. Yang, S.; Tak, Y. J.; Kim, J.; Soon, A.; Lee, H., Support Effects in Single-Atom Platinum Catalysts for Electrochemical Oxygen Reduction. ACS Catal. 2017, 7 (2), 1301-1307, DOI 10.1021/acscatal.6b02899. 4. 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 21



catalysis of the hydrogen evolution reaction. Nat. Commun. 2016, 7, 13638, DOI 10.1038/ncomms13638. 5. Liu, S.; Tian, N.; Xie, A. Y.; Du, J. H.; Xiao, J.; Liu, L.; Sun, H. Y.; Cheng, Z. Y.; Zhou, Z. Y.; Sun, S. G., Electrochemically Seed-Mediated Synthesis of Sub-10 nm Tetrahexahedral Pt Nanocrystals Supported on Graphene with Improved Catalytic Performance. J. Am. Chem. Soc. 2016, 138 (18), 5753-5756, DOI 10.1021/jacs.5b13473. 6. Z. Y. Zhou, N. T., Z. Z. Huang, D. J. Chen and S. G. Sun, Nanoparticle catalysts with high energy surfaces and enhanced activity synthesized by electrochemical method. Faraday Discuss. 2009, 140, 81-92, DOI 10.1039/b803716g. 7. Xu, G.-R.; Hui, J.-J.; Huang, T.; Chen, Y.; Lee, J.-M., Platinum nanocuboids supported on reduced graphene oxide as efficient electrocatalyst for the hydrogen evolution reaction. J. Power Sources 2015, 285, 393-399, DOI 10.1016/j.jpowsour.2015.03.131. 8. Xia, B. Y.; Wu, H. B.; Yan, Y.; Lou, X. W.; Wang, X., Ultrathin and ultralong singlecrystal platinum nanowire assemblies with highly stable electrocatalytic activity. J. Am. Chem. Soc. 2013, 135 (25), 9480-9485, DOI 10.1021/ja402955t. 9. Yin, H.; Zhao, S.; Zhao, K.; Muqsit, A.; Tang, H.; Chang, L.; Zhao, H.; Gao, Y.; Tang, Z., Ultrathin platinum nanowires grown on single-layered nickel hydroxide with high hydrogen evolution activity. Nat. Commun. 2015, 6, 6430, DOI 10.1038/ncomms7430. 10. Li, C.; Sato, T.; Yamauchi, Y., Electrochemical synthesis of one-dimensional mesoporous Pt nanorods using the assembly of surfactant micelles in confined space. Angew. Chem. Int. Ed. 2013, 52 (31), 8050-8053, DOI 10.1002/anie.201303035. 11. Yang, S.; Kim, J.; Tak, Y. J.; Soon, A.; Lee, H., Single-Atom Catalyst of Platinum Supported on Titanium Nitride for Selective Electrochemical Reactions. Angew. Chem. Int. Ed. 2015, 55 (6), 2058-2062, DOI 10.1002/anie.201509241. 12. Yan, H.; Lin, Y.; Wu, H.; Zhang, W.; Sun, Z.; Cheng, H.; Liu, W.; Wang, C.; Li, J.; Huang, X.; Yao, T.; Yang, J.; Wei, S.; Lu, J., Bottom-up precise synthesis of stable platinum dimers on graphene. Nat. Commun. 2017, 8 (1), 1070, DOI 10.1038/s41467017-01259-z. 13. Wei, H.; Huang, K.; Wang, D.; Zhang, R.; Ge, B.; Ma, J.; Wen, B.; Zhang, S.; Li, Q.; Lei, M.; Zhang, C.; Irawan, J.; Liu, L. M.; Wu, H., Iced photochemical reduction to synthesize atomically dispersed metals by suppressing nanocrystal growth. Nat. Commun. 2017, 8 (1), 1490, DOI 10.1038/s41467-017-01521-4. 14. 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. 15. Naguib, M.; Kurtoglu, M.; Presser, V.; Lu, J.; Niu, J.; Heon, M.; Hultman, L.; Gogotsi, Y.; Barsoum, M. W., Two-dimensional nanocrystals produced by exfoliation of Ti3AlC2. Adv. Mater. 2011, 23 (37), 4248-4253, DOI 10.1002/adma.201102306.

22


Page 22 of 25

Page 23 of 25 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


16. Xiong, D.; Li, X.; Bai, Z.; Lu, S., Recent Advances in Layered Ti3C2Tx MXene for Electrochemical Energy Storage. Small 2018, 14 (17), 1703419, DOI 10.1002/smll.201703419. 17. Hong Ng, V. M.; Huang, H.; Zhou, K.; Lee, P. S.; Que, W.; Xu, J. Z.; Kong, L. B., Recent progress in layered transition metal carbides and/or nitrides (MXenes) and their composites: synthesis and applications. J. Mater. Chem. A 2017, 5 (7), 3039-3068, DOI 10.1039/c6ta06772g. 18. Anasori, B.; Lukatskaya, M. R.; Gogotsi, Y., 2D metal carbides and nitrides (MXenes) for energy storage. Nat. Rev. Mater. 2017, 2 (2), 16098, DOI10.1038/natrevmats.2016.98. 19. Xie, X.; Chen, S.; Ding, W.; Nie, Y.; Wei, Z., An extraordinarily stable catalyst: Pt NPs supported on two-dimensional Ti3C2X2 (X = OH, F) nanosheets for oxygen reduction reaction. Chem. Commun. 2013, 49 (86), 10112-4, DOI 10.1039/c3cc44428g. 20. Li, S.; Tuo, P.; Xie, J.; Zhang, X.; Xu, J.; Bao, J.; Pan, B.; Xie, Y., Ultrathin MXene nanosheets with rich fluorine termination groups realizing efficient electrocatalytic hydrogen evolution. Nano Energy 2018, 47, 512-518, DOI 10.1016/j.nanoen.2018.03.022. 21. Seh, Z. W.; Fredrickson, K. D.; Anasori, B.; Kibsgaard, J.; Strickler, A. L.; Lukatskaya, M. R.; Gogotsi, Y.; Jaramillo, T. F.; Vojvodic, A., Two-Dimensional Molybdenum Carbide (MXene) as an Efficient Electrocatalyst for Hydrogen Evolution. ACS Energy Lett. 2016, 1 (3), 589-594, DOI 10.1021/acsenergylett.6b00247. 22. Ling, C.; Shi, L.; Ouyang, Y.; Chen, Q.; Wang, J., Transition Metal-Promoted V2CO2 (MXenes): A New and Highly Active Catalyst for Hydrogen Evolution Reaction. Adv. Sci. 2016, 3 (11), 1600180, DOI 10.1002/advs.201600180. 23. Ling, C.; Shi, L.; Ouyang, Y.; Wang, J., Searching for Highly Active Catalysts for Hydrogen Evolution Reaction Based on O-Terminated MXenes through a Simple Descriptor. Chem. Mater. 2016, 28 (24), 9026-9032, DOI 10.1021/acs.chemmater.6b03972. 24. Handoko, A. D.; Fredrickson, K. D.; Anasori, B.; Convey, K. W.; Johnson, L. R.; Gogotsi, Y.; Vojvodic, A.; Seh, Z. W., Tuning the Basal Plane Functionalization of Two-Dimensional Metal Carbides (MXenes) To Control Hydrogen Evolution Activity. ACS. Appl. Energy Mater. 2017, 1 (1), 173-180, DOI 10.1021/acsaem.7b00054. 25. Gao, G.; O’Mullane, A. P.; Du, A., 2D MXenes: A New Family of Promising Catalysts for the Hydrogen Evolution Reaction. ACS Catal. 2016, 7 (1), 494-500, DOI 10.1021/acscatal.6b02754. 26. Pandey, M.; Thygesen, K. S., Two-Dimensional MXenes as Catalysts for Electrochemical Hydrogen Evolution: A Computational Screening Study. J. Phys. Chem. C 2017, 121 (25), 13593-13598, DOI 10.1021/acs.jpcc.7b05270. 27. Zhu, C.; Fu, S.; Shi, Q.; Du, D.; Lin, Y., Single-Atom Electrocatalysts. Angew. Chem. Int. Ed. 2017, 56 (45), 13944-13960, DOI 10.1002/anie.201703864. 28. Li, P.; Zhu, J.; Handoko, A. D.; Zhang, R.; Wang, H.; Legut, D.; Wen, X.; Fu, Z.; Seh, Z. W.; Zhang, Q., High-throughput theoretical optimization of the hydrogen evolution reaction on MXenes by transition metal modification. J. Mater. Chem. A 2018, 6 (10), 4271-4278, DOI 10.1039/c8ta00173a. 23



29. Alhabeb, M.; Maleski, K.; Anasori, B.; Lelyukh, P.; Clark, L.; Sin, S.; Gogotsi, Y., Guidelines for Synthesis and Processing of Two-Dimensional Titanium Carbide (Ti3C2Tx MXene). Chem. Mater. 2017, 29 (18), 7633-7644, DOI 10.1021/acs.chemmater.7b02847. 30. Li, J.; Yuan, X. T.; Lin, C.; Yang, Y. Q.; Xu, L.; Du, X.; Xie, J. L.; Lin, J. H.; Sun, J. L., Achieving High Pseudocapacitance of 2D Titanium Carbide (MXene) by Cation Intercalation and Surface Modification. Adv. Energy Mater. 2017, 7 (15), 1602725, DOI 10.1002/aenm.201602725. 31. Ghidiu, M.; Lukatskaya, M. R.; Zhao, M. Q.; Gogotsi, Y.; Barsoum, M. W., Conductive two-dimensional titanium carbide 'clay' with high volumetric capacitance. Nature 2014, 516 (7529), 78-81, DOI 10.1038/nature13970. 32. Nayak, P.; Jiang, Q.; Mohanraman, R.; Anjum, D.; Hedhili, M. N.; Alshareef, H. N., Inherent electrochemistry and charge transfer properties of few-layered twodimensional Ti3C2Tx MXene. Nanoscale 2018, 10 (36), 17030-17037, DOI 10.1039/c8nr01883a. 33. Lian, P.; Dong, Y.; Wu, Z.-S.; Zheng, S.; Wang, X.; Sen, W.; Sun, C.; Qin, J.; Shi, X.; Bao, X., Alkalized Ti3C2 MXene nanoribbons with expanded interlayer spacing for high-capacity sodium and potassium ion batteries. Nano Energy 2017, 40, 1-8, DOI 10.1016/j.nanoen.2017.08.002. 34. Mashtalir, O.; Naguib, M.; Mochalin, V. N.; Dall'Agnese, Y.; Heon, M.; Barsoum, M. W.; Gogotsi, Y., Intercalation and delamination of layered carbides and carbonitrides. Nat. Commun. 2013, 4, 1716, DOI 10.1038/ncomms2664. 35. Li, Y. H.; Xing, J.; Yang, X. H.; Yang, H. G., Cluster size effects of platinum oxide as active sites in hydrogen evolution reactions. Chemistry 2014, 20 (39), 12377-80, DOI 10.1002/chem.201402989. 36. Hantanasirisakul, K.; Zhao, M.-Q.; Urbankowski, P.; Halim, J.; Anasori, B.; Kota, S.; Ren, C. E.; Barsoum, M. W.; Gogotsi, Y., Fabrication of Ti3C2Tx MXene Transparent Thin Films with Tunable Optoelectronic Properties. Adv. Electron. Mater. 2016, 2 (6), 1600050, DOI 10.1002/aelm.201600050. 37. Halim, J.; Cook, K. M.; Naguib, M.; Eklund, P.; Gogotsi, Y.; Rosen, J.; Barsoum, M. W., X-ray photoelectron spectroscopy of select multi-layered transition metal carbides (MXenes). Appl. Surf. Sci. 2016, 362, 406-417, DOI 10.1016/j.apsusc.2015.11.089. 38. Wang, Y.; Wang, L.; Tong, M.; Zhao, X.; Gao, Y.; Fu, H., Co-VN encapsulated in bamboo-like N-doped carbon nanotubes for ultrahigh-stability of oxygen reduction reaction. Nanoscale 2018, 10 (9), 4311-4319, DOI 10.1039/c7nr09538d. 39. Yang, S.; Chung, D. Y.; Tak, Y. J.; Kim, J.; Han, H.; Yu, J. S.; Soon, A.; Sung, Y. E.; Lee, H., Electronic structure modification of platinum on titanium nitride resulting in enhanced catalytic activity and durability for oxygen reduction and formic acid oxidation. Appl. Catal. B 2015, 174, 35-42, DOI 10.1016/j.apcatb.2015.02.033. 40. Xing, Z.; Han, C.; Wang, D.; Li, Q.; Yang, X., Ultrafine Pt Nanoparticle-Decorated Co(OH)2 Nanosheet Arrays with Enhanced Catalytic Activity toward Hydrogen Evolution. ACS Catal. 2017, 7 (10), 7131-7135, DOI 10.1021/acscatal.7b01994. 24


Page 24 of 25

Page 25 of 25 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


41. Seh, Z. W.; Kibsgaard, J.; Dickens, C. F.; Chorkendorff, I.; Norskov, J. K.; Jaramillo, T. F., Combining theory and experiment in electrocatalysis: Insights into materials design. Science 2017, 355 (6321), 1-12, DOI 10.1126/science.aad4998.

Graphic abstract

A series of Pt/Ti3C2Tx-based catalysts are designed with modulated interactions between Pt and the terminals for enhanced HER performance firstly.

25


Achieving high efficient catalysts for hydrogen evolution reaction by

Recommend Documents