Fabrication of CdS@1T-MoS2 core-shell nanostructure for enhanced visible-light-driven photocatalytic H2 evolution from water splitting
TL;DR: CdS@1T-MoS2 composites with core-shell structure were synthesized through a hydrothermal treatment followed by a solvothermal treatment in this paper.
Abstract: CdS@1T-MoS2 composites with core-shell structure were synthesized through a hydrothermal treatment followed by a solvothermal treatment. Nanosized CdS particles were coated by a thin 1T-MoS2 shell to form efficient heterojunction, as demonstrated by transmission electron microscopy images and X-ray photoelectron spectroscopy. Under visible-light irradiation, CdS@1T-MoS2 composites with the MoS2/CdS weight ratio of 0.5 exhibit the highest photocatalytic performance and the H2 evolution rate reached 2.67 mmol h−1 g−1, which is 50 times that of single 1T-MoS2 and 10 times that of single CdS. 1T-MoS2, as a cocatalyst, donates the composites fast charge transfer ability and the high H2 evolution activity, while the intimate heterojunction between CdS core and 1T-MoS2 shell greatly increase the separation efficiency of photo-induced electron-hole pairs, as demonstrated by the electrochemical and PL results, resulting in the remarkable photocatalytic performance of the composites. This study supplies a facile and efficient strategy to develop the photocatalysts with boosted performance for hydrogen energy application.
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TL;DR: In this paper, a simple approach based on combining template-assisted liquid-phase deposition and hydrothermal techniques was introduced to synthesize BiVO4-TiO2/reduced graphene oxide (rGO) heterostructure nanocomposites.
Abstract: Fabricating heterostructures has been recognized as an effective strategy to improve visible-light photocatalytic H2 production performance. Therefore, a simple approach based on combining template-assisted liquid-phase deposition and hydrothermal techniques was introduced to synthesize BiVO4-TiO2/reduced graphene oxide (rGO) heterostructure nanocomposites. The ternary hetero-nanostructures were composed of TiO2 nanotubes, with an average diameter of 100 nm and tens micrometers in length, BiVO4 nanoparticles and various amounts of rGO nanosheets. The highest photocatalytic H2 production rate of 1427.1 μmol.h − 1 g − 1 with an apparent quantum yield of 6.4% at 420 nm was achieved at optimum rGO content (3 wt.%) under visible-light irradiation, which was 2.5 and 1.5 times higher than that of TiO2 nanotubes)563.5 μmol.h − 1 g − 1) and BiVO4-TiO2 (915.7 μmol.h − 1 g − 1), respectively. The excellent enhancing effect of rGO on photocatalytic performance of the heterojunction formed between these materials was attributed to the large surface area, light absorption capacity due to band gap engineering, and separation of photo-generated charge carriers. It demonstrates the design of the ternary BiVO4-TiO2/rGO hetero-nanostructures that was proposed in the present strategy could effectively separate the electron-hole pairs for sustainable photocatalytic H2 production, as was verified by PL, TRF and EIS photospectroscopy measurements.
19 citations
TL;DR: In this article, a series of Pt-loaded strontium titanate (SrTiO3)-based photocatalysts exhibited superior visible-light-driven hydrogen (H2) production activity by sensitization with xanthene dyes.
Abstract: In this work, strontium titanate (SrTiO3)-based photocatalysts exhibited superior visible-light-driven photocatalytic hydrogen (H2) production activity by sensitization with xanthene dyes. A series of Pt-loaded SrTiO3 (Pt/STO) photocatalysts were successfully prepared to systematically investigate the dependence of photocatalytic performance on the types of sacrificial agents and dyes. Photocatalytic experiments demonstrated that triethanolamine (TEOA) sacrificial agent and Eosin Y (EY) photosensitizer were the proper choice for remarkable enhancement of photocatalytic activity, and the H2 yield of the optimal system containing 1.0 wt% Pt/STO reached 491.5 μmol in 2.5 h under visible light irradiation. The reasons causing the results were that TEOA could enhance the adsorption of xanthene dyes on SrTiO3-based photocatalysts, and bromine groups-containing EY has a high intersystem crossing yield. Electrochemical tests, PL results and fluorescence lifetime further demonstrated the efficient electron transfer behavior occurred from photoexcited EY to the conduction band of SrTiO3. This study emphasized the potential application of SrTiO3-based materials in the field of solar hydrogen production.
15 citations
01 Feb 2022
TL;DR: In this article , a comprehensive review of the 1T-MS2 (M = W, Mo)-based solar-to-hydrogen evolution system is presented, as well as their roles and functional mechanisms for photocatalytic H2 evolution.
Abstract: Photocatalytic water splitting is a promising strategy to produce hydrogen as a sustainable and clean energy carrier, based on abundant solar energy and semiconductor photocatalysts, and it has received extensive research and discussion over the past several decades. It is challenging, however, to achieve an efficient solar-to-hydrogen evolution process with a single particulate photocatalyst due to the weak solar spectrum harvest and the rapid recombination of photogenerated electron-hole pairs during the photocatalysis reaction. Combining semiconductors to create different co-catalysts presents a viable solution to the above issues. Recently, semiconductor photocatalysts modified by different transition metal sulfide-based co-catalysts with designed functions, especially in light absorption enhancement and charge-carrier-separation efficiency promotion, have attracted much attention. As continued breakthroughs have been made in the preparation, modification, and solar-to-hydrogen evolution application of the 1T phase MS2 (M = W, Mo) co-catalyst-based photocatalysis system in recent years, we believe that a comprehensive review of this kind of co-catalyst would further promote its research and development to address the energy and environmental challenges that we are currently facing. Herein, recent studies and progress are summarized on the fabrication of 1T phase MS2 (M = W, Mo)-based co-catalyst materials, as well as their roles and functional mechanisms for photocatalytic H2 evolution. Finally, concluding perspectives on the opportunities in and challenges for the further exploration of the 1T-MS2 (M = W, Mo)-based solar-to-hydrogen evolution system are presented.
9 citations
TL;DR: In this paper, a comprehensive review of the 1T-MS2 (M = W, Mo)-based solar-to-hydrogen evolution system is presented, as well as their roles and functional mechanisms for photocatalytic H2 evolution.
9 citations
TL;DR: In this article , a novel Mo vacancy defective MoS2/CdS composites were obtained by a facile hydrothermal method and the photocatalytic performance of the prepared composites was evaluated from the perspective of decomposing water to produce H2.
8 citations
References
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TL;DR: The active site for hydrogen evolution, a reaction catalyzed by precious metals, on nanoparticulate molybdenum disulfide (MoS2) is determined by atomically resolving the surface of this catalyst before measuring electrochemical activity in solution.
Abstract: The identification of the active sites in heterogeneous catalysis requires a combination of surface sensitive methods and reactivity studies. We determined the active site for hydrogen evolution, a reaction catalyzed by precious metals, on nanoparticulate molybdenum disulfide (MoS2) by atomically resolving the surface of this catalyst before measuring electrochemical activity in solution. By preparing MoS2 nanoparticles of different sizes, we systematically varied the distribution of surface sites on MoS2 nanoparticles on Au(111), which we quantified with scanning tunneling microscopy. Electrocatalytic activity measurements for hydrogen evolution correlate linearly with the number of edge sites on the MoS2 catalyst.
4,930 citations
TL;DR: The ability of different metal surfaces and of the enzymes nitrogenase and hydrogenase to catalyze the hydrogen evolution reaction is analyzed and a necessary criterion for high catalytic activity is found: that the binding free energy of atomic hydrogen to the catalyst is close to zero.
Abstract: The electrochemical hydrogen evolution reaction is catalyzed most effectively by the Pt group metals. As H2 is considered as a future energy carrier, the need for these catalysts will increase and alternatives to the scarce and expensive Pt group catalysts will be needed. We analyze the ability of different metal surfaces and of the enzymes nitrogenase and hydrogenase to catalyze the hydrogen evolution reaction and find a necessary criterion for high catalytic activity. The necessary criterion is that the binding free energy of atomic hydrogen to the catalyst is close to zero. The criterion enables us to search for new catalysts, and inspired by the nitrogenase active site, we find that MoS2 nanoparticles supported on graphite are a promising catalyst. They catalyze electrochemical hydrogen evolution at a moderate overpotential of 0.1−0.2 V.
3,302 citations
TL;DR: By partially oxidizingMoS2, it is found that the activity of 2H MoS2 is significantly reduced after oxidation, consistent with edge oxidation, and 1T MoS 2 remains unaffected after oxidization, suggesting that edges of the nanosheets are not the main active sites.
Abstract: We report chemically exfoliated MoS2 nanosheets with a very high concentration of metallic 1T phase using a solvent free intercalation method. After removing the excess of negative charges from the surface of the nanosheets, highly conducting 1T phase MoS2 nanosheets exhibit excellent catalytic activity toward the evolution of hydrogen with a notably low Tafel slope of 40 mV/dec. By partially oxidizing MoS2, we found that the activity of 2H MoS2 is significantly reduced after oxidation, consistent with edge oxidation. On the other hand, 1T MoS2 remains unaffected after oxidation, suggesting that edges of the nanosheets are not the main active sites. The importance of electrical conductivity of the two phases on the hydrogen evolution reaction activity has been further confirmed by using carbon nanotubes to increase the conductivity of 2H MoS2.
1,856 citations
TL;DR: In this paper, the authors present the electrocatalytic properties of a highly conductive MoS2 hybrid material, and demonstrate that the origin of the HER activity is closely related to the amount of edges in the layered MOS2.
Abstract: This perspective covers the use of molybdenum disulfide and related compounds, generally termed MoSx, as electro- or photoelectrocatalysts for the hydrogen evolution reaction (HER). State of the art solutions as well as the most illustrative results from the extensive electro- and photoelectrocatalytic literature are given. The research strategies currently employed in the field are outlined and future challenges pointed out. We suggest that the key to optimising the HER activity of MoS2 is divided into (1) increasing the catalytic activity of the active site, (2) increasing the number of active sites of the catalyst, and (3) improving the electrical contact to these sites. These postulations are substantiated by examples from the existing literature and some new results. To demonstrate the electrocatalytic properties of a highly conductive MoS2 hybrid material, we present the HER activity data for multi-wall MoS2 nanotubes on multi-wall carbon nanotubes (MWMoS2@MWCNTs). This exemplifies the typical data collected for the electrochemical HER. In addition, it demonstrates that the origin of the activity is closely related to the amount of edges in the layered MoS2. The photoelectrocatalytic HER is also discussed, based on examples from literature, with an emphasis on the use of MoSx as either (1) the co-catalyst providing the HER activity for a semiconductor, e.g. Mo3S+4on Si or (2) MoS2 as the semiconductor with an intrinsic HER activity. Finally, suggestions for future catalyst designs are given.
1,189 citations
TL;DR: A molecule is reported that mimics the structure of the proposed triangular active edge site fragments of molybdenum disulfide (MoS2), a widely used industrial catalyst that has shown promise as a low-cost alternative to platinum for electrocatalytic hydrogen production.
Abstract: Inorganic solids are an important class of catalysts that often derive their activity from sparse active sites that are structurally distinct from the inactive bulk. Rationally optimizing activity is therefore beholden to the challenges in studying these active sites in molecular detail. Here, we report a molecule that mimics the structure of the proposed triangular active edge site fragments of molybdenum disulfide (MoS(2)), a widely used industrial catalyst that has shown promise as a low-cost alternative to platinum for electrocatalytic hydrogen production. By leveraging the robust coordination environment of a pentapyridyl ligand, we synthesized and structurally characterized a well-defined Mo(IV)-disulfide complex that, upon electrochemical reduction, can catalytically generate hydrogen from acidic organic media as well as from acidic water.
1,078 citations