The development of efficient and stable photocatalysts is key to achieving highly efficient photocatalytic hydrogen evolution. Compared with photocatalysts containing only one type of semiconductor, heterojunction structure photocatalyst combining two or more semiconductors show altered band alignment at the interface, which promotes the separation of photogenerated carriers and inhibits carrier recombination. Thus, this kind of photocatalysts usually exhibit higher hydrogen evolution rates. To date, binary‐metal‐sulfide/titanium oxide (BMS/TiO2) heterojunction photocatalysts, such as CdS/TiO2, MoS2/TiO2, and ZnS/TiO2, have shown great promise for photocatalytic hydrogen evolution. Compared with BMS/TiO2, recently developed ternary‐metal‐sulfide/TiO2 (TMS/TiO2) photocatalysts have the advantages of low toxicity, a tunable band structure, and favorable chemical stability, enabling a higher photocatalytic hydrogen evolution rate. In this review, TMS/TiO2 heterojunction photocatalysts are thoroughly summarized and the semiconductor properties of TMSs are firstly introduced. Afterwards, photocatalytic hydrogen evolution applications based on TMS/TiO2 heterojunction photocatalysts are reviewed and discussed in detail, mainly focusing on the heterojunction type, band structure, and photogenerated carrier separation and transport. Finally, our conclusions and the perspective based on the potential for the further improvement of TMS/TiO2 based photocatalysts are presented.
Efficient solar-to-hydrogen (STH) conversion through water splitting relies on the development of low-cost photocatalysts with high photoactivity and stability. Zn x Cd 1Àx S, an emerging metal sulfide (MS) solid solution for STH, possesses several unique advantages, such as a tunable bandgap, abundant elemental constituents, and high stability. Although Zn x Cd 1Àx S-based photocatalysts are investigated for hydrogen evolution, their photoactivity still has to be enhanced for commercial applications. Herein, the design concept, crystal and band structure properties, and original photoactivity of Zn x Cd 1Àx S are briefly introduced, and Zn x Cd 1Àx S solutions with different morphologies and structures, modifications, synthesis methods, and vacancy engineering are then discussed. Subsequently, the combination of Zn x Cd 1Àx S and cocatalysts and several representative Zn x Cd 1Àx S-based heterojunction photocatalysts for hydrogen evolution are reviewed and discussed in detail. Finally, the unsolved issues in the application of Zn x Cd 1Àx S photocatalysts and their potential solutions for developing advanced Zn x Cd 1Àx S-based photocatalysts are discussed.
Photocatalyst with excellent semiconductor properties is the key point to realize the efficient photocatalytic hydrogen evolution (PHE). As a representative binary metal sulfide (BMS) semiconductor, cadmium sulfide (CdS) possesses suitable bandgap of 2.4 eV and negative conduction band potential, which has a great potential to realize efficient visible‐light PHE performance. In this work, CdS with unique cubic/hexagonal phase junction is facilely synthesized through a sulfur‐rich butyldithiocarbamate acid (BDCA) solution process. The results illustrate that the phase junction can efficiently enhance the separation and transfer of photogenerated electron–hole pairs, resulting in an excellent PHE performance. In addition, the sulfur‐rich property of BDCA solution leads to the absence of additional sulfur sources during the synthesis of CdS photocatalyst, which greatly simplifies the fabrication process. The optimal PHE rate of the BDCA‐synthesized phase junction CdS photocatalyst is 7.294 mmol g–1 h–1 and exhibits a favorable photostability. Moreover, density function theory calculations indicated that the apparent redistribution of charge density in the cubic/hexagonal phase junction regions gives a suitable hydrogen adsorption capacity, which is responsible for the enhanced PHE activity.
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