Photocatalytic Hydrogen Evolution Using Ternary‐Metal‐Sulfide/TiO₂ Heterojunction Photocatalysts

Abstract

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.

Recent Advances in the Hydrogen Evolution Reaction of ZnxCd1−xS‐Based Photocatalysts

“…The conduction and valence band potential (E CB and E VB , respectively) of Zn x Cd 1Àx S can be calculated using the following empirical equation. [9,24,25] E CB ¼ χ-E e -1=2E g (1)…”

“…Cocatalyst loading is one of the most efficient strategies for improving the photoactivity of MS photocatalysts. [9] Generally, noble metals, such as Pt, Au, and their alloys, can act as electron sinks, provide sufficient active sites, and enhance charge separation, resulting in improved photoactivity for MS photocatalysts. [43,44] Shu et al reported a Pt x Fe 1Àx alloy as a cocatalyst to improve the photocatalytic HER performance of a ZnCdS photocatalyst.…”

“…The construction of heterojunctions is another effective way to enhance the photoactivity of MS photocatalysts for hydrogen production. [9][10][11] For bare semiconductor photocatalysts, the [45] photogenerated electrons can readily return to the valence band and recombine with the photogenerated holes due to the strong Coulombic force between the electronÀhole pairs (Figure 6a). Therefore, the hydrogen production of single-semiconductor photocatalysts is usually poor due to their low charge separation efficiency.…”

“…[1][2][3][4][5][6][7][8] Photocatalytic hydrogen evolution (PHE) through water splitting using solar energy is an ideal technique for solar-to-hydrogen (STH) conversion. [9][10][11] In 1972, Fujishima and Honda reported that hydrogen evolution could be achieved through photoelectrochemical water splitting on a TiO 2 electrode. [12] However, owing to the wide bandgap of TiO 2 (%3.2 eV), hydrogen evolution could only occur under UV light absorption, which only accounts for 4% of solar light.…”

“…In particular, as semiconductors, metal sulfides (MSs) have narrow bandgaps, appropriate band structures, and large specific surface areas; therefore, they are suitable for achieving PHE under visible light. [9][10][11][13][14][15] Binary MSs have layered structures and other unique semiconductor properties for PHE and have great potential for achieving a high hydrogen evolution reaction (HER) efficiency. Zheng et al systematically summarized several binary MS photocatalysts for the HER, including CdS, MoS 2 , CuS, and other representative binary MSs.…”