Electron transfer dynamics of quaternary sulfur semiconductor/mos2 layer-on-layer for efficient visible-light h2 evolution

Abstract

Photocatalytic water reduction into H2 provides huge charm for simultaneously resolving fossil energy shortage and environmental issues. Seeking photocatalysts with characteristics of low-cost, environmental friendliness and visible light response, and accelerating the charge separation remain significant challenges to develop high efficient solar-to-H2 conversion systems. Here, quaternary sulfur semiconductor Zn0.4Ca0.6In2S4 (ZCIS) microspheres composed of cross-linked nanosheets and ZCIS microspheres modified with MoS2 (ZM-X) were designed and prepared via hydrothermal methods. Detailed characterizations indicated that the layer structured MoS2 nanosheets were mainly deposited on the surface of ZCIS nanosheet to form a 2D-2D structure that greatly increased the contact surface area for charge transfer, which was critical to the high photocatalytic performance for H2 evolution. Femtosecond time-resolved diffuse reflectance spectroscopy was used to evaluate the transfer dynamics of photogenerated electrons in ZCIS and ZM-X and revealed that an additional decay route within 5 ps for the photogenerated electrons in ZCIS after combining with MoS2 appeared which could be ascribed to the electron injection from ZCIS to MoS2. In addition, it was also demonstrated that ZM-3.0 (ZCIS with 3 wt% MoS2 loading amount) exhibited the fastest electron injection within only 1.12 ps and the highest efficient injection efficiency of 69.9%. As a result, ZM-3.0 exhibited the evolution rate of 3.5 μmol h-−1 under visible light irradiation (λ ≥ 420 nm), which was 27 times higher than that of ZCIS (0.13 μmol h−1). The results indicate that the quaternary sulfur semiconductor has great potential as a new kind of photocatalysts for solar energy conversion.