Bifunctional multiple transition metal phosphide modification of ZnIn2S4 photocatalysts to enhance photocatalytic hydrogen evolution

Abstract

Obtaining hydrogen through photocatalytic water decomposition presented a reliable strategy to alleviate the energy crisis. ZnIn₂S₄ is a promising candidate for photocatalysts, however, the application of ZnIn₂S₄ was severely inhibited due to the recombination of photogenerated carriers and the slow surface reaction kinetics. In order to enhance the photocatalytic hydrogen evolution performance of ZnIn₂S₄, transition metal phosphide (TMP) catalysts with different numbers of transition metal elements were synthesized and compounded with ZnIn₂S₄ in this work. The TMP/ZnIn₂S₄ composite photocatalyst constructed a direct Z-scheme heterojunction to effectively inhibit the recombination of carrier recombination. Additionally, the multiple metal phosphides accelerated reaction kinetics, acting as co-catalysts to further enhance the photocatalytic performance. Meanwhile, with the increase in the transition metal elements, the catalytic reaction kinetics of TMPs was improved significantly while the charge transfer resistance gradually declined because of the synergistic effect between different metal atoms. The bifunctional multiple transition metal phosphide modification of ZnIn₂S₄ resulted in (MnFeCoNi)P_x/ZnIn₂S₄ exhibiting the best photocatalytic performance with a hydrogen evolution rate of 2796.17 μmol/(h·g), which is approximately twice that of the pure ZnIn₂S₄ catalyst. This work provided a strategy for optimizing the photocatalytic hydrogen production of ZnIn₂S₄ and a comprehensive approach to investigate the mechanism of multiple transition metal phosphide catalysts.