Ag-Pd alloy decorated ZnIn 2 S 4 microspheres with optimal Schottky barrier height for boosting visible-light-driven hydrogen evolution

Rapid charge carrier recombination rate and insufficient light harvesting capacity are two dominating drawbacks encountered in zinc indium sulfide (ZnIn 2 S 4 ) for photocatalytic applications. Herein, a chemical reduction method was performed to combine bimetallic Ag-Pd alloy nanoparticles (NPs) with spherical-like ZnIn 2 S 4 (ZIS). By optimizing Ag:Pd molar ratio and overall loading amount, the optimal Ag 0.25 Pd 0.75 -ZIS sample exhibited a maximum H 2 evolution rate (125.4 mu mol/h) under visible light, which was higher than that of ZIS, Ag-ZIS and Pd-ZIS. The loading of Ag NPs contribution to PHE reaction by its plasmonic effect was negligible compared to that of Pd loading (Schottky effect). The apparent quantum yield (AQY) values over Ag 0.25 Pd 0.75 -ZIS sample could reach up to 18.3% at 400 nm and 15.8% at 420 nm. The enhanced activity for photocatalytic hydrogen evolution (PHE) over Ag 0.25 Pd 0.75 -ZIS sample was mainly due to the bimetallic synergistic effect that presented as follows. Firstly, the plasmon hybridization by loading Ag-Pd bimetallic alloy can significantly increase light harvesting capacity of ZIS. Secondly, the optimal Schottky barrier height formed between Ag-Pd alloy and ZIS interface was beneficial for prolonging electron-hole pair lifetimes, promoting charge carrier separation and thus facilitating PHE efficiency. Density functional theory (DFT) analysis indicated that the adsorption energy of H * over Pd 0.75 Ag 0.25 alloy was very close to zero and thus theoretically possessed the highest activity for H 2 evolution, which is in line with experimental results. Combined theoretical calculation with experimental results, a reasonable photocatalytic mechanism was proposed and verified. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

By combining Ag-Pd alloy nanoparticles with ZnIn2S4, the photocatalytic activity for hydrogen evolution was significantly enhanced due to the synergistic effect of bimetallic Ag-Pd alloy. The optimal Ag0.25Pd0.75-ZIS sample exhibited higher H2 evolution rate and apparent quantum yield compared to pure ZIS, Ag-ZIS, and Pd-ZIS. The enhanced activity was attributed to increased light harvesting capacity and prolonged electron-hole pair lifetimes.