A AgPd3/2D-CdS photocatalyst: The function of AgPd3 cocatalyst, and the enhanced photocatalytic hydrogen generation property under visible light
Precious metals loading strategy is an effective method to increase the reactivity of CdS based photocatalysts for hydrogen evolution from water splitting under visible light. The key problem of such strategy is the affecting mechanism, which determined by the composition, species and structure of the loaded metals. In this study, AgPd bimetallic nanoclusters (Ag x Pd y ) were prepared and then loaded onto the surface of snowflake-like CdS and the affecting mechanism was qualitatively and quantatively investigated through both instrumental analysis and computational method. The composition and structure of synthesized samples were examined through XRD, TEM, and XPS, by which the successful synthesis of AgPd bimetallic nanocluster alloys with an average particle size of approximately 3 nm were confirmed. Further, the hydrogen evolution performance of Ag x Pd y /CdS was tested under visible light and the prepared AgPd 3 /CdS achieved a hydrogen evolution rate of 73.93 mmol h −1 g −1 , which is a 28 % improvement over Pd/CdS and a 381 % improvement over CdS, with an AQY of 44.68 % at 420 nm. The photoelectrochemical tests (LSV, I-T, EIS, PL, and TR-PL), ESR, and TRPL were applied to qualitatively demonstrate the function of Ag x Pd y nano-cocatalyst, and the testing results indicated that the cocatalyst significantly enhances the separation and transfer efficiency of photoinduced electrons, while further lowering the hydrogen evolution reaction energy barrier. Based on that, affecting mechanism was further determined through DFT simulation quantitatively. The prediction results indicated that the unique nanoclusters structure of AgPd 3 contribute with the high work function and low d band center position increase the transfer efficiency of the photoinduced charge carriers. This study quantitatively revealed the relationship among compostion, structure and reactivity of the photocatalysts, provided an method to investigate the affecting mechanism of bimetallic hydrogen evolution photocatalysts and contributed to the advancement of renewable energy development.
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