Site-Selective Deposition of Reductive and Oxidative Dual Cocatalysts To Improve the Photocatalytic Hydrogen Production Activity of CaIn₂S₄ with a Surface Nanostep Structure

Photocatalytic hydrogen production from water exhibits great potential for solar energy conversion. In this work, using monoclinic CaIn2S4 with a surface nanostep structure as a model photocatalyst, we demonstrate a facile and efficient strategy for the construction of AOx/AuCu/CaIn2S4 (A = Mn, Ni, and Pb) composites by site-selective photodeposition of the reductive cocatalyst AuCu alloy and oxidative cocatalyst AOx on the edge and groove sites of CaIn2S4 nanosteps, respectively. Compared to single-cocatalyst composites (AuCu/CaIn2S4 and AOx/CaIn2S4) and CaIn2S4, the simultaneous deposition of AuCu and AOx spatially separate the photogenerated charges and the photocatalytic reaction sites, therefore effectively improving the separation efficiency of charge carriers. Meanwhile, the synergistic effect of AuCu and AOx dual cocatalysts notably reduces the apparent activation energy for the photocatalytic hydrogen production reaction. These novel dual-cocatalyst composites show enhanced performance for hydrogen production under visible light irradiation. A high rate of hydrogen production of 95.75 mmol h–1 g–1 is achieved over the MnOx/AuCu/CaIn2S4 composite with the deposition of 0.5 wt % AuCu and 0.2 wt % MnOx. Our work sheds new lights on designing efficient photocatalytic materials with site-selective surface deposition of reductive and oxidative dual cocatalysts for solar energy conversion.