Ag cluster hot electrons synergize Ni-doped CaIn2S4 for efficient seawater H2O2 photosynthesis

Photocatalytic overall H2O2 production in seawater represents a promising low-carbon technology. However, there are still some drawbacks remaining, like the limited light-capturing efficiency and the low charge carrier separation rate. Herein, a two-step hydrothermal and photodeposition process was developed to synthesize Ag clusters-supported Ni-doped CaIn2S4 (Ag/Ni-CIS) composites for overall H2O2 photosynthesis in seawater under visible light. By doping Ni, the electronic structure of CIS was adjusted so as to narrow the band gap and broaden the scope of light absorption. The introduction of Ag clusters along with surface plasmon resonance effect could optimize interfacial electron transfer, enhance charge separation efficiency, and activate surface water molecules to generate •OH through plasmonic hot holes and electric-field activation. the optimal 0.5Ag/1-Ni-CIS composite achieved the higher H2O2 photosynthesis rate than pristine CIS and 1-Ni-CIS in seawater without any sacrificial agents, because of Ni doping and Ag clusters loading. In-situ diffuse reflectance infrared transform spectroscopy and electron spin resonance measurements confirmed the overall H2O2 photosynthesis, and corresponding mechanism for overall H2O2 photosynthesis in seawater were systematically investigated. This work elucidates the synergy of Ni doping and Ag loading in dual 2e− pathways, offering insights for designing efficient photocatalysts for seawater H2O2 production.