Tuning interfacial charge transfer of CuS/CaIn2S4 heterojunctions for efficient H2O2 photosynthesis from seawater

Photocatalytic oxygen reduction reaction (ORR) in seawater provides an efficient, cost-effective and sustainable pathway for hydrogen peroxide (H 2 O 2 ) production. However, developing the stable and high-efficiency seawater photocatalysts remains a crucial challenge due to the high concentration of Cl − and rapid charge carrier recombination rate. Here we fabricated 2D/2D CuS/CaIn 2 S 4 (CuS/CIS) heterostructured photocatalysts for visible-light-driven H 2 O 2 photosynthesis from seawater and O 2 under ambient condition. The introduction of CuS in CuS/CIS composites benefited superior light harvesting and the charge carrier separation. The optimized 5-CuS/CIS had an exceptional H 2 O 2 photosynthesis rate of 1194.0 μmol∙g −1 ∙h −1 with stable reusability in seawater, outperforming their counterparts. Additionally, 5-CuS/CIS possesses the higher H 2 O 2 photosynthesis rate in seawater and single salt-based solutions than that in deionized water. The corresponding enhancement mechanism of H 2 O 2 photosynthesis in seawater was discussed in depth. Thorough experimental analysis and theoretical calculations corroborate the two-step one-electron ORR path for H 2 O 2 photosynthesis. Through systematic characterization, we pinpoint the photo-reduction active sites governing H 2 O 2 formation and reveal optimized interfacial charge transfer pathways. This study offers new insights into designing stable heterostructured photocatalysts to facilitate charge carrier separation and achieve high-efficiency for H 2 O 2 photosynthesis from seawater.