Promoting Charge Separation in CuInS2/CeO2 Photocatalysts by an S-scheme Heterojunction for Enhanced Photocatalytic H2 Production

Low charge separation efficiency significantly hampers the performance of photocatalytic hydrogen production. Constructing heterojunctions emerges as a crucial strategy to enhance photocatalytic activity by improving charge separation. An S-scheme heterojunction not only effectively separates the photogenerated charge in composite photocatalysts but also preserves optimal redox capabilities. This study presents the first report of CuInS2/CeO2 (CIS/CeO2) and demonstrates how charge separation within CIS/CeO2 to enhance photocatalytic hydrogen production through the construction of an S-scheme heterojunction. The UV–visible-driven hydrogen production rate of CIS/CeO2 is 4.6 and 9.4 times higher than that of CIS and CeO2 alone, respectively. The improved photocatalytic performance primarily stems from enhanced charge separation promoted by the S-scheme heterojunction. The charge transfer pathway was confirmed as an S-scheme mechanism through a combination of band structure experiments, density functional theory (DFT) calculations on work function, internal electric field, and charge differential density distribution, alongside electron paramagnetic resonance (EPR) experiments. Multiple perspectives were employed to elucidate the reasons behind facilitating efficient charge separation. This research provides valuable insights for advancing photocatalytic performance.