Bi2O2CO3/CdS S-Scheme Heterojunction with Efficient Interfacial Charge Separation for Optimized H2O2 Photosynthesis from Seawater

Abstract Exploring highly efficient photocatalytic materials is of utmost importance for the efficient generation of hydrogen peroxide (H 2 O 2 ) in seawater. However, the catalytic performance of such materials is constrained by low solar energy conversion efficiency and inadequate charge carrier separation. In this study, narrow-bandgap CdS nanoparticles with high reducibility, synthesized via a hydrothermal method, are coupled with Bi 2 O 2 CO 3 (BOC) nanosheets to construct S-scheme BOC/CdS heterojunctions. These heterojunctions effectively optimize charge transfer, broaden light absorption, accelerate charge separation and migration, maintain strong redox capabilities, and enable dual pathways for two-electron water oxidation and oxygen reduction. Systematic characterizations, including in situ X-ray photoelectron spectroscopy/Fourier transform infrared spectroscopy, Kelvin probe force microscopy, electron spin resonance, and femtosecond transient absorption spectroscopy, are performed to elucidate the H 2 O 2 generation pathways, clarify the charge transfer and separation mechanisms, and confirm the S-scheme mechanism. The optimized BOC/CdS heterojunction demonstrates superior H 2 O 2 production in seawater, reaching 1904 μmol/(g h), which is 17.96-fold that of BOC and 2.13-fold that of pure CdS. Moreover, its performance in seawater is remarkable compared to that in deionized water. Overall, this research presents a viable strategy for designing S-scheme catalysts to enhance H 2 O 2 photosynthesis from seawater.