Single atom Cu-O₂N bridge between BiVO₄ and COFs toward photoelectrochemical seawater splitting

Photoelectrochemical (PEC) water splitting has great potential for solar energy conversion to hydrogen. However, the slow charge transfer in the photoanodes remains a core issue limiting the PEC performance. In this study, we address this issue by constructing a single-atom bridge (SAB) Cu-O₂N at the interface between BiVO₄ and covalent organic framework (COF) layer. X-ray absorption fine spectra and theoretical calculations demonstrate that the single-atom bridge is formed by the interfacial coordination reconstruction between BiVO₄ and COF layers and create intermediate electronic states to facilitate the hole extraction. As a result, the SAB photoanode exhibits enhanced PEC water oxidation performance. Specifically, it achieves a photocurrent density of 4.84 mA·cm⁻² at 1.23 V vs. reversible hydrogen electrode (RHE) in PEC simulant seawater splitting with a cocatalyst, higher than nearly all the previously reported BiVO₄-based photoanodes. This work offers valuable insights into fast charge transfer in PEC systems and proposes a promising strategy for designing efficient photoelectrodes for seawater splitting.