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.

Using first-principles calculations, we systematically investigated the hydrogen evolution reaction (HER) potential of 27 types of homogeneous dual-atom M₂-N₆-graphene catalysts. Shared nitrogen atoms between dual metal atoms were identified as crucial adsorption sites for hydrogen atoms. Notably, we found that relying solely on the free energy of hydrogen adsorption ( ${\mathrm{\Delta }G}_{{\mathrm{H}}^{\ast }}$) could exclude the extremely unfavorable substrates, but may lead to misleading assessments of HER activation for substrates with modest ${\mathrm{\Delta }G}_{{\mathrm{H}}^{\ast }}$. Thermodynamic activity evaluation reveals that M₂-N₆-graphene (M = Cr, Co, Ni, Cu, Os, Pt) models exhibit promising HER activities. Kinetic analysis, based on the Volmer–Tafel mechanism, determined that the hydrogen coverage and relative distance between the adsorbed hydrogen atoms in the Tafel step affect the reaction energy barrier significantly. The coverage limits depend on the reaction free energy of the non-spontaneous third hydrogen adsorption step. By integrating the kinetic metric with thermodynamic assessments, we propose that the Co₂-N₆-graphene model displays superior HER activity. We further recommend selecting one of the metal positions in M_aM_b-N₆-graphene to be Cr and excluding Cu and Ni elements during the selection of the second metal atom when designing heterogeneous M_aM_b-N₆-graphene for alkaline HER catalyst. This study establishes a convenient workflow and provides valuable insights for the rational design of efficient HER catalysts.

There are increasing concerns about the environmental impact of rising atmospheric carbon monoxide concentrations, thus it is necessary to develop new catalysts for efficient CO oxidation. Based on first-principles calculations, the potential of γ-graphyne (GY) as substrate for metals in the 4th and 5th periods under single-atom and dual-atoms concentration modes has been systematically investigated. It was found that single-atom Co, Ir, Rh, and Ru could effectively oxidate CO molecules, especially for single Rh. Furthermore, proper atoms concentration could boost the CO oxidation activity by supplying more reaction centers, such as Rh₂/GY. It was determined that two Rh atoms in Rh₂/GY act different roles in the catalytic reaction: one structural and another functional. Screening tests suggest that substituting the structural Rh atom in the center of acetylenic ring by Co or Cu atom is a possible way to maintain the reaction performance while reducing the noble metal cost. This systemic investigation will help in understanding the fundamental reaction mechanisms on GY-based substrates. We emphasize that properly exposed frontier orbital of functional metal atom is crucial in adsorption configuration as well as entire catalytic performance. This study constructs a workflow and provides valuable information for rational design of CO oxidation catalysts.