Integrative Active Sites of Cathode for Electron-Oxygen-Proton Coupling To Favor H 2 O 2 Production in a Photoelectrochemical System.

The oxygen reduction process generating H 2 O 2 in the photoelectrochemical (PEC) system is milder and environmentally friendly compared with the traditional anthraquinone process but still lacks the efficient electron-oxygen-proton coupling interfaces to improve H 2 O 2 production efficiency. Here, we propose an integrated active site strategy, that is, designing a hydrophobic C-B-N interface to refine the dearth of electron, oxygen, and proton balance. Computational calculation results show a lower energy barrier for H 2 O 2 production due to synergistic and coupling effects of boron sites for O 2 adsorption, nitrogen sites for H + binding, and the carbon structure for electron transfer, demonstrating theoretically the feasibility of the strategy. Furthermore, we construct a hydrophobic boron- and nitrogen-doped carbon black gas diffusion cathode (BN-CB-PTFE) with graphite carbon dots decorated on a BiVO 4 photoanode (BVO/g-CDs) for H 2 O 2 production. Remarkably, this approach achieves a record H 2 O 2 production rate (9.24 μmol min -1 cm -2 ) at the PEC cathode. The BN-CB-PTFE cathode exhibits an outstanding Faraday efficiency for H 2 O 2 production of ∼100%. The newly formed h -BN integrative active site can not only adsorb more O 2 but also significantly improve the electron and proton transfer. Unexpectedly, coupling BVO/g-CDs with the BN-CB-PTFE gas diffusion cathode also achieves a record H 2 O 2 production rate (6.60 μmol min -1 cm -2 ) at the PEC photoanode. This study opens new insight into integrative active sites for electron-O 2 -proton coupling in a PEC H 2 O 2 production system that may be meaningful for environment and energy applications.