Photoinduced Charge Separation via the Double-Electron Transfer Mechanism in Nitrogen Vacancies g-C3N5/BiOBr for the Photoelectrochemical Nitrogen Reduction

Due to the harsh reaction conditions, high energy consumption, and numerous carbon emissions of the traditional Haber–Bosch method, the fixation of nitrogen under environmentally friendly and milder conditions is of great importance. Recently, photoelectrochemical (PEC) strategies have attracted extensive attention, where the catalysts with the advantages of cost-effectiveness and improved efficiency are critical for the nitrogen reduction reaction (NRR). Herein, we synthesized nitrogen vacancies that contained g-C3N5 (NV-g-C3N5) and combined with BiOBr to construct the p–n heterostructure NV-g-C3N5/BiOBr, in which the double-electron transfer mechanism was constructed. In one side, the nitrogen vacancies store the electrons coming from the g-C3N5 and provide for the nitrogen activation when needed; in addition, NV-g-C3N5/BiOBr further separates photoinduced electrons and holes because of the matched “Z”-shaped energy band structure. The double-electron transfer mechanism effectively retards the recombination of charge carriers and ensures the support of high-quality electrons, which results in excellent PEC NRR performance without the addition of noble metals. Although yields and durability are insufficient, the described double-electron transfer mechanism manifests the potential of the non-noble metal material in the PEC NRR, providing a foundation for the design of a more affordable and efficient photocathode in nitrogen reduction.