Insights into Dynamic Surface Bromide Sites in Bi4O5Br2 for Sustainable N2 Photofixation

Abstract Simulating photosynthesis has long been one of the ideas for realizing the conversion of solar energy into industrial chemicals. Heterogeneous N 2 photofixation in water is a promising way for sustainable production of ammonia. However, a mechanistic understanding of the complex aqueous photocatalytic N 2 reduction is still lacking. In this study, a light‐dependent surface hydrogenation mechanism and light‐independent protection of catalyst surface for N 2 reduction are revealed on ultrathin Bi 4 O 5 Br 2 (BOB) nanosheets, in which the creation and annihilation of surface bromine vacancies can be controlled via a surface bromine cycle. Our rapid scan in situ FT‐IR spectra verify that photocatalytic N 2 reduction proceeds through an associative alternating mechanism on BOB surface with bromine vacancies (BrV‐BOB). This work provides a new strategy to combine light‐dependent facilitated reaction with light‐independent regeneration of catalyst for advancing sustainable ammonia production.