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

Simulating photosynthesis has long been one of the ideas for realizing the conversion of solar energy into industrial chemicals. Heterogeneous N2 photofixation in water is a promising way for sustainable production of ammonia. However, a mechanistic understanding of the complex aqueous photocatalytic N2 reduction is still lacking. In this study, a light-dependent surface hydrogenation mechanism and light-independent protection of catalyst surface for N2 reduction are revealed on ultrathin Bi4 O5 Br2 (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 N2 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.