Insights into Dynamic Surface Bromide Sites in Bi 4 O 5 Br 2 for Sustainable N 2 Photofixation.

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.