Electronic structure engineering of single atom bismuth on oxygen vacancy enriched BiOBr for efficient photocatalytic nitrogen fixation to ammonia

Bi single atoms are anchored at oxygen vacancies in BiOBr to construct Bi–Ov active sites. • Bi–Ov coupling enables electronic structure engineering and efficient charge transfer. • BiSAC@BiOBr-Ov achieves an NH 3 production rate of 3107.3 μmol·g −1 ·h −1 . • Bi–Ov sites promote N 2 activation and lower the barrier for *NNH formation. Photocatalytic nitrogen reduction offers a sustainable route to ammonia synthesis under ambient conditions, yet its practical implementation remains limited by inefficient visible-light utilization, rapid charge recombination, and insufficient N 2 activation. Herein, we report an electronically coupled dual-defect catalyst, in which atomically dispersed Bi species are anchored on oxygen-vacancy-rich (BiOBr-Ov) to construct Bi-Ov interfacial active sites for visible-light-driven ammonia production (BiSAC@BiOBr-Ov). Structural and spectroscopic such XRD and XAFS analyses confirm that Bi incorporation preserves the tetragonal BiOBr framework while stabilizing vacancy-associated electrons and reconstructing the local electronic environment. As a result, BiSAC@BiOBr-Ov exhibits enhanced visible-light absorption, a narrowed band gap, suppressed carrier recombination, reduced interfacial charge-transfer resistance, and optimized conduction-band-related energetics. These electronic advantages translate into a markedly improved NH 3 generation rate of 3107.3 μmol⋅g −1 ⋅h −1 , which is 3.8 and 8.1 times higher than those of BiOBr-Ov and pristine BiOBr, respectively, together with an apparent quantum efficiency (AQE) of 1.38% at 420 nm and excellent cycling stability. Isotope-labelling and control experiments verify that gaseous N 2 and water are the nitrogen and proton sources, respectively. In situ FTIR identifies hydrogenated N x H y intermediates during illumination, while DFT calculations reveal lowered work function, increased near-Fermi-level states, strengthened N 2 adsorption, and a reduced barrier for the key *NNH formation step at the Bi-Ov interface. This work demonstrates that coupling single-atom Bi with oxygen vacancies is an effective strategy for promoting interfacial charge transfer and N 2 activation in BiSAC@BiOBr-Ov catalysts for solar ammonia synthesis. Download: Download high-res image (208KB) Download: Download full-size image