Synergistic Enhancement of Photocatalytic Nitrate Reduction Over Fe-Doped Bi/Bi2WO6 via Lewis Acidic Sites and Surface Plasmon Resonance

Photocatalytic reduction of nitrate (NO 3 − ) to ammonia (NH 3 ) has garnered growing attention as a sustainable route for simultaneous nitrate pollution remediation and value-added ammonia synthesis under ambient conditions. However, its efficiency remains severely limited by the intrinsically high structural stability of nitrate anions and inefficient charge-carrier utilization. In this study, a Fe-doped Bi/Bi 2 WO 6 photocatalyst (H-Fe-B/BWO) is constructed via a facile hydrothermal method followed by calcination in a reducing atmosphere. The experimental results reveal that the optimized H-Fe-B/BWO exhibits significantly enhanced photocatalytic nitrate reduction performance, achieving an NH 3 production rate of 2.419 mmol g cat −1 h −1 with a high selectivity of 99.3% in the presence of ethylene glycol (EG), representing an approximately 4.5-fold improvement compared with pristine Bi 2 WO 6 . The remarkable enhancement originates from the synergistic effect between Lewis acidic sites generated by Fe dopants with unsaturated coordination environments and the surface plasmon resonance of metallic Bi, which collectively facilitates nitrate activation and improves charge-carrier separation and utilization. This work provides a rational strategy for designing efficient photocatalysts for selective NO 3 − -to-NH 3 conversion under environmentally benign conditions, contributing to sustainable nitrogen management and circular economy-driven resource recovery. Graphical The enhanced photocatalytic nitrate-to-ammonia conversion over H-Fe-B/BWO can be summarized as a cooperative process involving surface reaction chemistry and charge-carrier dynamics. Fe dopants introduced into the Bi 2 WO 6 lattice generate coordinatively unsaturated metal centers, which function as Lewis acidic sites capable of strongly interacting with nitrate anions through O-metal coordination. This interaction promotes nitrate adsorption and induces structural distortion of the NO 3 − species, thereby lowering the activation barrier for the initial N─O bond cleavage. Simultaneously, reductive calcination leads to the in situ formation of metallic Bi on the catalyst surface, which serves as a plasmonic component under visible light irradiation. The surface plasmon resonance of metallic Bi not only broadens the light-harvesting capability but also enhances local electromagnetic fields, facilitating the separation and migration of photogenerated charge carriers. As a result, photogenerated electrons are more efficiently delivered to nitrate species adsorbed at Lewis acidic sites, enabling a sustained multi-electron reduction pathway toward ammonia while suppressing competing reactions. The intimate coupling between nitrate activation at Fe-derived Lewis acidic sites and plasmon-induced charge utilization accounts for the high activity and selectivity observed over the H-Fe-B/BWO photocatalyst.