Regulating Exciton Dissociation and Spin-Dependent Oxygen Activation via Bi-NiO Dual Active Sites for Deep Photocatalytic NO Oxidation

Abstract Efficient photocatalytic mitigation of nitrogen oxides (NOx) under ambient conditions remains challenging due to limited charge-carrier separation and poor selectivity in regulating reactive oxygen species (ROS), which often results in undesirable NO2 accumulation. In this study, bismuth molybdate (Bi2MoO6) was employed as a model photocatalyst, on which dual active sites composed of plasmonic metallic Bi nanoparticles and ultrasmall spin-polarized NiO were in situ constructed. Plasmonic Bi enhances visible-light absorption and hot-electron generation via localized surface plasmon resonance, while NiO establishes a spin-selective electron-transfer pathway that facilitates efficient O2 activation. This cooperative interface suppresses exciton recombination and promotes a superoxide (·O2–)-dominated oxidation pathway. Consequently, the optimized Bi-NiO@BMO achieves 77.0% NO removal, 76.7% nitrate selectivity, and minimal NO2 accumulation (<11 ppb), representing a 9.7-fold enhancement compared with pristine Bi2MoO6. In practical applications, the PTFE-assisted loading technique allows the material to be fixed onto ceramic foam, achieving an 84% NO removal efficiency and further enhancing photocatalytic performance. Spectroscopic analyses combined with density functional theory (DFT) calculations confirm that the plasmon–spin interaction lowers the free-energy barriers for ·O2– formation and deep NO oxidation. This work provides a mechanistic insight into plasmon-spin-regulated ROS generation and offers a rational design strategy of highly selective photocatalysts for environmental NOx abatement.