Transformation pathway and toxic intermediates inhibition of photocatalytic NO removal on designed Bi metal@defective Bi₂O₂SiO₃

The design of highly efficient visible-light photocatalysts and the elucidation of decomposition mechanisms are the two key tasks in environmental remediation. Herein, we utilized theoretical calculations to design a Bi metal–based visible-light photocatalyst (Bi@BiOSi) with surface plasmon resonance (SPR) properties, showing that the unique electron delivery channel was formed at the Bi metal/Bi₂O₂SiO₃ interface. The Bi@BiOSi nanosheets were used for photocatalytic removal of ppb-level atmospheric NO, with Bi metal–based SPR resulting in enhanced visible light capture and charge separation efficiency, whereas oxygen vacancy induced the formation of a midgap level and promoted O₂ activation. As a result, generation of superoxide and hydroxyl radicals over Bi@BiOSi was promoted, favoring photocatalytic NO removal. To elucidate the reaction mechanism, the products distribution during adsorption and photocatalytic NO oxidation on Bi@BiOSi were determined by in situ DRIFTS, which revealed that the increased production of reactive species inhibited the toxic intermediates (N₂O₄) formation and increased the selectivity of the NO-to-NO₃– transformation via the synergy of oxygen vacancy and Bi metal. Thus, this work provides new insights into the design of non-noble metal-based photocatalysts and establishes a novel method of inhibiting the toxic intermediates production in photocatalysis for efficient and safe air purification.