Targeted NO oxidation with synchronized NO2 suppression via dynamic Bi0/Biδ+@defective sites on Bi4Ti3O12 microspheres

Solar-driven photocatalysis offers a sustainable pathway for the deep oxidation of NO to harmless nitrate (NO3-), yet achieving both high efficiency and strict selectivity of products simultaneously remains a critical challenge. Herein, we report the rational design of Bi4Ti3O12 photocatalysts enriched with dynamic Bi0/Bi+@defective sites, which precisely regulate carrier dynamics and reaction pathways during photocatalytic NO oxidation. Time-dependent operando Raman spectroscopy and density functional theory (DFT) calculations unravel the dynamic evolution mechanism of Bi0/Bi+@defective sites. The frontier Pz orbital of Bi0 donates electrons to NO, generating the Bi+@defective coordination and the key intermediate NO that avoids NO2 formation. Subsequently, photoexcited electrons from Bi4Ti3O12 catalyst endow the unoccupied Pz orbital of Bi+ and the antibonding orbital of H2O, regenerating Bi0@defective coordination and forming ·OH radicals, thereby accelerating the overall reaction rate. As a result, Bi4Ti3O12 microspheres enriched with dynamic Bi0/Bi+@defective sites exhibit an outstanding efficiency of NO conversion (55.6%), accompanied by an exceptionally low NO2 selectivity (0.057%). More importantly, in situ FTIR and DFT calculations further confirm that dynamic Bi0/Bi@defective sites facilitate the spontaneous activation of H2O, enabling the direct conversion of NO to NO3 via a NO-mediated pathway. This work provides fundamental insights into the design of photocatalysts with dynamic active sites for environmental purification.