Molecular Dipole-Driven Polarization-Related Interfacial Regulation of BiOI for Photocatalytic Nitrate-to-Ammonia Conversion

Abstract Photocatalytic nitrate reduction to ammonia (PcNRA) offers a sustainable route for nitrate remediation and green NH3 synthesis under mild conditions. BiOI has attracted attention due to its narrow band gap, strong visible-light absorption, layered structure, and suitable electronic structure for reduction reactions. However, rapid charge recombination limits its photocatalytic performance. Herein, a molecular dipole-induced interfacial regulation strategy was developed to construct an organic–inorganic hybrid photocatalyst (TP/BiOI) with polarization-related interfacial characteristics. The iron tetraphenylporphyrin (FeTPP) modified TP/BiOI interface promoted interfacial charge redistribution and directional carrier migration and optimized the surface potential to promote NO3– enrichment. In addition, FeTPP modified the interfacial wettability and enhanced the irradiation-induced thermal response of TP/BiOI, which may provide an additional favorable local microenvironment for interfacial reactions. These effects, together with improved charge utilization, contribute to enhanced *H-mediated nitrate hydrogenation. As a result, TP/BiOI achieved an NH3 production rate of 5718.9 μmol·g–1·h–1, 73.8% higher than that of pristine BiOI (3290.4 μmol·g–1·h–1), outperforming most reported state-of-the-art catalysts. This work demonstrates that molecular dipole-induced interfacial polarization can effectively regulate charge distribution and the interfacial microenvironment, providing a new strategy for designing efficient organic–inorganic hybrid photocatalysts for solar-driven nitrate-to-ammonia conversion.