Atomic-mismatch-induced interstitial Bi doping in Nb₂O₅ networks: A synergistic electronic-structural strategy for ultrafast charge trapping and efficient photocatalysis

Niobium pentoxide (Nb₂O₅) is a promising photocatalyst due to its excellent chemical stability, non-toxicity, and suitable band positions. However, its wide bandgap and rapid charge recombination severely limit its solar-light utilization and photocatalytic efficiency. To overcome these limitations, we report an atomic-mismatch-driven interstitial bismuth doping strategy that synergistically constructs three-dimensionally interconnected Nb₂O₅ networks with an overall thickness of only 0.54 nm. This unique design not only tailors the electronic structure by introducing shallow-level defects and narrowing the bandgap but also optimizes the material's morphology for enhanced surface reactivity and charge transport. The optimized material (BiNO-2) exhibits exceptional photocatalytic activity, degrading 99.1% of the model pollutant new coccine within 15 min under simulated solar light, a rate 11 times higher than that of pristine Nb₂O₅ and surpassing commercial P25. The catalyst also demonstrates excellent versatility by efficiently degrading diverse pollutants including cationic dyes and pharmaceuticals. Mechanistic studies reveal that the degradation proceeds via hole- and hydroxyl-radical-mediated pathways, leading to cleavage of the toxic azo-aromatic core and a significant reduction in the ecological toxicity of the products. This work presents a generalized electronic-structural co-engineering strategy driven by atomic-mismatch principles, offering an environmentally safe and kinetically superior photocatalyst for sustainable water remediation.