Nb2O5-based photocatalysts for CO2 reduction: Advances and prospects

Photocatalytic CO 2 reduction represents a promising strategy for solar-to-fuel conversion, yet its mechanistic validity and visible-light performance remain widely debated. Niobium pentoxide (Nb 2 O 5 ) has emerged as a distinctive oxide platform for CO 2 reduction owing to its delocalized 4d-derived conduction band, tunable Nb 4+ –Vo defect states, and band-edge positions compatible with multi-electron CO 2 reduction and oxidative half-reactions. Unlike previous reviews that primarily focus on material modifications, this work provides a comprehensive outline of Nb 2 O 5 -based photocatalytic systems adopted for CO 2 reduction. The review was introduced by a concise discussion of Nb 2 O 5 core merits as a potent catalyst for CO 2 reduction. Then, the CO 2 reduction process was discussed from thermodynamic, kinetic, and mechanistic perspectives. Afterwards, we critically analyzed how morphology and bandgap engineering, controlled defect engineering, heterojunction formation, and cocatalyst integration can modulate charge-carrier dynamics, CO 2 adsorption, intermediate stabilization, and product selectivity. In addition, a theoretical insight based on density functional theory (DFT) calculations was conveyed to unravel the structure-activity interplay and reaction mechanism of CO 2 conversion over Nb 2 O 5 -based photocatalytic systems. Finally, current limitations and outlooks are provided to motivate future studies on developing Nb 2 O 5 -based photocatalysts with adequate reactivity, selectivity, and stability.