Oxygen Vacancy Induced Atom-Level Interface in Z-Scheme SnO₂/SnNb₂O₆ Heterojunctions for Robust Solar-Driven CO₂ Conversion

The modulation of Z-scheme charge transfer is essential for efficient heterostructure toward photocatalytic CO 2 reduction. However, constructing a compact hetero-interface favoring the Z-scheme charge transfer remains a great challenge. In this work, an interfacial Nb–O–Sn bond and built-in electric field-modulated Z-scheme O v -SnO 2 /SnNb 2 O 6 heterojunction was prepared for efficient photocatalytic CO 2 conversion. Systematic investigations reveal that an atomic-level interface is constructed in the O v -SnO 2 /SnNb 2 O 6 heterojunction. Under simulated sunlight irradiation, the obtained O v -SnO 2 /SnNb 2 O 6 photocatalyst exhibits a high CO evolution rate of 147.4 μmol h –1 g –1 from CO 2 reduction, which is around 3-fold and 3.3-fold of SnO 2 /SnNb 2 O 6 composite and pristine SnNb 2 O 6, respectively, and favorable cyclability by retaining 95.8% rate retention after five consecutive tests. As determined by electron paramagnetic resonance spectra, in situ Fourier transform infrared spectra, and density functional theory calculations, Nb–O–Sn bonds and built-in electric field induced by the addition of oxygen vacancies jointly accelerate the Z-scheme charge transfer for enhanced photocatalytic performance. This work provides a promising route for consciously modulating Z-scheme charge transfer by atomic-level interface engineering to boost photocatalytic performance.