Amine-Mediated In Situ Oxygen Vacancy Generation in SnO₂ Nanocrystals for Selective CO₂ Photoreduction

Photocatalytic CO₂ reduction over tin dioxide (SnO₂) is promising for solar-to-chemical conversion, yet its efficiency is hindered by rapid charge recombination and sluggish surface reaction kinetics. Here, we develop an amine-mediated in situ oxygen-vacancy generation strategy, in which amine-functionalized carbon nanotubes regulate SnO₂ crystallization to construct oxygen-vacancy-rich SnO₂ nanocrystals with strongly coupled SnO₂/CNT interfaces. The interfacial amine groups coordinate with Sn precursors during growth, promoting oxygen vacancy formation while enhancing interfacial coupling and CO₂ adsorption through Lewis acid-base interactions. The generated oxygen vacancies modulate the local electronic structure, facilitate interfacial charge transfer, and regulate surface reaction pathways. The optimized OV-SnO₂@NCNT catalyst achieves a CO yield of 174.8 µmol g^-1, approximately 4.0 times higher than that of SnO₂@OCNT, with a high CO selectivity of 82.9%. Spectroscopic and electrochemical analyses reveal enhanced charge separation and carrier utilization efficiency enabled by the oxygen-vacancy-rich SnO₂/CNT interface. Combined in situ FT-IR measurements and density functional theory calculations demonstrate that oxygen vacancies promote CO₂ activation, stabilize key CO₂-derived intermediates, and facilitate selective CO generation by regulating intermediate adsorption behavior. This work provides an interface-directed defect-engineering strategy for controllable oxygen vacancy construction and rational regulation of reaction pathways toward selective solar-driven CO₂ conversion.