Even in ultralow quantities, oxygen vacancies (V O ) drastically impact key properties of metal oxide semiconductors, such as charge transport, surface adsorption, and reactivity, playing central roles in functional materials performance. Current methods used to investigate V O often rely on specialized instrumentation under far from ideal reaction conditions. Hence, the influence of V O generated in situ during catalytic processes has yet to be probed. In this work, we assess in situ extrinsic surface V O formation and lifetime under photocatalytic conditions which we compare to photocatalytic performance. We show for the first time that lifetimes of in situ generated atomic V O play more significant roles in catalysis than their concentration, with strong correlations between longer-lived V O and higher photocatalytic activity. Our results indicate that enhanced photocatalytic efficiency correlates with goldilocks V O concentrations, where V O densities must be just right to encourage carrier transport while avoiding charge carrier trapping.

We show the impact of structural, chemical and interfacial features of gold–titania composites on solar and visible photocatalytic gas phase reduction of CO2 and the specificities of the hot electron-based process.