Defect engineering is a strategy that has been widely used to design active semiconductor photocatalysts. However, understanding the role of defects, such as oxygen vacancies, in controlling photocatalytic activity remains a challenge. In this talk I will discuss the use of chemically triggered fluorogenic probes to study the spatial distribution of active regions in individual tungsten oxide nanowires using super-resolution fluorescence microscopy. Through quantitative, coordinate-based colocalization of different probe molecules activated by the same nanowires, we demonstrate that the nanoscale regions most active for the photocatalytic generation of hydroxyl radicals also possess a greater concentration of oxygen vacancies. Chemical modifications to remove or block access to surface oxygen vacancies, supported by calculations of binding energies of adsorbates to different surface sites on tungsten oxide, show how these defects control catalytic activity at both the ensemble and single-particle level. These findings reveal that oxygen vacancies activate surface-adsorbed water molecules towards oxidation by using photogenerated holes to produce hydroxyl radicals, a critical intermediate in the photocatalytic oxidation of water, methane, and environmental pollutants.
Bryce Sadtler / University of California, Berkeley
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