Increasing the Activity and Selectivity of TiO2-Supported Au Catalysts for Renewable Hydrogen Generation from Ethanol Photoreforming by Engineering Ti3+ Defects

We examine in detail the roles of Ti3+ defects and the associated oxygen vacancies in the activity and selectivity of TiO2-supported Au catalysts (Au@TiO2) for renewable hydrogen production by photoreforming of ethanol. A series of Au@TiO2 catalysts was synthesized using varied exposure to reducing agent NaBH4. The electronic structure of the series of Au@TiO2 catalysts was examined spectroscopically and showed that increased exposure to NaBH4 increased the concentration of Ti3+ defects and the associated oxygen vacancies in TiO2, and increased the amount of electron-rich Au. The activity and selectivity of the catalysts increased as the concentration of defect sites increased. During ethanol photoreforming, the Au@TiO2 catalyst with the highest concentration of defects produced high purity H-2 at a record rate of similar to 7093 mu mol g(cat)(-1) h(-1) and the carbon-carbon bond (C-C) cleavage of ethanol to form CH4 and CO2 was significantly inhibited. Extensive spectroscopic data support the conclusion that TiO2 surface oxygen vacancies adjacent to Au may be active catalytic sites that assist the adsorption and activation of ethanol as well as the delivery of photogenerated charge carriers to the activated species during the photoreforming of ethanol.