Advantageous Role of Ir Supported on TiO Nanosheets in Photocatalytic CO Reduction to CH: Fast Electron Transfer and Rich Surface Hydroxyl Groups.

Ir-based heterogeneous catalysts for photocatalytic CO reduction have rarely been reported and are worthy of investigation. In this work, TiO nanosheets with a higher specific surface area and more oxygen vacancies were employed to support Ir metal by impregnation (Imp) and ethylene glycol (EG) reduction methods. In comparison with Ir/TiO (Imp) and TiO, Ir/TiO (EG) exhibited excellent photocatalytic performance toward CO reduction, especially for CH production on account of the oxygen defect of TiO and rich surface hydroxyl groups produced from the interaction between TiO nanosheets and metallic Ir. ESR suggested that the oxygen defect was significant for CO adsorption/activation. Furthermore, metallic Ir was beneficial for photogenerated electron transfer, surface hydroxyl generation, and adsorption of the CO intermediate, generating more available electrons and reducing agents for CH production. CO DRIFTS confirmed the key synergistic interaction between the oxygen defect and metallic Ir in the photoreduction from CO to CH.