Photoreduction of CO2 using black TiO2 films under solar light

• The porous black TiO2 is in-situ obtained by a simple hydrothermal method.
• The catalyst shows high CO2 methanation efficiency of 12 μmol/g h under solar light.
• The existence of substantial Ti3+ and oxygen vacancies improve the catalytic activity.

Black TiO2 films with unique porous structures have been successfully obtained in-situ on Ti plates by a simple hydrothermal treatment using H2O2 solution. The samples were used as photocatalysts to reduce CO2 under simulated sunlight irradiation at room temperature in the presence of H2O. The films have excellent grid-like structures providing more active photocatalysis sites and exhibit extremely high CO2 photoreduction efficiency with favourable selective formation of CO and CH4 (with highest production rates of 115 and 12 μmol/g h, respectively) compared to conventional TiO2 (Degussa P25) (0.28 and 0.019 μmol/g h, respectively). The structural deviation from standard crystalline anatase with the existence of substantial Ti3+ and oxygen vacancies is the critical factor for expanding the absorbance of TiO2 into the visible light region and the resulting excellent photocatalytic performance under simulated sunlight irradiation.

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