PdCu alloy anchored defective titania for photocatalytic conversion of carbon dioxide into methane with 100% selectivity

The photoreduction of CO2 into CH4 with simultaneous high activity and selectivity is a promising strategy to increase energy supply and alleviate global warming. However, the absence of the active sites that is responsible for the adsorption and activation of CO2 and the generation of CO and H2 via side reactions often lead to poor efficiency and low selectivity of the catalyst. Herein, Cu, Pd, and PdCu metal clusters cocatalyst-anchored defective TiO2 nanotubes (Cu/TiO2-SBO, Pd/TiO2-SBO, and Pd1Cu1/TiO2-SBO) were designed via a simple solution impregnation reduction and applied for photocatalytic conversion of CO2 to CH4. The Pd1Cu1/TiO2-SBO photocatalyst exhibits excellent catalytic performance among the other catalysts for photoreduction of CO2 into CH4. More interestingly, the product selectivity of CH4 reaches up to 100% with a rate of 25 µmol g−1 h−1. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) simulations indicate that the main reasons for the high selectivity of CH4 are attributed to the PdCu alloy and oxygen vacancies, which jointly enhance the photoinduced carrier separation and lower energy barriers of key intermediates. Moreover, due to the tunable d-band center of the Cu site in the PdCu alloy, the generated intermediates can be well prevented from poisoning and promoted to participate in further reactions. Hopefully, the current study will provide insight into the development of new, highly selective photocatalysts for the visible light-catalytic reduction of CO2 into CH4.