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>Advanced catalytic CO2 hydrogenation on Ni/ZrO2 with light induced oxygen vacancy formation in photothermal conditions at medium-low temperatures
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Advanced catalytic CO2 hydrogenation on Ni/ZrO2 with light induced oxygen vacancy formation in photothermal conditions at medium-low temperatures
Selective CH4 formation from CO2 hydrogenation is an appealing yet challenging sunlight-driven or thermal-driven process due to low solar energy utilization efficiency or high energy input. Herein, we report an enhanced catalytic CO2 hydrogenation in photothermal conditions on Ni/ZrO2 catalysts, which provided higher performance than "dark" thermal catalysis at medium-low temperatures (<= 350 degrees C). With the assistance of sunlight, CO2 conversion and CH4 selectivity were achieved to 82% and 100% at 350 degrees C over 3 wt% Ni/ZrO2 catalyst, which maintained excellent activity and stability for 48 h during the catalyst durability test. The experiment and catalyst characterization results revealed that the illumination stimulated the photothermal effect of Ni and promoted dissociation of H-2, conducive to the formation of oxygen vacancies in ZrO2. The existing oxygen vacancies provided strong alkaline adsorption of O2- species on the CO2 surface and enhanced the interaction between the metal and support, which was beneficial to CO2 activation. The raised Ni doping amount would increase the catalytic active sites and thermal accumulation centers, resulting in the dramatic increase of CO2 conversion at low temperatures (<= 300 degrees C), while reducing along with the elevated temperature due to switched reaction state and deposited carbon on the catalysts. Additionally, density functional theory (DFT) calculations confirmed the experimental observation, showing that the oxygen vacancies on ZrO2 facilitate both CO2 adsorption and hydrogen spillover to further enhance CO2 hydrogenation.
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