Photothermal catalytic CO2 hydrogenation over molybdenum carbides: Crystal structure and photothermocatalytic synergistic effects

Molybdenum carbides possess both platinum-like properties and a certain degree of semi-conductivity and are good candidates as photothermal CO2 hydrogenation catalysts. Herein, the crystal structure and photothermocatalytic synergistic effects on CO2 hydrogenation were explored. The catalysts of β-Mo2C, α-MoC, and their mixed phases were prepared by adjusting the carburization circumstances of the precursor, and their structural, surface, photothermal conversion and activity for CO2 hydrogenation under thermal and photothermal conditions were systematically investigated. It is found that the generated carbon vacancies of the α-MoC phase promote the adsorption of CO2, whereas H2 adsorption is facilitated over β-Mo2C. Consequently, α-MoC and β-Mo2C mixed phases are more favorable for CO2 hydrogenation at 130 °C. As compared to thermocatalysis, the activity of photothermal catalytic CO2 hydrogenation increases by at least 45 % on the same catalysts, due to the light-promoted surface intermediate (formate species) dissociation. The present work supplies a new insight into photothermocatalytic synergistic effect.