Enhanced CO2 Hydrogenation to Methanol via Plasma-Treated Ni/Ga2O3 Catalysts

In this work, Ni/Ga2O3 catalysts were prepared via the cold plasma method. The Ni/Ga2O3 composite treated with plasma exhibited superior performance, achieving a CO2 conversion of 13.8% and a methanol selectivity of 56% at 300°C and 5 MPa. These values were notably greater than those obtained with catalysts prepared through calcination or chemical reduction. Compared with the calcination method, cold plasma treatment results in smaller particle sizes (4.12 nm) because of the low temperature of the plasma, which increases the number of active sites. Additionally, high-energy electron bombardment within the plasma field strengthens the interaction between Ni and the Ga2O3 support. This enhanced metal‒support interaction, which is stronger than that achieved via calcination or chemical reduction, plays a critical role in improving the catalytic activity for the CO2 hydrogenation reaction. The intricate mechanism of CO2 hydrogenation on the Ni/Ga2O3-plasma-H2 catalyst was elucidated via a combination of advanced characterization techniques and in situ DRIFTS analysis. Hydrogen dissociates on Ni nanoparticles and subsequently spills over onto the Ga2O3 support, whereas oxygen vacancies promote CO2 adsorption, resulting in the formation of bidentate carbonate species as key intermediates. These intermediates are then hydrogenated to produce methanol.