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.