Efficient CH₃OH formation on H₂/Ar plasma-treated CoO sites for CO₂ + H₂ + H₂O DBD system

Packing heterogeneous catalysts to achieve a better plasma-catalyst synergy is critical to promoting CO2 conversion into high-value chemicals. Herein, a series of CoO-based catalysts were synthesized, and the treated H-2/Ar-CoO possessed the highest CH3OH selectivity (39.6%) in the CO2 + H-2 + H2O system, about four times higher than the initial CoO (10.0%). Systemic characterizations showed that H-2/Ar plasma treatment significantly increased the oxygen vacancy (O-v) concentration of H-2/Ar-CoO by Ar+ bombardment and synchronous H reduction. Considering the key role of CH3O on CH3OH generation upon kinetic simulations, we proposed that the O-v in H-2/Ar-CoO could accelerate the CH3O/OH adsorption and further recombine with H/CH3, in which the H2O provided abundant OH/H radicals via electron-impact process. This study highlighted the importance of using H2O with O-v-rich catalysts for plasma-enabled CH3OH synthesis.