Insight into the synergistic effect between plasma and oxygen vacancy in direct oxidation of CH4 to CH3OH by molecular O2 at mild condition

The direct conversion of methane into the value-added chemical methanol using molecular oxygen was investigated via plasma catalysis under mild condition. An efficient synergistic effect between plasma and catalyst was achieved using an oxygen vacancy-rich ZnO/Al 2 O 3 catalyst. A high methanol selectivity of 48.5 % and a high synergy factor of 2.1 could be achieved simultaneously over ZnO/Al 2 O 3 R300 catalyst. The presence of oxygen vacancies played a crucial role in methanol formation. A close relationship between oxygen vacancy content and methanol selectivity was established. In situ DRIFT and optical emission spectra were employed to identify key intermediates, and a plausible reaction mechanism was proposed. The CH 3 and CH 3 O species were the key intermediates on the catalyst surface. The oxygen vacancy could efficiently adsorb the O radicals and accelerate the formation of CH 3 O species. This work offers insights into the rational engineering of efficient catalyst for plasma catalysis process.