“Vacancy-Driven CO ₂ -To-Methanol”─Interface Synergy Effects of Cu–Fe/HZSM-5 Catalysts under Nonthermal Plasma

To enhance the conversion efficiency and product selectivity in CO2 hydrogenation to methanol, we prepared a series of Cu–Fe bimetallic catalysts with varied Cu/Fe ratios supported on HZSM-5 by an initial impregnation method and evaluated them in a dielectric barrier discharge (DBD) nonthermal plasma reactor. Among these, the Cu7Fe3/HZSM-5 catalyst achieved a CO2 conversion of 12.1% and a methanol selectivity of 9.6% in plasma-assisted CO2 hydrogenation, with activity decay below 3% over 400 min of continuous operation. The catalyst structure and surface properties were systematically investigated by SEM, XRD, BET, XPS, H2-TPR, CO2-TPD and CO-TPD. Catalytic performance was assessed under optimized plasma reaction conditions (CO2/H2 = 1:3, total flow 70 mL·min–1, discharge power 20 W, circulating water temperature 30 °C). Furthermore, in situ DRIFTS indicated an oxygen vacancy-dominated formate pathway: oxygen vacancies in FeOx strengthened CO2 chemisorption and induced polarization of the C═O bond; Cu+ sites facilitated sequential hydrogenation of formate intermediates (HCOO*); and the Cu0-HZSM-5 interface optimized H* spillover, collectively suppressing CH4 formation. These results underscore that vacancy engineering and metal–zeolite interfacial effects are pivotal in steering plasma-catalytic CO2-to-methanol selectivity.