“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 CO 2 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 Cu 7 Fe 3 /HZSM-5 catalyst achieved a CO 2 conversion of 12.1% and a methanol selectivity of 9.6% in plasma-assisted CO 2 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, H 2 -TPR, CO 2 -TPD and CO-TPD. Catalytic performance was assessed under optimized plasma reaction conditions (CO 2 /H 2 = 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 FeO x strengthened CO 2 chemisorption and induced polarization of the C═O bond; Cu + sites facilitated sequential hydrogenation of formate intermediates (HCOO*); and the Cu 0 -HZSM-5 interface optimized H* spillover, collectively suppressing CH 4 formation. These results underscore that vacancy engineering and metal–zeolite interfacial effects are pivotal in steering plasma-catalytic CO 2 -to-methanol selectivity.