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Plasma-catalytic CO 2 hydrogenation for methanol production is gaining increasing interest, but our understanding of its reaction mechanism remains primitive. We present a combined experimental/computational study on plasma-catalytic CO 2 hydrogenation to CH 3 OH over a size-selected Cu/γ-Al 2 O 3 catalyst. Our experiments demonstrate a synergistic effect between the Cu/γ-Al 2 O 3 catalyst and the CO 2 /H 2 plasma, achieving a CO 2 conversion of 10% at 4 wt % Cu loading and a CH 3 OH selectivity near 50%, further rising to 65% with H 2 O addition (for a H 2 O/CO 2 ratio of 1). Furthermore, the energy consumption for CH 3 OH production was more than 20 times lower than with plasma only. We carried out density functional theory calculations over a Cu 13 /γ-Al 2 O 3 model, which reveal that the interfacial sites of the Cu 13 cluster and γ-Al 2 O 3 support show a bifunctional effect: they do not only activate the CO 2 molecules but also strongly adsorb key intermediates to promote their hydrogenation further. Reactive plasma species can regulate the catalyst surface reactions via the Eley−Rideal (E−R) mechanism, which accelerates the hydrogenation process and promotes the generation of the key intermediates. H 2 O can promote the CH 3 OH desorption by competitive adsorption over the Cu 13 /γ-Al 2 O 3 surface. This study provides new insights into CO 2 hydrogenation through plasma catalysis, and it provides inspiration for the conversion of some other small molecules (CH 4 , N 2 , CO, etc.) by plasma catalysis using supported-metal clusters.

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