Direct dioxygen evolution in collisions of carbon dioxide with surfaces

Abstract

The intramolecular conversion of CO_2 to molecular oxygen is an exotic reaction, rarely observed even with extreme optical or electronic excitation means. Here we show that this reaction occurs readily when CO_2 ions scatter from solid surfaces in a two-step sequential collision process at hyperthermal incidence energies. The produced O_2 is preferentially ionized by charge transfer from the surface over the predominant atomic oxygen product, leading to direct detection of both O_2+ and O_2−. First-principles simulations of the collisional dynamics reveal that O_2 production proceeds via strongly-bent CO_2 configurations, without visiting other intermediates. Bent CO_2 provides dynamic access to the symmetric dissociation of CO_2 to C+O_2 with a calculated yield of 1 to 2% depending on molecular orientation. This unexpected collision-induced transformation of individual CO_2 molecules provides an accessible pathway for generating O_2 in astrophysical environments and may inspire plasma-driven electro- and photo-catalytic strategies for terrestrial CO_2 reduction.