Direct dioxygen evolution in collisions of carbon dioxide with surfaces
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.
Additional Information© 2019 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received 09 December 2018; Accepted 29 April 2019; Published 24 May 2019. Data availability: All relevant raw data, experimental and computational, are available from the authors upon request. Code availability: The computational code is available from the authors upon request. This report was based on work funded by NSF (Award no. 1202567) and by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy (Award no. DE-SC0004993). P.S. is grateful for a postdoctoral fellowship funded by the Deutsche Forschungsgemeinschaft. Author Contributions: Y.Y. and K.P.G. designed the experiments. P.S. and T.F.M. designed the simulations. Y.Y. conducted experimental measurements, while P.S. performed the computations. All authors participated in analyzing the results and writing the paper. The authors declare no competing interests.
ErrataThe original version of this Article contained errors in Fig. 1. The titles at the top of each panel a, b, c were incorrectly given as 'CO2+/Au → CO2+ A', 'CO2+/Au → CO2+ B' and 'CO2+/Au → O2– C' instead of the correct panel a, b, c 'CO2+/Au → CO2+', 'CO2+/Au → O2+' and 'CO2+/Au → O2–', respectively. This has been corrected in the PDF and HTML versions of the Article.
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