CO 2 capture via oxalate formation in metal-decorated graphene Inioluwa C. Afolabi 1 , Yasmine Alham-dani 2 , Ben Shi 1 , Andrea Zen 3 , Angelos Michealides 1 1 Yusuf Hamied Department of Chemistry, University of Cambridge, UK, 2 Department of Earth Sciences, University College London, UK; 3 Dipartimento di Fisica Ettore Pancini, Università di Napoli Federico II, Italy Carbon capture, utilization and storage (CCUS) is an active research area today because of its importance in mitigating the effects of climate change. For CCUS to thrive, there is a need for high-performing materials that could capture CO 2 sustainably and preferably convert it to a useful chemical feedstock. Graphene as a carbon material possesses excellent properties such as high surface area making it suitable for gas storage applications. However, it has been reported to bind CO 2 too weakly for viable capture [1,2]. Metal decoration has been predicted to strengthen the adsorption energy, but it is unclear if it could foster the conversion of CO 2 to a useful chemical intermediate in graphene-based materials [3]. This work harnessed density functional theory with random structure search to understand the adsorption of CO 2 on metal-decorated graphene. The adsorption of 1-7 CO 2 on 5 metal-decorated graphene systems (Na, K, Ca, Sr and Ti) is considered. Generally, the adsorption strength of the metal atoms for CO 2 increases in the order Ti > Ca > Sr > Na > K and the increased strength seen in Ti, Ca and Sr is due to the formation of oxalate(s). Analysis of the electronic structure in the systems considered reveals that the governing adsorption mechanism involves an ionic charge transfer from the metal adatom to the CO 2 molecules, resulting in bent reactive CO 2 anion, which dimerises to form an oxalate upon the adsorption of 2 CO 2 molecules. It is also found that the maximum number of CO 2 that can be chemisorbed in Ca, Sr and Ti relates to the valence charge on the metal atom; with Ca and Sr having the maximum capacity for 2 CO 2 and Ti, 4 CO 2 in the form of oxalate(s). The oxalate(s) formed in these materials give new insight into their capacity for CO 2 sequestration and their viability for CCUS applications. References 1. Chu, S., & Majumdar, A. (2012). Opportunities and challenges for a sustainable energy future.nature,488(7411), 294-303.C. Wang, Y. Fang, H. Duan, G. Liang, W. Li, D. Chen, and M. Long, “Dft study of co2 adsorption properties on pristine, vacancy and doped graphenes,” Solid State 2. Communications, vol. 337, 10 2021.Y. Lu, Y. Xu, J. Zhang, Q. Zhang, L. Li, and J. Tian, “Adsorption of carbon dioxide gas by modified graphene: A theoretical study,” ChemistrySelect, vol. 7, 2 2022.
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