Fe/Nx clusters embedded in graphene with tunable properties for gas separation

Abstract Increasing concerns about capture and separation of CO2 and its impact on the global warming are motivating researchers to discover new materials and strategies for efficient CO2 capture. Here, we explored the possibility of conductive Fe/Nx clusters embedded in graphene (Fe/Nx/G) as an adsorbent for electrocatalytically switchable CO2 capture. Using density functional theory including long-range dispersion corrections, we investigated the adsorption process of CO2 on Fe/Nx/G (x = 0, 2, and 4) systems with various charge states. We found that CO2 molecule - forms weak interaction with the neutral Fe/Nx/G systems. On the contrary, the adsorption behavior of CO2 molecule on the Fe/Nx/G systems can be significantly enhanced by adding extra charges into the Fe/Nx/G. Our results show that by removing the charges, CO2 molecule automatically desorbs from Fe/N4/G. Thus, by switching on/off the charges carried by Fe/Nx/G systems the CO2 capture/release procedures can be easily controlled without any energy barrier. Moreover, these Fe/Nx/G systems are highly selective for separating CO2 from its mixtures with methane, hydrogen, and nitrogen. These predictions open the route for the further studies of charge-modulated systems with switchable capture/release capabilities that present high selectivity for CO2.