Unveiling Active Sites of CO2 Reduction on Nitrogen-Coordinated and Atomically Dispersed Iron and Cobalt Catalysts
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© 2018 American Chemical Society. Herein, we report the exploration of understanding the reactivity and structure of atomically dispersed M-N4 (M = Fe and Co) sites for the CO2 reduction reaction (CO2RR). Nitrogen coordinated Fe or Co site atomically dispersed into carbons (M-N-C) containing bulk- and edge-hosted M-N4 coordination were prepared by using Fe- or Co-doped metal-organic framework precursors, respectively, which were further studied as ideal model catalysts. Fe is intrinsically more active than Co in M-N4 for the reduction of CO2 to CO, in terms of a larger current density and a higher CO Faradaic efficiency (FE) (93% vs. 45%). First principle computations elucidated that the edge-hosted M-N2+2-C8 moieties bridging two adjacent armchair-like graphitic layers is the active sites for the CO2RR. They are much more active than previously proposed bulk-hosted M-N4-C10 moieties embedded compactly in a graphitic layer. During the CO2RR, when the dissociation of∗COOH occurs on the M-N2+2-C8, the metal atom is the site for the adsorption of∗CO and the carbon atom with a dangling bond next to an adjacent N is the other active center to bond∗OH. In particular, on the Fe-N2+2-C8 sites, the CO2RR is more favorable over the hydrogen evolution reaction, thus resulting in a remarkable FE.
author list (cited authors)
Pan, F., Zhang, H., Liu, K., Cullen, D., More, K., Wang, M., ... Li, Y
complete list of authors
Pan, Fuping||Zhang, Hanguang||Liu, Kexi||Cullen, David||More, Karren||Wang, Maoyu||Feng, Zhenxing||Wang, Guofeng||Wu, Gang||Li, Ying