Single-Atom catalysts supported by nanographene networks for efficient CO2 electroreduction: A first-principles study

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Single-atom materials based on novel 2D nanographene networks and 3d transition metal atoms are constructed. Their structural and thermal stabilities in addition to the catalytic performance toward CO2 reduction are investigated using DFT calculations. Single metal atoms namely, Sc, Ti... Zn are strongly held by the pore C-atoms with high binding energy. Moreover, the dynamical and thermal stabilities are proved by the real vibrational frequencies and the molecular dynamics simulations at 500 K. Comparing the free energy of hydrogen evolution with that of the determinant intermediate in CO2 reduction shows that all the 3d metals, except Cu and Mn, are selective to CO2 reduction. Although the 3d single atom catalysts require a high potential for the overall CO2 conversion to CH3OH or CH4, they show exceptional catalytic performance toward CO2 to CO conversion. The calculated overpotential for CO-production using Sc and Ti is extremely low at 0.13 V making them competitive with the expensive Pt-catalysts. The overall CO2 reduction can be enhanced by considering 4d metals; for instance, an Au-based catalyst significantly reduces the overall energy required for CO2 conversion to CH3OH. Therefore, the constructed single-atom materials with high stability and promising catalytic activity are potential candidates for CO2 electrolysis.