Two-Dimensional Transition Metal Porphyrin Sheets as a Promising Single-Atom-Catalyst for Dinitrogen Electrochemical Reduction to Ammonia: A Theoretical Study

Artificial ammonia (NH3) synthesis from molecular nitrogen (N-2) in aqueous solutions under mild conditions is one of the most attractive and challenging processes in chemistry. In this work, by means of density functional theory (DFT) computations, transition metal (TM) atoms were anchored to porphyrin (Pp) sheets as N-2 capture (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru) and reduction catalysts and their catalytic activities were systematically investigated. Among them, the 2D Mo-Pp sheet exhibits the best catalytic performance for N-2 capture and reduction to NH3. Importantly, the 2D Mo-Pp sheet shows a high thermal stability up to 500 K and thus holds great promise for experimental synthesis. N-2 can be effectively reduced via the distal reaction pathway with a negative N-2 adsorption free energy and an energy barrier of 0.58 eV, indicating its good catalytic performance for N-2 reduction. We believe our work could provide a novel catalyst for electrochemical reduction of N-2 to NH3 at mild conditions.