Theoretical insights into the mechanism of nitrogen-to-ammonia electroreduction on TM/g-C9N10

The discovery of metals as catalytic centers for nitrogen reduction reactions (NRR) has stimulated great enthusiasm for single-atom catalysts (SACs). However, the poor activity and low selectivity of NRR are far away from the industrial requirement. Herein, density functional theory (DFT) calculations are performed to design the new SACs and explore the electronic property and NRR performance. The single transition metal (TM = Sc to Zn) atom supported on a novel graphitic carbon nitride (g-C9N10), i.e. TM/g-C9N10 SACs are firstly proposed. It is found that most TM atoms can strongly bind with g-C9N10 through a TM-3 N configuration. Six TM/g-C9N10 (TM= V, Cr, Mn, Fe, Ni and Cu) SACs with end-on configurations are initially screened out by a series of property calculation. Finally, Mn/g-C9N10 is supposed to be the most promising candidate for NRR, due to a low overpotential of 0.125 V through the distal pathway and high NRR selectivity. Multiple-level descriptors (ΔG*N2, bond length, CDD, COHP and PDOS) shed light on the origin of NRR activity from the viewpoint of energy and electronic properties. The transition state energy barrier ensures the experimental feasibility in real conditions. Our findings are expected to broaden the understanding of SACs for N2 fixation and contribute to the design of novel substrates with effectively improved performance.