Density Functional Theory Study of Single-Atom V, Nb, and Ta Catalysts on Graphene and Carbon Nitride for Selective Nitrogen Reduction

Electrocatalytic nitrogen fixation using single-atom catalysts (SACs) offers a promising strategy for the sustainable production of NH₃. On the basis of density functional theory, we systematically explored the potential for N₂ electroreduction of single-atom catalysts (SACs) covering V, Nb, and Ta transition metal (TM) centers supported by graphene and g-C₃N₄ substrates. The single Nb-atom embedded on g-C₃N₄ nanosheet possesses outstanding nitrogen reduction reaction (NRR) catalytic activity and exhibits better performance than graphene with a considerably smaller maximum ΔG value (0.05 eV). The single Nb atom on g-C₃N₄ with more negative valence provides structural advantages for hosting empty d-orbitals for strong N₂ and N₂H adsorption, as well as more single d-electrons to further promote back-donation to activate the NN triple bond. This work may be helpful in developing more effective TM-based SACs for N₂ reduction through varying substrate effect toward the same single-atom catalysts.