Mechanistic insights and descriptor-guided design of nanodiamond-supported transition metal single-atom catalysts for electrocatalytic nitrogen reduction reaction

Nanodiamond, with its large specific surface area and abundant surface defects, serves as an ideal support for transition metal single-atom catalysts (TM-SACs) in the electrocatalytic nitrogen reduction reaction (eNRR). Herein, we constructed a series of nanodiamond-supported TM-SACs (TM@NDs, TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Pt) and systematically investigated their eNRR performance and mechanisms using density functional theory. Reaction free energy analyses show that Sc-s, Cr-s, Fe-s, and Co-s outperform the Ru (0001) benchmark, while V-s, V-d, and Mn-d exhibit comparable activity. Furthermore, reactive lobes and spin-modulated band centers are identified as key descriptors linking the electronic structure to catalytic activity. The eNRR performance correlates strongly with the electron localization function intensity of the reactive lobes and the spin-modulated localized d-band center for the spin-up channel. These findings provide new insights into the design and mechanistic understanding of diamond-based SACs for efficient eNRR.