Hexagonal MBenes-Supported Single Atom as Electrocatalysts for the Nitrogen Reduction Reaction

The electrocatalytic nitrogen reduction reaction (NRR) is currently constrained by sluggish reaction kinetics and poor selectivity because of the difficulties in activating inert N=N triple bonds and the existence of competing hydrogen evolution reaction (HER). Therefore, electrocatalysts with high activity, selectivity, and stability are highly desired. Herein, by means of first-principles calculations, we investigated the electrocatalytic NRR performance of a series of transition metal atoms (e.g., 3d, 4d, and 5d) embedded in defective hexagonal MBene nanosheets [h-Zr(Hf)(2)B2O2] and identified that h-Zr(Hf)(2)B2O2 could be an excellent platform for electrocatalytic NRR. On the basis of our proposed screening criteria, 16 candidates are efficiently selected out from 50 systems, among which, Zr2B2O2-Cr stands out with high selectivity to NRR against HER and the ultralow limiting potential (-0.10 V). The value is much lower than that of the well-established stepped Ru(0001) surface (-0.43 V). The origin of the high activity toward NRR is attributed to the synergistic effect of the single atom (SA) and the M atoms in the substrate. More impressively, a composition descriptor is further proposed on the basis of the inherent characteristics of the catalysts [number of valence electrons of SA and electronegativity of the SA and Zr(Hf) atoms], which helps to better predict the catalytic performance. Our work not only contributes to the development of highly efficient NRR electrocatalysts but also extend the application of h-MBenes in electrocatalysis.