N2 electrochemical reduction on two dimensional transition metal monoborides: A density functional theory study

Electrochemical reduction of N-2 at ambient conditions is emerging as a promising route and can be powered by sustainable energies. Large overpotential and the competing hydrogen evolution reaction (HER) are the two major issues associated with the N-2 reduction. Thus, the development of efficient electrocatalysts with low overpotential is of utmost significance for electrochemical nitrogen reduction reaction (NRR). In this theoretical study, we report a valuable insight toward a novel two dimensional (2D) transition metal monoboride (TMB) material possessing efficient electrocatalysts application for NRR, investigated by density functional theory method. Through systematically exploring the Gibbs free energy of N-2 adsorption on the different TMB (TM = Cr, Mn, Fe, Co, Ni and Mo) nanosheets and analyzing adsorption energy of N2H and NH2 species on these catalysts, we found MoB nanosheets may be the optimum choice as an electrocatalyst for NRR. Moreover, our results also indicate that NRR on MoB nanosheets via the enzymatic pathway is the most favored pathway and *NH*NH -> *NH*NH2 is potential-limiting step with a very low applied overpotential of 0.14 V. In addition, the limiting potentials of NRR (-0.30 V) and HER (-0.48 V) on MoB nanosheet suggest that NRR is prefer to happen on the catalyst. Overall, this study demonstrates that MoB nanosheets as a novel 2D monolayer, which might be utilized as an efficient electrocatalyst for NRR at ambient conditions.