Transition Metal Diborides: A New Type of High-performance Electrocatalysts for Nitrogen Reduction

Nitrogen reduction reaction (NRR) to produce ammonia via electrochemical methods at ambient conditions is of great significance for sustainable development of energy. However, searching for the highly efficient catalysts is still a great challenge. In this study, we report a type of novel electrocatalysts named transition metal diborides (TMB2) with a high-activity, -selectivity, -conductivity and super-stability for NRR. We have computationally calculated the binding energies of N-2 and H2O on three TMB2 (TM=V, Nb and Ti), and the results show that all the three TMB2 can selectively adsorb and significantly activate N-2. Further investigations of the NRR on the three TMB2 with two possible mechanisms, named associative Heyrovsky mechanism (AHM) and dissociative Heyrovsky mechanism (DHM), suggest that the VB2 is the most efficient electrocatalyst among them with a low limiting reaction energy of just 0.28 eV. Moreover, our calculated results have proved that the TMB2 used as electrocatalysts are highly recyclable as the binding energies of N-2 on them are much larger than those of NH3. Consequently, our study demonstrates for the first time the mechanisms of NRR on TMB2, which offers a new type of electrocatalysts with high efficiency and durability for sustainable NH3 production.