The effect of grain boundary in hexagonal boron nitride on catalytic activity of nitrogen reduction reaction

Designing high-efficiency electrocatalysts is of great significance to produce ammonia via electroreduction reaction of nitrogen (NRR). To this end, grain boundary catalysis (GBC) has emerged as a promising strategy experimentally. Herein, based on first principles calculations, we modeled the grain boundary (GB) structures of hexagonal boron nitride (h-BN), then 12 transition metal atoms (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Mo, Ru, and Rh) were anchored on the GB structures to construct single-atom catalysts, the most ideal overpotential of NRR is as low as 0.13 V for Mo adatoms on GB. Additionally, more sophisticated situations in regard to h-BN GB were considered, meanwhile electronic structure analysis was also conducted. We found that, the configuration and density of GB can hardly influence the catalytic activity at GB, while the coordinated B bonded with Mo strongly modified the spin states and the bonding strengths within certain intermediates, leading to this excellent NRR catalytic activity. This work not only provides a new strategy for the development of highly efficient and stable NRR electrocatalysts, but also enhances the understanding on the origin of GBC.