Boron Nanosheet: An Elemental Two-Dimensional (2D) Material for Ambient Electrocatalytic N2-to-NH3 Fixation in Neutral Media

The Haber-Bosch process for industrial NH3 production suffers from harsh reaction conditions and serious CO2 emission. Electrochemical N-2 reduction offers a carbon-neutral alternative for more energy-saving NH3 synthesis but requires active electrocatalysts for the N-2 reduction reaction (NRR). In this Letter, boron nanosheet (BNS) is proposed as an elemental two-dimensional (2D) material to effectively catalyze the NRR toward NH3 synthesis with excellent selectivity. When tested in 0.1 M Na2SO4, such BNS catalyst attains a high Faradaic efficiency of 4.04% and a large NH3 yield of 13.22 mu g h(-1) mg(cat)(-1) at -0.80 V vs reversible hydrogen electrode, with strong electrochemical durability. Density functional theory calculations suggest that the B atoms of both oxidized and H-deactivated BNS can catalyze the NRR more effectively than clean BNS, and the rate-determining step is the desorption process of the second NH3 gas.