zengxiwei

Ammonia (NH₃) is an essential chemical that is widely used in agriculture and industry applications. The industry-scale Haber-Bosch process accounts for ∼1.5% of global energy consumption and a significant CO₂ emission annually, due to the extreme inertness of N₂ and carbon emission for producing H₂ precursor. The electrochemical reduction of N₂ (NRR) in aqueous solutions at ambient conditions is extremely challenging and requires rational design of electrocatalytic centers. Previous reports predominantly used metal-based electrocatalysts, and the efficiency has generally been extremely low. In this work, we demonstrate for the first time boron-doped graphene as an efficient metal-free NRR electrocatalyst in aqueous solutions at ambient conditions.

Electrochemical N₂ reduction in aqueous solutions at ambient conditions is extremely challenging and requires rational design of electrocatalytic centers. We demonstrate a boron-doped graphene as an efficient metal-free N₂ reduction electrocatalyst. Boron doping in the graphene framework leads to redistribution of electron density, where the electron-deficient boron sites provide enhanced binding capability to N₂ molecules. Density functional theory calculations reveal the catalytic activities of different boron-doped carbon structures, in which the BC₃ structure enables the lowest energy barrier for N₂ electroreduction to NH₃. At a doping level of 6.2%, the boron-doped graphene achieves a NH₃ production rate of 9.8 μg·hr⁻¹·cm⁻² and one of the highest reported faradic efficiencies of 10.8% at −0.5 V versus reversible hydrogen electrode in aqueous solutions at ambient conditions. This work suggests the strong potential of atomic-scale design for efficient electrocatalysts for N₂ reduction.