Single-atom transition metals supported on B-doped g-C3N4 monolayers for electrochemical nitrogen reduction†

Electrochemical reduction of naturally abundant nitrogen (N₂) under ambient conditions is a promising method for ammonia (NH₃) synthesis, while the development of a highly active, stable and low-cost catalyst remains a challenge. Herein, the N₂ reduction reaction of TM@g-BC₃N₄ in electrochemical nitrogen reduction has been systematically investigated using density functional theory (DFT) calculations and compared with that of TM@g-C₃N₄. It was found that TM atoms are more stably anchored to g-BC₃N₄ than to g-C₃N₄. The adsorption free energy of N₂ molecules on Fe@g-BC₃N₄ has the greatest change compared with that on Fe@g-C₃N₄, decreasing by 1.08 eV. The spin charge density around the Fe atom in Fe@g-BC₃N₄ increases significantly compared with that in Fe@g-C₃N₄, and the total magnetic moment of the system increases by 3.26μ_B. The limiting potential (−0.57 V) of Fe@g-BC₃N₄ in nitrogen reduction is decreased by 0.06 V compared with that of Fe@g-C₃N₄ (−0.63 V), and the desorption free energy of ammonia molecules decreases from 1.72 eV to 0.46 eV. The Fe atom has higher catalytic activity, the ammonia molecule is easier for desorption, and nitrogen reduction performance is better. This provides an important reference for the application of g-C₃N₄-based single atom catalysts in the field of nitrogen reduction.