Efficient electrocatalytic reduction of nitric oxide (NO) to ammonia (NH₃) on metal-free B₄@g-C₃N₄ nanosheet

The combustion of fossil fuels releases substantial amounts of nitric oxide (NO), posing serious environmental and health risks. Addressing NO pollution effectively is, therefore, a pressing need. Conversion of NO into valuable chemicals is an appealing strategy with dual benefits, including waste utilization and sustainable energy transformation. In this study, we investigate the metal-free electrocatalytic reduction of NO (NORR) to NH₃ on a B₄ atomic cluster supported by a g-C₃N₄ nanosheet (B₄@g-C₃N₄) using density functional theory (DFT). Our findings reveal that NO is efficiently activated on the B₄@g-C₃N₄ catalyst, favoring side-on and N end-on adsorption configurations. Significant electron transfer and strong adsorption energies confirm the chemisorption of NO. The NORR exhibits an impressively low limiting potential (U_L) of −0.29 V in the gas phase, which decreases further under solvent effects and varying charge states (−2e^-, −1e^-, +1e^-, +2e^-). Additionally, the high negative U_L values for competing side reactions such as H₂ (−0.42 V), N₂ (−0.29 V), and N₂O (−0.72 V) underscore the selectivity of B₄@g-C₃N₄ for ammonia synthesis. These results highlight the promising potential of B₄@g-C₃N₄ nanosheets for eco-friendly ammonia production from NO, providing a theoretical basis for future experimental efforts to combat NO pollution.