N-doped carbon-iron heterointerfaces for boosted electrocatalytic active and selective ammonia production.

Abstract

The electrochemical conversion of waste nitrate (NO₃^-) to valuable ammonia (NH₃) is an economical and environmentally friendly technology for sustainable NH₃ production. It is beneficial for environmental nitrogen pollution management and is also an appealing alternative to the current Haber-Bosch process for NH₃ production. However, owing to the competing hydrogen evolution reaction, it is necessary to design highly efficient and stable electrocatalysts with high selectivity. Herein, we report a rational design of Fe nanoparticles wrapped in N-doped carbon (Fe@N₁₀-C) as a high NH₃ selective and efficient electrocatalyst using a metal-organic framework precursor. We constructed a catalyst with new active sites by doping with nitrogen, which activated neighboring carbon atoms and enhanced metal-to-carbon electron transfer, resulting in high catalytic activity. These doped N sites play a key role in the NO₃^- electroreduction. As a result, the Fe@N₁₀-C nanoparticles with optimal doping of N demonstrated remarkable performance, with a record-high NO₃^- removal capacity of 125.8 ± 0.5 mg N g_cat^-1 h^-1 and nearly 100 % (99.7 ± 0.1%) selectivity. The catalyst also delivers an impressive NH₃ production rate of 2647.7 μg h^-1 cm^-2 and high faradaic efficiency of 91.8 ± 0.1%. This work provides a new route for N-doped carbon-iron catalysis application and paves the way for addressing energy and environmental issues.