Anchored Fe Atoms for N=O Bond Activation to Boost Electrocatalytic Nitrate Reduction at Low Concentrations

Electrocatalytic nitrate reduction reaction (NO3RR) is a facile and competitive way to remove NO3--N, but it still faces challenges of cost and reactivity. Herein, we synthesize a single-atom iron electrode (Fe-SAs/g-C3N4) by a facile one-step pyrolysis method and demonstrate a strategy for NO bond activation with isolated Fe-N-4 as the active centre for efficient NO3RR. The catalyst achieved the NO3--N removal capacity of 9857.5 mg N/g Fe, which was the highest among previous studies, and a high faradaic efficiency of 77.3%, even at a low nitrate concentration (50 mg N/L). The designed pathway combined with electrochlorination can completely convert by-products to harmless nitrogen gas. Theoretical research confirmed the contribution of coexisting hydrogen evolution reaction suppression and NO3RR boosted by NO activation on Fe-N-4. This work offers a new paradigm for designing the efficient, stable, and energy conservation single-atom cathode for development of NO3--N removal from water bodies.