Anchored Fe atoms for N O bond activation to boost electrocatalytic nitrate reduction at low concentrations

Electrocatalytic nitrate reduction reaction (NO 3 RR) is a facile and competitive way to remove NO 3 - -N, but it still faces challenges of cost and reactivity. Herein, we synthesize a single-atom iron electrode (Fe SAs /g-C 3 N 4 ) by a facile one-step pyrolysis method and demonstrate a strategy for N O bond activation with isolated Fe−N 4 as the active centre for efficient NO 3 RR. The catalyst achieved the NO 3 - -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 NO 3 RR boosted by N O 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 NO 3 - -N removal from water bodies. • The Fe-based SACs achieved a maximum NO 3 - -N removal capacity (9857.5 mg N/g). • A high faradaic efficiency (77.3%) was achieved at mild and low NO 3 - -N concentrations (50 mg N/L). • The N O activation effect by Fe−N 4 active centre was identified as a critical factor of NO 3 - -N removal efficiency. • Low energy consumption (0.34 kWh/mol) and stability reflected the significance of Fe SAs /g-C 3 N 4 .