A three-step relay mechanism enables the highly selective reduction of NO3⁻ to N2 under acidic conditions

The electrocatalytic reduction of nitrate (NO ₃ ⁻) to N ₂ (NO₃RR), represents a promising approach for alleviating nitrogen pollution in water environments. Most of the current research efforts are concentrated on neutral or alkaline conditions, where precious metals or Cl⁻ are utilized to improve the efficiency of NO ₃ ⁻ conversion into N ₂ . However, a portion of industrial NO ₃ ⁻ wastewater is acidic. necessitating a prior neutralization step that not only increases operational costs but may also result in secondary pollution. Here, we developed a three-step relay mechanism for achieving efficient NO ₃ RR reactions in acidic media without the use of precious metals or Cl⁻, which includes a three-electron oxygen reduction reaction (3e⁻ ORR), electronic structure reconstruction, and NO ₃ RR. Under 0.05 M H₂SO₄ and 0.1 M KNO₃, the yield and selectivity of N ₂ were 10.03 mg mg _cat .⁻ ¹ h⁻ ¹ and 81.92%, respectively, and it operated stably for 112 h at 120 mA/cm². Moreover, it demonstrates outstanding NO ₃ ⁻ removal rates at concentrations of 100 mg/L and 200 mg/L. This three-step relay strategy paves the way for the application of NO₃RR under acidic conditions, thereby opening up new avenues for research in this area.