Pulse-Engineered Ion Redistribution Suppresses Cation Interference in Electrocatalytic Nitrate Reduction

Electrocatalytic nitrate reduction (eNO₃RR) to ammonia offers a sustainable route for nitrate remediation and nitrogen resource recovery. However, its implementation in real wastewater remains challenging, with limited strategies to address interference from coexisting ions. Here, we identify Mg²⁺ as a representative precipitation-prone impurity and demonstrate that pulsed electrolysis effectively alleviated its inhibitory effects. Under optimized pulsed conditions, the nitrate removal and ammonia yield rate reached 98.0% and 3544.7 μg h^-1 cm^-2, respectively, restoring the lost performance under static operation with Mg²⁺ (85.3% and 2821.5 μg h^-1 cm^-2) and matching the Mg²⁺-free baseline (96.1% and 3449.0 μg h^-1 cm^-2). Mechanistic studies revealed three key functions of pulsing: (i) suppression of local pH elevation, which limits Mg²⁺ precipitation and particle growth on the catalyst surface; (ii) dynamic modulation of interfacial ion distributions, reducing Mg²⁺ accumulation via electric-field-induced repulsion; and (iii) K⁺ enrichment at the interface, which increases the energy barrier (1.15 eV) for Mg²⁺ adsorption and enhances NO₃^- conversion. The pulsed strategy also effectively mitigated cationic interference in complex multi-ion wastewater analogs, demonstrating its broad applicability. Our findings uncover the mechanistic basis of pulsed electrolysis-induced ion redistribution in complex water matrices, establishing a generalizable framework to enhance the eNO₃RR and other electrocatalytic water treatment processes under realistic conditions.