Unlocking Selective Electrochemical Regulation via Interlayer Anion Competition for Nitrate Extraction from Wastewater

Abstract Electrochemical separation technology offers an effective approach to recycle valuable nitrogen from industrial wastewater, but its separation efficiency is reduced by competitive electrostatic interactions from multiple ions. By engineering a competitive chemical reaction to facilitate site‐specific electrochemical binding of NO 3 − , this approach offers a promising route for high‐efficiency anion separation in complex solutions. Herein, a novel [Bi 2 O 2 ] 2+ layered Faraday electrode was designed with two‐dimensional channels for NO 3 − migration and multiple sites that boost its interaction through combined electrostatic and coordination forces. In addition, by strategically introducing exogenous anions, the induced antisite cation defects at Bi 3+ sites enhance the coordination of subsequent NO 3 − insertion, achieving a NO 3 − removal capacity of 182.47 mg g −1 . Meanwhile, the highly charged CO 3 2− enhances its repulsion against other competitive anions, leading to an impressive removal ratio of 90.78% for NO 3 − in multi‐ion solutions. More importantly, exogenous CO 3 2− intercalation reverses the interlayer binding energy hierarchy between NO 3 − and SO 4 2− , converting the substitution by NO 3 − (−13.12 eV) more thermodynamically favorable than that by SO 4 2− (−12.16 eV), enabling spontaneous NO 3 − uptake. Our work provides new insights for designing NO 3 − ‐selective electrodes, enhancing understanding of anion‐interface interactions.