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

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 NO₃ ^-, this approach offers a promising route for high-efficiency anion separation in complex solutions. Herein, a novel [Bi₂O₂]²⁺ layered Faraday electrode was designed with two-dimensional channels for NO₃ ^- 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 Bi³⁺ sites enhance the coordination of subsequent NO₃ ^- insertion, achieving a NO₃ ^- removal capacity of 182.47 mg g^-1. Meanwhile, the highly charged CO₃ ^2- enhances its repulsion against other competitive anions, leading to an impressive removal ratio of 90.78% for NO₃ ^- in multi-ion solutions. More importantly, exogenous CO₃ ^2- intercalation reverses the interlayer binding energy hierarchy between NO₃ ^- and SO₄ ^2-, converting the substitution by NO₃ ^- (-13.12 eV) more thermodynamically favorable than that by SO₄ ^2- (-12.16 eV), enabling spontaneous NO₃ ^- uptake. Our work provides new insights for designing NO₃ ^--selective electrodes, enhancing understanding of anion-interface interactions.