The In Situ Assembly of an Equipotential Cathode for Nitrite Enrichment Enabling Electrochemical Nitrate Reduction to N2

Electrocatalytically reducing NO₃^– to N₂ is of great significance for environmental remediation and global nitrogen cycling. However, it is currently hindered by low N₂ selectivity since adsorbate N-intermediates are hard to migrate and couple each other during the N–N coupling step. Herein, an in situ assembly strategy was taken to attach Pd@Cu₂O nanoparticles with CuO nanowire arrays to form an equipotential cathode CuO-Pd@Cu₂O, which optimized N₂ selectivity to 91%, much higher than that of directly loaded Pd–Cu cathode (55%). Theoretical calculations combined with in situ spectroscopies demonstrated that the equipotential cathode can shield the electric field and enrich NO₂^– intermediate inside. Meanwhile, a unique reaction pathway was revealed that the enriched NO₂^– can directly couple with *N and also tune the Pd d-band center, avoiding the hurdles in N–N coupling. The approach here provides a new perspective in cathode design and a mechanistic understanding for the N–N coupling reaction.