Atomic-Level Modulation of N-Bridge-Induced Built-In Electric Fields for Enhanced Hydrogen Spillover in Ammonia Electrosynthesis

The fabrication of a highly efficient catalyst to boost hydrogen spillover is pivotal for electrocatalytic reduction of nitrate to ammonia (NO₃ RR). Here, we report a novel N-rich imidazole ionic liquid connector to create N-bridged Cu, Pd dual sites in N-doped carbon-defect graphene (CuPd-NG). This design induces the formation of a built-in electric field (BEF) via the N-bridge to accelerate hydrogen spillover in the NO₃ RR. Through systematic experiments and theoretical analyses, the N-bridge disrupts the electronic equilibrium between Cu and Pd, resulting in a weak BEF between these two metals. The localized charge polarization caused by BEF facilitates the dissociation of water molecules to generate *H at the Pd site, and subsequent *H can rapidly migrate from the Pd to Cu site through the unique Pd–N–Cu bond, thereby increasing *H coverage on the Cu site for the subsequent NO₃ RR process. Unexpectedly, the CuPd-NG achieves a desirable ammonia yield of 0.96 mmol h^–1 cm^–2 at −0.6 V (vs RHE) and a high Faradaic efficiency of 97.2% at −0.3 V (vs RHE). Furthermore, with CuPd-NG as the cathode, a high-performing Zn-NO₃^– battery can be assembled. The design of the N-bridged-induced BEF regulation mechanism provides novel insights for enhancing NO₃ RR performance by promoting hydrogen spillover at the atomic level.