Hydrogen Spillover‐Enabled Pd/CeO ₂ Interface Catalysis for Highly Efficient Electrochemical Nitrate‐to‐Ammonia Conversion

The electrocatalytic nitrate reduction reaction (NO 3 RR) provides a sustainable route for nitrogen pollution remediation and ammonia production under ambient conditions. However, the process involves sluggish multi‐electron/proton transfer and suffers from competing hydrogen evolution (HER) which severely limits efficiency and selectivity. Herein, we construct a Pd x ‐CeO 2 /C composite catalyst, in which strong interactions between Pd and CeO 2 induce interfacial electronic redistribution, thereby effectively modulating the Pd electronic structure. This interfacial coupling enhances water dissociation, accelerates the generation of reactive *H, and promotes its spillover from Pd to CeO 2 . In‐situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) confirms that hydrogen spillovers facilitate stepwise hydrogenation of intermediates while suppressing HER. Density functional theory calculations further reveal that Pd‐Ce interactions inhibit HER and enable N─O side‐on adsorption, shifting the potential‐determining step and lowering the reaction barrier, thus boosting electrocatalytic activity. As a result, the optimized 5 wt.% Pd‐CeO 2 /C delivers a Faradaic efficiency of 98.0% for ammonia at −0.4 V (vs. RHE), and achieves an ammonia yield rate of 4.17 mmol/(mg Pd ∙h) at −0.6 V. This work offers new insights into the application of interfacial engineering for efficient electrocatalytic ammonia synthesis.