Hydrogen Spillover-Enabled Pd/CeO2 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.