Hydrogen Spillover-Enabled Pd/CeO₂ Interface Catalysis for Highly Efficient Electrochemical Nitrate-to-Ammonia Conversion

Abstract

The electrocatalytic nitrate reduction reaction (NO₃RR) 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-CeO₂/C composite catalyst, in which strong interactions between Pd and CeO₂ 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 CeO₂. 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-CeO₂/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.

Keywords

CeO2 / hydrogen spillover / interface catalysis / Pd catalysts / rare earth

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