Electric-Field-Assisted Oxygen-Vacancy Engineering Promotes Low-Temperature Ammonia Decomposition over Ru/CeO2 through Interfacial H Migration

Ammonia decomposition provides a promising route for on-demand hydrogen production, but conventional thermocatalytic systems are constrained by severe kinetic limitations at low temperatures, limiting their compatibility with low-grade heat utilization. Herein, we develop an electric-field-assisted oxygen-vacancy engineering strategy to promote low-temperature NH3 decomposition over Ru/CeO2 catalysts. Ru/CeO2 catalysts with tunable oxygen-vacancy concentrations were prepared via a pre-impregnation and solid-state grinding method. Structural and spectroscopic characterizations reveal that oxygen vacancies intrinsically strengthen Ru–CeO2–x interfacial electronic interactions, promote charge redistribution, and generate relatively electron-enriched Ru sites. More importantly, the applied electric field further amplifies this vacancy-mediated interfacial regulation and facilitates H-species transfer/removal. The optimized Ru/CeO2-OV3 EF catalyst achieves 35.3% NH3 conversion at 150 °C under a high GHSV of 30,000 mL gcat–1 h–1 and exhibits an electric-field-assisted apparent activation energy of only 12.28 kJ mol–1. In situ DRIFTS, TPD measurements, impedance analysis, and DFT calculations collectively suggest that defect-associated O sites near oxygen vacancies provide favorable accommodation sites for migrated H species, while the electric field promotes interfacial polarization and accelerates H transfer from Ru sites to the CeO2–x surface. This synergistic effect reduces H coverage on Ru active centers, regenerates available Ru sites for sustained NH3 activation, and enables stable low-temperature operation. This work clarifies how an external electric field amplifies oxygen-vacancy-mediated interfacial electron/H transfer and provides a rational strategy for efficient low-temperature hydrogen production from ammonia.