Low-temperature Ammonia Decomposition: Unveiling the Critical Synergistic Role of Potassium and Ceria in Boosting Ru/γ-Al2O3 Catalytic Activity

Efficient hydrogen production via ammonia decomposition is considered a promising direction for future carbon-free energy systems. In this study, a catalyst system based on Ruthenium (Ru) as the main active metal, promoted by Potassium (K) and Ceria (CeO2) on γ-Al2O3 support was developed, which was chosen for its high surface area, low cost, and excellent thermal stability. Potassium acts as an electronic promoter that can enrich the Ru surface and assist the removal of nitrogen-containing intermediates, while CeO2 provides a redox-active oxide environment that can participate in Ru–Ce interfacial modification. As a result of these cooperative promotional effects, the K-Ru/Ce/γ-Al2O3 catalyst achieved 100% NH3 conversion at 475 °C, with an H2 formation rate of 30.67 mmol H2·gcat-1 min-1, even when operated at a high WHSV of 30,000 mL·gcat-1 h-1. The optimized catalyst also maintained stable NH3 conversion during a 60 h time-on-stream test at 450 °C, giving an average conversion of 90.94%. These results indicate competitive performance among recently reported Ru-based catalysts. The structural and surface characteristics of the catalysts were further clarified by TEM-EDS, XPS, XRD, and BET analyses, which supported that the enhanced catalytic performance was mainly associated with electronic modulation of Ru and modification of the Ce–O/Ru–Ce–O interfacial environment, rather than with major geometric changes in Ru particle size.