Subnanometer Ru Sites on CeO₂ Oxygen Vacancy Clusters: A Highly Efficient and Durable Catalyst for Ammonia...

Decomposing ammonia to produce hydrogen is a promising approach to address challenges in hydrogen storage and transport. While Ru-based catalysts have demonstrated high activity, their long-term stability under industrial conditions remains a critical hurdle. Here, we develop a reductive synthesis strategy to fabricate rod-shaped ceria (CeO₂-Rod_Red) featuring high-density oxygen vacancy clusters, where Ru clusters are effectively anchored via robust Ru-O-Ce³⁺ linkages formed at 450 °C under N₂ atmosphere. The resulting Ru/CeO₂-Rod_Red-450N₂ catalyst achieves an impressive 99.0% NH₃ conversion at 450 °C, approaching the thermodynamic equilibrium (99.6%), and shows exceptional stability over 1000 h of operation. Integrated experimental characterization and density functional theory calculations reveal that the abundant Ce³⁺ species and oxygen vacancy clusters create an electron-rich surface with high electron conductivity, which facilitates hydrogen spillover from Ru clusters onto CeO₂ to form dynamic Ce-OH groups. The reversible formation and dehydrogenation of these hydroxyl groups accelerate H₂ release while suppressing hydrogen poisoning of Ru active sites. By continuously removing adsorbed H atoms via spillover, this mechanism promotes N-N coupling and lowers the energy barrier for the rate-limiting N₂ desorption step. This work offers a general strategy for designing highly efficient and stable ammonia decomposition catalysts through rational construction of interfacial active sites.