Subnanometer Ru Sites on CeO ₂ Oxygen Vacancy Clusters: A Highly Efficient and Durable Catalyst for Ammonia Decomposition

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 (CeO 2 -Rod Red ) featuring high-density oxygen vacancy clusters, where Ru clusters are effectively anchored via robust Ru–O–Ce 3+ linkages formed at 450 °C under N 2 atmosphere. The resulting Ru/CeO 2 -Rod Red -450N 2 catalyst achieves an impressive 99.0% NH 3 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 Ce 3+ species and oxygen vacancy clusters create an electron-rich surface with high electron conductivity, which facilitates hydrogen spillover from Ru clusters onto CeO 2 to form dynamic Ce–OH groups. The reversible formation and dehydrogenation of these hydroxyl groups accelerate H 2 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 N 2 desorption step. This work offers a general strategy for designing highly efficient and stable ammonia decomposition catalysts through rational construction of interfacial active sites.