Site-specific Ce occupation in a perovskite enables defect engineering and Ni stabilization for efficient ammonia decomposition

Ammonia decomposition is an attractive route for carbon-free hydrogen production, yet Ni-based catalysts are limited by insufficient activity and severe sintering at high temperatures. Herein, Ni supported on Ce-induced perovskites were employed in ammonia decomposition. Notably, we found that site-specific Ce occupation in the support governs the defect chemistry, Ni stabilization, and catalytic performance by constructing LaAlO 3 –Ce-based supports with distinct Ce locations. When Ce is present as a separate CeO 2 phase, a LaAlO 3 -CeO 2 composite is formed, in which interfacial CeO 2 domains moderately improve Ni dispersion and suppress sintering via moderate anchoring. In contrast, A-site incorporation of Ce into the LaAlO 3 lattice induces pronounced lattice distortion and abundant oxygen vacancies, significantly enhancing support basicity and interfacial electron donation. These defect-rich environments stabilize electron-enriched Ni species, strengthen metal-support interactions, and facilitate the recombination and desorption of surface N species, thereby accelerating N* recombination during ammonia decomposition. Consequently, the Ni/LaCeAlO 3 achieves over 90% NH 3 conversion at 600 ℃ with a hydrogen production rate of 524 mmol‧g Ni −1 ‧min −1 , outperforming Ni/LaAlO 3 and Ni/LaAlO 3 -CeO 2 while maintaining excellent stability over 60 h. Kinetic analysis, together with NH 3 -TPSR and in situ DRIFTS, suggests a stepwise dehydrogenation pathway with facilitated H removal and accelerated N 2 formation, directly associated with Ce-induced oxygen vacancies and defect-mediated electronic modulation. This work demonstrates that A-site-specific Ce incorporation in perovskite oxides offers a decisive advantage over conventional composite supports, providing an effective strategy for defect engineering and the development of active and durable non-noble metal catalysts for ammonia-to-hydrogen conversion.