In Situ Structural Evolution of Sr‐Promoted Perovskite Catalysts During Ammonia Decomposition

ABSTRACT For the successful implementation of hydrogen technologies based on green H 2 feedstocks, storage remains a major challenge alongside sustainable production, limiting its widespread use as energy carrier. In particular, ammonia has emerged as a promising hydrogen carrier, enabling the on‐demand release of H 2 via thermocatalytic decomposition (cracking). This study presents Sr‐promoted LaCoO 3 ‐based catalysts capable of achieving complete ammonia conversion. Activation of the LaCoO 3 precursor in reducing gas atmosphere leads to the exsolution of the transition metal and the formation of metallic cobalt on the La 2 O 3 matrix. In situ x‐ray powder diffraction was employed to monitor the structural evolution during the catalytic reaction and to determine the microstructure properties of the active metal. The incorporation of Sr 2+ promoters significantly enhances the reducibility of the system, facilitates controlled Co exsolution, and influences the size of the metallic Co nanoparticles exposed on the surface. The best performance was achieved with catalysts containing low strontium loadings (10–20 mol.%), reaching nearly 92% NH 3 conversion at 550°C while maintaining excellent long‐term stability with minimal activity loss. These findings provide insight into the role of promoters at a mechanistic level and highlight the importance of rational design strategies for next‐generation catalysts for sustainable hydrogen production.