Highly synergistic Ni/CeO2 interface with optimized NH3 pretreatment for enhanced catalytic ammonia decomposition

This study investigates synergistic effects in Ni/CeO 2 catalysts for ammonia decomposition, comparing impregnation and mechanical mixing preparation methods. The impregnated catalyst achieved >90 % NH 3 conversion above 500 °C, outperforming Ni/SiO 2 and mixed counterparts. Strong interactions at the Ni-CeO 2 interface facilitated the formation of Ni-O-Ce bonds, lattice distortion, and oxygen vacancies (O v )/Ce 3+ species, enhancing Ni dispersion (34.7 nm vs. 73.1 nm) and electron transfer. Optimal NH 3 pretreatment (550 °C, 1.5 h) generated metallic Ni 0 as the primary active species, with higher Ni 0 content (XPS) and reducibility (H 2 -TPR). The novelty lies in establishing how NH 3 pretreatment dynamically assembles contiguous Ce 3+ -O v -Ni 0 triads. These sites facilitate rate-limiting N 2 desorption through localized electron donation from O v and Ce 3+ to Ni 0 , which weakens N-N bonds (NH 3 -TPD). Impregnation-derived synergy: (i) enhances Ni dispersion/reduction, (ii) promotes O v formation, and (iii) enables NH 3 -pretreatment-induced assembly of contiguous Ce 3+ -O v -Ni 0 triads that create electron-rich sites, lowering the activation barrier. This work provides a foundation for designing cost-effective catalysts via atomic-scale control of metal-support interactions.