Preparation and ammonia decomposition performance of solid solution supported Nibased catalysts

Abstract

The development of efficient and stable catalysts for ammonia decomposition is crucial for hydrogen production, addressing the challenges of hydrogen storage and transport. Nickel-based catalysts are promising alternatives to noble metals but suffer from issues like sintering and low stability. This study focuses on the preparation and performance of solid solution-supported Ni-based catalysts, specifically using Ce-Zr-O and Y-Zr-O carriers, to enhance catalytic activity and durability. Ni 2.5 / CeₓZr₁₋ₓO 2 and Ni 2.5 / YₓZr₁₋ₓO₂ catalysts were synthesized via the solgel method. XRD confirmed the formation of fluorite-structured Ce-Zr solid solutions (Ce 0.16 Zr 0.84 O 2 , Ce 0.5 Zr 0.5 O 2 , Ce 0.6 Zr 0.4 O 2 ), while the Y-Zr system formed only a Y 0.18 Zr 0.82 O 2 phase due to ionic radius mismatch. Characterization techniques including SEM, BET, XPS, H₂-TPR, and TPD revealed that the Ni/Ce 0.6 Zr 0.4 O 2 catalyst exhibited a high specific surface area (122.35 m²/g), abundant oxygen vacancies, excellent Ni dispersion, and optimal metal-support interaction. The Ni/ Ce 0.6 Zr 0.4 O 2 catalyst achieved nearly 100% ammonia conversion at 550°C under a gas hourly space velocity (GHSV) of 12,000mL•g cat ⁻¹•h⁻¹, significantly outperforming catalysts supported on pure oxides or Y-Zr solid solutions. It also demonstrated high hydrogen production rates and exceptional stability over a 60-hour test with less than 5% activity loss. The enhanced performance is attributed to the synergistic effects of the Ce-Zr solid solution, which improves oxygen mobility, stabilizes the structure, and facilitates NH 3 activation and N₂ desorption. This work provides a viable strategy for designing non-noble metal catalysts with high efficiency and stability for industrial ammonia decomposition.