Ni based catalysts and 13X zeolite: Influence of promoters on hydrogen production of ammonia decomposition

Heterogeneous catalytic decomposition of blue ammonia presents a promising pathway for carbon-free hydrogen production. In this study, Ni based catalysts utilizing 13X zeolite were prepared and investigated to achieve high ammonia conversion below 500 °C. Among catalysts with varying Ni loadings, 15%Ni/13X exhibited the highest activity. The influence of the support was evaluated, with 13X achieving superior performance due to its balanced acidic-basic properties that facilitate efficient NH₃ adsorption and product desorption. Performance was further enhanced through transition metal promotion, with Co showing the most significant improvement due to its synergistic effects on Ni reducibility and by providing additional active sites for ammonia decomposition. The addition of 5% K further increased low-temperature conversion by enhancing surface basicity and accelerating H₂ desorption. Kinetic analysis revealed that the Co and K catalytic additives exhibited lower apparent activation energies and higher intrinsic reaction rates than 15%Ni/13X, confirming that promoter induced modifications in reducibility and acid-base properties promote the rate determining N-H bond cleavage step. In contrast, Mo, Fe, and Zn promoted catalysts showed reduced activity, likely due to unfavorable surface modifications. Stability tests demonstrated that 15%Ni/13X maintained NH₃ conversion above 92% during prolonged operation. Post-reaction XRD and XPS confirmed the formation of stable metallic Ni⁰ species and the preservation of structural integrity, highlighting the importance of rational catalyst design for durable and efficient ammonia-based hydrogen production.