Catalytic Ammonia Decomposition Over Co Supported on Ceo2-Al2o3 For Hydrogen Production

Ammonia is the best source of hydrogen for carbon-free fuel cells, but realizing the goal of a green, low-energy ammonia decomposition hydrogen production process depends on catalytic materials with excellent ammonia dehydrogenation properties. Ce-doped Al2O3 supports can improve the ammonia decomposition activity of Co catalysts. The structural effect of the supports prepared by co-precipitation on the active metallic cobalt was investigated to improve the dispersion of Ce in the Al2O3 skeleton. In this study, a series of Co/CeO2-Al2O3 mesoporous catalysts were synthesized by deposition precipitation method and used in the hydrogen production reaction by ammonia decomposition. The catalyst materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N2 physical adsorption analysis, and hydrogen programmed warming reduction. The catalytic performance of the solid catalysts was evaluated at different temperatures and flow rates at atmospheric pressure. The optimized Co/CeO2-Al2O3 catalyst maintained high activity below 550 °C and achieved 88% ammonia conversion and 8.7 mmol H2▪g-1▪min-1 hydrogen yield at 9000 mL▪h-1▪gcat-1, which represent competitive performances among the catalysts of the current technology. Ce-doped Al2O3 prepared under the same conditions showed significantly improved Co dispersion and yielded the highest catalytic activity due to the high Ce composition and homogeneity in the backbone as well as the high Lewis basic sites enhancing the limiting step of NH3 decomposition. The activity of the studied ceria-based catalysts normalized per unit mass of the loaded catalysts showed consistency in the activity porosity relationship. The good performance of this catalyst and the use of non-precious metals in the structure provide a viable avenue for the application of ammonia as a hydrogen carrier for on-board hydrogen production.