Hydrogen production from ammonia decomposition using Co/γ-Al2O3 catalysts – Insights into the effect of synthetic method

• Published in: International journal of hydrogen energy Vol. 45; no. 51; pp. 27210 - 27220
• Main Authors: Bell, T.E., Ménard, H., González Carballo, J.-M., Tooze, R., Torrente-Murciano, L.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 16-10-2020
• Subjects: Alumina; Ammonia decomposition; Cobalt; Heterogeneous catalysis; Hydrogen; Synthesis method; Synthesis method; Heterogeneous catalysis; Hydrogen; Cobalt; Ammonia decomposition; Alumina
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.07.090

Chemical hydrogen storage in molecules such as ammonia (>17 wt% H2) have the unique potential to overcome the current storage and transport limitations of the H2 economy. However, sustainable on-demand production of hydrogen via ammonia decomposition, requires the development of novel transition metal-based catalysts beyond the current use of highly active but expensive ruthenium to ensure economic feasibility. In this paper, we provide fundamental understanding of the effects of a range of synthetic methods of Co/γ-Al2O3 catalysts on the resulting ammonia decomposition activity. The main activity determining factors are collectively the reducibility of the cobalt species and their particle size. This systematic work demonstrates that decreasing the cobalt particle size enhances the ammonia decomposition catalytic activity. However, a careful balance is required between a strong metal-support interaction leading to small particle sizes (promoted by precipitation methods) and the formation of inactive cobalt aluminate species (encouraged by adsorption methods). In addition, impurities such as boron and chloride remaining from particular synthetic methods were found to have detrimental effects on the activity.
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•High H2 production from ammonia on cobalt-based catalysts.•Guidance for future cobalt-based catalysts development to replace scarce Ru.•Cobalt particle size plays a key parameter on ammonia decomposition activity.•Cobalt catalyst preparation method affects its size and interaction with support.•Strong-cobalt support interaction leads to formation of unreducible and inactive species.