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Abstract

Cracking of ammonia, a hydrogen carrier with high storage capacity, gains increasing attention for fuel cell systems for heavy load transportation. In this work, we studied the influence of metal loading and synthesis temperatures on the properties of Co@Al₂O₃ catalysts. The combination of in situ bulk characterization methods with in situ surface spectroscopy provides insights into the structure-property relation of the Co catalyst on the γ-Al₂O₃ support. At too high temperatures, the formation of CoAl₂O₄ during synthesis or during the catalytic reaction itself results in inactive mixed metal aluminium spinels which do not contribute to the catalytic reaction. The amount of ‘active’ Co catalyst thus varies significantly as well as its catalytic activity. The latter is correlated to the size of the reduced Co particles on the alumina support. The experiments also highlight that the state of the catalyst changes after reaction which strongly emphasizes the necessity of in situ studies.