Engineering and optimising barium cerate-supported cobalt catalyst for ammonia synthesis

Abstract

Ammonia synthesis under mild reaction conditions remains a key challenge to realising a carbon-free society. The development of efficient catalysts for ammonia synthesis is therefore of great interest nowadays. Here, the effects of the cobalt deposition method and loading on the physicochemical properties and catalytic performance of Sm-doped BaCeO₃-supported Co catalysts were systematically investigated. Catalysts were prepared by deposition–precipitation, wet impregnation, and physical mixing methods. Depending on the method used, the catalyst properties varied in terms of chemisorptive properties and catalytic activity. The favourable activity observed for catalysts prepared by deposition–precipitation and wet impregnation methods was attributed to a more diverse surface landscape that facilitates hydrogen and nitrogen adsorption and activation. Then, by using the deposition–precipitation method, a series of catalysts with Co loadings from 10 to 50 wt% was synthesised. Catalytic testing revealed a clear dependence of activity on Co loading, with the highest reaction rate and intrinsic turnover frequency observed for the catalyst loaded with 40 wt% Co. This behaviour was explained not only by the greater number of adsorption sites but also by the structural sensitivity of cobalt in ammonia synthesis, where a diverse surface landscape with various adsorption sites improved the catalytic performance.