Advances in catalysts development and catalytic activity trends of conventional metal oxides and inorganic perovskites for hydrogen production via ammonia decomposition: a review

Hydrogen is widely regarded as a potential alternative to fossil fuels. However, its inherently low volumetric density hinders its direct storage and transport. Ammonia has emerged as a viable hydrogen carrier for addressing this limitation. This work reviews all available literature on ammonia cracking from year 2010 to 2024. Articles on ammonia cracking in internationally accepted indexed journals were reviewed and a comparison among different catalytic materials was made. It evaluates the pathways of ammonia decomposition, emphasising the reaction mechanisms and possible rate-determining steps. The primary focus is on metal oxides as leading catalyst precursors and the potential of inorganic perovskites as direct catalysts and catalytic supports for catalytically active metals such as Ru, Ni, Co and Fe for ammonia decomposition. Several descriptors for catalytic activity, including nitrogen binding energies onto the catalytically active sites, basicity, and promotional effects, are herein critically explored. Furthermore, the role of support material properties, metal-support interactions, and catalyst deactivation processes in shaping activity is analysed. Lastly, this review also highlights insights from theoretical and computational studies that contribute to advancing catalyst design for ammonia decomposition.