Recent advances in ammonia decomposition for hydrogen production: From multiple catalytic pathways to Ru-based thermocatalysts

Ammonia is a practical hydrogen carrier because of its high hydrogen density, mature storage and transport network, and ability to release hydrogen without direct CO x formation during decomposition. However, the life-cycle carbon intensity of the ammonia-to-hydrogen pathway depends on the ammonia-production route and the energy sources used for hydrogen recovery. Several routes have been developed to recover hydrogen from ammonia, including thermocatalytic, photocatalytic, plasma-assisted, and electrochemical processes. Their operating principles are different, but the overall performance is often controlled by the same surface events: N–H bond cleavage, coupling of adsorbed nitrogen atoms, and the release of N 2 . Accordingly, research is shifting from isolated catalytic paradigms toward cooperative and multimodal strategies, while thermocatalysis remains the mechanistic and structural basis for most integrated systems. This review summarizes recent advances in ammonia decomposition for hydrogen production, focusing on Ru-based thermocatalysts. From a structure–electronic–kinetic perspective, bimetallic engineering, support/interface regulation, defect engineering, and electronic promotion are discussed in relation to Ru electronic structure, metal–support interactions, reaction kinetics, and catalyst stability. Future directions for low-Ru-loading, durable, and reactor-compatible ammonia-to-hydrogen catalysts are also highlighted.