Electrocatalytic Ammonia Oxidation Reaction: From Active Site Regulation to Industrial Device Systems
The electrocatalytic ammonia oxidation reaction (AOR) is pivotal for sustainable energy conversion and storage, enabling direct ammonia fuel cells (DAFCs), ammonia electrolysis, and solid oxide fuel cells. This review critically examines recent advances in AOR catalysis, emphasizing active-site regulation, interfacial engineering, and device-oriented catalyst development. For noble-metal catalysts, optimizing adsorption and dehydrogenation of NHx intermediates while mitigating poisoning is essential for sustained activity. Non-noble-metal systems, particularly Ni-based catalysts, require precise control of reconstructed working-state phases such as NiOOH-like species to balance activity and selectivity. Interfacial engineering, including heterointerfaces, defect structures, and doped coordination environments, strongly influences the competition between AOR and oxygen evolution reaction (OER), as well as product branching toward N2 or oxygenated nitrogen species. The review underscores that catalyst optimization now extends beyond bulk composition to the precise regulation of the interfacial reaction microenvironment. Furthermore, practical device operation is governed by membrane/electrolyte compatibility, mass transport, ammonia crossover, thermal management, and long-term durability. Bridging fundamental catalyst studies with deployable ammonia energy technologies requires coordinated optimization from active materials to electrode architectures and full-device systems. This review provides a comprehensive framework for designing next-generation AOR catalysts and accelerating their integration into industrial energy systems.