Next-Generation Electrochemical Ammonia Synthesis: Integrating Materials Innovation with Scalable Systems

Electrochemical ammonia synthesis offers a promising sustainable alternative to the Haber–Bosch process, but progress remains fragmented across catalysis, ammonia validation, and reactor engineering. This review investigates an integrated framework combining catalyst design, reaction mechanisms, analytical validation, and reactor engineering to interlink the activation of nitrogen with consistent ammonia verification for high-yield ammonia synthesis. The roles of electronic structure, defect chemistry, active sites, interfacial effects, and electrolytes promote nitrogen activation, ammonia selectivity, and inhibit the competitive hydrogen evolution reaction. Conventional electrochemical nitrogen reduction and alternative pathways, including nitrate and nitrite reduction, plasma-assisted synthesis, and lithium-mediated nitrogen reduction, are critically compared using common performance criteria encompassing reaction mechanisms, ammonia productivity, Faradaic efficiency, energy consumption, stability, and scalability. Specifically, the review pays attention to a critical assessment of ammonia quantification methods, which include colorimetric techniques, ion chromatography, nuclear magnetic resonance, and isotope labelling to reduce errors in ammonia quantification. The review further bridges catalyst-level performance and practical reactor operation by evaluating flow cells, gas-diffusion electrodes, membrane-based and zero-gap configurations, and stack architectures in terms of mass transport, current density, reactant utilization, product separation, and energy efficiency. Finally, this review identifies the energy barriers in the engineering to transition from laboratory scale to scalable ammonia generation.