Recent Advances in Membrane Electrode Assembly Based Nitrate Reduction Electrolyzers for Sustainable Ammonia Synthesis

The electrochemical reduction from nitrate (NO3RR) to ammonia (NH3) provides a decentralized and environmentally friendly route for sustainable ammonia production while addressing the urgent issue of nitrate pollution in water bodies. Recent advancements in NO3RR research have improved catalyst designs, mechanistic understanding, and electrolyzer technologies, enhancing selectivity, yield, and energy efficiency. This review explores cutting-edge developments, focusing on innovative designs for catalysts and electrolyzers, such as membrane electrode assemblies (MEA) and electrolyzer configurations, understanding the role of membranes in MEA designs, and various types of hybrid and membrane-free reactors. Furthermore, the integration of NO3RR with anodic oxidation reactions has been demonstrated to improve overall efficiency by generating valuable co-products. However, challenges such as competitive hydrogen evolution, catalyst degradation, and scalability remain critical barriers to large-scale adoption. We provide a comprehensive overview of recent progress, evaluate current limitations, and identify future research directions for realizing the full potential of NO3RR in sustainable nitrogen cycling and ammonia synthesis.