Electrochemical ammonia recovery from wastewater: The critical roles of electrode engineering toward scale-up

Ammonia is indispensable for producing fertilizers that sustain the global population, yet its agricultural application contributes significantly to water pollution. Electrochemical technologies offer a renewable-energy-driven and chemical-free pathway for recovering ammonia directly from wastewater, representing a critical step toward a circular nitrogen economy and net-zero emissions in the wastewater sector. Nevertheless, translating lab-scale advances to industrialization remains constrained by technological hurdles. Emerging electrode-engineering strategies promise scalable, membrane-less electrochemical systems, but a systematic and comparative assessment is lacking. In this review, we first present the electrochemical ammonia recovery pathway and elucidate the mechanisms of various electrode materials in this process. Secondly, we critically evaluate state-of-the-art scalable electrode systems for electrochemical ammonia recovery. Thirdly, we comparatively analyze the ammonia recovery performance at both the electrode-material and electrode-system levels, comprehensively discussing the current challenges and future research opportunities toward technological scale-up. Finally, we outline key research targets toward next-generation electrochemical engineering for sustainable ammonia recovery and wastewater treatment.