Toward net energy-positive ammonia electrolysis: A 3,000 cm2 Bi-Polar electrolyzer for hydrogen production and ammonia remediation

Ammonia electrolysis presents a viable solution for sustainable hydrogen generation and ammonia remediation, addressing urgent environmental challenges. This study addresses the challenges of scaling up ammonia electrolysis from the bench scale (double-cell stack 140 cm 2 cell) to the pilot scale (six-cell stack, 3000 cm 2 ), focusing on the design, catalyst synthesis, and testing of a large-scale ammonia electrolyzer. This work utilized a Pt 3 Ir catalyst synthesized in a 15 g batch size and applied via an automated spray-coating method to ensure uniform distribution across electrode surfaces. A zero-gap bipolar cell design was utilized for both systems to facilitate efficient scaling. The pilot scale achieved a comparable current density and faradaic efficiency to the bench scale electrolyzer, demonstrating successful scale-up without compromising the core electrochemical reactions. The study concludes that ammonia electrolysis is a promising technology for ammonia removal in wastewater treatment, with the potential for the coproduction of hydrogen as a valuable byproduct. • Ammonia electrolyzer scaled up 21x with no performance loss. • Developed 3000 cm 2 cell, the largest known, for pilot plant integration. • Achieved 87 mA/cm 2 cycle average current density. • Progress toward net energy-positive conversion of wastewater ammonia into hydrogen.