Hydrogen production via aqueous ammonia electrolysis: electrolyte optimization, product selectivity, and efficiency analysis

This study presents a comprehensive investigation of aqueous ammonia electrolysis as an alternative method for hydrogen production. It explores various experimental conditions, energy, and Faradaic efficiencies, and the underlying electrochemical mechanisms. Cyclic voltammetry and electrolysis tests were conducted at different current densities (ranging from 50 to 700 mA) to determine the optimal conditions for hydrogen gas (H₂) generation. Gas chromatography with a thermal conductivity detector (GC-TCD) was used to confirm the production of hydrogen and verify the absence of gaseous nitrogen. Alongside the solution-phase analyses, these findings provide clear evidence for the formation of soluble by-products, primarily nitrite (NO₂ − ) and nitrate (NO₃ − ), as both species were detected and quantified in our measurements. The Faradaic efficiency reached 98%, while energy efficiency ranged from 59% to 75%. The results are compared with existing literature, emphasizing ammonia's potential as a sustainable hydrogen carrier and highlighting the current limitations of the process in aqueous media. • Aqueous ammonia electrolysis was optimized using 200 mM NH₄Cl in 500 mM NH₄OH. • Cyclic voltammetry revealed the best hydrogen evolution performance at 200 mM NH₄Cl. • Applied currents of 50, 75, and 100 mA were selected based on CV-defined catalytic stability. • Hydrogen was the only gaseous product detected; no N₂ formation occurred under any condition. • Faradaic efficiencies of 96–98% and energy efficiencies up to 75% were achieved.