A membrane-free electrochemical cell designed for sustainable applications: experimental investigation

Ammonium formate (NH 4 HCO 2 ) has been explored as a hydrogen-rich fuel for membrane-free electrochemical systems. Its performance was assessed under different operational parameters, including variations in electrode pairing, temperature, and electrolyte environment. The study particularly considered how such factors influence both the achievable cell voltage and the specific capacity, providing insight into the role of system configuration and medium composition in governing the overall efficiency. Elevated temperature significantly improved electrochemical performance, increasing specific capacity from ∼ 15 mAh/g to more than ∼ 75 mAh/g in stainless steel-stainless steel and ∼ 80 mAh/g in aluminum-stainless steel configurations. Among additives, 0.1 M H 2 O 2 yielded the highest capacities (∼90–100 mAh/g) and voltages (>800 mV), whereas the higher concentration (1 M) generally suppressed performance. The results demonstrated that ammonium formate is a promising hydrogen carrier for membrane-free electrochemical systems. Elevated temperature, appropriate additive selection, and asymmetric electrode configurations significantly enhanced electrochemical performance, resulting in higher specific capacities and cell voltages.