H2SO4-doped polybenzimidazole membranes for hydrogen production with acid-alkaline amphoteric water electrolysis

Acid-alkaline amphoteric water electrolysis is considered as a potential approach for efficient hydrogen production at industrial scale; however, to date synthesized or post-functionized polymer for constructing membranes can hardly meet the requirement of either electrolysis performance or durability aspects. Herein, we synthesize a series of H2SO4-doped PBI-based membranes, including poly (2,2 '-(m-phenylene)-5,5 '-bibenzimidazole) (m-PBI) and poly (4,4 '-diphenylether-5,5 '-bibenzimidazole) (OPBI), for application in acid-alkaline amphoteric water electrolysis system. The H2SO4 doping content, water uptake, swelling ratio, chemical durability and proton conductivity of m-PBI and OPBI membranes are characterized and compared with the perfluorinated sulfonated membrane (Nafion 115). Specifically, the m-PBI membrane doped in 3.0 M H2SO4 attains a current density of 800 mA cm(-2) at cell voltage of 2.0 V at 60 degrees C when applied in an amphoteric water electrolysis, which is superior to the performance of commercial units. Moreover, such system reveals a long-term stability when operating at the current density of 100 mA cm(-2) for 40 h, with an energy consumption of 3.35 kWh m(-3) H-2, offering a possibility for low-energy consumption and scaled hydrogen production technology.