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 °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 H2, offering a possibility for low-energy consumption and scaled hydrogen production technology. [Display omitted] •The m-PBI and OPBI membranes were applied for acid-alkaline amphoteric water electrolysis first time.•The influence of electrolyte concentration and temperature was investigated systemically.•A current density of 800 mA cm−2 at 2.0 V was achieved to produce hydrogen.•The energy consumption for hydrogen production was reduced significantly.