Diphenylanthracene-based ion exchange membranes with high conductivity and robust chemical stability for acid-alkaline amphoteric water electrolysis

A novel polymer enriched with quaternary ammonium cation groups and having a star-branched crosslinking network is synthesized from bulky diphenylanthracene, the flexible 1, 6-dibromohexane and tris(dimethylaminomethyl) phenol. The enriched quaternary ammonium cations enable the membranes with both high anion exchange capacity and acid doping levels. The prepared membranes show a proton conductivity of 262 mS cm−1 and a hydroxide conductivity of 149 mS cm−1 at 80 °C under 100 % relatively humidity. The hydrated membrane with exchangeable hydroxide ions exhibits a tensile stress at break of 44.7 MPa at room temperature. A steady proton conductivity and a hydroxide conductivity retention rate as high as 93 % are achieved by the prepared membranes after soaking in 3 mol/L H2SO4 or 6 mol/L KOH at 80 °C for 1000 h. A current density of 996 mA cm−2 is obtained at 80 °C under 2.0 V by the amphoteric water electrolytic cell using the prepared membrane as the diaphragm. The energy consumption of this system is 2.7 kWh Nm−3 operating at a current density of 100 mA cm−2 for 64 h, offering a possibility of low energy consumption for hydrogen production.