Ion exchange capacity controlled biphenol-based sulfonated poly(arylene ether sulfone) for polymer electrolyte membrane water electrolyzers: Comparison of random and multi-block copolymers
Song-Yi Han, Duk Man Yu, Yong‐Hwan Mo, Su Min Ahn, Jang Yong Lee, Tae‐Ho Kim, Sang Jun Yoon, Sung‐Kwon Hong, Young Taik Hong, Soonyong So
Abstract
Conventionally, highly proton conductive perfluorosulfonic acid (PFSA) ionomers are used for an electrolyte membrane in a polymer electrolyte membrane water electrolyzer. As alternatives to the expensive and highly hydrogen permeable PFSA membranes, hydrocarbon-based sulfonated poly(arylene ether sulfone) proton conducting polymers (BPSH) are synthesized by varying their ion exchange capacity (IEC) from 1.2 to 2.0 meq/g, and the way to employ ion conducting units into polymers (random versus block). BPSH membranes show much lower hydrogen permeability (20 − 45 barrer) than that of PFSA membranes (~115 barrer for Nafion) at 80 °C and 100%RH. Random BPSH membranes show slightly higher selectivity of proton to hydrogen than the membranes from multi-block BPSH copolymers at a similar IEC may due to the enhanced hydrogen barrier property by less-developed hydrophilic phase. The best performing random BPSH with the IEC ~ 1.9 meq/g shows better performance (5.3 A/cm2) than the similarly thick (~50 μm) Nafion 212 (4.8 A/cm2) at 1.9 V, but the higher degradation rate (951 μV/h) than Nafion 212 (613 μV/h) at an accelerated stress test with the 360 consecutive alternating current densities of 3 and 0.02 A/cm2, simulating on and off a water electrolyzer.