Thickness-controlled porous polyethylene/hydrocarbon ionomer composite membranes for durable proton exchange membrane water electrolysis

Hydrocarbon (HC)-based composite membranes reinforced with porous polyethylene (PE) substrates are investigated for proton exchange membrane water electrolysis (PEMWE). Sulfonated poly(arylene ether sulfone) with 50 mol% sulfonation (SPAES50) is used as the ionomer, and a porous PE compatible with SPAES50 is incorporated to improve the mechanical robustness and dimensional stability. A series of composite membranes with different thicknesses are fabricated to examine the effect of the HC ionomer-to-PE thickness ratio. The composite membranes exhibit enhanced dimensional stability and reduced hydrogen permeability, with the latter being 70% lower than that of Nafion212 owing to the rigid SPAES50 backbone and the suppressed membrane swelling caused by PE. Although the incorporation of non-proton-conductive PE results in lower proton conductivity than that of SPAES50, the composite membranes with thickness ratios of 1:1:1 and 1.5:1:1.5 (HC:PE:HC) show proton conductivities comparable to that of Nafion212. In PEMWE single-cell tests, the composite membrane with a 1:1:1 thickness ratio achieves a current density of 5.40 A/cm 2 at 1.9 V, exceeding that of Nafion212 (5.19 A/cm 2 ). Moreover, this membrane exhibited a lower degradation rate of 130 μV/h compared to pristine membranes. Consequently, the 1:1:1 configuration is identified as the optimal design for PE-reinforced HC composite membranes in PEMWE. • Thickness-controlled PE/HC composite membranes improve mechanical stability in PEMWE. • Porous PE reinforcement reduces swelling and hydrogen permeability by ∼70%. • An optimal 1:1:1 thickness ratio demonstrates performance comparable to Nafion212. • The S/PE-1.0 membrane exhibits a low degradation rate during long-term PEMWE operation.