Anomalous behavior of proton transport and dimensional stability of sulfonated poly(arylene ether sulfone) nonwoven/silicate composite proton exchange membrane with dual phase co-continuous morphology

Herein, anomalous behavior of proton conductivity and dimensional stability of sulfonated poly(arylene ether sulfone) (SPAES) nanofiber nonwoven fabric/silicate composite membrane (denoted as ‘SN/S membrane’) featuring dual phase co-continuous morphology, which could be potentially applied to proton exchange membrane fuel cells (PEMFCs), is systematically investigated. The SN/S membrane is fabricated via in situ sol–gel synthesis of tetraethoxysilane (TEOS)/3-glycidyloxypropyltrimethoxysilane (GPTMS) mixture directly inside the electrospun SPAES nonwoven. In comparison to a typical SPAES (matrix)/silicate (domain) composite membrane, the SN/S membrane having structural uniqueness provides significant improvement in relative humidity (RH) variation-driven dimensional change, although its proton conductivity is decreased due to the presence of ionically inert continuous silicate phase. A noteworthy finding of this study is that the phase morphology of composite proton exchange membranes plays a crucial role in determining the membrane properties such as proton conductivity and dimensional stability.