title: Highly flexible, proton-conductive silicate glass electrolytes for medium-temperature/low-humidity proton exchange membrane fuel cells.
abstract: We demonstrate highly flexible, proton-conductive silicate glass electrolytes integrated with polyimide (PI) nonwoven fabrics (referred to as "b-SS glass electrolytes") for potential use in medium-temperature/low-humidity proton exchange membrane fuel cells (PEMFCs). The b-SS glass electrolytes are fabricated via in situ sol-gel synthesis of 3-trihydroxysilyl-1-propanesulfonic acid (THPSA)/3-glycidyloxypropyl trimethoxysilane (GPTMS) mixtures inside PI nonwoven substrates that serve as a porous reinforcing framework. Owing to this structural uniqueness, the b-SS glass electrolytes provide noticeable improvements in mechanical bendability and membrane thickness, in comparison to typical bulk silicate glass electrolytes that are thick and easily fragile. Another salient feature of the b-SS glass electrolytes is the excellent proton conductivity at harsh measurement conditions of medium temperature/low humidity, which is highly important for PEMFC-powered electric vehicle applications. This beneficial performance is attributed to the presence of a highly interconnected, proton-conductive (THPSA/GPTMS-based) silicate glass matrix in the PI reinforcing framework. Notably, the b-SS glass electrolyte synthesized from THPSA/GPTMS = 9/1 (mol/mol) exhibits a higher proton conductivity than water-swollen sulfonated polymer electrolyte membranes (here, sulfonated poly(arylene ether sulfone) and Nafion are chosen as control samples). This intriguing behavior in the proton conductivity of the b-SS glass electrolytes is discussed in great detail by considering its structural novelty and Grotthuss mechanism-driven proton migration that is strongly affected by ion exchange capacity (IEC) values and also state of water.
authors.affiliation: Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Korea.
authors.forename: Hyeon-Ji
authors.initials: HJ
authors.lastname: Lee
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Won
authors.forename: Jun-Muk
authors.initials: JM
authors.lastname: Lim
authors.forename: Young Taik
authors.initials: YT
authors.lastname: Hong
authors.forename: Sang-Young
authors.initials: SY
authors.lastname: Lee