Water induced phase segregation in hydrocarbon proton exchange membranes

• Published in: Journal of energy chemistry 2018-11, Vol.27 (6), p.1517-1520
• Main Authors: Lyu, Kangjie, Peng, Yanqiu, Xiao, Li, Lu, Juntao, Zhuang, Lin
• Format: Article
• Language: English
• Subjects: Molecular dynamics simulation; Phase segregation; Proton conductivity; Proton exchange membrane; Sulfonated poly(ether ether ketone)
• ISSN: 2095-4956
• DOI: 10.1016/j.jechem.2018.05.009

Proton exchange membranes (PEMs) are a key material for proton exchange membrane fuel cells (PEMFCs). Non-fluorinated hydrocarbon PEMs are low-cost alternatives to Nafion, but limited by the low proton conductivity, because of the weak phase segregation structure and narrow ion-transport channels. Various efforts have been taken to improve the performance of hydrocarbon PEMs, but mostly with complex methodologies. Here we demonstrate a simple, yet very efficient method to create phase segregation structure inside a typical hydrocarbon PEM, sulfonated poly(ether ether ketone) (SPEEK). By simply adding appropriate amounts of water into the DMF solvent, the resulting SPEEK membrane exhibits widened ion-transport channels, with the phase size of 2.7 nm, as indicated by both molecular dynamic (MD) simulations and transmission electron microscope (TEM) observations, and the proton conductivity is thus improved by 200%. These findings not only further our fundamental understanding of hydrocarbon PEMs, but are also valuable to the development of low-cost and practical fuel cell technologies. By simply adding water into the DMF solution of SPEEK, phase segregation structure can efficiently form in the resulting membrane, with the proton conductivity increased by 200%. [Display omitted]