Enhanced proton conductivity under low humidity of sulfonated poly(ether ether ketone) composite membrane enabled by multifunctional phosphonic acid polymeric submicrocapsules

• Published in: Journal of power sources 2013-10, Vol.240, p.258-266
• Main Authors: Nie, Lingli, Dong, Hao, Han, Xi, He, Guangwei, Wu, Hong, Jiang, Zhongyi
• Format: Article
• Language: English
• Subjects: Chemistry; Electrochemistry; Ethers; Exact sciences and technology; Fourier transforms; General and physical chemistry; Infrared spectroscopy; Ketones; Membranes; Phosphonic acid polymeric submicrocapsule; Phosphonic acids; Properties of electrolytes: conductivity; Proton conductivity; Proton exchange membrane; Relative humidity; Scanning electron microscopy; Sulfonated poly(ether ether ketone); Water retention
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.04.009

Phosphonic acid polymeric submicrocapsules (PASCs) are synthesized and incorporated into a sulfonated poly(ether ether ketone) (SPEEK) matrix to prepare composite membranes. The microstructure and physicochemical properties of the PASCs and the membranes are characterized by transmission electron microscopy (TEM), energy dispersive X-ray (EDX), field emission scanning electron microscope (FESEM), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Compared with the SPEEK control membrane, the PASC-filled composite membranes exhibit elevated water uptake and proton conductivity at 25 °C and 100% relative humidity (RH). The proton conductivity depends strongly on water content within the membranes. Under 40 °C and 20% RH, the composite membrane filled with 15 wt.% PASCs (128 nm lumen) shows the highest proton conductivity of 0.0142 S cm−1 after 90 min testing, about twelve times higher than that of the SPEEK control membrane (0.0011 S cm−1), which is positively correlated with the water retention of the membrane. These results suggest that the PASC-filled composite membranes may find encouraging application as efficient water-retention and proton-conduction materials in proton exchange membrane fuel cells (PEMFCs). •The phosphonic acid polymeric submicrocapsules are designed and synthetized.•The submicrocapsules have multifunctions in water retention and proton transfer.•The composite membranes exhibit high water uptake and water retention.•The composite membranes exhibit high proton conductivity under low humidity.