Quaternary phosphonium-functionalized poly(ether ether ketone) as highly conductive and alkali-stable hydroxide exchange membrane for fuel cells

• Published in: Journal of membrane science Vol. 466; pp. 220 - 228
• Main Authors: Yan, Xiaoming, Gu, Shuang, He, Gaohong, Wu, Xuemei, Zheng, Wenji, Ruan, Xuehua
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.09.2014; Elsevier
• Subjects: Alkaline membrane fuel cells; Applied sciences; Chemistry; Colloidal state and disperse state; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Ethers; Exact sciences and technology; Exchange resins and membranes; Forms of application and semi-finished materials; Fuel cells; General and physical chemistry; Hydroxide exchange membrane; Hydroxides; Ionomers; Membranes; Phosphonization; Poly(ether ether ketone); Polyetheretherketones; Polymer industry, paints, wood; Polymers; Quaternary phosphonium; Solvents; Technology of polymers; Phosphonization; Poly(ether ether ketone); Quaternary phosphonium; Alkaline membrane fuel cells; Hydroxide exchange membrane; Polymeric membrane; Fuel cell; Quaternary phosphonium compound
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2014.04.056

A series of quaternary phosphonium-functionalized poly(ether ether ketone)s (PEEK-QPOHs) have been synthesized by phosphorization reaction, and their membranes have been prepared by a solution casting method. Ion exchange capacity (IEC) of PEEK-QPOH membranes ranges from 0.89 to 1.19mmolg−1 with the degree of chloromethylation from 70% to 126%. Not only are PEEK-QPOH polymers soluble in typical high-boiling-point membrane-forming solvents, but also they are soluble in some low-boiling-point water-miscible solvents (low alcohols), implying their ability to serve as both membranes and ionomers. PEEK-QPOH membranes showed high hydroxide conductivity, e.g., a PEEK-QPOH 126% membrane (with IEC of 1.19mmolg−1) exhibited 61 and 89mScm−1 at 20°C and 60°C, respectively. Based on the same polymer backbone of PEEK, quaternary phosphonium-functionalized PEEK membranes are more hydroxide-conductive and more alkali-stable than quaternary ammonium- and imidazolium-functionalized counterparts. All these properties indicate PEEK-QPOH is one of the most promising HEM materials for potential applications in alkaline membrane fuel cells. [Display omitted] •Quaternary phosphonium-functionalized PEEK HEMs were successfully prepared.•PEEK-QPOHs are soluble in low-boiling-point solvents.•PEEK-QPOH HEMs exhibit good alkali stability.•PEEK-QPOH HEMs exhibit high hydroxide conductivity (e.g., 89mScm−1 at 60°C).