Synthesis and characterisation of chitosan–nitrogen polyphosphonic acid poly(organosiloxane) high temperature proton exchange membranes for fuel cells

Abstract

One kind of acid–base high temperature proton exchange membrane was synthesised from chitosan (CS), 3-aminopropyltriethoxysilane (APTES) and amino trimethylene phosphonic acid (ATMP) by sol–gel process. In order to prevent phosphonic acid from leaching out, ATMP was introduced as proton conductor as well as cross-linker. Fourier transform infrared suggests that the Si–OC2H5 in APTES appears as a hydrolysis–polycondensation yielding Si–O–Si network, and the introduction of ATMP leads to the protonation of the amino group. These membranes are thermally stable up to ∼180°C and show excellent oxidative stability. In addition, the proton conductivity of CS/APTES/ATMP membranes increases with increasing temperature, reaching the value of 0·0578 S cm− 1 at 140°C under normally anhydrous condition, which indicates that the acid–base pair and hydrogen bond network in CS/APTES/ATMP membranes are favourable to proton transfer.