Preparation of high-temperature proton exchange membranes based on aminopropyltriethoxysilane and amino trimethylene phosphonic acid

The development of proton exchange membranes (PEMs) with excellent performance becomes an important issue for proton exchange membrane fuel cells (PEMFCs). Acid–base hybrid high-temperature PEMs were prepared from aminopropyltriethoxysilane (APTES) and amino trimethylene phosphonic acid (ATMP) by sol–gel process. Fourier-transform infrared (FTIR) spectra revealed that phosphonic acid and amino group could have been protonized, and siloxane groups were hydrolysed and condensed to yield Si–O–Si network. These membranes were thermally stable up to 200°C and showed excellent dimensional stability in water. In addition, SEM analysis revealed that many nanoparticles appeared in the membranes, and energy dispersive spectrum (EDS) results proved that many phosphate ions were present on the surface of the nanoparticles. This phenomenon became obvious with increasing acidity of sol in sol–gel process. Proton conductivity results indicated that the above structure was favourable for the formation of hydrogen bond and the proton conductivity increases with the increase in temperature, the highest conductivity can reach 4.93 × 10− 2 S cm− 1 at 140°C under anhydrous condition.