Nafion/SiO2@TiO2-palygorskite membranes with improved proton conductivity

This work deals with the synthesis of SiO2@TiO2 supported palygorskite fibers and their use as a filler for proton exchange membrane fuel cells in order to improve their performance. SiO2@TiO2-palygorskite nanostructured particles were synthesized separately with original route to ensure the growth of TiO2 and then of SiO2 on the surface of the clay. Accordingly, the introduction of the synthetic filler (SiO2@TiO2-paly) into the electrolyte membrane (Nafion) aims to improve mechanical, thermal, and proton conductivity properties. The TiO2 nanoparticles were generated via a sol-gel process on the external surface of palygorskite. Then, SiO2 nanoparticles were synthetized using a similar sol-gel process, onto the TiO2-palygorskite particles to produce the final SiO2@TiO2-palygorskite particles. The physico-chemical properties of the nanostructured particles were studied by X-ray diffractometry, Fourier transform infrared, scanning electron microscopy, and transmission electron microscopy. Nafion based composite membranes were prepared using SiO2@TiO2-palygorskite and TiO2-palygorskite as a control standard. The composite membranes show improved mechanical properties, thermal stability, water retention, and proton conductivity compared to the neat Nafion membrane. Proton conductivities (at 100 degrees C and 100% relative humidity) increased from 65.0 mS/cm for neat Nafion to 70.4 mS/cm and to 128.6 mS/cm when incorporated TiO2-Paly (6% in weight) and SiO2@TiO2-Paly (6% in weight), respectively.