Fabrication of functionalized nanosilicone particles-doped biodegradable eco-friendly proton exchange membranes

The functionalized nanosilicone particles with high sulfonic and carboxyl groups were prepared and incorporated into chitosan matrix to fabricate the doped biodegradable eco-friendly electrolyte materials. The functionalized nanosilicone particles not only were as crosslinkers and proton conductors, but also could form the compact silicone network. Compared with the undoped membrane, the doped ones showed better water retention, methanol barrier, thermal and mechanical stability. In particular, lower methanol uptake and diffusion in higher methanol concentration were very advantageous for reducing fuel wastage and increasing cell efficiency. The lowest methanol diffusion coefficient obtained in 12 M methanol (5.60 × 10⁻⁸ cm² s⁻¹) was less than 1/56 of that of Nafion^® 117. In addition, proton conductivity of the doped membranes was significantly affected by nanosilicone particles content. The highest conductivity value obtained with 30% nanosilicone particles was 0.074 S cm⁻¹ at 80 °C, which was very close to the value of Nafion^® 117 at same conditions. The decreased methanol diffusion and improved conductivity conferred the super selectivity. In our work, the maximum selectivity was 5.30 × 10⁵ Ss cm⁻³ which was approximately 33.5 times of that of Nafion^® 117, indicating that the doped membranes were promising candidates for proton exchange membrane applications. Furthermore, the addition of functionalized nanosilicone particles endowed the membranes with many other advantages, including cost-effectiveness and simple preparation, which also improved the application potential of natural polymer chitosan as direct methanol fuel cell membrane material.