Polybenzimidazole/SiO2 hybrid membranes for high temperature proton exchange membrane fuel cells

• The introduction of SiO2 in the PBI membrane has positive effect of the HT-PEMFC performance.
• PBI/SiO2 hybrid membrane shows higher proton conductivity and acid retention properties than PBI membrane.
• Dispersed SiO2 functioned as proton conduction channels in the PBI matrix.

Polybenzimidazole/Silicon dioxide (PBI/SiO2) hybrid membranes were prepared and characterized as alternative materials for high temperature proton exchange membrane fuel cell (HT-PEMFC). The PBI/SiO2 membranes were cast from a PBI polymer synthesized in the laboratory and contained 5 wt. % SiO2 as inorganic filler. Scanning electron microscopy (SEM) analysis showed that the uniform and homogeneous distribution of SiO2 particles in the hybrid membrane. The existence SiO2 has improved the acid retention and proton conductivity properties. A maximum conductivity of 0.1027 S/cm at 180 °C was obtained for the PBI/SiO2 hybrid membrane. Gas diffusion electrodes (GDE) were fabricated by ultrasonic coating technique with 1 mg Pt/cm2 catalyst loading for both anode and cathode. The membranes were tested in a single HT-PEMFC with a 5 cm2 active area operating at the temperature range of 140 °C–180 °C. Single HT-PEMFC tests indicated that PBI/SiO2 hybrid membrane was more stable and also performed better than pristine PBI membrane. Maximum current density was observed for PBI/SiO2 membrane at 165 °C and cell voltage of 0.6 V as 0.24 A/cm2. The results suggested that PBI/SiO2 hybrid membrane is promising electrolytes for HT-PEMFC with improved fuel cell performance.