Cell performance enhancement with titania-doped polybenzimidazole based composite membrane in intermediate temperature fuel cell under anhydrous condition

Abstract

Polybenzimidazole (PBI) electrolyte and TiO₂-doped PBI electrolyte membranes were fabricated for application in intermediate temperature hydrogen fuel cells. These membranes and their assembled cells were characterized by field emission scanning electron microscopy, optical microscope, conductivity measurement, and fuel cell evaluation. Metal oxide particles have a high affinity for phosphoric acid. Hence, TiO₂ was added to the PBI electrolyte membrane at various concentrations to increase the retention of phosphoric acid. The proton conductivity of the electrolyte membrane with TiO₂ nanoparticles and their influence on the fuel cell power generation characteristics were investigated under anhydrous condition at 150°C. The TiO₂/PBI electrolyte membrane achieved output characteristics more than twice that of the pure PBI electrolyte membrane. It was observed that the addition of TiO₂ improved the phosphate holding power of the electrolyte membrane. TiO₂/PBI membrane retained high conductivity values at the higher temperatures as a result of its high doping level and high water retention capacity. TiO₂ (2 wt %)/PBI composite membrane showed the best performance with a power density of 434 mW cm⁻². These results suggest that TiO₂/PBI-based composite membranes are promising electrolytes for intermediate temperature polymer electrolyte membrane fuel cells.