High temperature composite membranes based on polybenzimidazole and dendrimer amines functionalized SBA-15 mesoporous silica for fuel cells
In this study SBA-15, melamine-based dendrimer amines functionalized SBA-15 mesoporous silica (MDA-SBA-15), and 1,3-di(3-methylimidazolium) propane dibromide dicationic ionic liquid (pr(mim)2Br2) were used in order to improve the proton conductivity, thermal, and mechanical stability of phosphoric acid (PA) doped polybenzimidazole (PBI)-based composite membranes for application in high-temperature proton exchange membrane (PEM) fuel cells. The effect of the porous structure of the mesoporous silica was investigated on the performance of the PA doped PBI-based membrane containing pr(mim)2Br2 under high temperature. The experimental results implied that the MDA-SBA-15 containing the groups of NH2, and melamine-based dendrimer amines (MDA) on the internal wall of its pores provides special sites for the further interaction with pr(mim)2Br2, PBI, and PA in the composite membranes. The presence of NH2, MDA groups play an important role in creating several pathways for proton exchange in the composite membranes. The PA-doped PBI-based composite membranes containing 4.5 % w/w pr(mim)2Br2, and 1.5 % w/w MDA-SBA-15 exhibit a high proton conductivity of 0.22 S/cm at 180 °C under dry condition. The current density of 1.18 A/cm2, and power density of 0.60 W/cm2 at 0.50 V and 180 °C confirm the enhanced potential of the PA doped PBI-based composite membranes for application in high-temperature PEM fuel cells.