Polybenzimidazole/cerium dioxide/graphitic carbon nitride nanosheets for high performance and durable high temperature proton exchange membranes

A novel membrane was fabricated from polybenzimidazole (m-PBI) and cerium dioxide/graphitic carbon nitride nanosheets (m-PBI-X wt%/CeO2/g-C3N4) in order to achieve long-term durability and excellent performance as high temperature proton exchange membrane (HT-PEM) for fuel cells (FCs). The CeO2 nanoparticles was employed to disperse 2D graphitic carbon nitride nanosheets (g-C3N4) in the PBI solution as confirmed by SEM, and also to scavenge the possible hydroxyl radicals when the membrane is operated in the fuel cell device. Unlike to other composite membrane in which the introduction of nanoparticles generally resulted in the sacrificing of mechanical properties, the well dispersed g-C3N4 and CeO2 in PBI membrane induced the excellent mechanical properties. Moreover, the abundant nitrogen atom in g-C3N4 showed strong interaction force with phosphoric acid as confirmed by theoretical calculation. Thus, high proton conductivities of composite membrane have been observed. Thus, the m-PBI/1% CeO2/g-C3N4 composite membrane showed the highest peak power density of 540 mW cm−2 at 160 °C, which is higher than that of the pristine m-PBI membrane (359.31 mW cm−2) under the same testing condition. Most importantly, the durability test demonstrated that the voltage has no obvious attenuation during the 200 h test indicating its excellent stability under the fuel cell device environment at 160 °C. These results indicated that the m-PBI-X wt%/CeO2/g-C3N4 composite membranes was a promising membrane for the application of HT-PEMFCs.