A polybenzimidazole/sulfonated graphite oxide composite membrane for high temperature polymer electrolyte membrane fuel cells

Polybenzimidazole/graphite oxide (PBI/GO) and PBI/sulfonated graphite oxide composite membranes were prepared for high temperature polymer electrolyte membrane fuel cells. The membranes were loaded with phosphoric acid to provide suitable proton conductivity. The PBI/GO and PBI/SGO membranes were characterized by XRD which showed that the d-spacing reflection (001) of SGO in PBI matrix was shifted from 2θ = 11°, meaning that the PBI molecules were intercalated into the SGO layers during the membrane preparation process. A low acid loading level reduced the free acid in the membranes which avoided water loss and thus conductivity loss. The ionic conductivities of the PBI/GO and PBI/SGO membranes, with low acid loading, were 0.027 S cm−1 and 0.052 S cm−1 at 175 °C and 0% humidity. Fuel cell performance with SGO/PBI membranes gave a maximum power density of 600 mW cm−2 at 175 °C.