A PBI‐Sb 0.2 Sn 0.8 P 2 O 7 ‐H 3 PO 4 Composite Membrane for Intermediate Temperature Fuel Cells

Fine particles of a solid proton conductor Sb 0.2 Sn 0.8 P 2 O 7 were incorporated in PBI‐H 3 PO 4 membranes with 20 wt.%. In SEM figures, the Sb 0.2 Sn 0.8 P 2 O 7 particles exhibited even and uniform distribution in the PBI‐Sb 0.2 Sn 0.8 P 2 O 7 membrane. Influences of the immersing time and the concentration of H 3 PO 4 solution for immersion on H 3 PO 4 loading level were investigated. H 3 PO 4 loading level was found an important factor on membrane conductivity. Incorporation of Sb 0.2 Sn 0.8 P 2 O 7 in the PBI‐H 3 PO 4 membrane resulted in greater membrane conductivities. In the single cell tests, the peak power density of the membrane electrode assembly (MEA) with the PBI‐Sb 0.2 Sn 0.8 P 2 O 7 ‐H 3 PO 4 membrane was also greater than that of a MEA with PBI‐H 3 PO 4 membrane. One MEA using PBI‐Sb 0.2 Sn 0.8 P 2 O 7 ‐H 3 PO 4 membrane achieved a peak power density of 0.67 W cm –2 at 175 °C with H 2 /O 2 and exhibited satisfactory stability.