Expanded Graphite-Epoxy-Flexible Silica Composite Bipolar Plates for PEM Fuel Cells

Silica impregnated expanded graphite-epoxy composites are developed as bipolar plates for proton exchange membrane (PEM) fuel cells. These composite plates were prepared by solution impregnation, followed by compression molding and curing. Mechanical properties, electrical conductivities, corrosion resistance, and contact angles were determined as a function of impregnated content. The plates show high flexural strength with 5% methyltrimethoxysilane (MTMS) addi-tion (20 MPa) and in-plane conductivity of 131 S cm(-1) that meet the DOE target (>100 S cm(-1)). Corrosion current values as low as 1.09 mu A cm(-2) were obtained. The contact angle was found to be 80 degrees. Power density of 1 W cm(-2) was achieved with custom made expanded graphite-polymer composite plates. High efficiency values were obtained at low current regions.