Electrically conductive amorphous carbon coating on metal bipolar plates for PEFC

Ti bipolar plates coated with amorphous carbon (a-C) film were developed for polymer electrolyte membrane fuel cells (PEMFC). The a-C films were coated at various growth temperatures. A low growth temperature caused the resistivity of the a-C film to be high. An a-C film coating with high resistivity resulted in an increase in the contact resistance between the surface of the bipolar plate and the membrane electrode assembly (MEA) of up to 440 Ωcm2 which results in a decrease in the output power of the fuel cell. On the other hand, an a-C film coating with a low resistivity of 10− 3 Ω cm was formed by an increase in the growth temperature of up to 600 °C. The bipolar plate coated with this a-C film showed low contact resistance (20 mΩ) between its surface and the MEA. Therefore, the fuel cell assembled from Ti bipolar plates coated with the a-C film at 600 °C showed an output power of 1.8 W, giving it an output 1.4 times higher than the output of a bare (not a-C coated) Ti bipolar plate fuel cell.