Catalyst layer-free carbon-coated steel—An easy route to bipolar plates of polymer electrolyte membrane fuel cells: Characterization on structure and electrochemistry

Stainless steel coated with carbon by CVD process has been evaluated as a low-cost and small-volume substitute for graphite bipolar plate in polymer electrolyte membrane fuel cell (PEMFC). Carbon film was grown at 690–930 °C under gas-mixture of C2H2–H2. Scanning electron microscopy and X-ray diffractometry were used to characterize surface morphology and crystal structure of resultant carbon films, which were found to depend much on reaction temperature. Interfacial contact resistance (ICR), hydrophobicity and chemical stability of obtained specimens were measured to compare with commercial highly oriented pyrolytic graphite (HOPG). All carbon films investigated in this study show improved ICR and hydrophobicity of SUS304 substrate to the level of HOPG. Amorphous carbon layer with continuous film structure prepared at 810 °C shows the best protection of SUS304 substrate against the attack of H(aq)+ (anodic side) and the best resistance of the coated carbon from gasification (cathodic side) in the simulated PEMFC environment.