Evaluation of change in nanostructure through the heat treatment of carbon materials and their durability for the start/stop operation of polymer electrolyte fuel cells

Carbon supports of electrocatalysts for polymer electrolyte fuel cells were heat treated with the aim of proposing carbon materials with high corrosion resistance and with the sufficient nanostructure to interact with platinum particles, simultaneously. Two kinds of commercially available state-of-the-art carbon black materials, Vulcan XC-72 and Ketjen Black EC600-JD, were heat treated at 1100, 1600, and 2000 °C in order to produce the graphitized surface. Eight different Pt/C catalysts were synthesized, and their durability was examined using an electrochemically accelerating potential cycle protocol, considering a practical condition of fuel cell vehicles. Their durability was evaluated through the change in electrochemically active surface area, oxygen reduction reactivity, and platinum particles in TEM images. As expected, higher graphitization degree lead to increasing in corrosion resistance, but at the same time resulted in reducing the immobilization ability of platinum on carbon supports. Therefore, an optimum condition with both high corrosion resistance and sufficient interaction with platinum particles was investigated. Consequently, in this study we have found graphitization at 1600 °C is an optimum temperature among 1100, 1600, and 2000 °C to obtain highest durability for Pt/C catalysts, and the graphitization degree is an important factor to develop catalysts with high durability.