Preparation of Porous Carbon Material Composed of Ozone-Treated Carbon Fiber and Evaluation of Corrosion Resistance in Hot Phosphoric Acid

Abstract

An experimental study was carried out to find how to upgrade surface properties of carbonaceous porous materials used as an electrode substrate in Phosphoric Acid Fuel Cells. The porous materials were made by forming of carbon fibers prepared through ozone treatment (OCF hereafter) with resin binders, and then baking and graphitization were performed. Comparison was performed with those prepared by use of carbon fiber as received (NCF hereafter). As a result, the ozone treatment affected greatly to the performance of the porous materials, showing decrease of electrochemical corrosion loss in 20% by weight compared to the one made by using NCF. The porous material made of OCF showed approximately 4% higher porosity and 30% lower specific surface area than those of NCF. From the observation under an electron microscope, it was found the surface of OCF was covered more widely and uniformly by the binder than that of NCF, and the stress produced during carbonization of the binder brought larger shrinkage to the porous materials made of OCF, furthermore, graphitizability of the carbonaceous material made from binder was increased by the relaxation of remaining stress during the graphitization. There appeared no change in electrical and thermal conductivity, while a small decrease in mechanical strength was observed, due to the increase in the porosity. However, such disadvantage as above will be avoided by choosing binder content and forming pressure.