Proposal for improving the durability of carbon material for phosphoric acid fuel cells (PAFC) by revealing the corrosion factors

In order to improve durability of phosphoric acid fuel cells (PAFC), it is essential to suppress the corrosion rate of carbon, a major PAFC material. In this study, we examined the factors which influence on corrosion rates of carbon material in hot phosphoric acid. The carbon corrosion rate can be suppressed by lowering the oxygen content and reducing impurity of the content. The higher the level of graphitization carbon is used, the lesser the corrosion rate is. The fluorination of carbon surface is effective improving the corrosion resistance in case of using the sample with lower graphitization level. Among several factors affecting the durability of carbon fiber/carbon composite, the crystallite orientation of carbon fiber greatly influence the corrosion condition of carbon fiber/carbon composite. Also, a binder will influence on corrosion condition. As to what kind of material should be used for carbon fiber/carbon composite, our study revealed that the onion folded carbon fiber bound with phenol resin seems more effective in term of their durability.