EVALUATION OF AN EFFECTIVE PLATINUM METAL-SURFACE AREA IN A PHOSPHORIC-ACID FUEL-CELL

The effective platinum metal surface area in a real phosphoric acid fu el cell was evaluated by in situ cyclic voltammetry which has been dev eloped in our laboratory. It was found that the in situ electrochemica l platinum surface area of a phosphoric acid fuel cell under real oper ational conditions was around 25 m2/g. It was concluded that this low value came from the isolation of the platinum particles from a carbon support, which was revealed by transmission micrography and the distor tion of an in situ cyclic voltammogram. Furthermore, x-ray photoelectr on spectroscopy analyses of long-term operated electrodes showed that two or three-fluorines were detached from the polytetrafluoroethylene (PTFE) surface. The timing of PTFE degradation was in good agreement w ith the change in the in situ EC-MSA.