DEVELOPMENT AND ELECTROCHEMICAL STUDIES OF GAS-DIFFUSION ELECTRODES FOR POLYMER ELECTROLYTE FUEL-CELLS

Electrochemical studies on low catalyst loading gas diffusion electrod es for polymer electrolyte fuel cells are reported. The best performan ce is obtained with an electrode formed from 20 wt % Pt/C, 0.4 mg Pt c m(-2) and 1.1 mg Nafion(R) cm(-2) in the catalyst layer and 15% PTFE i n a diffusion layer of 50 mu m thickness, for both the cathode and the anode. However, it is also observed that the platinum requirement can be diminished to values close to 0.2 mg Pt cm(-2) in the cathode and 0.1 mg Pt cm(-2) in the anode, without appreciably affecting the good characteristics of the fuel cell response. The experimental fuel cell data were analysed using theoretical models of the electrode structure and of the fuel cell system. It is seen that most of the electrode sy stems present limiting currents and some also show linear diffusion co mponents arising from diffusion limitations in the gas channels and/or in the thin him of electrolyte covering the catalyst particles.