ELECTRODICS AT THE GAS-DIFFUSION PLATINUM-ELECTRODES - H3PW12O40 PROTON CONDUCTING LIQUID ELECTROLYTE INTERFACE

The optimization procedure of gas diffusion electrode (anode and catho de) development is described for a new type of low temperature fuel ce ll using as proton conducting electrolyte a concentrated aqueous solut ion of H3PW12O40 acid. The procedure consists of full factorial design of experiments performed by varying three variables: (a) content of p olytetrafluoroethylene (PTFE) in the catalyst layer of electrodes; (b) content of fluoroethylenepropylene (FEP) in the diffusional (supporti ng) layer of electrodes; and (c) thickness of the diffusional layer of electrodes on three levels (low, medium and high) during the measurem ents of hydrogen permeability through dry electrodes, measurements of electrolyte absorption in the electrodes and during the electrochemica l measurements of polarization curves for oxygen reduction, hydrogen o xidation and of the oxygen gain in a half-cell at room temperature. Th e results obtained demonstrate that the electrochemical activity in th e half-cell reactions is regulated by the gas permeability of diffusio nal layer and wettability of the catalyst layer. The strongest influen ce on the observables has the polymer content in the diffusional layer . However, in the case of anode optimization, a strong interaction bet ween the polymer content iii the catalytic layer and polymer content i n the diffusional layer has been demonstrated. Copyright (C) 1996 Else vier Science Ltd