Modelling of a double-layered PTFE-bonded oxygen electrode

Abstract

A new mathematical model for the catalyst layer of a PTFE-bonded electrode has been developed. The model is based on the assumption that the catalyst layer contains porous aggregates of catalyst particles flooded with electrolyte and surrounded by a network of gas-supplying hydrophobic pores. It is also assumed that oxygen must diffuse through an electrolyte film surrounding each porous aggregate before it can diffuse further into the pores of the aggregate. This model predicts a doubling of the Tafel slope under certain conditions and this coincides with the predictions of the flooded agglomerate model as well as the cylindrical gas pore model. However, the model can also explain the behaviour of the catalyst layer in limiting current conditions which the other two models mentioned above are unable to do. Thus the equation derived for the limiting current for a double-layered PTFE-bonded oxygen electrode agrees well with published experimental data. © 1987.