Modelling of mass transfer within the PEM fuel cell active layer: limitations at the particle level

A microscopic approach is proposed for predicting the behaviour of the acti ve layer from the local mass transfer equations at the catalytic particle l evel. The model takes into account diffusion and electrochemical reaction w ithout ohmic drop limitation and is numerically performed for three geometr ic descriptions of the active layer using the finite element method. Diffus ion limitations within the whole active layer are confirmed, but diffusion and competition effects at the particle level are also pointed out. As a pr actical conclusion, these effects at the particle level, almost negligible for oxygen reduction, are significantly influent for hydrogen oxidation.