Influence of ionomer adhesion ratio of catalyst layer on electrode characteristics of polymer electrolyte fuel cell

Abstract

Optimization of the catalyst layer structure is necessary to realize high performance and low cost of a polymer electrolyte fuel cell (PEFC). The catalyst layer is normally composed of Pt/C powder and an ionomer. The adhesion state of ionomer to Pt/C powder not only changes the proton transport route but also influences the microstructure of the electrode, which is an important factor in controlling cell performance. In this study, in order to investigate the adhesion state of ionomer, we developed the new measurement technique of the specific surface area of catalyst layer. The measurement method was based on the gas adsorption method (N2), and the adhesion ratio of the ionomer was determined from the ratio of the specific surface area before and after removal of the ionomer in the catalyst layer. In addition, the electrode characteristics of the catalyst layer were also measured, and the relationship between the ionomer adhesion ratio and the cell performance was discussed. As a result, it was found that the adhesion ratio of ionomer was correlated with electrode characteristics, meaning that the adhesion ratio of ionomer should be an important parameter for improving cell performance.