Optimization of catalyst application method using Inkjet coating machine

Abstract

A popularization of Polymer Electrolyte Fuel Cell (PEFC) is expected as a clean energy. However, the manufacturing cost is still expensive, and it is required to reduce the manufacturing cost for further spread. The cost of platinum catalyst in the catalyst layer of the membrane electrode assembly (MEA) accounts about 50% of the total manufacturing cost. Therefore, the reduction of the amount of platinum catalyst is necessary for further popularization of PEFC. Generally, because the catalyst layer (CL) of MEAs is manufactured by the doctor blade method, this method has some problems such as poor dispersion of Pt catalyst in the CL and difficulty in controlling the membrane thickness. Although our laboratory proposes the application of inkjet coating method to the manufacturing process of CL to solve these problems, it is clarified that this method has some problems such as the crack of catalyst layer surface and increase of the ohmic resistance. Therefore, we were clarified points to be considered in the inkjet coating method by evaluating two drawing methods by ink jet printer such as a continuous (Inkjet-A) and an intermittent coating methods (Inkjet-B). As a result, although in the continuous coating method, ink droplets agglomerate, which contributes to the separation of the platinum catalyst and ionomer and makes it worsens ohmic and diffusion resistances, in the intermittent coating method, the ink droplets dried on their own and did not agglomerate, and the degree of separation between the platinum catalyst and ionomer was low. In the inkjet coating method, drawing the applied ink droplets so that they dry alone contributes to improved cell performance.