Improvement of Cell Performance in Low-Pt-Loading PEFC Cathode Catalyst Layers Prepared by the Electrospray Method

Abstract

© The Author(s) 2016. The reduction of Pt loading in cathode catalysts is an important subject for developing polymer electrolyte fuel cells. In order to solve this problem without sacrificing performance, we prepared a uniform catalyst-coated membrane (CCM) by an electrospray (ES) method with a low Pt loading, 0.05 mg Pt cm -2 , which is one-tenth of the typical cathode Pt loading. The ES process has several advantages for the fabrication of thin catalyst layers (CLs), such as smaller droplets and accurate position control, compared with the pulse-swirl-spray (PSS) method. Highly uniform CLs were evaluated by use of a standard evaluation cell (area 29.2 cm 2 ). The ES method makes it possible to control precisely the coating area and reduce the losses of the catalyst ink. CLs cross sections prepared by focused ion beam milling indicated that the total occupation fraction of the pores in the CLs prepared by the ES method was about twice as large as that for the PSS method. The ES method improved the ionomer coverage, led to increased electrochemically active surface area, and constructed more porous CLs. The highly porous CLs prepared by the ES method contributed to the improvement of the cell performance.