Exploring critical parameters of electrode fabrication in polymer electrolyte membrane fuel cells

Microstructure and electrochemical properties of the cathode catalyst layers (CCL) of a polymer electrolyte membrane fuel cells (PEMFC) have great impact on the performance and durability of the cell. The aim of this work is to establish a link between CCL structure and fuel cell performance. To obtain CCLs with unique structures six types of electrodes were prepared, each with a different coating technique but with the same Pt loading. The coating techniques are airbrush, screen printing, inkjet printing, dry spraying, doctor blade and drop casting. Moreover, intrinsic properties of PEMFC electrodes such as porosity, permeability, diffusivity as well as ionomer distribution are determined by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) and Atomic Force Microscopy (AFM). Overall, 12 parameters have been evaluated. Generally, CCLs with low fractions of uncovered Pt/C show higher performance at low current densities. In this case the more homogeneous ionomer distribution leads to a higher catalyst utilization. At high current densities transport properties of the CCL have to be considered in addition to the catalyst utilization to explain their performance. The CCL prepared by screen printing shows a low fraction of uncovered Pt/C in combination with good transport properties, leading to the best performance at high currents.