Direct Spraying of Catalyst Inks for PEMFC Electrode Manufacturing

Automated manufacturing techniques are needed to reduce production costs for polymer electrolyte membrane (PEM) fuel cell electrodes. The work presented in this paper focuses on the use of a low pressure, low volume direct spray valve that uses air pressure to atomize fluids and transfer them to a gas diffusion layer (GDL) to produce a gas diffusion electrode (GDE). Two of these electrodes would then be joined with a polymer electrolyte membrane to produce a fuel cell membrane electrode assembly (MEA). Accurate and reproducible deposition methods such as this will result in less wasted materials, especially platinum, and increased throughput compared to common laboratory-scale techniques such as paint brushing and Mayer-rod coating. In this study, the production of inks will be discussed including a catalyst ink containing platinum nano-particles supported on carbon (20% loading by weight) and a similar analog ink which is identical except for that it does not contain the platinum. Two different substrates, mylar transparency film and actual carbon paper GDL substrate will be used and presented in this study. Ink rheology (viscosity, solids content, etc.) will also be discussed as it pertains to optimizing spray pattern uniformity and process efficiency. Initial results of thickness measurements which are used for determining uniformity and the required overlapping of multiple coats will be presented. In addition, a comparison of scanning electron microscopy (SEM) images of electrode surface structures prepared by mayer-rod and spraying will be shown. A brief discussion of the future work planned by the authors in order to study the effects of processing variables on actual fuel cell performance will also be given.