Direct deposition of catalyst layers on polymer electrolyte membrane (PEM) for fuel cells with controlled platinum distribution by inkjet printing

Abstract

This paper discusses the use of inkjet printing technology for the direct deposition of catalyst layers onto 8 μm or 15 μm thick polymer electrolyte membranes (PEM) with the view to industrial production. Here, the challenges in applying larger material quantities within a few seconds and the impact on the homogeneity of the catalyst layers and the platinum distribution is presented. Different approaches for the deposition and drying of the catalyst material as well as detailed investigations of the printed layers are conducted. As result, a sequential deposition of defined smaller material quantities to a 12 cm² area is an expedient approach to control and restrict the flow of wet material and achieve homogeneous catalyst layers directly on these thin membranes with least swelling and minor crack formation. As a quality control, micro X-ray fluorescence (XRF) measurements were carried out and reveal a drastically reduced material agglomeration and therefore, a uniform platinum distribution for the mentioned printing approach. Furthermore, the electrochemical analysis in terms of electrochemical impedance spectroscopy (EIS), the resulting O₂ diffusion resistances as well as protonic resistance and the U-I-characteristics reveal a clear trend of the performance depending on the platinum loading, number of printed layers and porosity. By implementing the most favorable printing approach, a current density of 1.58 A/cm² at 0.6 V cell voltage with a peak power density of 1.21 W/cm² could be achieved.