Electrochemical Performance of Thin-Film Pt3y Electrodes in PEMFC

In current polymer electrolyte fuel cells (PEMFC), high amounts of platinum catalysts is required due to the sluggish kinetics of the oxygen reduction reaction (ORR). As such it is important to find ways to increase the activity of the ORR catalyst. Previous studies have shown that alloying platinum with yttrium results in a catalyst which is more than six times as active as sole Pt in half cell rotating disk electrode measurements [1]. The model electrodes in this study are prepared by sputtering a well-defined layer of alloy catalyst onto a gas diffusion layer (GDL). In this manner the composition and thickness of the film can be controlled. These electrodes are studied with single cell PEMFC measurements to characterize the materials, similar to previous work done with these types of electrodes [2]. Using these methods the electrochemical surface area (ECSA), ORR activity, and stability are evaluated. The effects of different MEA preparations will also be investigated. Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis as well and X-ray photoelectron spectroscopy (XPS) are used to characterize the structure of the alloy catalyst as well as the bulk and surface compositions, i.e. platinum to yttrium ratio. This characterization is performed on both as-prepared samples and electrodes after being used in the PEMFC. The main focus is to determine the role of yttrium in platinum thin-film platinum electrodes, and if the excellent activity in half cell experiments will also be seen in real PEMFC measurements. References [1] J. Greeley, I. E. L. Stephens, A. S. Bondarenko, T. P. Johansson, H. A. Hansen, T. F. Jaramillo, J. Rossmeisl, I. Chorkendorff and J. K. Nørskov , Nature Chemistry, 2009, 1, 552-556 [2] M. Wesselmark, B.Wickman,C.Lagergren,G.Lindbergh, Electrochimica Acta, 2013, 111, 152-159