(36c) Effect of Hydrophilic Layer Property on the Activity of Pulse Deposited Pt Catalyst in Pem Fuel Cells

Pulse electrodeposition of Pt on different hydrophilic carbon substrates was applied to use as electrocatalysts for polymer electrolyte membrane fuel cell (PEMFC) cathode. During the pulse electrodeposition of Pt, the thickness of the Pt catalyst layer is controlled by the electrolyte penetration into the uncatalyzed carbon electrode. To maximize the effective surface area of the Pt and the contact between Pt and the PFSI, it is critical to prepare a proper carbon support which has optimized hydrophilic properties. Pulse electrodeposition of platinum was performed on the pretreated carbon electrode using a Pt plating bath by controlling the pulse deposition parameters such as the peak current density, duty cycle and the total charge density. The hydrophilic property of GDL and the effective surface area of Pt deposited GDL were estimated by cyclic voltammagrams (CVs) in 0.5 M H₂SO₄. Electron probe microanalysis (EPMA) and scanning electron microscopy (SEM) were employed to measure the thickness of the Pt catalyst layer and to determine the concentration profile of Pt across the cross-sectioned MEA. The effective surface area of Pt catalyst generated using wetting agent showed higher value when compared to that of the other activation methods with excellent distribution of Pt over the surface and very low loading of Pt. Furthermore the thickness of Pt catalyst layer can be controlled by the wetting time in the range of less than micron to several microns.

[1] H. Kim, N.P. Subramanian, B.N. Popov, Journal of Power Sources, 138 (2004) 14. [2] H. Kim, B.N. Popov, Electrochemical and Solid-State Letters, 7 (2004) A71.