SELECTIVE ELECTRODEPOSITION OF CATALYST WITHIN MEMBRANE-ELECTRODE STRUCTURES

A method that allows one to selectively electrodeposit catalyst within the thin active layer of a membrane-electrode assembly is described. The active layer corresponds to the location of electrochemical reaction in a fuel cell. The method is based on the unique chemistry of the membrane/gas-diffusion-electrode interface, where metal deposits tend to concentrate if dilute-electrolyte solutions are used for deposition. Examples of copper and platinum deposition from aqueous copper sulfate and tetrammine platinum (II) chloride, respectively, demonstrate the generality and effectiveness of the method. Electron probe microanalysis, backscattered electron images, and electrochemical experiments are used to characterize the catalyzed membrane-electrode assemblies. Transport and kinetic parameters are obtained for the Pt(NH3)4Cl2 electrolyte; the parameters can be used in future modeling work to understand and optimize the catalyzation process.