ELECTRODEPOSITION OF CATALYTIC METALS USING PULSED ELECTRIC FIELDS

摘要

A gas diffusion electrode (200) for a proton exchange membrane fuel cell is prepared by electrodeposition of a catalytic metal in nanocrystalline form on a substrate (202) by contacting an electrically conductive substrate (202) and a counterelectrode (216) with a plating bath (214) containing ions of a metal to be deposited on the substrate (202) and passing a pulsed electric current between the substrate and the counterelectrode (216) having pulses that are cathodic with respect to t he substrate (202) and have a short on-time and/or a short duty cycle with a frequency from about 10 hertz to about 5000 hertz. In a preferr ed embodiment the electric current is a modulated reversing electric current having pulses that are cathodic with respect to the substra te (202) and pulses that are anodic with respect to the substrate (202), the cathodic pulses having a short on-time and/or short duty cycle, t he charge transfer ratio of the cathodic pulses to the anodic pulses being greater than one, and the frequency of the pulses ranging from about 0.5 hertz to about 5 kilohertz.