Fabrication of Thin Palladium Membrane by Electroplating Coexisting with Supercritical Carbon Dioxide

A supported thin palladium membrane was fabricated using electroplating coexisting with supercritical carbon dioxide, named supercritical electroplating. In this unique electroplating, immediate dissolution of hydrogen formed via water electrolysis into supercritical carbon dioxide as well as fabrication of a dense metallic film consisting of nano-size crystals will be expected by dispersion of conductive plating solution into inconductive supercritical carbon dioxide. Commercially available palladium plating baths, however, cannot be applied to supercritical electroplating aqueous solution with acidic property, because they were developed to extend the service life by the formation of stable palladium complex in ammonium aqueous solution with basic property. In this study, a new bath composed of PdCl2, KBr, KNO2, H3BO3, Glycine and surfactant was developed for the supercritical palladium plating. As a result, a defect-free palladium film could be fabricated on a porous conductive support.