Conventional electroless plating method is limited by the non-uniformity in depositions of Pd-grains on porous substrates and results in defective films. Even if the defects are filled, fabricated film becomes comparatively thicker. In order to fabricate defect free, relatively thinner membrane, control of Pd-grain sizes and their subsequent uniform agglomeration are critical. The oxidation-reduction reactions between Pd-complex and hydrazine result in evolution of ammonia and nitrogen gas bubbles. When adhered to the substrate surface and in the pores, these gas bubbles hinder uniform Pd-film deposition. To over these limitations, we investigated the role of surfactants in electroless plating, what we call Surfactant Induced Electroless Plating (SIEP) in fabricating thin and defect-free Pd-film on microporous stainless steel substrate.

Polycrystalline palladium (Pd) was deposited on microporous stainless steel substrate using suitable surfactant in various concentrations in typical electroless plating formulation. To elucidate the role of surfactant in solid-liquid and solid-gas interface during grain coarsening, we used surfactant concentrations as in terms of critical micelle concentration (CMC). The microstructure of the Pd-film was characterized by Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD). The type of surfactant (anionic, cationic and nonionic) and their relative CMCs greatly influence the grain size and surface morphology of the deposited Pd-film. We were successful in fabricating defect-free, thin Pd-film on microporous stainless steel substrate using a cationic surfactant. The surfactant molecules play an important role in the plating process in tailoring grain size and the process of agglomeration by removing tiny gas bubbles through adsorption at the gas-liquid interface. We studied the hydrogen permeability and selectivity for each of the membranes fabricated in this study at elevated temperature. Results show that membranes with agglomerated grains (finer grain size) possess relatively higher permeability and selectivity. In this presentation we will present some of these results along with a proposed deposition mechanism for SIEP.