Pure nickel coating on a mesoporous alumina membrane: Preparation by electroless plating and characterization

This work concerns the preparation and characterization of a composite inorganic membrane based on nickel supported on a tubular porous ceramic for use in high temperature hydrogen separation. The characteristics required of this material for a high hydrogen permselectivity are a defect-free coating and thermal stability. Thus, electroless plating of nickel using hydrazine as reducing agent enables a metallic nickel coating to be deposited directly on an asymmetric alumina support having a mesoporous top layer composed of γ-alumina. To optimize conditions for reduction of the metal ion, variables including the temperature, the nature of the nickel salt, the choice of stabilizer and the hydrazine concentrations in the plating bath were studied. Metallic nickel was found to be dispersed both in and on the γ-alumina. After heat treatment at high temperature, a thin and uniform pure Ni˙ layer (thickness ≈ 1–1.5 μm), characterized by scanning electron microscopy (SEM) and X-ray Diffraction (XRD), was formed. The separation performance of the Ni/ceramic membrane was investigated using single gases (hydrogen, nitrogen, carbon dioxide and methane) at room temperature. The results indicate that the mechanism of hydrogen transport is related to the Knudsen diffusion.