Fabrication of a novel Pd/γ-alumina graded membrane by electroless plating on nanoporous γ-alumina

This study investigated a method of electroless plating to fabricate a novel functionally graded Pd/γ-alumina/anodic alumina composite membrane. Electroless plating reactions were carried out on catalyzed anodic alumina surfaces and on catalyzed nanoporous γ-alumina in an electroless plating solution. The reactions readily formed a smooth Pd membrane on the catalyzed nanoporous γ-alumina, but failed to form a Pd membrane on the catalyzed anodic alumina. According to surface SEM images, assessment of the rate of Pd deposition into the nanoporous γ-alumina, and cross-section analysis by EPMA, the Pd membrane grew into the nanoporous γ-alumina in the direction of depth from 2 h up to 5 h during the electroless plating reaction, and then grew upward in the direction of thickness after 5 h. The agitation speed of the electroless plating bath influenced the growth of the Pd/γ-alumina graded layer from 2 to 5 h during the reaction, and also influenced the crystalline growth of the Pd.