Study On Ultrathin Palladium And Pd-Ag Alloy Membranes By PCD Methods

In recent years, the demand for highly pure hydrogen is increasing rapidly due to many fields such as those used in semiconductor manufactures and petrochemical processing. It is well known that Pd and its alloy membranes have been commonly used as hydrogen separators and hydrogenation /dehydrogenation membrane reactors. However, most of the available Pd membranes have not been up to the industrial standards, mainly due to the low hydrogen permeance, high cost, and undesirable mechanical stabilities. Three general approaches may be followed: to be deposited on a porous support, decrease Pd membrane thickness and optimize Pd membrane microstructure.The present study was based on the previous work and aimed in investigating optimizing and exploiting new process for palladium and alloy membranes for hydrogen with aid of XRD, SEM-EDS and AFM analysis. This paper reviews the principle, preparation and characterization of the palladium-based composite membranes and a novel photocatalytic deposition technique in our group is highlighted for membrane preparation. Compared with the previous work in our lab, the photocatalytic reaction rate can be well controlled by adding chelating agents and palladium crystalline grain became fine, which will make the metal membrane denser. Also, the enhancement of the photocatalytic deposition by the addition of EDTA may be caused by the upward shift of the conduction band energy of TiO2 due to the negative charge of the chelating agents.The PCD method was improved and ultra-thin Pd membranes supported on TiO2 outer tubes were prepared by the method, which is interpreted by the photocatalytic reaction at the TiO2 semiconductor/Pd (II) liquid film interface by directly irradiating. The TiO2 supports were prepared by the wet chemical method. And the reaction...