Effect of EDTA on preparation of Pd membranes by photocatalytic deposition

Ultra-thin palladium membranes (0.2 μm thickness) on TiO₂ supports were obtained by photocatalytic deposition. The presence of EDTA in an aqueous precursor solution for the Pd membranes was found to promote the formation of Pd membranes; the effect of chelating agents deposited on the Pd membrane was analyzed by SEM, EDS, and XPS. Compared with previous work in our laboratory, the photocatalytic reaction rate can be well controlled by the chelating agents and palladium crystalline grain become fine, which will make the metal membrane denser. Furthermore, EDTA can effectively retard the homogeneous reaction in favor of the incidence of ultraviolet light. 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. Furthermore, the tightness test experiment at room temperature showed that Pd membranes were dense and defect-free. A gas permeation experiment was conducted under 600 K and 0.01-0.1 MPa. Hydrogen permeability and hydrogen/nitrogen (H₂/N₂) selectivity were 1.1×10^-6 mol.m^-2. s^-1.Pa^-1 and 12 at 600 K, respectively.