Improved photocatalytic deposition of palladium membranes

In order to enhance ultra-thin palladium (Pd) membranes integrity, an improved photocatalytic deposition method (PCD) was developed for the Pd/TiO₂ composite membranes. The PCD reactions for Pd membranes occurred in the solution previously and the mechanism of the improved PCD method is interpreted by the photocatalytic reaction at the TiO₂ semiconductor/Pd(II) liquid film interface by directly irradiating. The reaction processes conducted in the liquid film could effectively avoid the homogeneous reaction and increase the irradiation efficiency. Ultra-thin tubular Pd membranes with the thickness of about 0.4 μm on TiO₂ semiconductor membranes were fabricated by the method. X-ray diffraction (XRD) and SEM analysis of the Pd/TiO₂ composite membranes indicated that the metal existed in the form of pure Pd element and Pd membrane surface appeared homogeneous. A gas permeation experiment was conducted under temperature of 612-704 K and pressure of 0.05-0.12 MPa. Hydrogen permeance and selectivity of hydrogen/nitrogen (H₂/N₂) were 4.8 × 10^-6 mol m^-2 s^-1 Pa^-1 and 120 at 704 K, respectively.