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.