Palladium membrane on TiO2 nanotube arrays-covered titanium surface by combination of photocatalytic deposition and modified electroless plating processes and its hydrogen permeability

Palladium membrane with high hydrogen permselectivity was successfully fabricated on the TiO2 nanotube arrays-covered titanium surface by photocatalytic deposition (PCD) under ultraviolet irradiation and subsequently improved and thickened using the modified electroless plating method. The TiO2 nanotube arrays were produced in situ on the surface of asymmetric porous titanium foil in 0.5 wt% hydrofluoric acid by using the anodization method. The resulting palladium membrane with thickness of about 10 μm was pure, homogeneous, lack of defects, and compact, as revealed by SEM, XRD and XPS characterization. The gas permeation experiment under temperature of 593 K–773 K and pressure of 0.3 MPa–0.7 MPa demonstrated that the palladium layers possessed high hydrogen permeability, but impermeability for nitrogen. The hydrogen permeation coefficient was 2.91 × 10−6 mol m−2 s−1 Pa−1 at 773 K at 0.7 MPa. The activation energy for hydrogen permeation and hydrogen pressure exponent were 12.63 kJ mol−1 and 1, respectively. In addition, the durability and stability of the palladium layers bound on the TiO2 nanotube arrays-covered titanium surface were investigated by the adhesion force test, thermal shocking test and high temperature stability test. Thus, the so-fabricated material is potentially useful for separating hydrogen from the hydrogen-containing gas at high temperature.