Preparation of a palladium composite membrane by an improved electroless plating technique

An ultrathin palladium membrane was prepared by an improved electroless plating technique on the surface of a porous titania ceramic substrate. A simple yet new and valuable activation technique named photocatalytic deposition (PCD) has been presented. The thickness of the resulting palladium membrane was about 0.3-0.4 μm. Hydrogen permeation through the composite membrane was proportional to the hydrogen partial pressure difference. The hydrogen permeability and H₂:N₂ selectivity through the palladium composite membrane are 6.3 × 10^-6 mol m^-2 s^-1 Pa^-1 and 1140 at 773 K, respectively. The activation energy for hydrogen permeation is 21.27 kJ/mol at the temperature range of 673-773 K. Long-term hydrogen permeation operation at 673 K indicated that the flux through the resulting membrane under hydrogen/nitrogen gradients requires 80 h to reach a steady state. The steady-state hydrogen flux showed no observable changes during the thermal cycles between 673 and 773 K.