Effects of Oxygen Poison on the Surface of Palladium Membrane

The oxidation of palladium membrane at different temperatures and the hydrogenization of the oxidized membrane at room temperature were carried out in a silica tubular furnace. The variation of surface phase was observed and analyzed by XPS, SEM and XRD. The effects of O(2) poison and hydrogenization on the surface morphology and composition of the Pd membrane were investigated. The results show that when the oxidation temperature is below 240 degrees C, the adsorptive capacity of O on the Pd surface is increased with the temperature rising but there is no obvious PdO. However, PdO together with micropores could be detected apparently at the oxidation temperature above 240 degrees C, and the mass ratio of PdO and the amount and dimension of the micropores are increased by further increasing the temperature. The Pd surface turns into PdO completely for the Pd membrane oxidized at 390 degrees C for 1 h. After hydrogenization, all of the PdO and free O on the Pd surface vanish; the surface phases of Pd membrane are reduced fully to the state before reaction, but the multiaperture surface is reserved. At 240 degrees C and the higher temperature, the oxidized Pd membrane can react with hydrogen, resulting in obvious plastic deformation.