Influence of H\u3csub\u3e2\u3c/sub\u3eS on the hydrogen flux of thin-film PdAgAu membranes

\u3cp\u3ePd-based membranes have the potential to be used for hydrogen purification and production in membrane reactors. However, the presence of impurities in the feedstock, such as H\u3csub\u3e2\u3c/sub\u3eS can poison the membrane, thus decreasing the hydrogen permeation by blocking and deactivating active sites of the Pd-alloy on the membrane surface. H\u3csub\u3e2\u3c/sub\u3eS at high concentrations can even destroy the membrane by the formation of Pd\u3csub\u3e4\u3c/sub\u3eS. It is known that alloying of Pd with Au enhances the membrane resistance to H\u3csub\u3e2\u3c/sub\u3eS. This work reports the performance of six PdAgAu/Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e supported membranes, prepared by electroless plating combined with PVD under exposure to trace amounts (<2 ppm) of H\u3csub\u3e2\u3c/sub\u3eS. The Au content shows not to play a significant role at these low concentrations. Exposure results suggest a dual influence of physisorbed H\u3csub\u3e2\u3c/sub\u3eS and chemisorbed S species. A Langmuir description shows that the influence of the partial pressure of hydrogen is negligible on the flux inhibition. In the post characterization the absence of Pd\u3csub\u3e4\u3c/sub\u3eS was shown, however the surface was affected by the exposure to H\u3csub\u3e2\u3c/sub\u3eS.\u3c/p\u3