Chlorinated ethenes, in particular trichloroethylene (TCE), constitute a class of compounds considered to be some of the most harmful groundwater contaminants. Promising TCE remediation methods have come from the investigation of catalytic methods. The use of Pd/Al₂O₃ catalysts under H₂ gas has been studied for the aqueous hydrodechlorination of TCE in both laboratory and pilot scale studies. Pd has been shown to convert TCE primarily to ethane and ethylene, with little formation of hazardous chlorinated byproducts.

In our previous works [1,2], we have compared the activity of Pd/Al₂O₃, Pd black, Pd nanoparticles (NPs), and bimetallic core-shell Pd/Au NP catalyst consisting of 0-2 calculated monolayers (MLs) of Pd atoms on the Au surface. While the difference in activities of the monometallic Pd catalysts can be related to exposed surface Pd, it was found that the Pd/Au NP catalyst exhibited rates of up to 1800 L/min/g_Pd, a rate ~70 times greater than that of conventional Pd/Al₂O₃ (12 L/min/gPd). The presence of Au could impact the deactivation behavior of the NP catalysts during TCE HDC in the presence of chloride and sulfide ions. In this talk, we present evidence that Au increases deactivation resistance in the presence of chloride and sulfide ions, and discuss several possible explanations. These results show promise for field treatment of chlorinated ethenes in groundwater, which can contain known Pd poisons.

[1] Nutt, M.O., Heck, K.N., Hughes, J.B., Wong, M.S., Eviron. Sci. & Tech. 39 (2005) 1346 [2] Nutt, M.O., Heck, K.N., Alvarez, P., Wong, M.S., Applied Catal. B., 69 (2006) 115