Trichloroethene, a common carcinogenic groundwater contaminant, can be degraded to ethane using Pd catalysts. Gold nanoparticles (NPs) with sub-monolayer Pd surface coverages (Pd-on-Au; Pd-Au NPs) can catalyze this reaction faster than Pd NPs. Pd surface coverage affects Pd-Au NP activity, but the effect of Au particle size is not known. Pd-Au NPs with diameters of 3, 7, and 10 nm and Pd surface coverages (Pd sc) between 0 and 150% were synthesized. Activity of the Pd-Au NPs exhibited a volcano-shape dependence on Pd sc irrespective of Au NP size. Maximum activity (turnover frequency~7 sec-1) was exhibited by 7 nm Au NPs with a Pd sc of 60-70%. Extended x-ray absorption fine structure spectroscopy revealed a strong correlation between particle activity and 2-dimensional Pd surface ensembles. This study provides strong evidence that 2-D Pd ensembles on Au NPs are the active sites for hydrodehalogenation reactions and introduces an atypical particle size effect.

Hydrodehalogenation activity of Pd-on-Au nanoparticles: A function of Au particle size and Pd surface coverage

243rd National Meeting (2012)

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