Bimetallic PtAu cluster-derived catalysts for the selective catalytic reduction of NO by propylene

Depth sectioning with the aberration-corrected scanning transmission electron microscope

“…Several examples of depth-resolved studies of such samples are given below. Several frames of a 50-frame focal series collected from TiO 2 powder impregnated with metal nanoparticles (1-3 nm in size and containing Pt and Au at a 1:2 proportion) (19,20) are given in Fig. 3.…”

Low Temperature Oxidation of CO over Cluster-Derived Platinum−Gold Catalysts

“…In contrast, when an oxidation treatment at 300 °C was used, no particles larger than 3 nm were formed, and the surface-averaged size of the metal particles was found to be on the order of 2 nm (Table 1), consistent with our previous reports. 6,7 These data do show that the close proximity between Pt and Au, which is originally present in the Pt 2 Au 4 (CtCBu t ) 8 bimetallic cluster precursor, prevents sintering for both metals on the SiO 2 surface. In this case, the treatment in O 2 at 300 °C appears to be more favorable than the corresponding treatment in H 2 .…”

“…However, little has been reported so far in the literature regarding supported bimetallic catalysts containing gold. One such example is the supported bimetallic Pt−Au catalysts prepared from a Pt 2 Au 4 (C⋮CBu t ) 8 cluster precursor that have been the focus of our recent work. − Such cluster-derived Pt 2 Au 4 catalysts supported on SiO 2 were examined for several reactions including the selective catalytic reduction of NO by propylene, the oxidation and hydrogenation of propylene, and the 16 O 2 / 18 O 2 exchange. In all of these cases, it was shown that the presence of Au substantially affects the catalytic properties of Pt, despite the fact that Au itself is inactive for these reactions.…”

Conversion of nitrogen(I,II) oxides on nanodispersed [Pt(Pd)-Au]/HY zeolite catalysts

“…Papers have recently appeared using gold deposited on metal oxides or within bimetallic clusters of (Pt-Au) catalysts, in particular in reactions of reduction of nitrogen oxides by hydrocarbons [3,4]. In [4] it is shown that during reduction of NO by carbon monoxide in the absence of oxygen, catalysts containing nanodispersed gold are better than catalysts containing platinum group metals: their activity is apparent even by 27°C, while complete conversion to N 2 is achieved at 150°C.…”

“…A number of factors explain the interest in highly dispersed bimetallic catalysts: the ability of the second metal to facilitate reduction of the first metal, the increase in the dispersity of the metal tending to form large particles, as a result of which the selectivity of the reaction changes and the activity of the first metal increases. A well known example is the palladium-gold system in the reaction of oxidation of hydrogen, when adding gold to the palladium increases the reaction rate 50-fold [2].Papers have recently appeared using gold deposited on metal oxides or within bimetallic clusters of (Pt-Au) catalysts, in particular in reactions of reduction of nitrogen oxides by hydrocarbons [3,4]. In [4] it is shown that during reduction of NO by carbon monoxide in the absence of oxygen, catalysts containing nanodispersed gold are better than catalysts containing platinum group metals: their activity is apparent even by 27°C, while complete conversion to N 2 is achieved at 150°C.…”