PdPt bimetallics

The measurement of catalytic activity of PdPt bimetallic nanoparticles over methane combustion showed that the difference in activity with increasing and decreasing reaction temperatures disappeared probably due to the synergestic effect of the formation of the PdPt bimetallic nanoparticles [176]. 

Au (or Ag) content. Decanethiol-protected AuPt alloy bimetallic nanoparticles of ca. 2.5 nm in particle size were similarly prepared [58]. The preparations of PdPt [59] and AuPd [60] bimetallic nanoparticles in water-in-oil (w/o) microemulsions can be realized in two-phase reaction system, in which a surfactant molecule itself works as a protecting agent in these cases. 

Other one-pot preparations of bimetallic nanoparticles include NOct4(BHEt3) reduction of platinum and ruthenium chlorides to provide Pto.sRuo.s nanoparticles by Bonnemann et al. [65-67] sonochemical reduction of gold and palladium ions to provide AuPd nanoparticles by Mizukoshi et al. [68,69] and NaBH4 reduction of dend-rimer—PtCl4 and -PtCl " complexes to provide dend-rimer-stabilized PdPt nanoparticles by Crooks et al. [70]. 

Co-complexation has been used to prepare a variety of bimetallic DENs, including PdPt [19,20], PdAu [21], and PdRh [22] (Table 1). In a typical study, for example the PdPt system studied by Scott, Datye, and Crooks [ 19], K2PdCl4 and K2PtCl4 are added to a dilute aqueous solution of G4-OH in a fixed metal-ion to dendrimer ratio of 40 1. The solution is stirred for four days to allow complete complexation of the metal ions with the interior ter-... 

Along with monometalUc Pd nanoparticles, we studied the synthesis and properties of PdAu, PdPt, and PdZn bimetallic nanoparticles prepared at a molar ratio of 4/1 in PS-b-P4VP micelles and their catalytic behavior in DHL hydrogenation [44]. Because the amount of Pd in all the bimetallic nanoparticles is much higher than that of the second metal, Pd mainly determines the catalytic properties. 

In the case of bimetalhc particles, adsorbed carbon monoxide is also regarded as a useful infrared probe of surface composition [54]. Based on that, we studied CO adsorption on monometallic Pd and bimetallic PdAu, PdPt and PdZn nanoparticles formed in the PS-fe-P4VP micellar solutions (Fig. 3.2). The samples, except PdAu, showed both terminal and bridging CO adsorption [55, 56], reveahng the... 

Fig. 3.2 FTIR spectra of CO adsorption on Pd (a) and bimetallic PdAu (b), PdPt (c) PdZn (d) nanoparticles formed In the PS-b-P4VP micelles. Reprinted from Ref [51], Copyright (2000), with permission from Elsevier.

The XRD data for bimetallic nanoparticles show that in aU cases small particles with diameter of 1.5-2.0 nm are formed with diffraction pattern typical for Pd(o). No crystalline stmcture for Au, Pt or Zn was found. The TEM image of PdPt nanoparticles formed in the PS-b-P4VP micelles is presented in Fig. 3.3. 

For bimetallic catalysts, in the equation of the model the denominator containing the coordination (adsorption) parameter is introduced, which shows a more pronounced impact of the coordination (adsorption) processes on DHL hydrogenation compared to the monometallic one. On the other hand, because the coordination (adsorption) parameter Q is very small for PdPt and PdZn nanoparticulate catalysts, the second component in the denominator can be omitted so the equation becomes W=k, i.e., identical to that found for Pd nanoparticles. Among all the catalysts, PdAu stands apart its model equation contains a squared term in the denominator [44], reveaUng the high impact of the substrate/product coordination (adsorption). 

Kakade, B.A., Tamaki, T., Ohashi, H. Yamaguchi, T Highly active bimetallic PdPt and CoPt nanocrystals for methanol electro-oxidation. J. Phys. Chem. C 116 (2012), pp. 7464-7470. 

PdCo PdPt/C) [163,164] and PdsPt/C [165] were found to demonstrate better alcohol tolerance and comparable and even better electrocatalytic performance than commercial Pt/C. A superior ORR activity and methanol tolerance as compared to commercial Pt/C and Pd/C catalysts have also been reported with a novel nanotubular mesoporous PdCu bimetallic nanocomposite comprising interconnected alloy nanoparticles with sizes around 3nm. The improved performance is related to the special structural configuration of the catalyst [166]. 

The bimetallic c-PdPt/TiS was analysed by STEM-EDX (Energy Dispersive X-ray analysis). The very high resolution of this analysis is unique (an electron beam with a diameter of 0.8 nm is used) and allows for the elemental analysis of individual metal ciystallites. A scan over the surface of the material showed that all peaks of Pt and Pd coincide, so the metal ciystallites are truly bimetallic (Figure 6). No monometallic metal ciystallites, indicated by a peak of only Pt or only Pd, were observed. 

The electronic properties of bimetallic (PdAu, PdPt, and PdZn) NPs were studied using XRD, TEM, XPS, and FTIR of the adsorbed CO. Bimetalhc based catalysts contained 1.5-2 nm NPs with a narrow particle size distribution, but with different NP morphology cluster-in-cluster for PdR and PdZn and core-shell for PdAu [15]. Adchtion of a modifying metal (Au, Pt and Zn) leads to a change of the NP electronic properties as well. 

Rosseler O, Ulhaq-Bouillet C, Bonnefont A, Pronkin S, Savinova E, Louvet A, Keller V, Keller N (2015) Structural and electronic effects in bimetallic PdPt nanoparticles on Ti02 for improved photocatalytic oxidation of CO in the presence of humidity. Appl Catal Environ 166 381-392... 

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