PdZn bimetallics

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.

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). 

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. 

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