Alcohol-reduction method

This alcohol reduction method is applied to the control of size and composition of not only the noble metal/noble metal [7] but the 3d-transition metal/noble metal nanoparticles [8] like magnetic FePt nanoparticles. 

An alcohol reduction method has been applied to the synthesis of polymer-stabilized bimetallic nanoparticles. They have been prepared by simultaneous reduction of the two corresponding metal ions with refluxing alcohol. For example, colloidal dispersions of Pd/Pt bimetallic nanoparticles can be prepared by refluxing the alcohol-water (1 1 v/v) mixed solution of palladium(II) chloride and hexachloro-platinic(IV) acid in the presence of poly(/V-vinyl-2-pyrrolidone) (PVP) at about 90-95°C for 1 h (Scheme 9.1.5) (25). The resulting brownish colloidal dispersions are stable and neither precipitate nor flocculate over a period of several years. Pd/ Pt bimetallic nanoparticles thus obtained have a so-called core/shell structure, which is proved by an EXAFS technique (described in Section 9.1.3.3). 

Pt/Ru bimetallic nanoparticles were prepared by coreduction of the corresponding metal salts in the presence of glucose (26). EXAFS data indicated the existence of a Pt-Ru bond in this case, proving the formation of bimetallic nanoparticles. Pd/Rh bimetallic nanoparticles, stabilized by PVP, were also prepared by the alcohol reduction method (27). 

Polymer-stabilized bimetallic nanoparticles containing both a light transition metal element and a precious metal element can also be prepared by a modified alcohol reduction method. For example, Cu/Pd bimetallic nanoparticles were successfully prepared with various Cu Pd ratios by refluxing a glycol solution of the hydroxides of Cu and Pd in the presence of PVP or by thermal decomposition of metal acetates. 

Fig. 9.1.4 Successive reduction of AuIV and Pd11 ions by an alcohol reduction method in the presence of PVP.

Alternative supports for catalysts preparation for low-temperature fuel cells using the alcohol reduction method... 

The work presented shows that an increase of the electrocatalytic activity can be obtained, if a suitable method for the catalyst synthesis is employed. In this sense, the Alcohol Reduction Method showed a positive effect, probably due to the good particle dispersion at the carbon surface and the suitable particle size distribution that this method produces. For the methanol oxidation results, an increase in the cell potential by PtRu/C electrocatalyst on Vulcan XC72 system was observed compared to the PtRu/C E-TEK formulation. This can be explained due to the better conductivity of this Carbon Suport, enhancing the speed of the electron transference in the Methanol Oxidation Reaction (MOR).These results can also be attributed to the good particle distribution at... 

An alcohol reduction method in which alcohol like ethanol can work both as a reductant and a solvent has been applied to the synthesis of polymer-capped bimetallic nanoclusters. They have been prepared by the simultaneous reduction of the two corresponding metal ions with refluxing alcohol. For example, colloidal dispersions of Pd/Pt bimetallic nanoclusters can be prepared by refluxing... 

Thermal decomposition of metal acetates in the presence of PVP was proposed by Bradley et whereas the preparative procedure of Esumi et was modified. In the Bradley method the Cu/Pd bimethallic nanoclusters produced contain less than 50 mol% of Cu, while in the modified alcohol reduction method, bimetallic nanoclusters containing 95 mol% of Cu could be obtained. ... 

Fig. 3.22 Successive reduction of Au(IV) and Pd(II) ions by an alcohol reduction method in the presence of PVP. [Reprinted from Fine Particles (T. Sugimoto ed.), p.439, Fig. 9.1.4, 2000 by courtesy of Marcel Dekker Inc.]...

Ni/Pd alloy bimetallic nanoclusters prepared by the improved alcohol reduction method under high temperature were applied to the catalysis for hydrogena-... 

Colloid Formation. Several platinum colloids prepared by the alcohol reduction method are listed in Tables I (nonionic polymers) and II (cationic polyelectrolytes). Examples of particles diameters as determined by TEM are given in Table m. In all cases colloids were formed, and most were stable for several weeks, even months. The TEM investigations showed that the particles were in most cases evenly distributed and about 1 - 5 nm in diameter. Depending on the polymer, a range of particle sizes and narrow size distributions were obtained. 

Ethanol electro-oxidation by PtSn/C, PtRh/C, and PtSnRh/C catalysts containing 20 wt.% metal loading and prepared by the alcohol reduction method has been studied by Spinace et al. [60]. These authors observed that the catalytic activity of the compositions PtRh/C 50 50 and 90 10 is lower than the activity of the catalyst PtSn/C with a composition of 50 50, and that the variation in the amount of Rh in the binary catalyst does not bring about a significant change in activity. However, when Rh is combined with the Sn in a ternary catalyst PtSnRh/C 50 40 10, there is an elevation in the catalytic activity, showing that the use of Rh as a third element improves the catalytic activity of ethanol oxidation. 

Oliveira Neto et al. [28] have investigated a series of PtRu/C, PtSn/C, and PtSnRu/C catalysts prepared by the alcohol-reduction method using an ethylene glycol/water solution. Particle sizes in the order of 2.7nm were achieved for the PtSn/C composition, which displayed catalytic activity close to 8.0 A gpt . Spinace et al. [60] have used the same method for the production of PtSn/C, PtRh, and PtSnRh/C catalysts. Their results were similar to those described in [28], i.e., small particle size (2.0nm), and uniform particle distribution on the carbon support, which culminated in significant catalytic activity for ethanol electro-oxidation. 

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