Pt-Ru nanoparticles

Recently five monometallic (Au, Pd, Pt, Ru, Rh) nanoparticles were investigated as electron mediators together with four core/shell bimetallic (Au/Pd, Au/Pt, Au/Rh, Pt/ Ru) nanoparticles [53,194-196]. The linear relationship was observed between the electron transfer rate coefficients and the hydrogen generation rate coefficient as shown in Figure 15. 

Fig. 6.13 TEM images obtained at an accelerating voltage of 200 kV of Pt-Ru nanoparticles synthesized following sequential sonication of 1 mM Pt(II) and 1 mM Ru(in) at 213 kHz. Two representative particles are shown at different magnifications [39]...

C. W. Hills, N. H. Mack, and R. G. Nuzzo, The size-dependent structural phase behaviors of supported bimetallic (Pt-Ru) nanoparticles, J. Phys. Chem. B 107, 2626-2636 (2003). 

He, Z., Chen, J., Eiu, D., Zhou, H., Kuang, Y. 2004. Electrodeposition of Pt-Ru nanoparticles on carbon nanotubes and their electrocatalytic properties for methanol electrooxidation. Diamond Related Mater 13 1764-1770. 

Cao, D., Bergens, S.H. 2004. Pt-Ru,, nanoparticles as anode catalysts for direct methanol fuel cells. J Power Sources 134 170-180. 

Che et al. also prepared Pt/Ru nanoparticle-filled carbon tubes with a diameter of 200 nm (40). They impregnated carbon-deposited film with a mixture of aqueous solutions of HiPtClf, and RuCI3. After drying in air, the metal compounds in the pores were reduced by H2 flowing at 580°C for 3 h. Then the underlying alumina was dissolved away in HF solution. TEM observation of this sample revealed the presence of Pt/Ru nanoparticles (about 1.6 nm) dispersed on the inner wall of the tubes. 

Figure 7 depicts histograms of size distribution of bimetallic nanoparticles in carbon matrix. Nanoparticles finely disperced in carbon matrix based on IRPAN are sized as 280% Pt-Re nanoparticles have the size as 6-7 nm. This metal-carbon nanocomposites can be used as possible catalyst materials in fuel cells. 

Several workers have attempted to use EXAFS to provide information on adsorbate induced segregation effects on bimetallic particles. Hills et al. [102] studied the effect of a hydrogen atmosphere on bimetallic Pt-Ru nanoparticles. Their interpretation of adsorbate induced segregation effects relied on comparing the coordination environments of Pt and Ru and trying to identify differences from what would be expected for a random distribtion of Pt and Ru within the particles. They concluded that hydrogen treatment at 673 K resulted... 

Adams et al. [78,79] have reported a series of synthesis of mixed-metal cluster compounds. One example, Pt2Ru4(CO)is, is depicted in Figure 1(b). This mixed cluster compound was investigated to study the effect of Pt-Ru nanoparticles developed after the precursor annealing on carbon [80]. In line with the spectroscopic and microscopic measurements, the authors demonstrated that mixed Pt-Ru nanoparticles, with an extremely narrow size distribution (particle size 1.4nm), reflect an interaction that depends on the nature of the carbon support. Furthermore, as revealed by EXAFS, the Pt-Pt, Pt-Ru, and Ru-Ru coordination distances in the precursor (2.66, 2.64, and 2.84 A) [79] changed to 2.73, 2.70, and 2.66 A, respectively, on the mixed-metal nanoparticles supported on carbon black, with an enhanced disorder [80]. Furthermore, some metal segregation could be... 

C. W. Hills, S. Nashner, A.I. Frenkel, J.R. Shapley, R.G. Nuzzo, Carbon support effects on bimetallic Pt-Ru nanoparticles formed from molecular precursors. Langmuir 1999, 15, 690-700. 

Pt is deposited only at the surface of Ru nanoparticles rather than throughout the Pt-Ru nanoparticles. The method facilitates tuning of the electronic and catalytic properties of Pt-Ru catalysts by controlling the Pt cluster size. In contrast to the Pt-Ru alloy catalysts, this structure has all the Pt atoms available for the catalytic reaction, which decreases the Pt loading. 

The synthesis and catalytic properties of Pd, Pt, Ru nanoparticles in nanostructures ofpolymers are described. The controlled growth of metal nanoparticles in a polymer matrix was achieved. The catalytic systems have been studied in selective oxidation of monosaccharide. These processes are of particular interest because the products are the intermediates in the synthesis of biology active substances. 

V. Selvaraj and M. Alagar, Pt and Pt-Ru nanoparticles decorated polypyrrole/multiwaUed carbon nanotubes and their catalytic activity towards methanol oxidation, Electrochem. Common., 9, 1145-1153 (2007). 

V. Selvaraj and M. Alagar, Ethylene glycol oxidation on Pt and Pt-Ru nanoparticle decorated polythiophene/multiwaUed carbon nanotube composites for fuel cell applications. Nanotechnology, 19, 045504 (2008). 

Selvaraj V, Vinoba M, Alagar M (2008) Electrocatalytic oxidation of ethylene glycol on Pt and Pt-Ru nanoparticles modified multi-walled carbon nanotubes. J Colloid Interf Sci 322 537-544... 

Inspired by the observation, that binary Pt=Ru nanoparticles supported on CNT showed a promising performance as anode catalysts in PEMFCs, Harris et al. [65] used density functional theory calculations to study the anchoring of the nanoparticles to the nanofibers. They found a strong metal-carbon bond ( 3 eV) with covalent character between the graphene structure and the metal (111) crystal planes, which might be the reason for the higher stability found in these systems. 

Park KC, Jang lY, Wongwiriyapan W, Moiimoto S, Kim YJ, Jung YC, Toya T, Endo M (2010) Carbon-supported Pt-Ru nanoparticles prepared in glyoxylate-reduction system promoting precursor-support interaction. J Mater Chem 20 5345-5354... 

Maxakato NW, Ozoemena KI, Arendse CJ (2010) Dynamics of electrocatalytic oxidation of ethylene glycol, methanol and formic acid at MWCNT platform electrochemically modified with Pt/Ru nanoparticles. Electroanalysis 22 519-529... 

Zhou W, Xu J, Du Y, Yang P (2011) Polycarbazole as an efficient promoter for electrocatalytic oxidation of formic acid on Pt and Pt-Ru nanoparticles. bit J Hydrogen Energy 36 1903-1912... 

BarczukPJ, TsuchiyaH, Macak JM, Schmuki P, Szymanska D, Makowski O, Miecznikowski K, Kulesza PJ (2006) Enhancement of the electrocatalytic oxidation of methanol at Pt/Ru nanoparticles immobilized in different WO3 matrices. Electrochem Solid State Lett 9(6) E13-E16... 

PtRu catalysts with MCMB as support [35] showed lower polarization characteristics than that with CB as support. Pt-Ru nanoparticles (1.6 nm) were supported on carbon nanotubes (200nm diameter, 8-10 um length) obtained by carbonization of PPy on an alumina membrane [36]. The amount and morphology of Pt nanoparticles depend on the types of carbon nanomaterlals, Including GNFs or CNTs [37]. Surfactant-stabilized Pt and Pt/Ru electrocatalysts for PEMFC had been prepared and investigated by X. Wang [38]. 

Pt and Pt/Ru nanoparticles into the diamond surface microstructure and to use these materials in electrocatalysis, as is discussed further below. 

Lebedeva and his coworkers have estimated that coefficient of CO diffusion (Deo) on the Pt plate is larger than 1 x 10 " cm /s [41]. On the contrary, Maillard and Babu have reported that the Deo on the Pt nanoparticles (3-7 nm in size) is 1 X 10 to 1 X 10 " cm /s [42,43]. These reports imply that higher surface Ru composition is required in the Pt-Ru nanoparticles since the Deo on the nanoparticles may have the lower values compared with those on the Pt plate/film. Therefore, an optimum surface Ru composition in the Pt-Ru nanoparticle catalysts becomes higher compared with the Pt-Ru plate/film ones. The higher surface Ru composition in the Pt-Ru nanoparticle catalysts results in a lower specific... 

Here, a simple calculation is performed oti the Pt-Ru nanoparticles 2 nm in size (Fig. 2). Beginning with a Pt sphere 2 nm in size, the sphere has 276 Pt atoms, and the surface Pt monolayer and the Pt core part are composed of 168 and 108 Pt atoms, respectively. Supposed that the surface Pt monolayer is replaced with a PtsoRuso monolayer, the bulk composition of this core/ shell microstruemred sphere is calculated to be Pt7oRu3o, which is close to the bulk composition of Pt73Ru27 showing the highest MOR activity in Fig. 4. This simple calculation supports that a microstructure close to Pt-rich core/PtsoRuso shell was formed in the Pt-Ru bimetallic nanoparticles. 

Larsen R, Masel RI. Kinetic study of CO tolerance during electeo-oxidation of formic acid on spontaneously deposited Pt/Pd and Pt/Ru nanoparticles. Electrochem Solid-State Lett 2004 7 A148-50. 

Figure 4.62. Examples of three-dimensional supports for extended reaction zone anodes in direct liquid fuel cells, (a) unpressed graphite felt UGF, (h) pressed graphite felt GF, (c) reticulated vitreous earhon RVC [250, 305]. (Reprinted from Electrochimica Acta, 51(25), Bauer A, Gyenge EL, Oloman CW, Eleetrodeposition of Pt-Ru nanoparticles on fibrous carbon substrates in the presence of nonionie surfactant Apphcation for methanol oxidation, 5356-64, 2006, with permission from Elsevier, and reproduced by permission of ECS— The Electrochemical Society, Gyenge EL, Oloman CW. The surfactant-promoted electroreduction of oxygen to hydrogen peroxide.)...

Tripkovic AV, Popovic KDJ, Lovic JD, Markovic NM, RamUovic V. Formic acid oxidation on Pt/Ru nanoparticles temperature effects. Materials Science Forum 2005 494 223-8. 

Bauer A, Gyenge EL, Oloman CW. Electrodeposition of Pt-Ru nanoparticles on fibrous carbon substrates in the presence of nonionic surfactant application for methanol oxidation. Eleetrochim Acta 2006 51 5356-64. 

Another example of the influence of heat treatment on the make of the catalyst and catalyst surface has been shown by Nashner et al. [101]. They supported and subsequently decomposed a PtRu5C(CO)i6 molecular cluster precursor at different temperatures in a H2 atmosphere. Carbon supported Pt/Ru nanoparticles of 1.5 nm average diameter were prepared in this manner. At 100 °C the particles consisted of a disordered structure, with a Pt enriched core and Ru on flie surface, while at 300 °C an inverted structure was formed, Pt being on the surface of the equilibrated nanoparticle. The schematic of the synthesis is shown in Figure 9.11. 

Sivakumar P, Ishak R, Tricoli V. Novel Pt-Ru nanoparticles formed by vapour deposition as efficient electrocatalyst for methanol oxidation Part I Preparation and physical characterizatioiL Electrochim Acta 2005 50 3312. 

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