PtRu characterization

Richarz F, Wohimann B, Vogel U, Floffschulz FI and Wandelt K 1995 Surface and electrochemical characterization of PtRu alloys Surf. Scl. 335 361-71... 

EXAFS characterization of supported PtRu/MgO prepared from a molecular precursor and organometallic mixture... 

The goal of this work was to prepare and characterize PtRu/MgO catalysts from cluster A which contained Pt-Ru bonds and compare with that prepared from a mixed solution of Pt(acac)2 and Ru(acac)3. The characterization methods included IR and EXAFS spectroscopy. Ethylene hydrogenation was used to test the catalytic activity of both PtRu/MgO catalysts. 

PtRu nanoparticles can be prepared by w/o reverse micro-emulsions of water/Triton X-lOO/propanol-2/cyclo-hexane [105]. The bimetallic nanoparticles were characterized by XPS and other techniques. The XPS analysis revealed the presence of Pt and Ru metal as well as some oxide of ruthenium. Hills et al. [169] studied preparation of Pt/Ru bimetallic nanoparticles via a seeded reductive condensation of one metal precursor onto pre-supported nanoparticles of a second metal. XPS and other analytical data indicated that the preparation method provided fully alloyed bimetallic nanoparticles instead of core/shell structure. AgAu and AuCu bimetallic nanoparticles of various compositions with diameters ca. 3 nm, prepared in chloroform, exhibited characteristic XPS spectra of alloy structures [84]. 

PtRu catalysts with controlled atomic ratios were prepared by adjusting the nominal concentrations of platinum and ruthenium salts in the solution, whereas different mean particle sizes could be obtained by adjusting some electric parameters of the deposition process, e.g., ton (during which the current pulse is applied) and toff (when no current is applied to the electrode), as determined by different physicochemical methods (XRD, EDX, and TEM) [40], Characterization by XRD led to determine the crystallite size, the atomic composition and the alloy character of the PtRu catalysts. The atomic composition was confirmed using EDX, and TEM pictures led to evaluate the particle size and to show that PtRu particles formed small aggregates of several tens of nanometers (Figure 9.10). 

Table 9.3 gives the physicochemical characterizations of the PtRu/C catalysts obtained under different experimental conditions (nominal metal atomic ratio in solution and value of tM). 

Alexeev OS, Graham GW, Shelef M, Adams RD, Gates BC (2002) y-Al O -Supported PtRu clusters prepared from [Pt Ru jlCOljj] Characterization by infrared and extended X-ray absorption fine structure spectroscopies. J Phys Chem B 106 4697... 

A preparation and characterization of new PtRu alloy colloids that are suitable as precursors for fuel-cell catalysts have been reported [43cj. This new method uses an organometallic compound both for reduction and as colloid stabilizer leading to a Pt/Ru colloid with lipophilic surfactant stabilizers that can easily be modified to demonstrate hydrophilic properties. The surfactant shell is removed prior to electrochemical measurements by reactive annealing in O2 and H2. This colloid was found to have nearly identical electrocatalytic activity to several other recently developed Pt/Ru colloids as well as commercially available Pt/Ru catalysts. This demonstrates the potential for the development of colloid precursors for bimetallic catalysts especially when considering the ease of manipulating the alloy composition when using these methods. 

Table 2.6 Characterization of the prepared PtRu catalysts Pt content (total, EDX surface, XRD), mean particle sizes d,...

Case Study 3 Surface-doped Pt/Ru/Co Carbon Based on the above-mentioned DFT calculations performed by Norskov [168] we have prepared trimetallic electrocatalysts having PtRu/C surface-doped with Co(0) in order to produce highly active but at the same time CO tolerant electrocatalysts. For example, Pt/Ru/Fe/C, Pt/Ru/Ni/C, and Pt/Ru/Co/C systems were manufactured with the metal ratios being 45 45 10 a/o and a total metal loading of 20 wt.% on Vulcan XC 72. The resulting catalysts were compared with the industrial PtsoRuso standard catalyst under identical conditions. Full characterization was done via a combination of TEM, XRD, XPS, andXAS measurements, further BET, and electrochemical tests [171]. 

One step methods. PtRuMo/C catalysts obtained by the impregnation manner revealed that the addition of a relatively small amount of Mo results in an electrocatalyst with a higher activity in CO or methanol electrooxidation than with the PtRu/C system. Moreover, Benker et al studied the effect of molybdenum precursor, and the physico-chemical characterization indicated that only traces of molybdenum were present in the samples when Mo (CO) 6 was used for the synthesis, while ammonium molybdate was an appropriate precursor for the synthesis of PtRuMo/C catalysts. On the other hand, a colloidal method developed by Bonnemann et alP was used to prepare carbon supported PtRuMo nanoparticles and established that this method provided a better tool for synthesizing PtRuMo (1 1 1) nanoparticles deposited on a carbon substrate, being more... 

PtRuMo ternary metal nanoparticles with a narrow size distribution (2.4 0.7 nm) were prepared by microemulsion,but without carbon support. Their characterization on the carbon electrode gave higher activity and longer stability for methanol oxidation than that of PtRu and pure Pt nanoparticles/carbon electrode. 

Guo JW, Zhao TS, Prabhuram J, Chen R, Wong CW (2005) Preparation and characterization of a PtRu/C nanocatalyst for direct methanol fuel cells. Electrochim Acta 51 754-763... 

Acharya, C.K., Sullivan, D.I., and Turner, C.H. (2008) Characterizing the interaction of Pt and PtRu clusters with boron-doped, nitrogen-doped, and activated carbon density functional theory calculations and parameterization./. Phys, Chem. C, 112 (35), 13607-13622. doi 10.102 l/jp8034488... 

Wang JX, Brankovic SR, Zhu Y, Hanson JC, Adzic RR (2003) Kinetic characterization of PtRu fuel cell anode catalysts made by sprmtaneous Pt deposition on Ru nanoparticles. 

After 10 h of operation the presenee of Ru islands on Pt inereased the oxidation current density approximately 20-fold in the case of PtRu-53, followed closely by PtRu-35. Combining cyclic voltammetry with surface NMR two COad populations were identified COad close to (or possibly on) Ru sites undergoing fast thermally activated diffusion and COad on Pt characterized by slow diffusion [91]. These two types of COad are responsible for two separate peaks in CO stripping voltammetry, at low ( 0.3 V) and high (above 0.4 V) potentials, respectively. Ru decreases the activation barrier for COad surface diffusion by reducing electron back-donation. 

Figure 4.21. DMFC polarization comparison between various supported anode catalysts PtRuWOx/C, PtRu/C (E-Tek Inc.) and Pt/C (E-Tek Inc.). 368 K. Pt load 0.4 mg cm l 1 M CH3OH. [118], (With kind permission from Springer Science+Business Media Journal of Applied Electrochemistry, Synthesis and characterization of carbon-supported PtRuWOx catal5rsts by spectroscopic and diffraction methods, 31, 2001, 793-8, Roth C, Goetz M, Fuess H, figure 7.)...

Figure 4.63 compares the effect of the novel extended reaction zone supports on the electrocatalytic activity of PtRu for methanol electrooxidation. The catalyst characteristics arc presented in Table 4.3. The catalyst surface morphology on all three supports could be characterized as predominantly mesoporous coating composed of nanoparticle agglomerates (Figure 4.64). 

Xue X, Liu C, Xing W, Lu T. Physical and electrochemical characterizations of PtRu/C catalysts by spray pyrolysis for electrocataljftic oxidation of methanol. J Electrochem Soc 2006 153 E79. 

Liu ZL, Lee JY, Chen WX, Han M, Gan LM. Ph5rsical and electrochemical characterizations of microwave-assisted polyol preparation of carbon-supported PtRu nanoparticles. Langmuir 2004 20 181-7. 

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