Pt/Ru alloy

Electro-catalysts which have various metal contents have been applied to the polymer electrolyte membrane fuel cell(PEMFC). For the PEMFCs, Pt based noble metals have been widely used. In case the pure hydrogen is supplied as anode fuel, the platinum only electrocatalysts show the best activity in PEMFC. But the severe activity degradation can occur even by ppm level CO containing fuels, i.e. hydrocarbon reformates[l-3]. To enhance the resistivity to the CO poison of electro-catalysts, various kinds of alloy catalysts have been suggested. Among them, Pt-Ru alloy catalyst has been considered one of the best catalyst in the aspect of CO tolerance[l-3]. 

The different kinds of adsorbed CO were observed by in situ infrared reflectance spectroscopy. The results showed that using bulk Pt-Ru alloys, the adsorbed CO species formed by dissociation of methanol, or from dissolved CO on the surface of the electrode, are different on R and on Ru. The adsorption of CO occurs on pure Pt and Ru and on alloys of different compositions, but a shift detected in the wave number of the... 

In-situ ATR-FTIR spectroscopic study of electro-oxidation of methanol and adsorbed CO at Pt-Ru alloy. J. Phys. Chem. B, 108, 2654-2659. 

Desai SK, Neurock M. 2003. First-principles study of the role of solvent in the dissociation of water over a Pt-Ru alloy. Phys Rev B 68 075420. 

Gasteiger HA, Markovic N, Ross PN Jr, Cairns EJ. 1994. CO electrooxidation on well-characterized Pt-Ru alloys. J Phys Chem 98 617-625. 

We have found new CO-tolerant catalysts by alloying Pt with a second, nonprecious, metal (Pt-Fe, Pt-Co, Pt-Ni, etc.) [Fujino, 1996 Watanabe et al., 1999 Igarashi et al., 2001]. In this section, we demonstrate the properties of these new alloy catalysts together with Pt-Ru alloy, based on voltammetric measurements, electrochemical quartz crystal microbalance (EQCM), electrochemical scanning tunneling microscopy (EC-STM), in situ Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). 

Ross PN, Kinoshita K, Scarpellino AJ, Stonehart P. 1975b. Electrocatalysis on binary alloys II. Oxidation of molecular hydrogen on supported Pt + Ru alloys. J Electroanal Chem 63 ... 

Wakisaka M, Mitsui S, Hirose H, Kawashima K, Uchida H, Watanabe M. 2006. Electronic structures of Pt-Co and Pt-Ru alloys for CO-tolerant anode catalysts in polymer electrol3de fuel cells studied by EC-XPS. J Phys Chem B 110 23489-23496. 

Chu D, Gilman S. 1996. Methanol electro-oxidation on unsupported Pt-Ru alloys at different temperatures. J Electrochem Soc 143 1685-1690. 

Ru atoms need to be physically present as distinctive Ru (nano)islands on the Pt surface rather than as an intermixture with Pt surface atoms of the Pt/Ru alloy [lanniello et al., 1994 Crown et al., 2000]. 

Gasteiger HA, Markovic NM, Ross PN, Caims EJ. 1994b. Electro-oxidation of small organic molecules on well-characterized Pt-Ru alloys, Electrochim Acta 39 1825. 

Koper MTM, Shubina TE, van Santen RA. 2002. Periodic density functional study of CO and OH adsorption on Pt-Ru alloy surfaces Implications for CO-tolerant fuel cell catalysts. J Phys Chem 106 686. 

Carbon-supported platinum (Pt) and platinum-rathenium (Pt-Ru) alloy are one of the most popular electrocatalysts in polymer electrolyte fuel cells (PEFC). Pt supported on electrically conducting carbons, preferably carbon black, is being increasingly used as an electrocatalyst in fuel cell applications (Parker et al., 2004). Carbon-supported Pt could be prepared at loadings as high as 70 wt.% without a noticeable increase of particle size. Unsupported and carbon-supported nanoparticle Pt-Ru, ,t m catalysts prepared using the surface reductive deposition... 

Since high current density at the maximum power density and the cost of the noble metals are important parameters for the commercialization of DMECs, H-CNE-supported Pt-Ru alloys maybe classified among the most efficient and cost-effective anode catalysts. It is also worth mentioning that the CNF-supported catalysts feature superior catalytic activity at the high temperatures where the mass transfer of methanol and oxygen is more favorable due to the fibrous network of CNEs. 

One particular application for which supported Au catalysts may find a niche market is in fuel cells [4, 50] and in particular in polymer electrolyte fuel cells (PEFC), which are used in residential electric power and electric vehicles and operate at about 353-473 K. Polymer electrolyte fuel cells are usually operated by hydrogen produced from methane or methanol by steam reforming followed by water-gas shift reaction. Residual CO (about 1 vol.%) in the reformer output after the shift reaction poisons the Pt anode at a relatively low PEFC operating temperature. To solve this problem, the anode of the fuel cell should be improved to become more CO tolerant (Pt-Ru alloying) and secondly catalytic systems should be developed that can remove even trace amounts of CO from H2 in the presence of excess C02 and water. 

H. Gasteiger, N. Markovic, P. N. Ross, and E. J. Cairns, J. Electrochem. Soc. 141 1296 (1994). Temperature-dependent methanol electro-oxidation on well-characterized Pt-Ru alloys. 

Reddington et al. (66) reported the synthesis and screening of a 645-member discrete materials library L9 as a source of catalysts for the anode catalysis of direct methanol fuel cells (DMFCs), with the relevant goal of improving their properties as fuel cells for vehicles and other applications. The anode oxidation in DMFCs is reported in equation 1 (Fig. 11.12). At the time of the publication, state-of-the-art anode catalysts were either binary Pt-Ru alloys (67) or ternary Pt-Ru-Os alloys (68). A systematic exploration of ternary or higher order alloys as anode catalysts for DMFCs was not available, and predictive models to orient the efforts were also lacking. 

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