Platinum/ruthenium

Platinum Platinum-coated titanium is the most important anode material for impressed-current cathodic protection in seawater. In electrolysis cells, platinum is attacked if the current waveform varies, if oxygen and chlorine are evolved simultaneously, or if some organic substances are present Nevertheless, platinised titanium is employed in tinplate production in Japan s. Although ruthenium dioxide is the most usual coating for dimensionally stable anodes, platinum/iridium, also deposited by thermal decomposition of a metallo-organic paint, is used in sodium chlorate manufacture. Platinum/ruthenium, applied by an immersion process, is recommended for the cathodes of membrane electrolysis cells. ... 

Investigations at Siemens in Erlangen, Germany, have used unsupported platinum-ruthenium anodes (4 mg/cm ) and platinum black cathodes (4 mg/cm ). Their best performances were 0.52 V at 400 mA/cml At Los Alamos National Laboratory in New MexicoJ the electrocatalyst was unsupported R-RuOx at the anode and unsupported R black at the cathode (R loading about 2 mg/cm ). In a subsequent study, the thinner Nafion 112 membrane was used to reduce the ohmic drop. Under pressure at 400 mA/cm cell potentials of 0.57 V with Oj and 0.52... 

The direct anodic oxidation of methanol became much more attractive after it was shown that platinum-ruthenium alloys are catalytically much more active in this reaction than pure platinum (pure ruthenium is totally inactive in this reaction). 

In 1965, synergistic (nonadditive) catalytic effects were discovered in elecho-chemical reactions. It was shown in particular that the electrochemical oxidation of methanol on a combined platinum-ruthenium catalyst will occur with rates two to three orders of magnimde higher than at pure platinum even though pure ruthenium is catalytically altogether inactive. 

It was seen when studying mixed systems Pt-WOj/C and Pt-Ti02/C that with increasing percentage of oxide in the substrate mix the working surface area of the platinum crystallites increases, and the catalytic activity for methanol oxidation increases accordingly. With a support of molybdenum oxide on carbon black, the activity of supported platinum catalyst for methanol oxidation comes close to that of the mixed platinum-ruthenium catalyst. 

In the late 1960s it was discovered (Entina, 1968 Binder et al., 1972) that a strong synergy effect exists in the platinum-ruthenium system. Alloys of these two metals are two to three orders of magnitude more active catalytically for the anodic oxidation of methanol than pure platinum, whereas pure ruthenium is altogether inactive for this reaction. Prolonged exploitation of such anodes is attended by a gradual decrease in catalytic activity of the alloys because of slow anodic dissolution of ruthenium from the surface layer. A similar simation is seen for platinum-tin alloys, which... 

Corrosion (spontaneous dissolution) of the catalyticaUy active material, and hence a decrease in the quantity present. Experience shows that contrary to widespread belief, marked corrosion occurs even with the platinum metals. For smooth platinum in sulfuric acid solutions at potentials of 0.9 to 1.0 V (RHE), the steady rate of self-dissolution corresponds to a current density of about 10 A/cm. Also, because of enhanced dissolution of ruthenium from the surface layer of platinum-ruthenium catalysts, their exceptional properties are gradually lost, and they are converted to ordinary, less active platinum catalysts. 

A period of high research activity in electrocatalysis began after it had been shown in 1963 that fundamentally, an electrochemical oxidation of hydrocarbon fuel can be realized at temperatures below 150°C. This work produced a number of important advances. They include the discovery of synergistic effects in platinum-ruthenium catalysts used for the electrochemical oxidation of methanol. 

Kabbabi A, Faure R, Durand R, Beden B, Hahn F, Leger JM, Lamy C. 1998. In situ FTIRS study of the electrocatalytic oxidation of carbon monoxide and methanol at platinum-ruthenium bulk alloy electrodes. J Electroanal Chem 444 41-53. 

Lu C, Rice C, Masel Ml, Babu PK, Waszczuk P, Kim HS, Oldfield E, Wieckowski A. 2002. UHV, electrochemical NMR, and electrochemical studies of platinum/ruthenium fuel cell catalysts. J Phys Chem B 106 9581-9589. 

Waszczuk P, Solla-Gull6n J, Kim HS, Tong YY, Montiel V, Aldaz A, Wieckowski A. 2001a. Methanol electrooxidation on platinum/ruthenium nanoparticle catalysts. J Catal 203 1-6. 

Waszczuk P, Lu GU, Wieckowski A, Lu C, Rice C, Masel MI. 2002. UHV and electrochemical studies of CO and methanol adsorbed at platinum/ruthenium surfaces, and reference to fuel cell catalysis. Electrochim Acta 47 3637-3652. 

Nashner MS, Frenkel Al, Adler DL, Shapley JR, Nuzzo RG. 1997. Structural characterization of carbon supported platinum-ruthenium nanoparticles from the molecular cluster precursor PtRu5(CO)i6. J Am Chem Soc 119 7760. 

Petrii OA, Podlovchenko BI, Fiumkin AN, Hira-Lal. 1965. The behaviour of platinized-platinum and platinum-ruthenium electrodes in methanol solutions. J Electroanal Chem 10 253-269. 

Vinodgopal K, He Y, Ashokkumar M, Grieser F (2006) Sonochemically prepared platinum-ruthenium bimetallic nanoparticles. J Phys Chem B 110 3849-3852... 

CONTROLLING PLATINUM, RUTHENIUM, AND OSMIUM REACTIVITY FOR ANTICANCER DRUG DESIGN... 

In our group, a major part of our research is devoted to the design of new anticancer drugs. Our recent efforts towards the discovery of new platinum-, ruthenium- and osmium-based anticancer agents provide the topic for this account and a section is devoted to each metal. We focus on recent results from our lab in the context of other developments and related research in this field (hence our coverage of the field is focused on these areas and is not comprehensive). 

CO (6). Another approach is to develop a CO tolerant anode catalyst such as the platinum/ruthenium electrodes currently under consideration. Platinum/ruthenium anodes have allowed the cells to operate, with a low level air bleed, for over 3,000 continuous hours on reformate fuel containing 10 ppm CO (23). 

Improvements in solid polymer electrolyte materials have extended the operating temperatures of direct methanol PEFCs from 60 C to almost 100 C. Electrocatalyst developments have focused on materials that have higher intrinsic activity. Researchers at the University of Newcastle upon Tyne have reported over 200 mA/cm at 0.3 V at 80 C with platinum/ruthenium electrodes having platinum loading of 3.0 mg/cm. The Jet Propulsion Laboratory in the U.S. has reported over 100 mA/cm at 0.4 V at 60 C with platinum loading of 0.5 mg/cm. Recent work at Johnson Matthey has clearly shown that platinum/ruthenium materials possess substantially higher intrinsic activity than platinum alone (45). 

Although there are no published data (which can be compared directly with the results obtained with nickel, iron, and aluminum surfaces), several studies with NO have been reported recently with platinum, ruthenium, and iridium 49, 50). In the main, these have relied on electron energy loss spectroscopy... 

Incorporating metal catalysts, such as platinum, ruthenium, cadmium, gold, vanadium, etc. on the surface of p-type... 

PEM fuel cells operate at relatively low temperatures, around 80°C. Low temperature operation allows them to start quickly (less warm-up time) and results in less wear on system components, resulting in better durability. However, they require that a noble-metal catalyst (typically platinum) be used to separate the hydrogen s electrons and protons, adding to system cost. The platinum catalyst is also extremely sensitive to CO poisoning, making it necessary to employ an additional reactor to reduce CO in the fuel gas if the hydrogen is derived from an alcohol or hydrocarbon fuel. This also adds cost. Developers are currently exploring platinum/ruthenium catalysts that are more resistant to CO. 

Bimetallic platinum-ruthenium nanoparticles were synthesized from the reaction of Pt(dba)2 (dba = dibenzyhdeneacetone) with Ru(COD)(COT) (COD = 1,5-cyclooctadiene COT = 1,3,5-cyclooctatriene) in various propor-... 

Controlling Platinum, Ruthenium,and Osmium Reactivity for Anticancer Drug Design... 

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