Ruthenium platinum alloys

Alloys with ruthenium Additions of ruthenium have a most marked effect upon the hardness of platinum, but the limit of workability is reached at about 15% ruthenium, owing to the fact that ruthenium belongs to a crystallographic system different from that of platinum. Apart from a somewhat greater tendency to oxide formation at temperatures above 800°C, the resistance to corrosion of ruthenium-platinum alloys is comparable to that of iridium-platinum alloys of similar composition. 

Fig. 1. Dependence of hydrogenation rate and potential displacement of catalyst on composition of ruthenium - platinum alloys during hydrogenation of dimethylethynylcarbinol in ethanol at 20"C. 1) Hydrogenation of triple bond 2) hydrogenation of double bond.

Ruthenium is a hard, white metal and has four crystal modifications. It does not tarnish at room temperatures, but oxidizes explosively. It is attacked by halogens, hydroxides, etc. Ruthenium can be plated by electrodeposition or by thermal decomposition methods. The metal is one of the most effective hardeners for platinum and palladium, and is alloyed with these metals to make electrical contacts for severe wear resistance. A ruthenium-molybdenum alloy is said to be... 

Ruthenium nowadays finds many uses in the electronics industry, particularly for making resistor tracks. It is used as an ingredient in various catalysts and, importantly, in electrode materials, e.g. Ru02-coated titanium elements in the chloralkali industry. Osmium tetroxide is a very useful organic oxidant and, classically, is used as a tissue stain. Both elements are employed in making certain platinum alloys. 

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... 

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. 

Ruthenium alloyed to platinum, palladium, titanium and molybdenum have many apphcations. It is an effective hardening element for platinum and palladium. Such alloys have high resistance to corrosion and oxidation and are used to make electrical contacts for resistance to severe wear. Ruthenium-palladium alloys are used in jewelry, decorations, and dental work. Addition of 0.1% ruthenium markedly improves corrosion resistance of titanium. Ruthenium alloys make tips for fountain pen nibs, instrument pivots, and electrical goods. Ruthenium catalysts are used in selective hydrogenation of carbonyl groups to convert aldehydes and ketones to alcohols. 

It is further important to note that all the current/voltage characteristics depicted in Fig. 6 are unchanged by the presence of liquid fuels such as methanol, formaldehyde, formic acid, or hydrazine. The phthalocyanine electrode remains completely inert toward such substances. For this reason, no mixed potential can be formed at a phthalocyanine electrode, as for example can occur at a platinum electrode, when it is used as cathode in a methanol cell containing sulfuric acid. This is shown by a comparison (see Fig. 7) of the stationary characteristics of the platinum alloy we found to be the most active in the presence of methanol, namely a Raney ruthenium—rhodium electrode, with an iron phthalocyanine electrode, both measured in 4.5 N H2SO4+2M CH3OH. 

Ruthenium occurs alloyed with platinum ores and osmiridium, as indicated in the tables of analyses (pp. 208, 258). Combined with sulphur it is found as the rare mineral laurite. Ru2S3,3 which occurs in platinum washings in Borneo and Oregon. That ruthenium is present in celestial bodies is evidenced by the fact that it was detected in the Perryville siderite discovered in 1906 (see this volume, Part II). 

Detection of Ruthenium in Platinum Alloys.—In order to detect the presence of ruthenium in platinum alloys, a portion of the alloy is fused with lead. The melt is extracted with nitric acid and the residue ignited in contact with air in order to volatilise the osmium. The mass may now contain platinum, iridium, rhodium and ruthenium, and is fused with potassium nitrate and hydroxide. The whole is dissolved in water, treated with excess of nitric acid and allowed to stand in a flask covered with filter-paper. In a few hours (12-24) the filter-paper darkens if ruthenium is present, in consequence of the evolution of vapour of its tetroxide. To confirm the presence of ruthenium, the paper is ignited and the ash fused with potassium nitrate and hydroxide. On extraction with water the orange colour of potassium ruthenate is obtained.1... 

Other specialized alloys have also been used to prepare skeletal metal catalysts. Raney ruthenium has been prepared from the ruthenium aluminum alloy. 20 A colloidal platinum has been prepared by the action of acetic acid on a platinum lithium alloy. l Skeletal nickel catalysts have been made from a number of intermetallic compounds of nickel with the rare earth elements, lanthanum and samarium. The rare earth element is removed from the alloy by reaction with diiodoethane or dibromoethane which convert the rare earths to the soluble halide salts. 22 Several multicomponent catalysts have also been prepared from the corresponding aluminum alloys. 23-126... 

The DSA-type anodes are inert , coated anodes made of a valve metal (titanium, niobium, or tantalum) base coated with an electrochemically active coating. The active coating is made either of noble metals or of mixed metal oxides. Noble metals in active coatings are usually platinum or platinum alloys. Mixed metal-oxide coatings contain active oxides and inert oxides the active components are usually ruthenium dioxide (R.UO2) and iridium dioxide (IrC>2) and the inert components are mostly titanium dioxide (TiC>2) and other oxides such as tantalum... 

The aim of this contribution is to present data on the preparation of catalysts containing as embedding species a large family of eolloids such as colloids of ruthenium, platinum, or palladium-gold alloys and triflate derivatives such as lanthanum and silver triflate or tert-butyldimethylsilyltrifluoromethanesulfonate (BMSTM). Silica, zirconia and tantalum oxides were used as carrier. All these preparations considered the polymeric sol-gel route using as starting materials silicon, zirconium or tantalum alcoxides. 

There still stands valid for platinum alloys the two metals that are able to promote methanol oxidation are ruthenium and tin. The case of ruthenium is interesting since it was also studied under UHV conditions [43,44]. The reaction of methanol on Pt/Ru alloys results in the production of carbon dioxide at lower potentials than on pure platinum. However, the presence of tin in Pt3Sn alloys only enhances methanol oxidation at low potentials, increasing carbon dioxide production (and diminishing carbon monoxide production) [45]. The addition of tin (II) ions to previously adsorbed methanol produces a fast oxidation process, demonstrated by DEMS experiments [46]. 

Rh, Pt, etc. Plans are under way in this laboratory for studies of the static and dynamic structure of CO on binary and ternary alloys (e.g., ruthenium/platinum/tin) in methanol for fuel-cell applications. Such alloys display enhanced resistance to CO poisoning, and the nature of this resistance is appropriate for NMR investigation. For example, Pt-CO bonding information such as Pt-C connectivities, CO orientation and clustering, are accessible by Ti, T2, isotope dilution, and related techniques. In fact, essentially all of the techniques used in the past 20 years to study the solid-gas interface should now be applicable to NMR-electrochemistry, with the added bonus of potential control. 

Ura] Urashima, Y, Wakabayashi, T, Masaki, T., Osmian Ruthenium and Platinum Alloys from Horokanai, Hokkaido, Japan (in Japanese), Kagoschima Dai. Rika Hokoku, 25(9), 165-171 (1976) (Experimental, Phase Diagram, 11)... 

Platinum-alloy catalysts in particular platinum-ruthenium alloys are also capable to mitigate the CO poisoning effect [41]. However, only moderately higher CO concentrations can be tolerated while the stability of the catalyst is questionable due to mthenium dissolution. 

Ruthenium is used most often as a hardening agent for platinum and palladium. The major alloy is Pt-Ru with 10-15% ruthenium. Special alloys with 30-70% ruthenium are used in applications in which resistance to severe wear and corrosion is required. Ruthenium is replacing iridium as a hardening agent because it is more effective and less expensive. The glassy metal aUoy MO cRui- c is known to have superconducting properties. 

A material that enhances the rate of an electrochemical reaction, such as the hydrogen oxidation reactitMi (HOR) or the oxygen reductirai reaction (ORR), without itself being consumed in the reaction. In most PEM fuel cells, the electrocatalysts are nanosized materials made from the precious metals group (PGM), usually platinum, palladium, and ruthenium, or alloys of these materials with nickel, cobalt, and manganese. 

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