Palladium, electrodeposition

Industry, however, favours electrodeposited palladium-nickel alloy since it is cheaper than palladium, harder and less prone to cracking, fingerprinting and formation of polymer films Its wear resistance is poor, so it is usually given a thin topcoat of hard (sometimes, soft) gold. ... 

Favier, F., Walter, E.C., Zach, M.P., Benter, T. and Penner, R.M., Hydrogen sensors and switches from electrodeposited palladium mesowire arrays, Science, 293,2227,2001. 

The texture of coatings and films deposited by various techniques do differ widely. Electrodeposited palladium serves as one of examples the best to illustrate the point. In this case and depending on current density and/or solution pH, three different deposits, in addition to no texture, can be obtained (111), (110), or even a combination of four separate components. Here, instead of specifying the fiber axes, we indicate planes that stay nearly fixed in orientation. This is the practice of a number of authors. 

Favier, Frederic, Waller, ich, C., Zach, Michael P., Benier, Thorsten, Penner, Reginald M., Hydrogen Sensors and Switches form Electrodeposited Palladium Mesowire Arrays , Science. Vol. 293, No 5538, Page 2227... 

Yu.M. Maksimov, E. A. Kolyadko, A.B. ShishUova, and B.I. Podlovchenko, Electrocatalytic behavior of a palladium-polyaniline system obtained by electrodepositing palladium into a preliminarily formed polyaniline film, Russ. J. Electrochem., 37, 777-781 (2001). 

Hydrogen sensors and switches from electrodeposited palladium mesowires arrays. Science 293 2227-2231... 

A channel MSR without any internals for mixing can also be used for three-phase reactions hydrogenation of /)-nitrotoluene to / -toluidine in microchannel reactors using different ways of preparation of the Pd catalyst [22]. Practically this reaction is free of by-products, that is, selectivity to / -toluidine is 100%. Depending on the operating conditions, the conversion was varied from 58 to 98% in MSR. The conversion for an electrodeposited palladium was 58%, for chemical deposited palladium was in between 58 and 98%, for impregnated catalyst on an electro-oxidized nanoporous substrate was 89%, and for fixed bed catalyst was 85%. Though the best MSR conversion is similar to that of a conventional fixed bed reactor, the increased heat removal allowed a pronounced decrease in reaction time down to some few minutes [23]. 

O2. More recently, performances with formic acid as fuel were increased up to 28 mW cm with electrodeposited palladium (Pd)-containing catalyst at the anode [39], An allpassive system (passive 10 M formic acid and quiescent air) was also recently announced with interesting first results (12.3 mW cm ) [40],... 

Naohara H, Ye S, Uosaki K (2001) Thickness dependent electrochemical reactivity of epitaxially electrodeposited palladium thin layers on Au(lll) and Au(lOO) surfaces. J Electroanal Chem 500 435 5... 

Favier F, Walter EC, Zach MP, Benter T, Penner RM (2001) Hydrogen sensors and switches from electrodeposited palladium mesowires arrays. Science 293 2227-2231... 

Shaidarova, L. G., A. V. Gedmina, I. A. Chelnokova, and G. K. Budnikov. 2006. Electrocatalytic oxidation and flow-injection determination of ascorbic acid at a graphite electrode modified with a polyaniline film containing electrodeposited palladium./. Anal. Chem. 61 601-608. 

Friction and wear of electrodeposited palladium contacts thin film lubrication with fluids and with gold, IEEE Trans. Compon. Hybr Manuf. TechnoL, 1986, CHMT-9, 485. 

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... 

Hardness of the aimealed metals covers a wide range. Rhodium (up to 40%), iridium (up to 30%), and mthenium (up to 10%) are often used to harden platinum and palladium whose intrinsic hardness and tensile strength are too low for many intended appHcations. Many of the properties of rhodium and indium. Group 9 metals, are intermediate between those of Group 8 and Group 10. The mechanical and many other properties of the PGMs depend on the physical form, history, and purity of a particular metal sample. For example, electrodeposited platinum is much harder than wrought metal. 

Aqueous Electrodeposition. The theory of electro deposition is well known (see Electroplating). Of the numerous metals used in electro deposition, only 10 have been reduced to large-scale commercial practice. The most commonly plated metals are chromium, nickel, copper, zinc, rhodium, silver, cadmium, tin, and gold, followed by the less frequendy plated metals iron, cesium, platinum, and palladium, and the infrequendy plated metals indium, mthenium, and rhenium. Of these, only platinum, rhodium, iddium, and rhenium are refractory. 

Palladium and gold Palladium electrodeposition is of special interest for catalysis and for nanotechnology. It has been reported [49] that it can be deposited from basic chloroaluminate liquids, while in the acidic regime the low solubility of PdCl2 and passivation phenomena complicate the deposition. In our experience, however, thick Pd layers are difficult to obtain from basic chloroaluminates. With different melt compositions and special electrochemical techniques at temperatures up to 100 °C we succeeded in depositing mirror-bright and thick nanocrystalline palladium coatings [10]. 

At first sight, electrodeposition of metals from nonaqueous solutions seems to offer a complete solution, there being no source of H present (in a system consisting of e.g., palladium chloride in a phenanthrene-anisole mixture). The potential limits inside which electrodeposition can take place can be far wider than those in aqueous solutions (some 2.0 V). A number of redox potentials in nonaqueous systems are given in Table 7.22. 

Only three of the metals, rhodium, palladium and platinum, need be considered. Of these only rhodium plating is of significant commercial importance, but the relatively low cost of palladium has made it attractive for contacts and printed circuits. Electrodeposited platinum is harder than the annealed bulk metal and finds applications in jewellery, the plating of scientific instruments, standard weights and parts of electrical apparatus. 

Ivekovic et al. [42] Fruit juice, yoghurt drink Glucose oxidase (GOx)/ into palladium hexacyanoferrate (PdHCF) hydrogel Nickel hexacyanoferrate (NiHCF) electrodeposited onto graphite electrode/-0.075V vs. SCE Nickel hexacyanoferrate... 

Between 1980 and about 2000 most of the studies on the electrodeposition in ionic liquids were performed in the first generation of ionic liquids, formerly called room-temperature molten salts or ambient temperature molten salts . These liquids are comparatively easy to synthesize from AICI3 and organic halides such as Tethyl-3-methylimidazolium chloride. Aluminum can be quite easily be electrode-posited in these liquids as well as many relatively noble elements such as silver, copper, palladium and others. Furthermore, technically important alloys such as Al-Mg, Al-Cr and others can be made by electrochemical means. The major disadvantage of these liquids is their extreme sensitivity to moisture which requires handling under a controlled inert gas atmosphere. Furthermore, A1 is relatively noble so that silicon, tantalum, lithium and other reactive elements cannot be deposited without A1 codeposition. Section 4.1 gives an introduction to electrodeposition in these first generation ionic liquids. 

Palladium is employed in a number of industrial applications and fundamental studies because of its high catalytic activity for many chemical reactions, e.g. its ability to absorb hydrogen [41], On the other hand, due to hydrogen absorption, only brittle Pd deposits can be obtained in aqueous solutions. The advantage of performing electrodeposition of Pd in ionic liquids is that hydrogen evolution does not occur. Sun et al. demonstrated that Pd and some of its alloys, namely Pd-Ag [42], Pd-Au [43] and Pd-In [44], can be obtained from the basic l-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid. Compact alloy deposits were obtained and the Pd content in the deposits increased with the increase in Pd mole fraction in the plating bath. 

---