Ruthenium layer thickness

Porous anode 1, used in SPE electrolysis (fig.1) consists of mixtxjre of ruthenium dioxide (75%) and iridium oxide bound to the graphite layer. Thickness of such layer depends on the amount of aphitc, covering the anode surface unit. In particular, if this amount is 40 g/m. correspondent thickness reaches 100 0jn [12]. Current feeding to anode is held with the help of point collector 6 (the metal net can sei e as this collector). Anode space is separated from the cathode one with the help of membrane SPE (2). Platinum black, serving as an anode 1, is 100 jim v/ide. Cathode point collector 3 is connected with graphite plate 5, that maintain direct contact with cathode. 

The typical metals in this category are silver, gold, and the platinum metals rhodium, palladium, platinum, and ruthenium. The demands for corrosion protection by noble metal coatings are a pore- and crack-free deposit and a layer thickness that is able to protect the substrate for the expected lifetime of the plated parts. 

Let us first consider what EXAFS might tell us in the case of bimetallic particles that are not too small - say a few nanometer in diameter. For a truly homogeneous alloy with a 50 50 composition, EXAFS should see a coordination shell of nearest neighbors with 50% Cu and 50% Ru around both ruthenium and copper atoms. If, on the other hand, the particle consists of an Ru core surrounded by a Cu shell of monatomic thickness, we expect that the Ru EXAFS shows Ru as the dominant neighbor, because only Ru atoms in the layer directly below the surface are in contact with Cu. The Cu EXAFS should see both Cu neighbors in the surface and Ru neighbors from the layer underneath, with a total coordination number smaller than that of the Ru atoms. The latter situation is indeed observed in Ru-Cu/Si02 catalysts, as we shall see below. 

To investigate the electrochemical properties of pure ruthenium also, ruthenium was chemically reduced and deposited as a thick layer on a platinum wire becaiise ruthenixim metal is not commercially available as a wire nor a plate due to its brittleness. A platinum wire (0.1 mm in diameter) was placed in an alkaline 0.05 M ruthenium (IQ) nitrosylnitrate solution containing 1 M hydrazine as a reducing agent and heated up to 60°C. The deposition did not start imtil the heat was applied. After the deposition, the electrode was washed with water and used for the electrochemical measurements. 

Like other non-oxidic semiconductors in aqueous solutions, surface oxidized and photocorrosive InP is a poor photoelectrode for water decomposition [19,27,32,33], To enhance properties several efforts have focused on coupling of the semiconductor with discontinuous noble metal layers of island-like topology. For example, rhodium, ruthenium and platinum thin films, less than 10 nm in thickness, have been electrodeposited onto p-type InP followed by a brief etching treatment to achieve an island-like topology on the surface [27,28]. In combination with a Pt counter electrode, under AM 1.5 illumination of 87 mW/cm the metal (Pt, Rh, Ru) functionalized p-InP photocathodes [27] see a reduction in the threshold voltage for water electrolysis from 1.23 V to 0.64 V, and in aqueous HCl solution a photocurrent density of 24 mA/cm with a photoconversion efficiency of 12% [27]. 

Nickel in Nanometer Materials. Coating a metal with an ultrathin layer of another metal creates properties not found separately in either of the materials. Considerable recent research has been directed toward improving the mechanical properties of bimetallic laminates, sometimes called composition modulatedfilms, which have interlayers only a few nanometers thick. Attractive properties also have been found for similar systems, called nanometer materials. Nickel has been used in combination with copper, ruthenium, and other metals for producing these new materials. 

The same approach was adapted in a later study. An efficient solid-state DSSC was fabricated using hybridized ruthenium dye 8. The hole conducting PEDOT was formed in situ via PEP. The thickness of the mesoporous Ti02 layer of the solar cell was varied. The highest efficiency (2.6% under 100 mW/ cm2 illumination) was achieved by using a 5.8- pm-thick Ti02 layer.52... 

In a reactor that is similar to a reformer, the reaction occurs in tubes that are heated externally to supply the endothermic heat of reaction129. Sintered corundum (a-Al203) tubes with an internal layer ( 15 microns thick) of platinum/ruthenium catalyst are used, hi some cases a platinum/aluminum catalyst may be used. To achieve adequate heat transfer, the tubes may be only % in diameter and 6V2 feet long. Selectivities of 90-91% for methane and 83-84% for ammonia are reached at 1200°C to 1300°C reaction temperatures. 

If, however, the selectivity of a reaction is influenced by the presence of a thick support layer on the channel walls, the use of a different type of monolith support than the classical carbon-coated monolith is recommended. This was shown in the ruthenium-catalyzed reaction. EPMA analyses showed that ruthenium species are present both in the pores of the outer carbon washcoat layer and on the surface of the carbon inclusions located inside the monolith walls. No ruthenium was found in the empty macropores of the cordierite, since (1) there is no strong interaction between the precursor and the cordierite, and (2) after impregnation and washing, the macropores are emptied first upon drying, due to the capillary forces. The presence of active phase in the walls of the monolithic substrate is undesired, since it makes the diffusion path of the reactants to the active ruthenium sites longer. To prevent deposition of ruthenium in the waU,... 

For successful application of carbon-coated monolithic catalysts, the deposition of active phase in the walls of a monolithic substrate should be prevented. To prevent deposition of ruthenium in the wall (1) substrates with nonporous walls can be used, or (2) the cordierite monolithic substrates can be modified with a-AEOs, blocking the macroporosity of the cordierite and rounding the channel cross section to enable a more uniform thickness of the carbon coating layer. Alternatively, ACM monoliths or integral carbon monoliths with very thin walls having a characteristic diffusion length similar to the activated carbon slurry catalysts can be employed. 

For reasons that are discussed in Section 19.4, the catalyst for the hydrogen electrode in polymer electrolyte membrane fuel cells is a mixed platinum-ruthenium catalyst applied to carbon black, rather than pure platinum. The overall thickness of modern MEA is about 0.5-0.6mm (of which 0.1 mm for the membrane, for each of the two GDLs, and for each of the two active layers). The bipolar plates have a thickness of about 1.5 mm, the channels on both sides having a depth of about 0.5 mm. 

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