Copper, coadsorption

Wu S, Lipkowski J, Tyiiszczak T and Hitchcock A P 1997 Eariy stages of copper eiectrocrystaiiization eiectrochemicai and in situ x-ray absorption fine structure studies of coadsorption of copper and chioride at the Au(111) eiectrode surface J.Phys. Chem. B 101 10 310-22... 

Secondly, absorbent particles such as charcoal and soot are intrinsically inert but have surfaces or infrastructures that adsorb SO, and by either coadsorption of water vapour or condensation of water within the structure, catalyse the formation of a corrosive acid electrolyte solution. Dirt with soot assists the formation of patinae on copper and its alloys by retaining soluble corrosion products long enough for them to be converted to protective, insoluble basic salts. 

Smith SPE, Ahruna HD. 1999h. The coadsorption of UPD copper and irreversibly adsorbed bismuth on Pt(lll) and Pt(lOO) electrodes. J Phys Chem B 103 6764-6769. 

The experimental evidence, first based on spectroscopic studies of coadsorption and later by STM, indicated that there was a good case to be made for transient oxygen states being able to open up a non-activated route for the oxidation of ammonia at Cu(110) and Cu(lll) surfaces. The theory group at the Technische Universiteit Eindhoven considered5 the energies associated with various elementary steps in ammonia oxidation using density functional calculations with a Cu(8,3) cluster as a computational model of the Cu(lll) surface. At a Cu(lll) surface, the barrier for activation is + 344 k.I mol 1, which is insurmountable copper has a nearly full d-band, which makes it difficult for it to accept electrons or to carry out N-H activation. Four steps were considered as possible pathways for the initial activation (dissociation) of ammonia (Table 5.1). 

Here, the dissociative adsorption of hydroi l radicals increases with increasing coadsorption of electropositive potassium atoms on the platinum surface. It has also been reported that coadsorption of electronegative oxygen molecules accelerates the adsorption of hydroxjd radicals on the surface of copper, silver and nickel [Thiel-Madey, 1987]. 

Early stages of copper electrodeposition and coadsorption of chloride on the Au(lll) electrode surface have been studied by Wu et al. [390] applying electrochemical methods and in situ X-ray absorption measurements. The results indicate a large degree of static disorder and exclude the presence of high-symmetry structures. Krznaric and Goricnik [391]... 

The coadsorption and IR spectroscopic studies cited in this section indicate that surface formate is readily formed from C02 and H2 or from CO and H20 vapors. It appears that the reaction of CO and H2 to formate is considerably more difficult. Moreover, while both formate and methoxide have been detected in methanol decomposition over ZnO and in the synthesis over the Zn0/Cr203 catalysts, no positive evidence of these species has so far been gathered for the copper-based catalysts. 

In summary, the results of TDS [13], photoemission [13,45] and scanning tunnelling microscopy [24,45] indicate that at low sulphur coverages the interactions between S and Ag on Ru(OOOl) can be classified as repulsive, in the sense that there is weakening of the Ru-Ag bond and no mixing of the adsorbates. Once the ruthenium substrate becomes saturated with sulphur, then attractive interactions between silver and sulphur are possible and AgS is formed [13,45]. Very similar trends are observed for the coadsorption of sulphur and copper on Ru(OOOl) [13,23]. 

Cadmium UPD deposition was studied by Bondos et al. They monitored this process on Cu( 111) and Au(l 11) surfaces and observed a (4x4) structure on the copper electrode, while on gold electrode they imaged a series of linear structures. They explained the formation of these stmctures by coadsorption of sulfate anions. 

C and n-octadecane-1,2-H at a concentration of 0.35 molar in stearic acid and studied the coadsorption of stearic acid and octadecane on polished surfaces of silver, platinum, copper and iron. The films were prepared by retraction from the melt at 40 C (at room temperature the mixture was solid). The proportion of n-octadecane in the film was assayed by differential extraction with cyclohexane. The results of the investigation adequately demonstrate that n-octadecane coadsorbs with stearic acid but not necessarily as a mixed oriented monolayer. Some of the data indicate that more than a single layer is present on the surface. Thus the structure of the long-chain material on the surface may be open to conjecture, but that each constituent adsorbs and in what relative amount is directly determined by radioactive assay. 

In addition, the OH coadsorption significantly influences the adsorption of all other double layer components [55. 56]. For example, in chloride containing media, a significant reduction of the Cl surface concentration was found, while the concentration of cations and surface water was significantly increased compared to the emersion from acidic solutions [55]. Even the adsorption of the strongly binding iodine on silver is pH dependent [31]. The results can be explained by a specific adsorption of OH on silver [55, 56, 59] this interpretation is consistent with the fact that appreciable amounts of adsorbed OH were also found for copper electrodes in alkaline solutions [60]. 

Considering the adsorption of anions induced by adatoms, it is quite evident that anions can have a profound effect on the metal monolayer formation. In some cases even anions can determine the structure of the metal adsorbate. For instance, the coadsorption structure of upd copper and halides on Pt(lll) and Au(lll) was studied extensively. These studies revealed the bilayer coadsorption structure of copper and halides. An ordered structure of halide ions is formed on an adlayer of copper deposited on the Pt(l 11) surface. 

Radioisotopic tracer techniques were applied to study the coadsorption of n-octadecane and stearic acid on a metal surface immersed in a n-octadecane solution of stearic acid. Dual labeling was employed for determining the surface concentrations of both n-octadecane and stearic acid. n-Octadecane was labeled with tritium and stearic acid with carbon-14. The results of half-hour adsorption experiments provide direct proof of coadsorption of polar and nonpolar materials on iron, copper, silver, and platinum surfaces. The films produced on silver and copper by 19-hour adsorption consisted of approximately one molecular layer of stearic acid and two molecular layers of octadecane. A new model is proposed to describe the structure of this thick coadsorbed film. 

In our theory in the initial stages of the process there is a strong coadsorption of copper with the bisulfate. At positive potentials V > 0.45 volts with respect to the standard (Ag/AgCl) electrode), the bisulfate is strongly adsorbed onto the clean Au(l 11) surface. This means that there is an ordered 1 3 x /3 structure for... 

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