Platinum electrodes surface coverage

Gihoy D, Conway BE. 1968. Surface oxidation and reduction of platinum electrodes— coverage kinetic and hysteresis studies. Can J Chem 46 875-876. 

Os) and [Os(v-bpy)2(phen)](phen is 4-methyl-1,10-phenanthroline) on platinum electrodes have been studied as a function of surface coverage and applied potential by measuring the characteristic RuKa and OsLa fluorescence... 

Figure 6. Cyclic voltammograms of a platinum disk-electrode modified with a film of the octanuclear dendrimer 2, measured in 0.1 M Bu NPFj/CHjClj. The surface coverage of electroactive ferrocenyl sites in the film is determined to be T = 2.01 x 10" mol cm . inset, scan rate dependence of the anodic peak current.

In the presence of Pb(II) ions in sulfuric acid, potential oscillations have been observed for galvanostatic oxidation of hydrogen on platinum electrode [129]. This behavior has been attributed to ad-sorption/oxidation/desorption processes of lead on the platinum surface. Lead at high values of coverage is oxidized to insoluble PbS04, which blocks the Pt surface. 

S02 equals 1, because S02 is formed in the rate-determining step and therefore reacts further in much faster elementary steps. This implies that the surface coverage of S02 equals zero or (1 - 0) equals l.The (1 - 0) for S02 cannot be eliminated in the same way. However, its elimination is possible when an additional condition is taken into account in the proposed mechanism. If it is presumed that k 2 k3, this means that most of the S02, formed in step 2, that does not react in the RDS, will react to adsorbed dithionite via the backward reaction of step 2. When Equation 6.18 is modified, taking into account the above assumptions, the following final rate equation for the oxidation of sodium dithionite at a platinum electrode is obtained ... 

Very thin films (ca. 10 nm) formed by electropolymerization can be used to effectively prevent signals due to interferences. Figure 1 shows a cyclic voltammogram for the electropolymerization of poly(l,3-DAB) onto a platinum ultramicroelectrode (25/un diameter). Note how the current decreases with each subsequent scan, indicating coverage of the electrode surface. 

Figure 5.8 Cyclic voltammograms for the Os2+/3+ redox reaction within spontaneously adsorbed [Os(OMebpy)2(p3p)Cl]+ monolayers. From right to left, the electrode materials are platinum, gold, carbon and mercury. The scan rate is 50 Vs-1, with a surface coverage of 1.0 0.1 x 10-1° mol cm-2 the supporting electrolyte is aqueous 1.0 M NaC104. Reprinted with permission from R. J. Forster, P. J. Loughman and T. E. Keyes,/. Am. Chem. Soc., 122,11948 (2000). Copyright (2000) American Chemical Society...

Figure 5.11 Voltammetric response for a 5 pm platinum electrode modified with a monolayer of [(pOp)Os(bpy)2(4-tet)Os(bpy)2Cl]3+, measured at a scan rate of 10 V s 1. The supporting electrolyte is 1.0 M LiCICh in acetonitrile, and the monolayer surface coverage is 9.8 x 10 n mol cm-2. The cathodic currents are shown as up, while the cathodic currents are shown as down. Reprinted with permission from R. J. Forster and T. E. Keyes, /. Phys. Chem., B, 105, 8829 (2001). Copyright (2001) American Chemical Society...

Figure 5.72 Typical Koutecky-Levich plots for the reduction of a 0.2 mM [Fe(H20)6]3+ solution in 0.1 M H2S04 at platinum electrodes modified with layers of different surface coverages of [Os(bpy)2(PVP)ioCl]+. From top to bottom, the surface coverages (in mol cm-2) are 1.7 x 10-1°, 1.8 x 10 9, 2.7 x 10-9, 5.0 x 10 9,1.1 x 10 8, and bare platinum. From R. J. Forster and J. G. Vos, /. Chem. Soc., Faraday Trans., 87,1863-1867 (1991). Reproduced by permission of The Royal Society of Chemistry...

It was first shown by electrochemically modulated infrared reflectance spectroscopy (EMIRS) that the main poisoning species formed during the chemisorption and oxidation of methanol on a platinum electrode is carbon monoxide CO, either linearly bonded, or bridge bonded to the surface. The coverage degree of the electrode surface by linearly bonded CO can reach 90% on a pure platinum electrode, so that most of the active sites are blocked... 

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