Platinum coverage

Carbon Monoxide Oxidation on Platinum Coverage Dependence of the Product Internal Energy... 

Quantum efficiencies for photoxidation were improved by platinization of the Ti02 photocatalyst, with the observed yield increasing linearly with platinum coverage [117-121], Acetone was the major product in the presence of air or silver ion, a result that was similar to those observed upon y irradiation or in the Fenton reaction. This similarity was interpreted as implying hydroxyl radical mediation of the observed oxidations. 

ErSi2 with various platinum coverages, (a) OmL, (b) 0.2ml, (c) 0.15mLand (d) 0.08mL. Source Reprinted with permission from You et ai. (2006). Copyright 2006, American Chemical Society. 

An interesting field of application is the protection of tantalum against hydrogen embrittlement by electrical connection to platinum metals. The reduction in hydrogen overvoltage and the shift of the free corrosion potential to more positive values apparently leads to a reduced coverage by adsorbed hydrogen and thereby lower absorption [43] (see Sections 2.1 and 2.3.4). 

Figure 2.2. Thermal desorption spectra of carbon monoxide, measured mass spectrometically at mass 28 (atomic units, a.u.), on a platinum (100) surface upon which potassium has been pre-adsorbed to a surface coverage of 0K.7 Reprinted with permission from Elsevier Science.

If a coverage of the platinum with hydrogen was specified this is indicated by (H), if the electrode was platinized this is indicated by (Pt). 

The crucial aspect is thus to determine the fate of the ( CHO), species. Possible mechanisms for its oxidative removal are schematically shown in Fig. 9. From this scheme, it appears that the desorption of the formyl species can follow different pathways through competitive reactions. This schematic illustrates the main problems and challenges in improving the kinetics of the electrooxidation of methanol. On a pure platinum surface, step (21) is spontaneously favored, since the formation of adsorbed CO is a fast process, even at low potentials. Thus, the coverage... 

Westermark, G. and Persson, 1. (1998) Chemisorption of tertiary phosphines on coinage and platinum group metal powders. An infrared reflectance absorption spectroscopic, enhanced Raman spectroscopic and surface coverage study. Colloids and Surfaces A -Physicochemical and Engineering Aspects, 144, 149-166. 

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

Biegler T, Rand DAJ, Woods R. 1971. Limiting oxygen coverage on platinized platinum Relevance to determination of teal platinum area by hydrogen adsorption. J Electroanal Chem 29 269-277. 

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