Surface electrochemistry at monocrystalline gold electrodes
Abstract
Carbon monoxide electrooxidation kinetics were studied at gold single crystals, and the mechanistic parameters were determined. Two interesting features are as follows. First CO oxidation, which was found to be accompanied by oxygen atom transfer from hydroxide, occurs 700 mV less positive than surface oxidation. Second, the reaction intermediate was identified by electrochemistry and additionally by infrared and Raman spectroscopy to be metal hydroxycarbonyl. CO adsorption at gold monocrystalline electrodes from the atmospheric gas phase as well as from solution was investigated. The ability of CO to adsorb to near saturation coverages from the atmospheric gas phase onto gold electrodes contrasts the absence of CO adsorption on gold in ultrahigh vacuum (uhv). The extent of CO adsorption from solution did not depend on the cation identity. Adsorption of CO was strongest in more alkaline solutions and at suitably negative electrode potentials. Adsorbed CO survived electrode transfer to a second cell under some conditions. The adsorbed CO was always found to inhibit the diffusion-controlled electrooxidation of solution CO. The CO adsorbs randomly at low coverage, and at high coverage it forms islands which are retained upon partial stripping. The use of rotated disk voltammetry to extract kinetic information failed due to increased CO adsorption when the electrode was rotated. The oxidation of formamide at polycrystalline electrodes was studied with the objective to relate changes in amide functional groups to electrooxidation behavior. The study was frustrated by the hydrolysis of amides, the coincidence of the oxidation wave of amides and of the gold surface, and the tendency of reactants to undergo photodecomposition in the laser beam during Raman spectroscopic measurements. Nevertheless, for the oxidation reaction of HCONH$\sb2$, intermediate and product species were clearly observed.
Degree
Ph.D.
Advisors
Weaver, Purdue University.
Subject Area
Analytical chemistry|Chemistry
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