Adsorption and Electrochemistry of BIS-1, 10-Phenanthroline Complexes of Copper (I,II) and Fungal Laccase A

Citation

Lee, Chi-Woo (1984) Adsorption and Electrochemistry of BIS-1, 10-Phenanthroline Complexes of Copper (I,II) and Fungal Laccase A. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/f4sv-x904. https://resolver.caltech.edu/CaltechTHESIS:11272018-091510836

Abstract

This thesis is an outcome of the efforts directed toward the theme "Electrocatalysis of dioxygen reduction by copper- containing molecules adsorbed on graphite electrodes."

In the first part, an electrochemical measurement of the rate of electron exchange between Cu(phen)₂⁺ adsorbed on graphite and Cu(phen)₂⁺⁺ in solution is described. The rate constant was estimated to be ca. 10⁵ M^-1 s^-1 by using rotating disk voltammetry. The origin of the previously reported but widely discrepant values (5 x 10⁷ M^-1 s^-1 and 50 M^-1 s^-1) in the literature is discussed, and a new estimate of ca. 10⁴ M^-1 s^-1 is obtained by applying Marcus theory in a form that allows explicitly for differences in reorganization energy between the oxidized and reduced halves of the reacting redox couples. The electrocatalytic studies of dioxygen reduction by Cu(phen)₂⁺ could not be done due to the low signal-to-noise ratio.

In the second part, the bioelectrocatalytic reduction of molecular oxygen by reduced fungal laccase A immobilized on pyrolytic graphite is described. The reduction produces exclusively water in the potential range studied (< 0 V vs. SSCE). The catalytic activity reaches its maximum at pH 3~4, and the lower limit on rate constant for the reduction in this pH range was estimated to be 1.5 x 10⁴ M^-1 s^-1.

Three appendices describe (i) potential step hydrodynamic chronocoulometry, (ii) a new method to determine the self- exchange rate constant for the redox couple in which the coordination numbers depend on the oxidation states, and (iii) a novel electrochemical method of detecting H₂O₂.

Thesis Files