Jump to main content
Jump to site search

Issue 42, 2010
Previous Article Next Article

Mechanistic studies of the ‘blue’ Cu enzyme, bilirubin oxidase, as a highly efficient electrocatalyst for the oxygen reduction reaction

Author affiliations

Abstract

The ‘blue copperenzyme bilirubin oxidase from Myrothecium verrucaria shows significantly enhanced adsorption on a pyrolytic graphite ‘edge’ (PGE) electrode that has been covalently modified with naphthyl-2-carboxylate functionalities by diazonium coupling. Modified electrodes coated with bilirubin oxidase show electrocatalytic voltammograms for the direct, four-electron reduction of O2 by bilirubin oxidase with up to four times the current density of an unmodified PGE electrode. Electrocatalytic voltammograms measured with a rapidly rotating electrode (to remove effects of O2 diffusion limitation) have a complex shape (an almost linear dependence of current on potential below pH 6) that is similar regardless of how PGE is chemically modified. Importantly, the same waveform is observed if bilirubin oxidase is adsorbed on Au(111) or Pt(111) single-crystal electrodes (at which activity is short-lived). The electrocatalytic behavior of bilirubin oxidase, including its enhanced response on chemically-modified PGE, therefore reflects inherent properties that do not depend on the electrode material. The variation of voltammetric waveshapes and potential-dependent (O2) Michaelis constants with pH and analysis in terms of the dispersion model are consistent with a change in rate-determining step over the pH range 5–8: at pH 5, the high activity is limited by the rate of interfacial redox cycling of the Type 1 copper whereas at pH 8 activity is much lower and a sigmoidal shape is approached, showing that interfacial electron transfer is no longer a limiting factor. The electrocatalytic activity of bilirubin oxidase on Pt(111) appears as a prominent pre-wave to electrocatalysis by Pt surface atoms, thus substantiating in a single, direct experiment that the minimum overpotential required for O2 reduction by the enzyme is substantially smaller than required at Pt. At pH 8, the onset of O2 reduction lies within 0.14 V of the four-electron O2/2H2O potential.

Graphical abstract: Mechanistic studies of the ‘blue’ Cu enzyme, bilirubin oxidase, as a highly efficient electrocatalyst for the oxygen reduction reaction

Back to tab navigation

Supplementary files

Publication details

The article was received on 24 Mar 2010, accepted on 05 Aug 2010 and first published on 20 Sep 2010


Article type: Paper
DOI: 10.1039/C0CP00018C
Citation: Phys. Chem. Chem. Phys., 2010,12, 13962-13974
  •   Request permissions

    Mechanistic studies of the ‘blue’ Cu enzyme, bilirubin oxidase, as a highly efficient electrocatalyst for the oxygen reduction reaction

    L. dos Santos, V. Climent, C. F. Blanford and F. A. Armstrong, Phys. Chem. Chem. Phys., 2010, 12, 13962
    DOI: 10.1039/C0CP00018C

Search articles by author

Spotlight

Advertisements