Comparison of Voltammetric Responses of Toluene and Xylenes at Iron(III)-Doped, Bismuth(V)-Doped, and Undoped β-Lead Dioxide Film Electrodes in 0.50 M H[sub 2]SO[sub 4]

Voltammetric activities are compared for the designated compounds in 0.50 M at the specified film electrodes configured as rotated disks. The effective number of electrons equiv mol −1 ) calculated from the Koutecky-Levich plot is for toluene oxidation at the electrode, compared to and at the and electrodes, respectively. Gas chromatography-mass spectrometry data confirm that the primary product of toluene oxidation is benzyl alcohol (2 equiv mol −1 ) at the electrode with production of small amounts of benzaldehyde (4 equiv mol −1 ) and benzoic acid (6 equiv mol −1 ). X-ray photoelectron spectroscopy data indicate the ratio of Fe:Pb is ca. 1:100 (atom:atom) in the films. By comparison, a Bi:Pb ratio of 33:100 (atom:atom) is easily attained in films. Nevertheless, the apparent heterogeneous rate constant for toluene oxidation is larger at the electrode compared to the electrode X-ray absorption near-edge structure data confirm speculation that iron exists in the 3+ oxidation state with octahedral coordination by O atoms in films. The large activity of the electrode is attributed to the benefit of adsorption of aromatic molecules at Fe(III) sites.