Electrocatalysis of Anodic Oxygen Transfer Reactions: Comparison of Structural Data with Electrocatalytic Phenomena for Bismuth‐Doped Lead Dioxide

Abstract

X‐ray structural data, O2 evolution overpotentials false(ηO2↑false) , and rate constants false(kfalse) are compared for anodic oxidation of Mn(II) false(n=5 eq mol−1false) and 2‐thiophene carboxylic acid (2‐TCA) at Bi‐doped PbO2 in 1.0M HClO4 . It is concluded that the rutile structure of pure β‐PbO2 deposited anodically from 1.0M HClO4 containing Pb(II) is retained even as the Bi(III) content is increased to normalBi/normalPb≥normalca.0.7 , i.e., mole fraction normalBi=0.4 . There is no evidence of a new oxide phase being formed. Crystallites of the normalBi‐PbO2 are deposited with an increasing preferential orientation of the 020‐plane parallel to the Au substrate surface as the ratio Bi/Pb is increased. Increasing values of k and decreasing values of ηO2↑ appear to be correlated with the increased preferential orientation. However, change in preferential orientation is concluded not to be the primary determining factor in the electrocatalytic phenomena. The kinetic results are discussed also on the basis of the so‐called “volcano plot” of ηO2↑ as a function of the enthalpy of transition false(normalΔHnormalt0false) between the two highest oxide phases for metal oxide electrodes.

Electrodeposited lead dioxide coatings

“…111 In view of the high rates of oxidation of organics at some doped coatings, it is not surprising that the studies have been extended to the complete oxidation of organics and hence for the removal of TOC/COD from effluent mimics. [115][116][117][118] Johnson and coworkers 109,111,112,[114][115][116]119,120,124,127 have made detailed studies of the mechanisms for the enhancement of rates by doping. They regard oxidations at lead dioxide anodes as oxygen transfer reactions rather than electron transfer reactions and therefore stress the importance of the activation of water as adsorbed OH radicals as the key step in the oxidations.…”

“…Lead dioxide anodes have also been used for the production of strong oxidising agents such as dichromate, 78,[111][112][113][166][167][168] manganese (III) 109,114,119,169,170 and cerium(IV). [169][170][171][172] Most commonly, these processes are used to regenerate the spent oxidising agent from the oxidation of organic compounds (e.g.…”

Anodic Materials with High Energy Efficiency for Electrochemical Oxidation of Toxic Organics in Waste Water

“…F -and Fe 3+ doping as mentioned above, could enhance the adhesion and mechanical strength (Feng & Johnson, 1991;Mohd & Pletcher, 2006). While Bi 3+ (Feng & Johnson, 1991;Iniesta et al, 2001c;Liu et al, 2008b;Mondal et al, 2001;Mohd & Pletcher, 2006;Yeo et al, 1989) and Co 2+ (Andrade et al, 2008;Velichenko et al,2002) were reported to enhance the organics oxidation and reduce the electrode fouling by organics. During the organics oxidation, it was suggested that the dopants promote the formation of adsorbed OH radicals by increasing the oxygen vacancies concentration in lead dioxide lattice.…”

Preparation of Fluorine‐Doped Lead Dioxide Modified Electrodes for Electroanalytical Applications

“…Other peak intensities also have different changes in terms of the different concentrations of F À . As the F level increases in F-PbO 2 , the diffraction peaks become narrower than that for undoped PbO 2 , which indicated that the F-PbO 2 deposits have larger crystallite than undoped PbO 2 , because diffraction peak width is inversely proportional to crystallite size [21]. Hence, it can be concluded that the presence of F À in the modifying solution apparently decreases the rate of nucleation of the oxide crystallization on the Pt substrate, allowing individual crystallites to become larger.…”