title: Parameterization of Water Electrooxidation Catalyzed by Metal Oxides Using Fourier Transformed Alternating Current Voltammetry.
abstract: Detection and quantification of redox transformations involved in water oxidation electrocatalysis is often not possible using conventional techniques. Herein, use of large amplitude Fourier transformed ac voltammetry and comprehensive analysis of the higher harmonics has enabled us to access the redox processes responsible for catalysis. An examination of the voltammetric data for water oxidation in borate buffered solutions (pH 9.2) at electrodes functionalized with systematically varied low loadings of cobalt (CoOx), manganese (MnOx), and nickel oxides (NiOx) has been undertaken, and extensive experiment-simulation comparisons have been introduced for the first time. Analysis shows that a single redox process controls the rate of catalysis for Co and Mn oxides, while two electron transfer events contribute in the Ni case. We apply a "molecular catalysis" model that couples a redox transformation of a surface-confined species (effective reversible potential, Eeff0) to a catalytic reaction with a substrate in solution (pseudo-first-order rate constant, k1f), accounts for the important role of a Brønsted base, and mimics the experimental behavior. The analysis revealed that Eeff0values for CoOx, MnOx, and NiOxlie within the range 1.9-2.1 V vs reversible hydrogen electrode, and k1fvaries from 2 × 103to 4 × 104s-1. The k1fvalues are much higher than reported for any water electrooxidation catalyst before. The Eeff0values provide a guide for in situ spectroscopic characterization of the active states involved in catalysis by metal oxides.
authors.affiliation: School of Chemistry and the ARC Centre of Excellence for Electromaterials Science, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Shannon A
authors.initials: SA
authors.lastname: Bonke
authors.affiliation: School of Chemistry and the ARC Centre of Excellence for Electromaterials Science, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Bond
authors.affiliation: School of Chemistry and the ARC Centre of Excellence for Electromaterials Science, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Leone
authors.initials: L
authors.lastname: Spiccia
authors.affiliation: School of Chemistry and the ARC Centre of Excellence for Electromaterials Science, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Alexandr N
authors.initials: AN
authors.lastname: Simonov