Glassy carbon tubular electrodes for the reduction of oxygen to hydrogen peroxide.

The oxygen reduction reaction (ORR) to produce hydrogen peroxide (H2O2) is of great industrial interest. Herein, a hydrodynamic electrochemical method is explored for use as a continuous method to produce H2O2 at the point-of-use. The ORR was studied in a tubular glassy carbon flow cell under a laminar flow regime.

Asymmetric Marcus-Hush theory for voltammetry.

The current state-of-the-art in modeling the rate of electron transfer between an electroactive species and an electrode is reviewed. Experimental studies show that neither the ubiquitous Butler-Volmer model nor the more modern symmetric Marcus-Hush model are able to satisfactorily reproduce the experimental voltammetry for both solution-phase and surface-bound redox couples. These experimental deviations indicate the need for revision of the simplifying approximations used in the above models.

Ammonium-directed olefinic epoxidation: kinetic and mechanistic insights.

The ammonium-directed olefinic epoxidations of a range of differentially N-substituted cyclic allylic and homoallylic amines (derived from cyclopentene, cyclohexene, and cycloheptene) have been investigated, and the reaction kinetics have been analyzed. The results of these studies suggest that both the ring size and the identity of the substituents on nitrogen are important in determining both the overall rate and the stereochemical outcome of the epoxidation reaction. In general, secondary amines or tertiary amines with nonsterically demanding substituents on nitrogen are superior to tertiary amines with sterically demanding substituents on nitrogen in their ability to promote the oxidation reaction.

Electrode kinetics at carbon electrodes and the density of electronic states.

Marcus-Hush theory relates the rate of electron transfer to the density of electronic states of the electrode material. Through use of a carbon microelectrode--for which the density of states is expected to vary as a function of potential--this predication is validated for graphitic materials by measurement of a variety of outer-sphere redox systems.

Mass transport to micro- and nanoelectrodes and their arrays: a review.

The use of micro- and nanoelectrodes and their arrays has become commonplace in modern electrochemistry. Numerical simulation is often required for detailed analysis of voltammetric data and this relies upon an understanding of the prevailing mass transport operating under the experimental conditions. The theoretical basis of our understanding of mass transport, particularly diffusion and migration, has developed greatly in recent years.

Edge plane pyrolytic graphite electrode covalently modified with 2-anthraquinonyl groups: theory and experiment.

An edge plane pyrolitic graphite (EPPG) electrode was modified by electrochemical reduction of anthraquinone-2-diazonium tetrafluoroborate (AQ2-N(2)(+)BF(4)(-)), giving an EPPG-AQ2-modified electrode of a surface coverage below a monolayer. Cyclic voltammograms simulated using Marcus-Hush theory for 2e(-) process assuming a uniform surface gave unrealistically low values of reorganisation energies, λ, for both electron transfer steps. Subsequently, two models of surface inhomogeneity based on Marcus-Hush theory were investigated: a distribution of formal potentials, E', and a distribution of electron tunneling distances, r(0).

Generator-collector experiments at a single electrode: exploring the general applicability of this approach by comparing the performance of surface immobilized versus solution phase sensing molecules.

We demonstrate proof-of-concept that generator-collector experiments can be performed at a single macroelectrode and used to determine mechanistic information. The practical advantages of such a system over conventional generator-collector techniques are also outlined. The single-electrode generator-collector technique is applied to study the known mechanism of oxygen reduction in aqueous conditions as a model system.