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Photocurrent-potential curves at polycrystalline ~-Fe20.~ electrodes in acidic solutions are reported to be similar to those found in basic solutions. Faradaic collection efficiency of 100% for photoelectrolyzed oxygen has been achieved in a closed cell configuration. Stable photocurrents has been demonstrated in various acidic media, and trace amounts of Fe(IID detected in the working solutions gave an indication of the dissolution rate. The stability of the a:Fe20.~ electrode is discussed and compared to other metal oxide photoanodes. * Electrochemical Society Active Member.

Steady‐state photooxidation currents at polycrystalline α‐Fe2O3 electrodes with low band bending were found to depend significantly on the reducing agents present in the electrolyte. Photooxidation of water at low band bending exhibited only transient character. Diffusion‐controlled photocurrents for the photooxidation of I− and normalFefalse(CN)64− in acidic solutions, and OH− in unbuffered neutral solution were observed at an α‐Fe2O3 RDE and could be fitted to the Levich equation. The steady‐state and the transient photocurrents are analyzed and discussed in terms of cathodic back‐reaction of intermediate products with conduction band surface forbidden electrons.

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BENZOATE ESTER RADICAL ANIONS 1565The double potential step method is particularly attractive for measuring the homogeneous rate constant for EC systems because the number of variables used for fitting can be reduced to one. By stepping to a sufficiently forcing potential, the electrochemical reaction becomes diffusion controlled, and thus the charge transfer rate parameters have no influence on the relaxation currents. The dependence on electrode area as well as the dependence on the concentration and diffusion coefficient of the electroactive species is removed by using the ratio of the forward and reverse currents.In conclusion, we have demonstrated by several methods (voltammetry, double potential step experiments, coulometry, and product isolation) that the reduction of benzoate esters in dilute (1 mM) nonaqueous medium involves an EC mechanism. The system becomes more complex at higher concentrations. The initially formed radical anion cleaves to form benzoate ion and alkyl radical. This is one of a very few examples of the reduction of organic compounds by an EC mechanism.ABSTRACT Competition reactions at a-Fe203 photoanodes were studied using the RRDE technique. It was foundthat iodide, bromide, and chloride ions were photo-oxidized in preference to water in acidic solutions. The competition ratio was measured as a function of halide-ion concentration, halide-ion flux, light intensity, electrode potential, and solution pH. A direct correlation between the disk photocurrent and the competition ratio at a given halide flux was demonstrated. A lack in selectivity for the dark current was also observed.