Surface Interrogation Scanning Electrochemical Microscopy (SI-SECM) of Photoelectrochemistry at a W/Mo-BiVO4 Semiconductor Electrode: Quantification of Hydroxyl Radicals during Water Oxidation
- Surface Interrogation Scanning Electrochemical Microscopy (SI-SECM) of Photoelectrochemistry at a W/Mo-BiVO4 Semiconductor Electrode: Quantification of Hydroxyl Radicals during Water Oxidation
- 박현서; Kevin C Leonard; Allen J Bard
- Issue Date
- The Journal of Physical Chemistry C
- VOL 117, NO 23, 12093-12102
- Reaction kinetics and surface coverage of water oxidation intermediates at a W/Mo-BiVO4 photoanode were studied using surface interrogation scanning electrochemical microscopy (SI-SECM). Adsorbed hydroxyl radicals (OH center dot) were produced during water oxidation at the semiconductor surface under UV-visible irradiation and were subsequently electrochemically titrated by tip-generated reductant without irradiation. The IrCl62-/3- redox couple was used to determine the surface concentration of OH. in acidic solution. On W/Mo-BiVO4, similar to 6% of the absorbed photons generate surface OH center dot with a coverage of 5.8 mC cm(-2). Less than 1% of the irradiated photons were eventually used for water oxidation under high intensity irradiation (similar to 1 W cm(-2)) at the photoanode. Assuming that the primary decay mechanism of the adsorbed OH center dot on W/Mo-BiVO4 is dimerization to produce hydrogen peroxide (H2O2), the rate constant was determined to be 4 X 10(3) mol(-1) m(2) s(-1). A faster decay rate of OH center dot was observed in the presence of excess methanol (a radical scavenger) in aqueous solution. In addition, quantitative analysis of the water oxidation processes at W/Mo-BiVO4 along with the quantum efficiency for the oxygen evolution reaction was determined using SECM.
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