Effect of Etching on Intrinsic and Dye-sensitized Photocurrents in Zinc Oxide Electrodes

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Abstract
The photoelectrochemical behavior of sintered zinc oxide electrodes was studied. The intrinsic photocurrent, generated by ultraviolet illumination of the zinc oxide electrode, significantly diminished by grinding the electrode surface with an abrasive, and was restored by etching in 2 M(M= mol dm3)HCl for ca. 120 s. The dye-sensitized photocurrent caused by rose bengal was also lowered by grinding, but the effect was not as large as in the case of the intrinsic photocurrent, and the photocurrent was restored in a much shorter time of etching. The dye-sensitized photocurrent for an insufficiently etched electrode was enhanced by addition of a reducing agent, e.g., hydroquinone or allylthiourea. However, no enhancement was observed for a well etched electrode. The results, together with the luminescence and reflection spectra of zinc oxide, were discussed by means of models for the semiconductor electronic bands.
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