Photoanodic Oxidation of D-Glucose on a Polycrystalline Zinc Oxide Electrode in an Alkaline Solution

Abstract

Anodic photocurrent on a polycrystalline ZnO electrode in analkaline solution was increased with addition of D-glucose. The increase in photocurrent due to glucose depended on the concentration of glucose and the intensity of light irradiated. No dissolution of the ZnO electrode was observed, but carbon dioxide was analyzed quantitatively as a final product. We suppose that ·OH radicals formed on the ZnO by a hole reaction oxidize glucose to give a intermediated reactive radical, from which an electron is injected to the conduction band of ZnO resulting in formation of an oxidized molecule. Then in the next step the oxidized form is further oxidized by the ·OH on the ZnO surface. These step-by-step oxidation reactions may continue until the final stage of carbon dioxide formation. In fact when gluconate or glucarate was added to the electrolyte solution, the currentdoubling effect was observed. From these results we propose a machanism of oxidation of D-glucose on the ZnO photoelectrode.