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Catalytic and photocatalytic effects of TiO2 nanoparticles on electrooxidation of common antioxidants on carbon paste

Catalytic and photocatalytic effects of TiO2 nanoparticles on electrooxidation of ascorbic, gallic, uric, p-coumaric, chlorogenic, and caffeic acids on carbon paste has been studied. Inflection points potentials, Ei, of anodic waves were found invariant to the scan rates and their medians, obtained for specific antioxidant/electrode combinations, were used for analyzing oxidation facilitation by TiO2. The Ei decrease, indicating TiO2 catalytic action, was most pronounced for the irreversible oxidation of gallic acid and least pronounced for reversible oxidation caffeic acid. Antioxidants show an increase in anodic charge by a factor of 2.24±0.32 with the introduction of TiO2 into the carbon paste and by an additional 20% as a consequence of UV illumination. The explanation involves lower oxidation overpotentials of studied antioxidants on TiO2 catalyst than on carbon paste and the increased active surface area on TiO2. UV illumination further aids the oxidation process by causing excitation of the TiO2 valence band electrons into the conduction band and creating a photocurrent.

titanium dioxide ; nanoparticle electrooxidation ; carbon paste ; photocatalytic effect

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