Physicochemical properties and photocatalytic activity of H₃PW₁₂O₄₀/TiO₂

For enhancing its photocatalytic activity, titanium dioxide P25 has been modified by adsorption of the heteropoly acid (HPA) H₃PW₁₂O₄₀ from aqueous solution at an HPA concentration of 0.2 to 5 mmol/L. The deposition of the HPA does not alter the phase composition or morphology of the photocatalyst but only causes a slight change in its diffuse reflectance spectrum. IR spectroscopic and XPS studies have confirmed that the HPA molecules on the TiO₂ surface are intact. The adsorption of the HPA increases the photovoltage and hydroxyl radical yield under UV irradiation. These characteristics reach their maximum values upon the adsorption of the HPA from its 0.5 mmol/L solution. Electrochemical measurements have demonstrated that the HPA increases the rate of interfacial electron transfer. The deposition of the HPA accelerates the gas-phase oxidation of acetaldehyde and the degradation of phenol and triethyl phosphate in the aqueous medium. The highest activity is shown by the catalyst obtained by the adsorption of H₃PW₁₂O₄₀ from its 0.5 mM solution. The results of this study suggest that the HPA is promising for modifying the surface of the TiO₂ photocatalyst.