Methylene blue photocatalytic degradation under visible irradiation on TiO2 thin films sensitized with Cu and Zn tetracarboxy-phthalocyanines

• We used an easy and inexpensive technique to sensitize TIO2 thin films.
• We compare two different magnetic metal complex phthalocyanines in photocatalytic mineralization process.
• We used a Haber–Weiss reaction through sensitizer-TiO2 catalyst to improve the photo-mineralization process.

We studied the effect of sensitization on photocatalytic properties of TiO2 thin films. We synthesized tetracarboxy-phthalocyanines of Cu (PcTcCu) and Zn (PcTcZn) for using Achar method; TiO2 thin films were deposited by doctor blade method, after that, thin films were sensitized through chemisorption method. Properties of TiO2 and sensitized-TiO2 thin films were studied by measurements of X-ray diffraction (XRD), infrared spectroscopy (IR) and absorption diffuse reflectance. The XRD patterns indicated that sensitization did not affect the crystalline phases radio of the TiO2 films; furthermore, the optical analysis showed that after sensitization process TiO2 photophysical properties improved greatly in visible regions. Photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution and, the pseudo-first order model was used to obtain kinetic information of the photocatalytic degradation. Results indicated that photocatalytic activities of PcTcZn–TiO2 and PcTcCu–TiO2 were 2.8 times and 3.6 times better than TiO2 thin films, these results also indicated that magnetic properties of metal complex in the phthalocyanines determines the efficiency of sensitizer in photocatalytic process. Finally the efficiency in photocatalytic process improved greatly when methylene blue photo-degradation were assisted with slight amount of H2O2.

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