Photocatalytic Degradation of Methylene Blue under Visible Light Using TiO2 Thin Films Impregnated with Porphyrin and Anderson-Type Polyoxometalates (Cu and Zn)

• Published in: Catalysts Vol. 12; no. 10; p. 1169
• Main Authors: Alexander Sanguino, Carlos Diaz-Uribe, Freider Duran, William Vallejo, Leidy Guzman, Daniela Ruiz, Esneyder Puello, Cesar Quiñones, Eduardo Schott, Ximena Zarate
• Format: Journal Article
• Language: English
• Published: MDPI AG 01-10-2022
• Subjects: Anderson-type polyoxometalates; heterogeneous photocatalysis; porphyrin; thin films; TiO2
• ISSN: 2073-4344
• DOI: 10.3390/catal12101169

In this work, tetra(4-carboxyphenyl)porphyrin (TCPP) and two Anderson-type polyoxomolybdates (containing Cu and Zn, respectively; CuPOM, ZnPOM) were synthesized and deposited on TiO2 thin films. The properties of the obtained materials were characterized through UV–vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), diffuse reflection spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The adsorption and photodegradation under the visible light irradiation of methylene blue (MB) were studied for TiO2, TCPP/TiO2, TCPP/CuPOM/TiO2 and TCPP/ZnPOM/TiO2 thin films in aqueous solution. The results of the diffuse reflectance showed two bands in the visible light spectrum for the TCPP/POM/TiO2 systems compared to unmodified TiO2 that does not show any bands in the same region of the spectrum. The TCPP/POM/TiO2 systems showed a higher removal of MB, with an adsorption rate near to 31% for the TCPP/CuPOM/TiO2 film compared to 9% adsorption on the TiO2 film. The kinetic results show that the pseudo-second order model was the best fitting model for the MB adsorption process onto fabricated materials. The photodegradation studies under visible light showed a better performance on TCPP/POM/TiO2 thin films, with an efficiency in the MB photodegradation of near 49% and 44% in aqueous solution for TCPP/CuPOM/TiO2 and TCPP/ZnPOM/TiO2, respectively. The reusability test indicated that the porphyrin films are moderately stable after the performed cycles.