Microwave assisted synthesis of mesoporous titania and relevant surface interactions with dye molecules

Introduction: Titania is the most widely studied and applied material for photocatalytic applications. Enhancing the surface area of a titania catalyst could significantly increase its activity as photocatalytic reactions typically proceed on or near the surface of the material. Conventional soft template synthesis routes like EISA or hydrothermal syntheses are time consuming processes, including long aging times and inefficient heating procedures. [1] Our work focuses on the use of microwave assisted methods for the synthesis of mesoporous titania. Microwaves can directly couple to the solvent molecules used during synthesis, making it possible to create very fast heating, avoiding slow heat transfer through different materials (air-metal-solution) typical for hydrothermal routes. In order to achieve the highest increase in photocatalytic activity, the material needs to be highly crystalline. In case of titania nanoparticles synthesized through hydrothermal methods, it has been shown before that microwave irradiation improves the crystallinity of the nanoparticles and allows reducing synthesis temperature and time [2], therefore it is also possible that microwave irradiation improves the degree of crystallinity in mesoporous titania. Results and Discussion: Mesoporous titania samples are prepared using an EISA and a hydrothermal route, with and without microwave irradiation. Rietveld analysis was used to determine that microwave irradiation was indeed able to enhance the degree of crystallinity in mesoporous titania. Other characteristics like specific surface area, particle size and band gap energy of the materials, were not affected by the microwave treatment. The different synthesis routes lead to materials with a different surface chemistry. This could be revealed by using FTIR to determine the surface groups. The isoelectric points of the materials were also investigated and are depended on the synthesis route. Conclusions: Using microwave irradiation it is possible to enhance the degree of crystalline material in mesoporous titania without a negative effect on other characteristics of the material. Different synthesis routes lead to materials with different surface properties which is important for specific applications of the materials. References [1] A. A. Ismail and. D. W. Bahnemann, J. Mater.Chem. 2011, 32, 11686-11707. [2] F. Dufour, S. Cassaignon, O. Durupthy, C. Colbeau-Justin and C. Chaneac, Eur. J. Inorg. Chem. 2012, 16, 2707-2715.

Jaar van publicatie:2014