Flash microwave-assisted solvothermal (FMS) synthesis of photoactive anatase sub-microspheres with hierarchical porosity

Cappelluti, M. D., Hadzifejzovic, E., Foord, J. and Gregory, D. H. (2020) Flash microwave-assisted solvothermal (FMS) synthesis of photoactive anatase sub-microspheres with hierarchical porosity. RSC Advances, 10, pp. 37233-37245. (doi: 10.1039/D0RA05796G)

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Abstract

The synthesis of nanostructured sub-microspheres of TiO2 anatase with hierarchical nano- and mesoporosity was successfully achieved by using an innovative approach that applies the principles of acidic digestion to microwave (MW) solvothermal synthesis. This process, termed flash microwave-assisted solvothermal (FMS) synthesis, facilitates the formation of spherical particles without surfactants or templating agents, exploiting the rapid reaction kinetics engendered by MW heating. Unlike many other MW-assisted solvothermal methods, the application of constant MW power leads to a rapid increase of the autogenous pressure, inducing burst-nucleation of small primary crystallites and subsequent rapid agglomeration into secondary particles, with reaction times reduced to minute-timescales. The use of non-aqueous polar solvents such as ethanol is key to the production of regular spheres with a narrow size distribution, composed of nanocrystallites. Morphology, porosity, specific surface area, phase composition, crystallite size and optical properties of the particles can be controlled via a judicious selection of physical and chemical synthesis parameters, especially precursor choice and acid concentration. The complex structure of the particles leads to surface areas of up to ca. 500 m2 g−1 with intergranular mesoporosity. The as-synthesised FMS particles show increased adsorption under dark conditions and selective de-ethylation of rhodamine B under visible light compared to a commercial photocatalyst (Degussa P25). The photodegradation mechanism hinges on the capacity of the spheres to accept electrons from the photoexcited state of molecules at the particle surface, with the large sphere surface area maximising adsorption capacity and improving the efficiency of the photocatalytic processes. The singular characteristics and properties of the particles could pave the way for further applications in water purification and optoelectronic devices.

Item Type:Articles
Additional Information:DHG thanks the University of Glasgow for a Lord Kelvin-Adam Smith Scholarship for MDC.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Cappelluti, Mauro Davide and Gregory, Professor Duncan
Authors: Cappelluti, M. D., Hadzifejzovic, E., Foord, J., and Gregory, D. H.
College/School:College of Science and Engineering
College of Science and Engineering > School of Chemistry
Journal Name:RSC Advances
Publisher:Royal Society of Chemistry
ISSN:2046-2069
ISSN (Online):2046-2069
Copyright Holders:Copyright © The Royal Society of Chemistry 2020
First Published:First published in RSC Advances 2020,10, 37233-37245
Publisher Policy:Reproduced under a Creative Commons Licence

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