Microwave assisted synthesis of Ta2O5 nanostructures for photocatalytic hydrogen production

This work reports the synthesis of highly crystalline tantalum (V) oxide nanoparticles via microwave assisted one-pot vapour hydrolysis, and their photocatalytic activity for hydrogen production. Ta2O5 nanoparticles were obtained using ethylene glycol, glycerol and ethanolamine as solvent templates and ammonium fluoride as additive. In order to remove the remaining organic residues on the surface and to improve the crystallinity and photocatalytic activities the samples were calcined at different temperatures. The surface areas of all samples were characterized via gas adsorption measurements and their optical band gaps were measured using diffuse reflectance UV-vis spectroscopy. Surface composition and chemical state of the elements were obtained from XPS spectroscopy. HR-TEM and XRD powder diffraction were performed to investigate the crystalline structure and phase composition of the samples. Among the three solvents only ethylene glycol leads to a direct formation of crystalline Ta2O5 nanoparticles while glycerol and ethanolamine form amorphous nanoparticles. The solvents not only tune the morphology of the nanostructures but also determine the surface fluorination. Nanoparticles with BET surface areas of 230-280 m(2)/g were obtained. The photocatalytic hydrogen production tests in aqueous methanol solutions show that almost all of the synthesised samples display highly improved hydrogen production compared to commercial Ta2O5. Additionally, the photocatalysts activities are further improved by photodeposition of platinum nanoparticles acting as co-catalyst. (C) 2018 Elsevier B.V. All rights reserved.