Influence of the sodium/proton replacement on the structural, morphological and photocatalytic properties of titanate nanotubes

Abstract

Titanate nanotubes (TNT) with different sodium contents have been synthesised using a hydrothermal approach and a swift and highly controllable post-washing processes. The influence of the sodium/proton replacement on the structural and morphological characteristics of the prepared materials was analysed. Different optical behaviour was observed depending on the Na + /H + samples' content. A band gap energy of 3.27±0.03 eV was estimated for the material with higher sodium content while a value of 2.81±0.02 eV was inferred for the most protonated material, which therefore exhibits an absorption edge in the near visible region. The point of zero charge of the materials was determined and the influence of the sodium content on the adsorption of both cationic and anionic organic dyes was studied. The photocatalytic performance of the TNT samples was evaluated in the rhodamine 6G degradation process. Best photodegradation results were obtained when using the most protonated material as catalyst, although this material has shown the lowest R6G adsorption capability.

The effect of ionic Co presence on the structural, optical and photocatalytic properties of modified cobalt–titanate nanotubes

“…1 . 12,28 This can be clearly seen in the diffractogram of the Co ion exchange TNT/Co(5%) sample, for which the above mentioned peak shifts from 2θ = 10.22° to 8.74°, as a result of the incorporation of cobalt via Na/Co ion exchange between the TiO 6 sheets. It should be noted that the observed decrease of the 2θ position implies an increase of the interlayers' distance, which is expected since the ionic radius of the Na + is smaller than that of hydrated Co 2+ .…”

“…12 After precipitation with 4 M ammonia solution, the Co-doped TNT precursors were obtained as a bluish grey solid (1% of Co) and greenish dark grey solid (5% of Co).…”

“…Therefore, the synthesis of TiO 2 -based materials with a broader range of light absorption and a lower charge recombination rate would be an important achievement towards the development of successful photoactive materials. 12 Stimulated by the discovery of carbon nanotubes, onedimensional nanostructured materials have become an intense research topic in nanotechnology owing to their unusual properties and a wide variety of potential applications. Among them, titanate nanotubes (TNT) are remarkable materials since they combine the conventional properties TiO 2 nanoparticles, with the properties of layered titanates, such as photocatalytic activity and ion-exchange ability.…”

“…Among them, titanate nanotubes (TNT) are remarkable materials since they combine the conventional properties TiO 2 nanoparticles, with the properties of layered titanates, such as photocatalytic activity and ion-exchange ability. [12][13][14][15] Additionally they have an open mesoporous morphology with a higher specific surface area than TiO 2 , which is a very important parameter for surface-based applications such as photocatalysis. Despite their high charge recombination rate and wide bandgap (ca.…”

“…3.3 eV), the TNTs' ion-exchange ability makes them potential materials for effective photocatalysts and solar energy cells' applications. 12,[15][16][17][18][19] However, to be used under visible solar light irradiation, new TNT sensitization processes are needed and will be welcomed. Therefore, the synthesis of TNT-based materials with either a broader range of light absorption and/or a lower charge recombination rate would be an important achievement towards the development of successful photoactive materials.…”