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  Nano-engineered tantalum-based materials for photocatalytic water splitting

Grewe, T. (2016). Nano-engineered tantalum-based materials for photocatalytic water splitting. PhD Thesis, Ruhr-Universität Bochum, Bochum.

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 Creators:
Grewe, Tobias1, Author           
Affiliations:
1Research Department Schüth, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445589              

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Free keywords: Amorpher Zustand; Fotokatalyse; Nanostrukturiertes Material; Tantalate; Wasserstofferzeugung
 Abstract: In this thesis, the design and nano-engineering of tantalum-based materials are studied to develop more efficient photocatalysts for water splitting. Structural parameters of the catalyst materials are modified by using different synthesis methods including hydrothermal synthesis, soft- and hard-templating, and an in-situ preparation method. The influences of the synthetic methodology on the structure of the catalyst including its morphology, crystal and energetic structure, and its activity towards hydrogen production are evaluated, highlighting the positive effect of composites and amorphous phases on the photocatalytic activity. Furthermore, a novel in-situ synthesis method for nanostructured materials is presented, allowing an efficient synthesis of highly active photocatalysts.
Using hydrothermal synthesis, a series of crystalline sodium tantalates samples with NaTaO3 and Na2Ta2O6 phases was prepared. A Na2Ta2O6 sample with the highest surface area showed the highest activity for water splitting. Furthermore, composite samples also showed a positive effect on the water splitting activity. In a second series, amorphous and crystalline sodium tantalates were obtained, revealing a positive effect on the water splitting activity through the combination of amorphous and crystalline NaTaO3 .
Soft-templating yielded amorphous tantalum oxide, which was Na-loaded using different concentrations of NaOH during synthesis. The Na-loading led to a band gap widening and an increase in photocatalytic activity. As a comparison to the soft-templated samples, Ta2O5 and NaTaO3 were synthesized via hard-templating, exhibiting highly crystalline and nanosporous samples with a large surface area. As a result, hard-templated NaTaO3 has the highest activity towards hydrogen production observed from all the samples reported in this thesis.
The development of an effective in-situ synthesis method for tantalum-based photocatalysts is presented. Via hydrolysis of alkoxide precursors, tantalum and sodium tantalum based oxo hydroxo compounds are prepared that exhibit an amorphous structure. The obtained sample exceeds the water splitting activity observed for the highly crystalline reference samples; furthermore, its efficient catalyst preparation method can make a significant contribution to its large scale production.

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Language(s): eng - English
 Dates: 2016-04-082016-04-08
 Publication Status: Issued
 Pages: 178
 Publishing info: Bochum : Ruhr-Universität Bochum
 Table of Contents: -
 Rev. Type: -
 Identifiers: -
 Degree: PhD

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