Thermo analytical characterization of tantalum oxide in the process for the development of tantalum nitride photoelectrodes

• Type: Article in International Scientific Journal
• Date: 2022-08

Authors

André Gonçalves (Author) Other; Francisco Sinfrônio (Author) Other; Alan de Menezes (Author) Other; Adélio Mendes (Author) FEUP

Journal

Title: Materials Today Communications

Vol. 32

ISSN: 2352-4928

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 0 Citations

Scopus

Other information

Authenticus ID: P-00X-27N

DOI: 10.1016/j.mtcomm.2022.104122

Abstract (EN): Thermogravimetric analysis and differential scanning calorimetry techniques were used to estimate the kinetic parameters of the oxidation of a tantalum metallic foil in the Ta3N5 photoelectrodes preparation process. Modelfree methods were used to determine the pre-exponential and activation energy of the Arrhenius equation related to the tantalum oxidation. The obtained kinetic model considers the existence of two independent oxidation events: [A ->(Fn) B] and [C ->(An) D ->(An) E]. X-ray powder diffraction analysis was used to identify the crystalline phases present in each sample. The sample oxidized at 5 degrees C.min(-1) (500 degrees C), contained two tantalum oxide polymorphs, Ta4O (25 +/- 5) % and Ta2O (25 +/- 2) %, and metallic tantalum showing a cubic structure. All the remaining samples presented a monophasic Ta2O5 with orthorhombic unit cells which showed a similar cell volume, but crystallite size increased with the temperature. The heating rate used in the oxidation of the Ta foils was verified to influence the photoelectrochemical performance of the prepared Ta3N5 photoelectrodes. Samples prepared with increasing heating rates evidenced a shift in onset potential towards higher potentials, and a more pronounced dark current. For the considered nitridation conditions of 8 hat 850 degrees C, the highest photocurrent performance was obtained with a heating rate of 5 degrees C.min(-1) to 700 degrees C.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9