Publication

The Influence of the Ammonolysis Temperature on the Photocatalytic Activity of beta-TaON

Michael Graetzel, Takashi Hisatomi
2013
Journal paper

Abstract

Phase-pure tantalum oxynitride (beta-TaON) powders were synthesized by thermal ammonolysis of Ta2O5 powders. X-ray diffraction revealed an enlargement of the unit cell and an increase of the crystallite size with increasing ammonolysis temperature. Scanning electron microscopy showed reduced particle sizes for beta-TaON synthesized at 800 and 900 degrees C compared to the precursor oxide. With increasing nitridation temperature the Brunauer-Emmett-Teller surface area was reduced and the nitrogen content increased. UV-Vis spectroscopy showed a bandgap energy of 2.6-2.4 eV. The highest oxygen evolution rate of 220 mu mol.g(-1).h(-1) was achieved for beta-TaON synthesized at 800 degrees C. The factors determining the photocatalytic activity of beta-TaON powders were found to be the specific surface area and defects in the beta-TaON.

Official source

https://infoscience.epfl.ch/record/185973?ln=en

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Ontological neighbourhood

Earth science

Geology: Mineralogy

Related concepts (33)

X-ray crystallography

X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information.

Dalton (unit)

The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass defined as 1/12 of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. The atomic mass constant, denoted mu, is defined identically, giving mu = 1/12 m(^12C) = 1 Da. This unit is commonly used in physics and chemistry to express the mass of atomic-scale objects, such as atoms, molecules, and elementary particles, both for discrete instances and multiple types of ensemble averages.

Neutron diffraction

Neutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material. A sample to be examined is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern that provides information of the structure of the material. The technique is similar to X-ray diffraction but due to their different scattering properties, neutrons and X-rays provide complementary information: X-Rays are suited for superficial analysis, strong x-rays from synchrotron radiation are suited for shallow depths or thin specimens, while neutrons having high penetration depth are suited for bulk samples.

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