Hydrogen photochromism in Nb₂O₅ powders

Abstract

In this paper, we report on the hydrogen photochromism in Nb2O5 powders with different structures. Four different powder phases were prepared by calcining Nb2O5·nH2O powders at various temperatures, and their morphology, structure, and electronic band structure were characterized by scanning electron microscopy, structural analyses, thermogravimetric analysis, differential scanning calorimetry, and optical spectroscopy. Nb2O5 powders with different structures and very different properties were formed after different high-temperature treatments of the polymorphous oxide. A pronounced photochromic effect was observed in the M and H phases of Nb2O5, whereas the other phases exhibited poor photochromic responses. Because photochromism arises due to the detachment of hydrogen atoms under the action of light from hydrogen donor molecules previously adsorbed on the oxide surface, the electronic band structure and the morphology have strong influences on the photochromic properties of Nb2O5 powders. For these reasons, a pronounced photochromic effect was achieved in the H phase.

Photochromic Response and Steady‐State Photoconductivity of Fibrous‐Reticulated α‐MoO3 Thin Films Prepared by Modified Spray Pyrolysis Technique

“…So, this effect has been investigated previously for several metal oxides (e.g., WO 3 , MoO 3 , TiO 2 , V 2 O 5 , Nb 2 O 5 , ZnO, etc.) . Coloration performance of a photochromic material can be mainly enhanced by restraining the recombination of the photoexcited carriers .…”

“…For molybdenum oxide thin films, considerable changes in their physical and chemical properties have been observed and evaluated after UV exposure (e.g., the increase in the optical absorption, electrical conductivity, and photoconductivity after the UV irradiation) . This work aims to investigate the thickness effect on the structural, morphological, optical, electrical, and photo‐electrical properties of the α‐MoO 3 sprayed thin films.…”

Synthesis and Characterization of Nano-Particles of Niobium Pentoxide with Orthorhombic Symmetry

“…A suitable combination of chemical, electronic and optical properties make this oxide useful in various applications [7][8][9][10]. However, this result is further needed in order to investigate the photoluminescence (PL) because the optical measurements provide important information about the electronic structure of niobium pentoxide [11][12][13].…”

Heterojunctions between amorphous and crystalline niobium oxide with enhanced photoactivity for selective aerobic oxidation of benzylamine to imine under visible light

“…This could be due to the disordering of the crystal structure during the proton exchange process. 37 The H-niobate and niobium oxide microbres exhibited slightly different UV-Vis absorption, as is shown in the UV-Vis spectra (Fig. 32,33 H + and Na + cations are both hard acids and bind tightly with H 2 O, the hard base, in the interlayer of metal oxides.…”