scholarly journals Hydrogenation of ZnFe2O4 Flat Films: Effects of the Pre-Annealing Temperature on the Photoanodes Efficiency for Water Oxidation

Surfaces ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Annalisa Polo ◽  
Charles R. Lhermitte ◽  
Maria Vittoria Dozzi ◽  
Elena Selli ◽  
Kevin Sivula
Keyword(s):  
Water Oxidation ◽  
Zinc Ferrite ◽  
Oxygen Vacancies ◽  
Annealing Temperature ◽  
The Other ◽  
Hydrogen Treatment ◽  
Film Morphology ◽  
Structure And Morphology ◽  
Type Character ◽  
Post Synthesis

The effects induced by post-synthesis hydrogenation on ZnFe2O4 flat films in terms of photoelectrochemical (PEC) performance of photoanodes for water oxidation have been deeply investigated as a function of the pre-annealing temperature of the materials. The structure and morphology of the films greatly affect the efficacy of the post synthesis treatment. In fact, highly compact films are obtained upon pre-annealing at high temperatures, and this limits the exposure of the material bulk to the reductive H2 atmosphere, making the treatment largely ineffective. On the other hand, a mild hydrogen treatment greatly enhances the separation of photoproduced charges in films pre-annealed at lower temperatures, as a result of the introduction of oxygen vacancies with n-type character. A comparison between present results and those obtained with ZnFe2O4 nanorods clearly demonstrates that specific structural and/or surface properties, together with the initial film morphology, differently affect the overall contribution of post-synthesis hydrogenation on the efficiency of zinc ferrite-based photoanodes.

scholarly journals Thermal Annealing Induced Controllable Porosity and Photoactive Performance of 2D ZnO Sheets

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1352 ◽  
Author(s):  
Yuan-Chang Liang ◽  
Chen-Shiang Hung ◽  
Wei-Cheng Zhao
Keyword(s):  
Oxygen Vacancies ◽  
Annealing Temperature ◽  
Ambient Air ◽  
Hydrogen Atmosphere ◽  
Crystal Defects ◽  
Annealing Atmosphere ◽  
Hydrogen Treatment ◽  
Electron Hole ◽  
X Ray ◽  
Surface Crystal

Porous ZnO sheets containing various degrees of a nanoscaled pore were successfully synthesized using a simple hydrothermal method and various postannealing procedures. The porosity features of the ZnO sheets can be easily tuned by changing both the annealing temperature and annealing atmosphere. The dense porous nature of ZnO sheets is beneficial to enhance light absorption. Moreover, the substantially increased oxygen vacancies in the ZnO sheets were observed especially after the hydrogen treatment as revealed in the X-ray photoelectron spectroscope and photoluminescence analyses. The high density of surface crystal defect enhanced the photoinduced electron-hole separation rate of the ZnO sheets, which is crucial for an improved photoactivity. The porous ZnO sheets formed at a hydrogen atmosphere exhibited superior photoactive performance than the porous ZnO sheets formed at the high-temperature ambient air annealing. The dense pores and massive crystal defects formed by a hydrogen atmosphere annealing in the ZnO crystals might account for the observed photoactive behaviors in this study.

Preparation of Nano-Sized Doped Ceria for SOFC Anodes

2005 ◽  
Vol 885 ◽  
Author(s):  
Jumpei Kobayashi ◽  
Hitoshi Takamura ◽  
Atsunori Kamegawa ◽  
Masuo Okada
Keyword(s):  
Particle Size ◽  
Oxygen Vacancies ◽  
Annealing Temperature ◽  
Bulk Material ◽  
The Other ◽  
Nano Particles ◽  
Doped Ceria ◽  
Oxidizing Agent ◽  
Mn Doped ◽  
Nitrate Solutions

ABSTRACTNano-particles of Pr and Mn-doped ceria have been prepared by mixing nitrate solutions and hexamethylenetetramine as an oxidizing agent, and their thermal stability has been investigated. The particle size was evaluated by means of XRD, BET and dynamic light scattering techniques. The particle size of Pr and Mn-doped ceria was found to be approximately 3 nm as prepared. Even though the particle size of doped ceria increases with increasing annealing temperature, the size of less than 15 nm was kept after annealing at 873 K for 10 h. On the other hand, the lattice constant of nano-sized ceria, for example 0.544 nm for 3 nm-size particles, decreases and reaches to the value of bulk material (0.541 nm) as annealing temperature increases. This suggests that the valence state of cerium and the amount of oxygen vacancies strongly depend on the particle size.

The Defect Structure of BaTiO3 Thin Films

1993 ◽  
Vol 310 ◽  
Author(s):  
L.A. Wills ◽  
B.W. Wessels
Keyword(s):  
Thin Films ◽  
Cross Section ◽  
Defect Structure ◽  
Oxygen Vacancies ◽  
Vacuum Annealing ◽  
Deep Level ◽  
Energy Levels ◽  
The Other ◽  
Optical Cross Section ◽  
Impurity Defects

AbstractThe defect structure of BaTiO3 thin films grown on (100) Si was examined using transient photocapacitance spectroscopy. The concentration, optical cross section and associated energy levels of both native and impurity defects in as-grown and annealed BaTiO3 films were evaluated. Deep level defects withpeak energies of Ev+1.8, Ev+2.4, Ev+2.7, Ev+3.0-3.1 and Ev+3.2-3.3 eV were observed in the as-grown films. Upon vacuum annealing, the concentration of the traps at Ev+3.0 and Ev+3.2 eV increased while the concentration of the traps at Ev+ 1.8 and Ev+2.4 eV decreased. The levels at Ev+3.0-3.1 and Ev+3.2-3.3 eV are attributed to oxygen vacancies. The other levels are tentatively ascribed to Fe and Fe related defects.

A Magnetically Ordered Non-Stoichiometric Zinc Ferrite for the Oxidative Dehydrogenation Reactions.

2001 ◽  
Vol 676 ◽  
Author(s):  
J. A. Toledo ◽  
N. Nava ◽  
X. C. Sun ◽  
X. Bokhimi
Keyword(s):  
Catalytic Activity ◽  
Oxidative Dehydrogenation ◽  
Spinel Structure ◽  
Zinc Ferrite ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Octahedral Sites ◽  
Tetrahedral Sites ◽  
Dehydrogenation Reactions ◽  
Hydrothermal Reduction

ABSTRACTZnFe2O4 nanoparticles were prepared by hydrothermal reduction approach. A considerable amount of α-Fe2O3 was segregated in the as-synthesized sample, which diffused into the tetrahedral and octahedral sites of the ZnFe2O4 spinel structure with increasing the annealing temperature. The introduction of Fe3+ into the tetrahedral positions was observed by Mössbauer spectra. Magnetization measurements showed an unusual ferrimagnetic behavior of the ZnFe2O4 phase, even at room temperature, confirming the introduction of Fe3+ into the tetrahedral sites of the spinel structure. Catalytic activity measured in the oxidative dehydrogenation of 1-butene reaction increased with increasing annealing temperature, indicating that those interactions of Fe3+ in tetrahedral and octahedral positions also promotes the activity and selectivity to butadiene formation.

scholarly journals Air Annealing Effect on Oxygen Vacancy Defects in Al-doped ZnO Films Grown by High-Speed Atmospheric Atomic Layer Deposition

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5043
Author(s):  
Chia-Hsun Hsu ◽  
Xin-Peng Geng ◽  
Wan-Yu Wu ◽  
Ming-Jie Zhao ◽  
Xiao-Ying Zhang ◽  
...  
Keyword(s):  
Atomic Layer Deposition ◽  
Band Gap ◽  
Photoelectron Spectroscopy ◽  
High Speed ◽  
Oxygen Vacancies ◽  
Annealing Temperature ◽  
Atomic Layer ◽  
Zno Films ◽  
X Ray ◽  
Layer Deposition

In this study, aluminum-doped zinc oxide (Al:ZnO) thin films were grown by high-speed atmospheric atomic layer deposition (AALD), and the effects of air annealing on film properties are investigated. The experimental results show that the thermal annealing can significantly reduce the amount of oxygen vacancies defects as evidenced by X-ray photoelectron spectroscopy spectra due to the in-diffusion of oxygen from air to the films. As shown by X-ray diffraction, the annealing repairs the crystalline structure and releases the stress. The absorption coefficient of the films increases with the annealing temperature due to the increased density. The annealing temperature reaching 600 °C leads to relatively significant changes in grain size and band gap. From the results of band gap and Hall-effect measurements, the annealing temperature lower than 600 °C reduces the oxygen vacancies defects acting as shallow donors, while it is suspected that the annealing temperature higher than 600 °C can further remove the oxygen defects introduced mid-gap states.

Hydrogenated CeO2−xSx mesoporous hollow spheres for enhanced solar driven water oxidation

2016 ◽  
Vol 52 (12) ◽  
pp. 2521-2524 ◽  
Author(s):  
Yuting Xiao ◽  
Yajie Chen ◽  
Ying Xie ◽  
Guohui Tian ◽  
Shien Guo ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Band Gap ◽  
Carrier Concentration ◽  
Water Oxidation ◽  
Doping Level ◽  
Oxygen Vacancies ◽  
Narrow Band ◽  
Hollow Spheres ◽  
Sulfur Doping

Hydrogenated CeO2−xSx mesoporous hollow spheres were prepared and exhibited much higher rates of O2 evolution than CeO2 and CeO2−xSx due to the synergistic effect of high sulfur doping level, narrow band gap, moderate oxygen vacancies and higher carrier concentration.

Argument Structure and Morphology

2019 ◽  
Author(s):  
Jim Wood ◽  
Neil Myler
Keyword(s):  
Argument Structure ◽  
Word Formation ◽  
The Other ◽  
Proper Treatment ◽  
Structure And Morphology ◽  
Theoretical Approaches ◽  
The One ◽  
Theoretical Issues

The topic “argument structure and morphology” refers to the interaction between the number and nature of the arguments taken by a given predicate on the one hand, and the morphological makeup of that predicate on the other. This domain turns out to be crucial to the study of a number of theoretical issues, including the nature of thematic representations, the proper treatment of irregularity (both morphophonological and morphosemantic), and the very place of morphology in the architecture of the grammar. A recurring question within all existing theoretical approaches is whether word formation should be conceived of as split across two “places” in the grammar, or as taking place in only one.

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