Correlated Atomic Resolution Microscopy and Spectroscopy Studies of Sn(Sb)O2 Nanophase Catalysts

doi:10.1006/jcat.2001.3456

Journal of Catalysis

Volume 205, Issue 2, 25 January 2002, Pages 266-277

https://doi.org/10.1006/jcat.2001.3456 Get rights and content

Abstract

A series of antimony-doped tin oxide (ATO), Sn(Sb)O₂, nanophase catalysts (containing 43 mol% Sb calcined at temperatures of 250, 600, and 1000°C, respectively) have been studied by correlated electron energy-loss spectroscopy (EELS) and Z-contrast imaging in a scanning transmission electron microscope (STEM) and by high-resolution electron microscopy (HREM). As reference materials, pure SnO₂, Sb₂O₃, and Sb₂O₅ are also analyzed. Results show that the particle size of these ATO catalysts increases with the calcination temperature. At low calcination temperatures, the catalyst contains crystalline nanoparticles surrounded by amorphous material, while the nanoparticles become well crystallized when calcined at higher temperatures. EEL spectra acquired from these ATO catalysts are qualitatively interpreted using ‘fingerprints’ from the reference materials. Results suggest that at low calcination temperatures (250°C), Sb exists in the pentavalent state Sb (V) either incorporated into the SnO₂ lattice or as an amorphous layer surrounding the SnO₂ crystals. At higher temperatures (≥600°C), Sb segregation occurs as trivalent Sb (III) at the surface and Sb (V) in the core of the majority of the nanoparticles. However, it should be noted that nearly no Sb was detected in some particles. The surface Sb (III) ions are proposed as active sites in the ATO catalysts.

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This work reports on a time-resolved study of the deactivation of electrochemical ozone production (EOP) active anodes using a novel approach to measure total ozone production. The reproducibility and change of the electrodes over time have been investigated using a number of electrochemical and physical techniques. The dissolution of antimony from the surface of the nickel- and antimony-doped tin oxide (NATO) electrode is the main process behind the deactivation of the EOP. When surface antimony is depleted, the continued deactivation seems to be connected to the dissolution of nickel. Despite tin (from the coating) and titanium (from the substrate) continuously dissolving during galvanostatic polarization of the NATO electrode, our experiments point to no connection between these processes and the EOP activity. In addition, the selectivity of the electrode is affected by electrolyte penetration, accessing fresh reaction sites that are active on the EOP. The results indicate that both antimony (III) and nickel present at the surface of the NATO are responsible for the EOP activity.
In search of the active chlorine species on Ti/ZrO<inf>2</inf>-RuO<inf>2</inf>-Sb<inf>2</inf>O<inf>3</inf> anodes using DEMS and XPS
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This result implies that Sb is surface-segregated from the bulk to the anode surface affecting the outmost 3–5 nm surface layers. Nevertheless, and according to Haverkamp et al. and Rockenberger et al., Sb2O5 phase should not be discarded from the subsurface to the core of the ternary oxide particles [25–27]. Thus, chemical interactions and related adsorption energies involved in the electrocatalysis should be affected.
Evidence to what it is identified in the literature as “active chlorine” in indirect oxidation processes occurring on Ti/ZrO₂-RuO₂-Sb₂O₃ anodes is provided in this study. To discriminate such behavior, different catalysts are prepared using the Pechini method varying ZrO₂ content, at different Zr/Ru molar ratios: 1, 0.5 and 0.3. The characterization of the materials using X-ray photoelectron spectroscopy (XPS) reveals that no solid solution (Ru-Zr) or any doping that affects the crystalline phase of Zr are obtained, while Sb₂O₃ was surface-segregated from the bulk to the anode surface affecting the outmost 3–5 nm surface layers. There are enormous impacts on the catalytic activity and adsorption properties of the structures as ZrO₂ content is increased. The presence of ZrO₂ and Sb₂O₃ shrink the number of favorable oxygen adsorption sites in Ti/ZrO₂-RuO₂-Sb₂O₃ catalysts, whence the adsorption energies for oxygen-metal interactions became lower than for Ti/RuO₂. Differential electrochemical mass spectroscopy (DEMS) and electrochemical experiments qualitatively indicate that a lower amount of ZrO₂ in the ternary electrode induce a better catalysis towards the oxygen evolution reaction (OER, O₂ production), while the ionic currents for $C l O^{-}$ and $H C l O$ species drop. This behavior suggests that chloride oxidation needs to encompass the mitigation of the OER as the percentage of ZrO₂ is increased in the anode. Active chlorine could stem from $H C l O_{a d s}$ species since it was produced in larger amounts than $C l O_{a d s}^{-}$ according to the pH of the electrolyte, and in adequate levels to generate the degradation of organic compounds.
Nanocrystalline antimony doped tin oxide (ATO) thin films: A thermal restructuring study
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Citation Excerpt :
The origin of coexistence of optical transmission and electrical conductivity in ATO is related to oxygen deficiency [19]also because the substitution of Sn4+ by Sb5+ creates a donor level near the conduction band. ATO's interesting behavior arises from this coexistence of oxygen vacancies with antimony doping [14], but their structural arrangement and restructuring with annealing remain unclear. ATO films were deposited using oxygen reactive DC magnetron sputtering.
Antimony doped tin oxide (ATO) is a transparent conducting oxide (TCO) with promising applications for solar energy utilization and for energy savings. In addition it has been shown how a thin ATO layer deposited on top of other TCOs could act as a protective coating against high temperature processes due to its good thermal stability.
ATO has been widely studied previously; however the role played by oxygen vacancies together with antimony doping, their structural arrangement and annealing restructuring processes remains unclear.
In the present work ATO thin films are deposited by DC magnetron sputtering at room temperature from a metallic target onto soda-lime glass substrates. As deposited samples present amorphous or nanocrystalline structures, as well as different electrical and optical properties depending on their deposition parameters. Then, a post-deposition annealing is performed from 250 °C to 450 °C in air or nitrogen atmosphere in order to study not only the evolution of the electrical, optical and structural properties but also the conduction mechanism.
Preparing transparent conductive Sn/Sb-O <inf>2 - X</inf> thin films by annealing bi-layer Sb/SnO <inf>2</inf> with pulse UV laser
2012, Materials Letters
Citation Excerpt :
In cases of both Sb/SnO2 and laser-irradiated Sb/SnO2, the decrease in resistivity (or increase in carrier concentration) may be explained by the increase in donors of oxygen vacancies/Sn4+ and acceptors of Sb3+. Sun et al. also reported that unsaturated Sb3+ sites in the surface are responsible for increasing the conductivity [12–14]. Straumal et al. [15] demonstrated that different valences of Mn ions effected the saturation magnetization and resulted in the formation of multilayer Mn segregation layer in ZnO grain boundaries.
Sb/SnO₂ bi-layer films were prepared on glass substrates using ion beam sputtering deposition (IBSD) and radio frequency (RF) magnetron sputtering deposition technology. The as-deposited bi-layer films were irradiated with a pulsed ultraviolet (UV) laser beam at 355 nm for the characteristic modulation which is expected to receive interest in the subtle transition. The effect of laser irradiation on the optical and electrical behavior and the chemical state of the films was investigated using X-ray photoelectron spectroscopy (XPS). The conductivity of Sb/SnO₂ after laser irradiation increased in comparison with that of SnO₂ and as-deposited Sb/SnO₂ thin films. The optical transmittance of laser irradiated Sb/SnO₂ increased from 41% to 47%.
Discharge power dependence of structural, optical and electrical properties of DC sputtered antimony doped tin oxide (ATO) films
2011, Solar Energy Materials and Solar Cells
Citation Excerpt :
Antimony doped tin oxide (ATO) is a transparent conducting oxide (TCO), which has been the focus of intensified study due to its technological importance as a solar energy material both in energy generation and in energy savings [1,2], and also because of its electrochemical properties [2–5], thermal and environmental stability [6–10] as well as low cost and easy fabrication [8,11].
Antimony doped tin oxide (ATO) is a transparent conducting oxide (TCO), which has been the focus of intensified study due to its wide range of technological applications and low cost. In the present work ATO films have been prepared by reactive DC magnetron sputtering from a metallic target at different discharge power densities without direct substrate heating. Then a post-deposition annealing at 350 °C in N₂ during 20 min was performed. There is a process window for the optimal sputter deposition of ATO with a minimum resistivity of about 3.3×10⁻³ Ω cm observed in samples deposited at a power density of 1.13 W/cm². These samples, which present a (2 1 1) preferential orientation, have good electrical conductivity and good transparency in the visible range. Higher values of sputtering discharge power density (1.24 W/cm²) change the preferential orientation to (1 0 1) because of the formation of oxygen vacancy planes. These samples are less conductive and transparent because their layered structure reduces the free charge mobility and allows the formation of Sb in its unusual oxidation state 4+ (between Sb³⁺ and Sb⁵⁺), which produces a sample blue darkening. Higher discharge power densities, above 1.41 W/cm², produce amorphous samples and an abrupt resistivity increase. The aim of the present work is to go into more depth in the knowledge of ATO in order to develop thin films with optimal electrical and optical properties.
Nonaqueous and template-free synthesis of Sb doped SnO<inf>2</inf> microspheres and their application to lithium-ion battery anode
2009, Electrochimica Acta
Antimony doped SnO₂ (ATO) microspheres composed of ATO nanoparticles were prepared by using a hydrothermal process in a nonaqueous and template-free solution from the inorganic precursors (SnCl₄ and Sb(OC₂H₅)₃). The physical properties of the as-synthesized samples were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption–desorption isotherms, and X-ray photoelectron spectrum (XPS). The resulting particles were highly crystalline ATO microspheres in the diameter range of 3–10 μm and with many pores. The as-prepared samples were used as negative materials for lithium-ion battery, whose charge–discharge properties, cyclic voltammetry, and cycle performance were examined. The results showed that a high initial discharge capacity of 1981 mAh g⁻¹ and a charge capacity of 957 mAh g⁻¹ in a potential range of 0.005–3.0 V was achieved, which suggests that tin oxide-based materials work as high capacity anodes for lithium-ion rechargeable batteries. The cycle performance is improved because the conducting ATO nanoparticles can also perform as a better matrix for lithium-ion battery anode.

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Regular ArticleCorrelated Atomic Resolution Microscopy and Spectroscopy Studies of Sn(Sb)O2 Nanophase Catalysts

Abstract

J. Catal.

Adv. Catal.

J. Catal.

J. Catal.

Sur. Sci.

J. Catal.

Appl. Catal. A

J. Catal.

J. Solid State Chem.

J. Solid State Chem.

J. Catal.

Ultramicroscopy

Ultramicroscopy

Nucl. Instrum. & Methods

Appl. Catal.

Appl. Catal. A

Adv. Catal.

Catal. Today

Micron

Appl. Catal. A

J. Chem. Soc., Faraday Trans. 1

J. Phys. Chem. B

Regular Article
Correlated Atomic Resolution Microscopy and Spectroscopy Studies of Sn(Sb)O₂ Nanophase Catalysts