Strong metal support interaction state in the Fe/TiO2 system- an XPS study
01 Oct 1995-Journal of Materials Science (Kluwer Academic Publishers-Plenum Publishers)-Vol. 30, Iss: 19, pp 4980-4985
TL;DR: In this article, strong metal support interaction with supported group VIII metals is associated with the phase transformation of the support employed, which is identified to have arisen from the formation of a ternary oxide phase and its subsequent reorganization under high temperature reduction conditions.
Abstract: Strong metal support interaction with supported group VIII metals is associated with the phase transformation of the support employed. The reduced uptake of hydrogen and the enhanced reactivity in CO hydrogenation in these systems are associated with the geometrical dispersion of the metal species, which is identified to have arisen from the formation of a ternary oxide phase and its subsequent reorganization under high temperature reduction conditions. XPS experimental evidence is provided for this postulate.
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TL;DR: In this paper, the phase structure, electrochemical properties and hydrogen storage mechanism as negative electrodes for nickel/metal hydride (Ni/MH) batteries have been investigated systematically, and the results of X-ray diffraction (XRD) analysis show both calcined powder and the charged/discharged samples after 10 cycles have orthorhombic structures.
73 citations
TL;DR: In this article, the effect of solid Fe2O3 and gaseous iron chlorides on the anatase-rutile phase transition was investigated in the temperature range of 750°-950°C via X-ray diffractometry and scanning electron microscopy.
Abstract: The effect of solid Fe2O3 and gaseous iron chlorides on the anatase-rutile phase transition was investigated in the temperature range of 750°-950°C via X-ray diffractometry and scanning electron microscopy. In both cases, iron diffusion in the anatase lattice decreased the transition temperature and increased the anatase-rutile transformation rate, in comparison with that in TiO2 fired in air. The enhancement effect of iron on the anatase-rutile transition is understood on the basis of oxygen-vacancy formation, which favors rutile nucleation. Solid-state iron diffusion between the contact points of TiO2 and Fe2O3 particles and vapor mass transport through gaseous chlorides were the primary mechanisms of iron mass transport to the TiO2 surface in the presence of both Fe2O3 and gaseous iron chlorides, respectively. The transformation rate at a given reaction temperature increased in the following order of reaction conditions: pure TiO2 in air, TiO2 in the presence of Fe2O3 in air, TiO2 in the presence of Fe2O3 in chlorine, and TiO2 in the presence of gaseous iron chlorides.
71 citations
TL;DR: In this paper, a strong interaction between iron and titanium atoms in the mixed oxide structure was found to influence the surface dispersion of Ti 3+ /Ti 4+ and Fe 2+ /Fe 3+ redox pairs.
53 citations
TL;DR: In this article, a method for the production of magnetically separable photocatalyst consisting of porous activated carbon, iron oxide particles and anatase titania particles was described, which can be easily magnetically separated by an external magnetic field.
50 citations
TL;DR: In this paper, a magnetically separable composite photocatalyst, titania-coated magnetic activated carbon (TMAC), was prepared by depositing of anatase titania onto the surface of magnetically activated carbon.
43 citations
References
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IBM1
TL;DR: The core and valence level XPS spectra of FexO (x ~ 0.90-0.95), Fe2O3 (α and γ), Fe3O4; and FeOOH have been studied under a variety of sample surface conditions as discussed by the authors.
577 citations
TL;DR: The metal-support interaction between iron and titania, which is initiated by reduction at 800 K and is responsible for the changes in ammonia synthesis kinetics, is due to titanium species at the surface of the metallic iron particles as mentioned in this paper.
220 citations
TL;DR: In this article, the application and physico-chemical properties of TiO2-based catalysts are discussed and the preparation procedure of a high surface area TiO 2 support is briefly summarized.
207 citations
TL;DR: In this paper, surface compositional changes were observed for TiO2 single crystal electrodes used for photo-electrolysis of water, and they were compared with a variety of titanium, titanium oxide and titanium hydride standard materials.
198 citations
TL;DR: In this paper, the authors studied the kinetics of the transformation of anatase from titanium sulphate to rutile and found that the transformation becomes immeasurably slow below ~695±10°C compared to ~610°C for pure anatase.
Abstract: The particle size and crystallite size of anatase increase markedly in the region of the crystal structure transformation. The unit cell of anatase seems to expand prior to the transformation to rutile. This expansion has been attributed to a displacive transformation of the type defined by Buerger. Smaller particle size and larger surface area seem to favour the transformation. The kinetics of the transformation of anatase prepared by the hydrolysis of titanium sulphate have been studied at different temperatures and are found to be considerably different from the kinetics of the transformation of pure anatase. The transformation becomes immeasurably slow below ~695±10°C compared to ~610°C for pure anatase. An induction period is observed in the transformation of anatase obtained from sulphate hydrolysis and the duration decreases with increase in temperature. The activation energy is ~120 kcal/mole, a value higher than that for the pure anatase-rutile transformation. The results have been interpreted in terms of the relative rates of nucleation and propagation processes. The activation energy for the nucleation process seems to be much larger than for the propagation process. The kinetics of the transformation of anatase samples doped with different amounts of sulphate ion impurity have also been studied and the transformation is found to be progressively decelerated with increase in the impurity concentration. The energy of activation for the transformation appears to increase progressively with increase in impurity concentration.
163 citations