Topic
Anatase
About: Anatase is a research topic. Over the lifetime, 24177 publications have been published within this topic receiving 795572 citations. The topic is also known as: octahedrite.
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TL;DR: In this paper, the Raman spectra of anatase have been observed in both natural and synthetic crystals and the six Raman active fundamentals predicted by group theory are all observed and assigned.
Abstract: Raman spectra of anatase have been observed in natural and synthetic crystals. Both crystals show the same spectral features. The Raman band occurring at 516 cm−1 at room temperature is split into two peaks centred at 519 cm−1 and 513 cm−1 at low temperature (73 K). The six Raman active fundamentals predicted by group theory are all observed and assigned. The spectra are analyzed by a simple model considering only short-range forces and the calculated vibrational frequencies are in good agreement with the observed Raman frequencies.
1,922 citations
TL;DR: In this paper, the role of rutile in mixed-phase titania photocatalyst was investigated by EPR spectroscopy, showing that the transition points between these two phases allow for rapid electron transfer from pure-phase rutiles to anatase.
Abstract: Charge separation characteristics of a high-activity, mixed-phase titania photocatalyst (Degussa P25) are probed by EPR spectroscopy. While previous proposals consider rutile as a passive electron sink hindering recombination in anatase, this research details the critical and active role of rutile in TiO2 formulations. The inactivity of pure-phase rutile is due in part to rapid rates of recombination. Yet, in mixed-phase TiO2, charges produced on rutile by visible light are stabilized through electron transfer to lower energy anatase lattice trapping sites. These results suggest that within mixed-phase titania (P25) there is a morphology of nanoclusters containing atypically small rutile crystallites interwoven with anatase crystallites. The transition points between these two phases allow for rapid electron transfer from rutile to anatase. Thus, rutile acts as an antenna to extend the photoactivity into visible wavelengths and the structural arrangement of the similarly sized TiO2 crystallites creates ca...
1,878 citations
TL;DR: It is demonstrated, through a combination of state-of-the-art materials simulation techniques and X-ray photoemission experiments, that a type-II, staggered, band alignment of ~ 0.4 eV exists between anatase and rutile with anatase possessing the higher electron affinity, or work function.
Abstract: The most widely used oxide for photocatalytic applications owing to its low cost and high activity is TiO2. The discovery of the photolysis of water on the surface of TiO2 in 19721 launched four decades of intensive research into the underlying chemical and physical processes involved2, 3, 4, 5. Despite much collected evidence, a thoroughly convincing explanation of why mixed-phase samples of anatase and rutile outperform the individual polymorphs has remained elusive6. One long-standing controversy is the energetic alignment of the band edges of the rutile and anatase polymorphs of TiO2 (ref. 7). We demonstrate, through a combination of state-of-the-art materials simulation techniques and X-ray photoemission experiments, that a type-II, staggered, band alignment of ~ 0.4 eV exists between anatase and rutile with anatase possessing the higher electron affinity, or work function. Our results help to explain the robust separation of photoexcited charge carriers between the two phases and highlight a route to improved photocatalysts.
1,839 citations
TL;DR: In this article, the relative amounts of anatase and rutile in mixtures were determined using diffractometry, and a method using the more precise technique of diffraction was developed.
Abstract: ITAXIUM DIOXIDE may be incorpoT rated into a plastics molding compound to adjust the dielectric constant to a desired value. Either anatase or rutile may be used; these allotropic forms differ in dielectric behavior. Xeither is available commercially in a pure state; a preparation consisting largely of one form is apt to contain, in addition to other impurities, an admixture of the other. In order to permit proper formulation of filled resins, therefore, it is desirable to establish a method for determining the relative amounts of anatase and rutile in mixtures. The application of photometry to this problem has been discussed (2,6). This paper develops a method using the more precise technique of diffractometry.
1,729 citations
TL;DR: The hybrid materials showed significantly enhanced Li-ion insertion/extraction in TiO2, and the specific capacity was more than doubled at high charge rates, as compared with the pureTiO2 phase.
Abstract: We used anionic sulfate surfactants to assist the stabilization of graphene in aqueous solutions and facilitate the self-assembly of in situ grown nanocrystalline TiO2, rutile and anatase, with graphene. These nanostructured TiO2-graphene hybrid materials were used for investigation of Li-ion insertion properties. The hybrid materials showed significantly enhanced Li-ion insertion/extraction in TiO2. The specific capacity was more than doubled at high charge rates, as compared with the pure TiO2 phase. The improved capacity at high charge-discharge rate may be attributed to increased electrode conductivity in the presence of a percolated graphene network embedded into the metal oxide electrodes.
1,679 citations