Mesoporous Tantalum Oxide. 1. Characterization and Photocatalytic Activity for the Overall Water Decomposition

Takahara, Yoshiko; Kondo, Junko N.; Takata, Tsuyoshi; Lu, Daling; Domen, Kazunari

doi:10.1021/cm000572i

Cited by 234 publications

(161 citation statements)

References 15 publications

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“…For this reason, water splitting reactions are often unbalanced in stoichiometry and often promoted by extensive use of sacrificial hole scavengers 1 . Particularly in the case of Ta 2 O 5 poor stoichiometry was also reported by Takahara and co-workers 20 . Within the scope of this work, oxygen productivity is greatly affected by Zn and Rh-Cr promotion.…”

Section: Understanding the Effects Of Zn Doping And Rh/cr Depositionsupporting

confidence: 69%

Understanding synergetic effects of Zn and Rh–Cr promotion to wide-bandgap Ga, Ta and Ti oxides in photocatalytic water splitting

Bazzo

Urakawa

2016

Catal. Sci. Technol.

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a Promotion of semiconductor metal oxides by specific chemical elements is a widespread approach to enhance photocatalytic water splitting activity. Extraordinary boosting in the activity has been recently reported by Zn (dopant) and Rh-Cr (co-catalyst) promotion to Ga-oxide based photocatalysts. Herein, we report the general applicability of the effectiveness of the promotion strategy used for Ga oxides to Ta and Ti oxides in water splitting under UV irradiation using a slurry reactor. Photophysic characterization (photoluminescence and its decay) was used to clarify the specific roles of Zn and Rh-Cr and their synergetic catalytic action. Our experiments indicate that Zn acts as a booster of charge separation lifetime. Zn-promotion alone, however, does not trigger a great boost in catalytic activity in absence of Rh-Cr. Only when Rh-Cr is added the charge separation boost is fully exploited and driven within the catalyst towards overall water splitting. Effective wavelength ranges of excitation UV light source were also investigated in detail, leading to questioning the dominant semiconductor bandgap model for this class of catalysts.

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Section: Understanding the Effects Of Zn Doping And Rh/cr Depositionsupporting

confidence: 69%

Understanding synergetic effects of Zn and Rh–Cr promotion to wide-bandgap Ga, Ta and Ti oxides in photocatalytic water splitting

Bazzo

Urakawa

2016

Catal. Sci. Technol.

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“…The highly oriented porous nanostructures are expected to enable the range of application of Nb 2 O 5 and Ta 2 O 5 to expand considerably: in the case of Nb 2 O 5 to use as dye-sensitized solar cell materials, 10 and in the case of Ta 2 O 5 to use as dielectric materials 9 and photocatalysis. 20 To obtain more highly ordered nanoporous structures, it may be worthwhile trying to control the crystal growth using external effects, e.g., under electric and magnetic fields, or on substrates with epitaxial relations. …”

Section: Resultsmentioning

confidence: 99%

Formation of highly oriented nanopores via crystallization of amorphous Nb2O5 and Ta2O5

Nakamura

Ishimaru

Sato

et al. 2013

Journal of Applied Physics

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Formation of self-oriented and -elongated nanopores in annealed amorphous Nb 2 O 5 and Ta 2 O 5 was analyzed by transmission electron microscopy. Along with their crystal growth, nanopores were spontaneously elongated in the a-axis direction perpendicular to the longitudinal b axis of the orthorhombic structures with strong anisotropy. In addition, the effect of tungsten on the nanovoid formation in annealed amorphous Nb 2 O 5 and Ta 2 O 5 was also studied. Additive tungsten atoms of a few atomic percent into Nb 2 O 5 and Ta 2 O 5 were found to make the aspect ratio of nanopores larger. Electron diffraction experiments revealed that the crystallized regions including elongated nanopores possess a variety of periodicity in the b-axis direction. This structural flexibility in the crystal growth of strong anisotropic structures seems to play an important role on the unidirectional growth of nanopores. V C 2013 AIP Publishing LLC. [http://dx

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“…To understand the complex atomic structure of the Ta2O3 plane, a triangular graph-paper representation is devised and used alongside oxidation state analysis to reveal infinite variations of the low-energy structural model. The structural disorder of Ta2O5 observed in experiments is attributed to the intrinsic structural variations, and oxygen vacancies that drive collective relaxation of the O sublattice.Tantalum pentoxide (Ta 2 O 5 ) is one of the most extensively studied transition metal oxides due to its potential for technological applications such as anti-reflection coatings, photocatalysis, and high-k dielectrics for highdensity transistors [1][2][3]. It has recently attracted interest as the material of choice for resistance-change memory and the related memristor [4][5][6], however, its crystalline structure, which is critical to its unique structural and electronic properties, is still unclear.…”

mentioning

confidence: 99%

“…Tantalum pentoxide (Ta 2 O 5 ) is one of the most extensively studied transition metal oxides due to its potential for technological applications such as anti-reflection coatings, photocatalysis, and high-k dielectrics for highdensity transistors [1][2][3]. It has recently attracted interest as the material of choice for resistance-change memory and the related memristor [4][5][6], however, its crystalline structure, which is critical to its unique structural and electronic properties, is still unclear.…”

mentioning

confidence: 99%

Hidden Structural Order in OrthorhombicTa2O5

Lee

Kim

et al. 2013

Phys. Rev. Lett.

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We investigate using first-principles calculations the atomic structure of the orthorhombic phase of Ta2O5. Although this structure has been studied for decades, the correct structural model is controversial owing to the complication of structural disorder. We identify a new low-energy highsymmetry structural model where all Ta and O atoms have correct formal oxidation states of +5 and −2, respectively, and the experimentally reported triangular lattice symmetry of the Ta sublattice appears dynamically at finite temperatures. To understand the complex atomic structure of the Ta2O3 plane, a triangular graph-paper representation is devised and used alongside oxidation state analysis to reveal infinite variations of the low-energy structural model. The structural disorder of Ta2O5 observed in experiments is attributed to the intrinsic structural variations, and oxygen vacancies that drive collective relaxation of the O sublattice.Tantalum pentoxide (Ta 2 O 5 ) is one of the most extensively studied transition metal oxides due to its potential for technological applications such as anti-reflection coatings, photocatalysis, and high-k dielectrics for highdensity transistors [1][2][3]. It has recently attracted interest as the material of choice for resistance-change memory and the related memristor [4][5][6], however, its crystalline structure, which is critical to its unique structural and electronic properties, is still unclear.Ta 2 O 5 has an orthorhombic phase up to ∼ 1350 • C, above which a transition to a tetragonal phase occurs [7,8]. Although the low-temperature orthorhombic phase is of technological relevance, it has proven difficult to characterize structurally. Early X-ray diffraction studies [9,10] found that the orthorhombic Ta 2 O 5 phase consists of two-dimensional (2D) layers of Ta 2 O 3 in the ab plane, and two-fold coordinated O atoms that connect the Ta atoms in adjacent layers (forming linear chains of -Ta-O-Ta-O-Ta-) along the c direction. In the Ta 2 O 3 plane, it was understood that the Ta atoms form a triangular arrangement, but the arrangement of O atoms was unresolved, with many weak superstructure lines [10]. Later, Roth and coworkers reported that the Ta 2 O 3 plane consists of a disordered array of Ta atoms in octahedral and pentagonal bipyramidal arrangements, with an 11-fold increase of the lattice parameters in the b direction [11]. The superstructure periodicity was shown to change when aliovalent cations, such as W or Li, were incorporated in small amounts to stabilize the phase [12,13]. The superstructures consist of a set of small-unit basic structures and invoked the concept of infinitely adaptive structures [14] for nonstoichiometric Ta 2 O 5−x thatwithin certain composition limits-every composition orders into a different superstructure.Extensive theoretical studies have been made with regards to the bulk properties, dielectric response, and oxygen vacancies (and their diffusion) of Ta 2 O 5 [15][16][17][18][19][20][21][22][23]. In these studies, the low-temperature Ta 2 O 5 pha...

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Mesoporous Tantalum Oxide. 1. Characterization and Photocatalytic Activity for the Overall Water Decomposition

Cited by 234 publications

References 15 publications

Understanding synergetic effects of Zn and Rh–Cr promotion to wide-bandgap Ga, Ta and Ti oxides in photocatalytic water splitting

Understanding synergetic effects of Zn and Rh–Cr promotion to wide-bandgap Ga, Ta and Ti oxides in photocatalytic water splitting

Formation of highly oriented nanopores via crystallization of amorphous Nb2O5 and Ta2O5

Hidden Structural Order in OrthorhombicTa2O5

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