Effects of La doping on structural, optical, electronic properties of Sr 2 Bi 2 O 5 photocatalyst

Obukuro, Yuki; Matsushima, Shigenori; Obata, Kenji; Suzuki, Toshiharu; Arai, M.; Asato, Eiji; Okuyama, Yuji; Matsunaga, Naoki; Sakai, Go

doi:10.1016/j.jallcom.2015.10.199

Cited by 25 publications

(21 citation statements)

References 30 publications

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“…It is known that Raman spectra broaden when lattice defects are introduced into the crystal because of the selection-rule failure for the wave vector. 13) As expected, in Fig. 1, the crystallinity of the prepared MgFe 2 O 4 is lowered remarkably by La addition.…”

Section: ¹1supporting

confidence: 81%

Morphology, microstructure, and surface area of La-added MgFe2O4 powder

Obata

Doi

Nishibori

et al. 2018

J. Ceram. Soc. Japan

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La-added and pure MgFe 2 O 4 powders were prepared from a malic acid complex, and the effect of La-adding on the microstructure and specific surface area of MgFe 2 O 4 powder were examined. There were no traces of impurity phases for pure MgFe 2 O 4 powder in the X-ray diffraction measurement after calcination in the range of 600 to 800°C. When La atoms were added to MgFe 2 O 4 , the crystallite growth of MgFe 2 O 4 was suppressed remarkably, resulting in a higher specific surface area in comparison with the pure material, and the lattice volume increased. X-ray photoelectron spectroscopy measurements showed that the binding energies of Mg 2s, , and La 3+ valence states, respectively. Scanning electron microscopy observations revealed that MgFe 2 O 4 powder shows an aggregation of granular particles and that the individual particles are tightly interconnected with each other, whereas smaller particles compared with pure MgFe 2 O 4 were observed for the La-added powder. It was found from the N 2 adsorption measurement, moreover, that the amount of mesopore increases with La addition.

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Section: ¹1supporting

confidence: 81%

Morphology, microstructure, and surface area of La-added MgFe2O4 powder

Obata

Doi

Nishibori

et al. 2018

J. Ceram. Soc. Japan

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“…In other words, the total density of states near the top of the valence band of these bismuthates also includes a considerable part of O‐2 p states hybridized with Bi‐6 p states (CaBi 6 O 10 ) and Bi‐6 s and 6 p states (Sr 2 Bi 2 O 5 ) . A similar contribution of Bi states in the total density of states have also been reported for Ca 4 Bi 6 O 13 , for La‐doped Sr 2 Bi 2 O 5 and tetragonal CaBi 2 O 4 . In the opinion of Li and co‐workers and Obukuro and co‐workers, this particularity of the band structure of Bi‐containing oxides makes them different from some other well‐known oxide photocatalysts such as TiO 2 , SnO 2 and WO 3 .…”

Section: The Resolutionsupporting

confidence: 70%

Considerations of Trends in Heterogeneous Photocatalysis. Correlations between Conduction and Valence Band Energies with Bandgap Energies of Various Photocatalysts

et al. 2019

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A principal objective of our work was to illustrate the existence of unknown trends in the E CB = f(E bg ) and the E VB = f(E bg ) behavior for certain classes of compounds that also included a set of bismuthate photocatalysts; new trends may easily be hidden within more general trends. Indeed, when the data for the bismuthates are added to data related to novel visible-lightactive (VLA) photocatalysts, the trend remains the same with high significance levels for the E VB = f(E bg ) linear correlation. Using well-known data for complex (ternary) oxides, the search for new trends in the behavior of the E CB = f(E bg ) and the E VB = f (E bg ) dependences opens up the potential to develop new VLA photocatalysts. The feasibility of new desired trends can be estimated a priori using a modern theoretical analysis of the electronic structure of targeted semiconductors; note that new trends in the behavior of E CB and E VB versus bandgap energy E BG have been established for CaBi 6 O 10 , Sr 2 Bi 2 O 5 , Sr 3 Bi 2 O 6 , and Sr 6 Bi 2 O 11 . We also re-examined earlier symmetric-type plots for a set consisting of a large number of simple (binary) and a set consisting of complex (ternary) metal oxides and find some significant differences. We herein report a novel trend in the empirical dependence of the energy positions of conduction bands (E CB ) and valence bands (E VB ) on bandgap energies (E bg ) for alkali earth metal bismuthate semiconductor photocatalysts for which we show that their dependences follow the linear functions E CB = A + BE bg and E VB = a + bE bg . However, contrary to earlier symmetric relationships of some metal oxides for which A = a = 1.23 eV, B = À 0.5, and b = 0.5 toward water splitting, the relationships found for the bismuthates show them to be asymmetric with negative slopes (B < 0, b < 0) and a converging point A = a = 4.5 eV. Also re-examined are the earlier symmetric-type plots for a set consisting of a large number of simple (binary) and a set consisting of complex (ternary) metal oxides and find some significant differences. Variations in both slopes (B < 0 and b > 0) and the converging point (1.4 eV < A = a < 2.0 eV) is demonstrated. The photoactivity of some strontium bismuthates is predicted toward the photoelectrochemical reduction of CO 2 from the novel trend in behavior of their bands' energy positions relative to their bandgap energies.

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“…The group of novel photoactive materials includes Bi-containing photocatalysts and photocatalytic composites [1,11]. bismuthates may be considered a priori as promising photocatalysts, particularly for both Cacontaining [12][13][14][15][16] and Sr-containing [17][18][19][20][21][22] bismuthates. The ternary systems Sr 2 Bi 2 O 5 , Sr 3 Bi 2 O 6 , and Sr 6 Bi 2 O 11 were chosen for detailed studies for several reasons.…”

Section: Introductionmentioning

confidence: 99%

Solid-state synthesis, characterization, UV-induced coloration and photocatalytic activity – The Sr6Bi2O11, Sr3Bi2O6 and Sr2Bi2O5 bismuthates

et al. 2020

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This article reports on two novel visible-light-active strontium bismuthate photocatalysts (Sr 6 Bi 2 O 11 and Sr 3 Bi 2 O 6) prepared by solid-state synthesis for which the number of strontium atoms exceeded the number of bismuth atoms in the cation sublattice; for comparison, the bismuthate Sr 2 Bi 2 O 5 was also reexamined. All three bismuthates were characterized by a variety of spectroscopic techniques (XRD, XPS, EDX, DR, Raman, SEM, and EIS). Both newly as-synthesized bismuthates displayed photocatalytic activity toward the photodegradation of substrates in the gas phase (acetaldehyde) and in aqueous media (phenol), with the Sr 6 Bi 2 O 11 phase exhibiting a significantly greater photoactivity than the Sr 3 Bi 2 O 6 phase; by comparison, the bismuthate Sr 2 Bi 2 O 5 was photocatalytically inactive. Detailed photocatalytic mechanisms have been proposed to explain how composition and structure of the three bismuthates affect their photocatalytic activity. The role of point defects in their crystal lattice is described for processes in which the photocatalytic activity was inhibited. Inferences made were aided by examining the UV-induced coloration of these ternary metal oxides that provided information regarding defect levels within their respective bandgaps; such defects acted as electron traps and thus affected the photocatalytic performance of the bismuthates.

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Effects of La doping on structural, optical, electronic properties of Sr 2 Bi 2 O 5 photocatalyst

Cited by 25 publications

References 30 publications

Morphology, microstructure, and surface area of La-added MgFe<sub>2</sub>O<sub>4</sub> powder

Morphology, microstructure, and surface area of La-added MgFe<sub>2</sub>O<sub>4</sub> powder

Considerations of Trends in Heterogeneous Photocatalysis. Correlations between Conduction and Valence Band Energies with Bandgap Energies of Various Photocatalysts

Solid-state synthesis, characterization, UV-induced coloration and photocatalytic activity – The Sr6Bi2O11, Sr3Bi2O6 and Sr2Bi2O5 bismuthates

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