The dependence of the conduction band edge of the alkali earth metal bismuthates on their composition

Shtarev, Dmitry S.; Blokh, Artem I.; Nashchochin, E.O.; Shtareva, Anna V.

doi:10.1007/s11082-018-1498-9

Cited by 9 publications

(3 citation statements)

References 25 publications

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“…In principle, this could be achieved by using the relationship E bg = f (χ) between bandgap energies E bg of the semiconductors and their electronegativities χ. Nonetheless, although such a relationship is known for various solids,− which include the alkali earth metal bismuthates, the results are empirical in nature and lead to rather coarse estimates of the bandgap energies that fluctuate for solids of a different nature, and thus would hardly be useful in the case under consideration.…”

Section: The Resolutionsupporting

confidence: 91%

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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Section: The Resolutionsupporting

confidence: 91%

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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“…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. Shtarev and coworkers [23] showed earlier that the potential of the bottom of the conduction band of strontium bismuthates can be determined from the ratio between the number of bismuth and strontium atoms in the cation sublattice.…”

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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“…Prospective photocatalysts based on strontium bismuthates may be used for water purification from organic and non-organic pollutants [1], or for a production of hydrogen based on reaction of photocatalytic water decomposition, etc. According to the theoretical studies [2], the most prospective compositions for these purposes are strontium bismuthates, where the number of strontium atoms exceeds the number of bismuth atoms in the cation sublattice, those bismuthates which are located between 50 and 100% mol. on phase diagram [3].…”

Section: Introductionmentioning

confidence: 99%

Strontium Bismuthates Sr2Bi2O5 and Sr6Bi2O11: Temperature Dependencies of Urbach Energy and Location of «Urbach Focus»

Nashchochin

Shtarev

Shtareva

et al. 2018

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We present information about temperature dependence of optical properties of two different strontium bismuthates. We demonstrate that temperature dependencies of Urbach energy of two strontium bismuthates differ radically. Abnormal behavior of Urbach focus of strontium bismuthate Sr2Bi2O5 is observed. We assume existence of phase transit in strontium bismuthate Sr2Bi2O5 at the temperature around 305 K.

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The dependence of the conduction band edge of the alkali earth metal bismuthates on their composition

Cited by 9 publications

References 25 publications

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

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

Strontium Bismuthates Sr<sub>2</sub>Bi<sub>2</sub>O<sub>5</sub> and Sr<sub>6</sub>Bi<sub>2</sub>O<sub>11</sub>: Temperature Dependencies of Urbach Energy and Location of «Urbach Focus»

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