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Journal ArticleDOI

Materials synthesis, characterization and DFT calculations of the visible-light-active perovskite-like barium bismuthate Ba1.264(4)Bi1.971(4)O4 photocatalyst

12 Mar 2020-Journal of Materials Chemistry C (The Royal Society of Chemistry)-Vol. 8, Iss: 10, pp 3509-3519

AbstractA perovskite-like barium bismuthate of the BaBi2O4 class, Ba1.264(4)Bi1.971(4)O4, has been prepared by solid-state synthesis and subsequently characterized by a number of experimental techniques (XPS, DRS, SEM, EDX and Raman spectroscopy), as well as by a DFT computational approach using the GGA Perdew–Burke–Ernzerhof (PBE) density functional to determine the energy band structure. XRD peaks were indexed to a rhombohedral cell (Rm) with parameters close to Ba0.156Bi0.844O1.422 (i.e., to Ba0.439Bi2.374O4), which upon Rietveld refinement gave Ba1.264(4)Bi1.971(4)O4. The Bi–O bond lengths determined from this refinement (1.86 and 2.31 A) accorded with the bond lengths estimated from Raman spectra (1.97 and 2.26 A). DFT calculations revealed the bismuthate to display two bandgaps that correspond to lower-energy indirect (2.28 eV) and to higher-energy direct (2.36 eV) electronic transitions in good agreement with the experimental bandgaps of 2.26 eV and 2.43 eV, respectively, from Tauc plots of DRS spectra. Relative to the indirect bandgap energy of 2.26 eV, the energies of the valence band and of the conduction band were, respectively, +1.14 eV and −1.12 eV. The photoactivity of Ba1.264(4)Bi1.971(4)O4 was examined toward the photoreduction of the greenhouse gas CO2 in aqueous media photoelectrochemically yielding alcohols and alkanes, while in the gas phase in an infrared cell reactor the products were carbon monoxide and alkanes.

Topics: Band gap (54%), Rietveld refinement (52%), Raman spectroscopy (52%), Bond length (50%), Electronic band structure (50%)

Summary (3 min read)

1. Introduction

  • The search for novel visible-light-active (VLA) semiconductor photocatalysts has been an active field of investigations for several decades.
  • Within the present context, a number of experimental5 and theoretical6,7 studies have reported an anomalous ratio in a series of alkaline-earth bismuthates between bandgap width and the energy of the conduction band.

2.1 Structure and composition of the as-synthesized barium bismuthate

  • The structure and the unit cell composition of the assynthesized barium bismuthate were investigated by X-ray diffraction methods.
  • Figure 1 displays the XRD pattern of the barium bismuthate and the results of the Rietveld analysis.
  • The small sum of the charges (+0.44) implies that the number of oxygen vacancies in the structure is overestimated, which is often the case in such systems because of difficulties in refining the occupancy of light ions in the presence of heavy metal ions.

J. Mater. Chem. C ARTICLE

  • Please do not adjust margins source was the 150-W Xenon lamp ; an optical cutoff filter removed UV wavelengths below 300 nm (light irradiance, 7 mW cm‒2) so as to prevent direct photolysis of phenol through light absorption by the substrate.
  • To determine the time course of the concentration of phenol, aliquot samples were collected at given intervals and then analyzed by HPLC analysis performed using a 1260 Infinity liquid chromatograph equipped with a UV/Vis detector and a C18 column (Agilent Technologies).
  • Prior to the chromatographic analysis, samples were filtered through a 0.2 μm Minisart filter to remove any solid particles.
  • The mobile phase was a 50/50 v/v mixture of methanol/water; the detection wavelength was 210 nm and the bandwidth was 4 nm.
  • The initial rate of the photocatalytic reaction, often taken as a characteristic of the activity of a photocatalyst, in the present case the as-synthesized barium bismuthate, was determined from the kinetic approximation: (2)𝐶(𝑡) = 𝐶0𝑒𝑥𝑝( ― 𝑘𝑡) so that (3)𝑑𝐶/𝑑𝑡(𝑡→0) = ―𝑘𝐶0 where k is the apparent quasi-first-order rate constant.

2.2. Electronic band structure of the barium bismuthate

  • The electronic band structure includes the energy position of the edges of the conduction (CB) and valence (VB) bands with respect to the vacuum level.
  • The positions of the conduction (ECB) and valence (EVB) bands, together with the bandgap energies (Eg), can be determined experimentally by measuring at least any two of these three values (i.e., ECB and Eg or EVB and Eg).
  • O4 sample was determined using the low-energy edge of the XPS spectrum in the O2p region , which gave +1.14 eV (relative to NHE) as the energy position of the top of the valence band.
  • The absorption spectrum displayed in Figure 6a clearly demonstrates that the material absorbs light well into the visible range.

2.3. Photoactivity of the Ba1.264(4)Bi1.971(4)O4 bismuthate toward CO2 reduction

  • The relative arrangement of energy bands and half-reaction potentials displayed in Figure 8 suggest that the bismuthate is a suitable material for carrying out the reduction of carbon dioxide and the formation of superoxide radical anions.
  • The preparations of the electrodes and the experimental details have been described elsewhere (see Experimental).
  • The photocathode compartment was filled with an oxygen-free KHCO3 aqueous solution, while the photoanode compartment contained an (NH4)2C2O4 aqueous solution.
  • Gas evolution was seen both in the photocathode and in the photoanode compartments of the photoelectrochemical cell.
  • The principal changes in the chromatograms occur in the retention time regions of 300, 500 and 600 sec.

3.1. Synthesis and characterization of the barium bismuthates

  • The novel barium bismuthate was prepared via a solid-state synthesis.
  • The mixture was then carefully ground in an agate mortar for 10 min in the presence of absolute ethanol (purity ≥ 99.8 % (GC), Vekton).
  • The morphology of the sample was determined by Scanning Electron Microscopy (SEM; TESCAN, Czech Republic; acceleration voltage, 20 kV).
  • The elemental composition and its distribution in the as-synthesized barium bismuthate sample were established by Energy Dispersive X-ray spectroscopy (EDX; X-MaxN, Oxford Instruments, UK).
  • Diffuse reflectance spectra, as R(λ), were recorded in the 375– 775 nm spectral range under ambient conditions on a Cary 5000 UV/Vis/NIR spectrophotometer equipped with a DRA 2500 external Page 11 of 20 Journal of Materials Chemistry C.

3.2. Photoactivity of the BaBi2O4-type bismuthate

  • 2.1. Photoelectrochemical CO2 reduction from aqueous solutions.
  • The electrical connection between the photoanode and phootcathode was established by a copper wire.
  • The retention times of these products from the chromatographic column were determined under otherwise identical experimental conditions.
  • To assess the photocatalytic visible-light-activity (or lack thereof) of the bismuthate sample the authors used the photodecomposition of phenol in an aqueous suspension in a batch-type reactor equipped with a quartz window for UV irradiation under ambient conditions.

4. Computational specifics

  • Periodic DFT calculations were performed using the GGA Perdew-Burke-Ernzerhof (PBE) density functional40,41 as implemented in the ABINIT 6.8.3 program.42.
  • A basis set in the form of the Troullier-Martins norm-conserving pseudopotentials43 was employed with a kinetic energy cutoff of 30 Hartree.
  • The R-3m symmetry of the material's crystal lattice determined from the XRD analysis was enforced in all calculations.
  • The electronic band structure and density of states were plotted using the Gnuplot 5.2 software package.
  • 45 Optical absorption spectra were computed based on the Bethe-Salpeter Equation.

5. Concluding remarks

  • This study reports on the synthesis and comprehensive characterization of a most promising semiconductor photocatalyst of the BaBi2O4 class, which following the Rietveld refinement can be described as Ba1.264(4)Bi1.971(4) O4.
  • Various experimental techniques (XPS, DRS, SEM, and EDX) were brought to bear on its characterization, and together with a computational approach (DFT) the relevant energy band structure of this novel material was determined.
  • Such an anomalous energy arrangement of the conduction band opens up unique possibilities for using this bismuthate for the photocatalytic reduction of a currently controversial greenhouse gas, carbon dioxide, while oxidative half- reactions appear rather unlikely as attested by the lack of photoinduced oxidation of phenol.
  • Chromatographic analyses of the reaction products revealed the main products differed somewhat: a mixture of carbon monoxide and alkanes from adsorbed CO2 in the gas/solid system versus a mixture of alcohols and alkanes from the liquid/solid system.
  • No attempts were made in the present study to optimize the experimental conditions.

Table of Contents entry

  • Crystal structure of the Ba1.264(4)Bi1.971(4)O4 perovskite-like system and associated electronic band structure and density of states.
  • XPS spectra and deconvolution results of the synthesized barium bismuthate Ba1.264(4)Bi1.971(4).
  • Results of chromatographic analyses from liquid aliquots taken from the photocathode compartment of the PEC cell before and during the photoelectrochemical reaction.

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Content maybe subject to copyright    Report

Materials Synthesis, Characterization and DFT Calculations
of the Visible-Light-Active Perovskite-like Barium
Bismuthate Ba1.264(4)Bi1.971(4)O4 Photocatalyst
Journal:
Journal of Materials Chemistry C
Manuscript ID
TC-ART-11-2019-006457.R1
Article Type:
Paper
Date Submitted by the
Author:
29-Jan-2020
Complete List of Authors:
Shtarev, Dmitry; Far Eastern State Transport University
Shtareva, A.V.; Far Eastern State Transport University
Kevorkyants, Ruslan; St. Petersburg State University, Photonics
Rudakova, A.V.; Saint Petersburg State University
Molokeev, Maxim S. ; Kirensky Institute of Physics SB RAS,
Bakiev, T.V.; Saint Petersburg State University
Bulanin, Kirill; Saint-Petersburg State University, Physics
Ryabchuk, V.K.; Saint Petersburg State University
Serpone, Nick; Universita di Pavia, Dipartimento di Chimica Organica
Journal of Materials Chemistry C

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or click the links below.
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FULL PAPER
When preparing your report, please:
Focus on the originality, importance, impact and reproducibility of the science.
Refer to the journal scope and expectations
.
State clearly whether you think the article should be accepted or rejected and give detailed comments
(with references) both to help the Editor to make a decision on the paper and the authors to improve it.
Inform the Editor if there is a conflict of interest, a significant part of the work you cannot review with
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Provide your report rapidly or inform the Editor if you are unable to do so.
Page 1 of 20 Journal of Materials Chemistry C

Responses to Editorial request (ORCID) and reviewers’ comments
The ORCIDs of all the authors now appear on page 9 of the manuscript
Referee: 1
1) Regarding the synthesis, does it go 100% to completion? There was no purification carried out
and thus my question
During the preparation of samples, we performed an evaluation of that synthesis of barium
bismuthate was 100% completion. With shorter synthesis times, the formation of pure barium
bismuthate was not observed. To demonstrate this, relevant results were added to the article,
which are given in Section 3.1 and supplementary information.
2) The authors state for the XPS data that "The two Gaussians at 531 eV and 532 eV are
associated with the O–C=O bonds of chemisorbed carbon dioxide molecules. The presence of
such chemisorbed species on the surface is characteristic of compounds containing alkaline earth
metals." In order to truly verify this, the authors should carry out TGA/MS analysis and
monitor the m/z value of the evolved gas unless they have already verified it.
The proposed by the reviewer TGA studies were conducted. Figure 1 shows the DTG curve of
the studied sample during its annealing in vacuum. Even at high temperatures (higher 500°C),
there are no noticeable changes in the mass of the sample.
Figure 1. TGA curve of barium bismuthate Ba
1.264(4)
Bi
1.971(4)
O
4
in vacuum.
The verification of chemisorbed carbon dioxide molecules was made by IR spectroscopy. Prior
to the gas-phase IR experiment, the sample was thermally treated at 350
o
C to reduce the amount
of physisorbed water molecules and chemisorbed carbon dioxide species on the bismuthate’s
surface. Nonetheless, even after such a treatment, the sample surface remained highly hydrated
and carbonated. Figure 2 shows the IR spectrum of such a treated barium bismuthate sample (this
spectrum is presented as spectrum 3 in Figure S3, in the Electronic Supplementary Information).
Page 2 of 20Journal of Materials Chemistry C

Figure 2. IR spectrum of treated barium bismuthate Ba
1.264(4)
Bi
1.971(4)
O
4
in vacuum at room temperature before the
CO
2
photoreduction experiment. The sample was preliminary thermo-treated at 350
o
C.
The IR spectrum of such a treated barium bismuthate sample revealed a broad absorption of
molecular water at 3600‒2700 cm
–1
. The intense absorption with two maxima at 1363 cm
–1
and
1442 cm
–1
are caused by the C=O stretching vibrations of surficial carbonates,[ F.A. Miller, C.H.
Wilkins, Analytical chemistry, 1952, 24, 1253-1294; G. Socrates, Infrared and Raman
characteristic group frequencies. Tables and Charts, Chichester: John Wiley & Sons, New York,
2001.] the presence of which was also detected by XPS spectroscopy. This can be explained by
the high affinity of carbon dioxide molecules for the surface of metal oxides containing alkaline-
earth metal ions.
It is also interesting that during the reaction, the spectral feature related to the CO
3
2-
carbonates
(ca. 1442 cm
-1
) decreases in intensity, while the absorption at higher (1700-1500 cm
-1
) and lower
(1300-1150 cm
-1
) wavenumbers increased. These spectral regions may be attributed to the
bicarbonate C=O stretching vibrations (HCO
3
‾).
These findings were presented on page 6 of the manuscript and in the Supplementary
Information section.
Referee 2:
1. The first one is that Eq.1 is not introduced or explained. The reader would surely wonder
why Eq.1 can be applied in this case. Is it specific of phonons or is it valid for bonds in
general?
Equation 1 was taken from reference [F.D. Hardcastle and I.E. Wachs, The Molecular Structure
of Bismuth Oxide by Raman Spectroscopy, J. Solid State Chem. 1992, 97, 319–331.]. This work
was devoted to the study of molecular structure of different bismuth oxides by Raman
spectroscopy. As a result, the authors found the empirical bond length/bond strength/Raman
stretching frequency relationships and suggested the unique and effective method of interpreting
Raman spectra of bismuth oxide species.
Thus, Equation 1 is applicable in the analysis of Raman spectra of compounds containing Bi‒O
bonds, as in the case of synthesized barium bismuthate Ba
1.264(4)
Bi
1.971(4)
O
4
.
Page 3 of 20 Journal of Materials Chemistry C

Accordingly, we have modified the text on page 3 to read:
“Using the empirical expression (eqn. 1) found for bismuth oxides that relates the Bi‒O bond
lengths (R) to the Raman stretching frequencies in cm
–1
(
)
42
makes it possible to calculate the
bond lengths for the Bi‒O vibrations at 647 cm
–1
and 315 cm
–1
of studied sample.”
(1)
𝜐
92760
𝑒
2.511𝑅
2. The second one is about the DFT frequency estimates. Did the authors try alternative
methods to calculate them respect to the traditional one implemented in their suite of
code, such as DFPT or a finite difference approach accounting for the potential energy
surface curvature?
We apologize for rather not understanding the reviewer's point here. Suffices to say that in the
presented work, no (phonon) frequencies were computed.
3. Finally, I advise the authors to better explain how the flatband potential measurements
have been performed.
To the extent that flatband potentials are determined electrochemically/photoelectrochemically,
techniques that were not used in the present work, we have modified the relevant text to state
“energy or energies” of the VB and/or CB.
Page 4 of 20Journal of Materials Chemistry C

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Abstract: A method is given for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector. The integration can be over the entire Brillouin zone or over specified portions thereof. This method also has applications in spectral and density-of-state calculations. The relationships to the Chadi-Cohen and Gilat-Raubenheimer methods are indicated.

42,677 citations


Journal ArticleDOI
TL;DR: It is found that these pseudopotentials are extremely efficient for the cases where the plane-wave expansion has a slow convergence, in particular, for systems containing first-row elements, transition metals, and rare-earth elements.
Abstract: We present a simple procedure to generate first-principles norm-conserving pseudopotentials, which are designed to be smooth and therefore save computational resources when used with a plane-wave basis. We found that these pseudopotentials are extremely efficient for the cases where the plane-wave expansion has a slow convergence, in particular, for systems containing first-row elements, transition metals, and rare-earth elements. The wide applicability of the pseudopotentials are exemplified with plane-wave calculations for copper, zinc blende, diamond, \ensuremath{\alpha}-quartz, rutile, and cerium.

12,365 citations


Journal ArticleDOI
Abstract: For the molecules Be2, F2, and P2 of Table I, the unrestricted Hartree-Fock solution breaks the singlet spin symmetry, even though the density-functional solutions do not. For these broken-symmetry solutions, the UHF atomization energies become 17, 220, and 141 kcalymol, respectively, and the mean absolute error of all the UHF atomization energies becomes 69.8 kcalymol. The PBE correlation energy of the two-electron ions of nuclear charge Z ! ` should be corrected to 20.0479 hartree, consistent with the PBE value v ­ 0.046644 stated in the Letter. The quoted value 20.0482 hartree was obtained from the more refined v ­ 0.046920 of G. G. Hoffman, Phys. Rev. B 45, 8730 (1992). Reference [6] should have been “A. C. Scheiner, J. Baker, and J. W. Andzelm, J. Comput. Chem. (to be published)”.

10,177 citations


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18 Jun 2004
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Frequently Asked Questions (2)
Q1. What are the contributions in this paper?

In this paper, the authors reported an anomalous ratio in a series of alkaline-earth bismuthates between bandgap width and the energy of the conduction band. 

However, such an anomalous energy arrangement of the conduction band opens up unique possibilities for using this bismuthate for the photocatalytic reduction of a currently controversial greenhouse gas, carbon dioxide, while oxidative half- reactions appear rather unlikely as attested by the lack of photoinduced oxidation of phenol.