Crystal structures of two new oxysulfides La5Ti2MS5O7 (M=Cu, Ag): evidence of anionic segregation

Using density functional theory (DFT) within the local density approximation (LDA), we calculate the physical and electronic properties of PbTiO 3 (PTO) and a series of hypothetical compounds PbTiO 3-x S x x = 0.2, 0.25, 0.33, 0.5, 1, 2, and 3 arranged in the corner-sharing cubic perovskite structure. We determine that replacing the apical oxygen atom in the PTO tetragonal unit cell with a sulfur atom reduces the x = 0 LDA calculated band gap of 1.47 eV to 0.43 -0.67 eV for x = 0.2 -1 and increases the polarization. PBE0 and GW methods predict that the compositions x = 0.2-2 will have band gaps in the visible range. For all values of x < 2, the oxysulfide perovskite retains the tetragonal phase of PbTiO 3 , and the a lattice parameter remains within 2.5% of the oxide. Thermodynamic analysis indicates that chemical routes using high temperature gas, such as H 2 S and CS 2 , can be used to substitute O for S in PTO for the compositions x = 0.2 -0.5.

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“…[19][20][21][22] Thus the current work is novel in that it explores the feasibility of synthesizing a purely corner-sharing perovskite phase.…”

Section: Introductionmentioning

confidence: 99%

Density functional theory study of hypotheticalPbTiO3-based oxysulfides

et al. 2014

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“…Figure A,B presents the X‐ray diffraction (XRD) patterns and diffuse‐reflectance spectroscopy (DRS) data acquired from the LTCS 0.4 Se 0.6 O samples prepared at 1073–1273 K, respectively. A reference XRD pattern of LTCSO obtained from Inorganic Crystal Structure Database is also presented in Figure A . Note that the diffraction peaks of LTCS 0.4 Se 0.6 O are located at lower angles because of the expansion of the unit cell .…”

Section: Resultsmentioning

confidence: 99%

“…XRD patterns and DRS data for LTCSO calcined at 1173–1323 K, LTCS 0.8 Se 0.2 O calcined at 1123–1273 K, and LTCS 0.6 Se 0.4 O calcined at 1123–1273 K are presented in Figures S1–S3 in the Supporting Information, respectively, along with the reference XRD pattern of LTCSO . In each case, LTCSO, LTCS 0.8 Se 0.2 O, and LTCS 0.6 Se 0.4 O were obtained as the major phases at all temperatures.…”

Section: Resultsmentioning

confidence: 99%

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Effects of Calcination Temperature on the Physical Properties and Hydrogen Evolution Activities of La₅Ti₂Cu(S_1‐_xSe_x)₅O₇ Photocatalysts

Nandy

Hisatomi

Katayama

et al. 2017

Part & Part Syst Charact

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La5Ti2Cu(S1‐xSex)5O7 (LTCS1‐xSexO) solid solutions are found to function as visible‐light‐driven photocatalysts to evolve H2 from aqueous solutions containing sacrificial electron donors. However, this photocatalytic activity is reduced with increasing Se concentrations because of excessive particle growth during calcination at high temperatures. In the present study, the physical properties and photocatalytic H2 evolution activities of LTCS1‐xSexO (0 ≤ x ≤ 0.6) solid solution photocatalysts synthesized by solid‐state reactions at varying temperatures are assessed. It is found that the photocatalyst particle sizes are reduced upon lowering the calcination temperature. In addition, the calcination temperature resulting in the highest photocatalytic H2 evolution rates for NiS‐loaded LTCS1‐xSexO is shown to become lower with increasing Se content. The H2 evolution activity of LTCS1‐xSexO (0.2 ≤ x ≤ 0.6) is improved several‐fold by optimizing the calcination temperature because the excessive growth of particles is avoided. The activity of these materials is further improved by coloading Pt and NiS cocatalysts. This work demonstrates the importance of controlling the particle size of narrow bandgap LTCS1‐xSexO oxysulfoselenides so as to effectively utilize visible light during photocatalytic H2 evolution.

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“…A thin layer of particulate photocatalysts, consisting of both HEP and OEP particles, is embedded in a conductive layer, which allows intimate mechanical and electrical contact within the particles and provides efficient electron transfer between the HEP and OEP. As mentioned above, the multiple oxysulfide La 5 Ti 2 CuS 5 O 7 exhibits a promising absorption edge of 650 nm . The photogenerated charges of La 5 Ti 2 CuS 5 O 7 could move through TiO x S 6− x and MS 4 along linear chains with high mobility.…”

Section: Mixed‐anion Photocatalystsmentioning

confidence: 98%

Development of Mixed‐Anion Photocatalysts with Wide Visible‐Light Absorption Bands for Solar Water Splitting

Cui

Zhang

2018

ChemSusChem

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Rapid fossil-fuel consumption, severe environmental concerns, and growing energy demands call for the exploitation of environmentally friendly, recyclable, new energy sources. Fuel-producing artificial systems that directly convert solar energy into fuels by mimicking natural photosynthesis are expected to achieve this goal. Among them, the conversion of solar energy into hydrogen energy through the photocatalytic water-splitting process over a particulate semiconductor is one of the most promising routes due to advantages such as simplicity, cheapness, and ease of large-scale production. Abundant metal oxide photocatalysts have been developed in the last century, but most are only active under UV-light irradiation. To harvest a much wider range of the solar spectrum, the development of photocatalysts with wide visible-light absorption bands has become increasingly popular this century. Herein, a brief overview of materials developed for promising solar water splitting, with an emphasis on a mixed-anion structure and wide visible-light absorption bands, is presented, with some basic information on the principles, approaches, and research progress on the photocatalytic water-splitting reaction with particulate semiconductors. Typical progress on research into one- and two-step (Z-scheme) overall water-splitting systems by utilizing mixed-anion photocatalysts is highlighted, together with research strategies and modification methods.

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Crystal structures of two new oxysulfides La5Ti2MS5O7 (M=Cu, Ag): evidence of anionic segregation

Cited by 50 publications

References 21 publications

Density functional theory study of hypotheticalPbTiO3-based oxysulfides

Density functional theory study of hypotheticalPbTiO3-based oxysulfides

Effects of Calcination Temperature on the Physical Properties and Hydrogen Evolution Activities of La₅Ti₂Cu(S_1‐_xSe_x)₅O₇ Photocatalysts

Development of Mixed‐Anion Photocatalysts with Wide Visible‐Light Absorption Bands for Solar Water Splitting

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Crystal structures of two new oxysulfides La5Ti2MS5O7 (M=Cu, Ag): evidence of anionic segregation

Cited by 50 publications

References 21 publications

Density functional theory study of hypotheticalPbTiO3-based oxysulfides

Density functional theory study of hypotheticalPbTiO3-based oxysulfides

Effects of Calcination Temperature on the Physical Properties and Hydrogen Evolution Activities of La5Ti2Cu(S1‐xSex)5O7 Photocatalysts

Development of Mixed‐Anion Photocatalysts with Wide Visible‐Light Absorption Bands for Solar Water Splitting

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Effects of Calcination Temperature on the Physical Properties and Hydrogen Evolution Activities of La₅Ti₂Cu(S_1‐_xSe_x)₅O₇ Photocatalysts