The atomic-scale structure of LaCrO<sub>3</sub>–NaTaO<sub>3</sub> solid solution photocatalysts with enhanced electron population

Sudrajat, Hanggara; Zhou, Yunyun; Sasaki, Tomoya; Ichikuni, Nobuyuki; Ōnishi, Hiroshi

doi:10.1039/c8cp07688j

Cited by 23 publications

(22 citation statements)

References 25 publications

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“…When the B-site cation is substituted with foreign, nonequivalent B′ cation, this symmetry restriction breaks down, producing the 830 cm –1 band. In a number of ABO 3 -perovskites doped with metal cations at the B site, strong Raman bands were detected at ∼820 cm –1 . ,− As also revealed in our previous studies, the substitution of Ta 5+ in NaTaO 3 with first-row transition-metal cations produced additional Raman bands at ∼830 cm –1 . − The intensity of the newly produced Raman bands was linearly correlated with the cation concentration, indicating that these bands were associated with the Ta site occupation by those metal cations.…”

Section: Resultssupporting

confidence: 67%

Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO₃ Photocatalysts

et al. 2021

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This study aims to investigate the behavior of photoexcited electrons in intentionally distorted Ba-doped NaTaO3 photocatalysts with time-resolved microwave conductivity and steady-state IR absorption induced by UV light. As probed by X-ray absorption fine structure and Raman spectroscopies, doping NaTaO3 with Ba2+ produces structural nonperiodicity and distorts the octahedral sublattice, proposedly resulting in the formation of electron traps. A higher density of shallow electron traps is suggested to be responsible for the longer electron lifetime and larger electron population, because shallowly trapped electrons are less likely to recombine with holes. The half-lifetime of photoexcited electrons is considerably long, even longer than 0.8 ms in the Ba-doped NaTaO3 sample with moderate distortion. The population of photoexcited electrons under Hg–Xe lamp irradiation increases by 32 times in this sample compared to that in undoped NaTaO3, generating H2/O2 mixtures with the rates of 385 μmol h–1 (H2) and 180 μmol h–1 (O2) when irradiated with a Hg lamp in the absence of cocatalyst and sacrificial compound. Moderate distortion seems favorable to produce shallow electron traps in comparison to large and small distortions, leading to the highest water splitting rate. The orders of photocatalysts based on their electron lifetime, electron population, and water splitting rate are identical, indicating that the photoexcited electrons worked in the water splitting reactions.

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Section: Resultssupporting

confidence: 67%

Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO₃ Photocatalysts

et al. 2021

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“…The maximum population with a dopant concentration of 1.8 mol % increased by 180 times relative to that in the pristine NaTaO 3 photocatalyst. Doping with Ca, Ba, or La also increased the steady‐state populations of excited electrons by 50 times or more.…”

Section: Steady‐state Population Of Band‐gapexcited Electronsmentioning

confidence: 99%

“…The lattice free from anion vacancy is advantageous for hole transport to increase quantum efficiency. Simultaneous doping with La 3+ and transition metal cations has been examined to sensitize NaTaO 3 to visible light . The NaTaO 3 –Sr(Sr 1/3 Ta 2/3 )O 3 solid solution photocatalysts are recognized as NaTaO 3 doped with one metal element, Sr.…”

Section: Solid Solutions For Accommodating Dopant Cationsmentioning

confidence: 99%

Sodium Tantalate Photocatalysts Doped with Metal Cations: Why Are They Active for Water Splitting?

Ōnishi

2019

ChemSusChem

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Sodium tantalate (NaTaO3) is the first semiconductor photocatalyst that produces hydrogen–oxygen mixed bubbles in the overall water splitting reaction, when appropriately doped with metal cations. A series of studies are reviewed herein to answer the question of why doping with metal cations raised the quantum efficiency of the reaction. Infrared absorption of band‐gap‐excited photocatalysts demonstrated that cation doping reduced the electron–hole recombination rate and the steady‐state population of charge carriers accordingly increased. In‐depth studies are focused on Sr cations incorporated through solid‐state, flux, and hydrothermal reactions. The recombination rate was reduced when Ta cations were exchanged with Sr cations. Sodium cations were simultaneously exchanged to balance the cationic and anionic charges with no need for creating oxygen anion vacancies. NaTaO3Sr(Sr1/3Ta2/3)O3 solid solution was formed as a result of the simultaneous doping. In addition to doping at the appropriate sites, the intraparticle distribution of Sr cations played an essential role to reduce the recombination rate. Strontium cations segregated to produce graded composition from the Sr‐rich surface to the Sr‐poor core. The bottom of the conduction band was raised at the Sr‐rich surface and the excited electrons were driven to the Sr‐poor core, leaving holes at the surface. However, the graded composition had a dual purpose; the excited electron population increased and its fractional contribution to the surface reaction decreased.

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“…Very recently, increased photocatalytic H 2 generation has been observed in BaBiO 3 /NaTaO 3 heterojunctions and attributed to efficient suppression of charge carriers recombination . Also, LaCrO 3 –NaTaO 3 solid solutions have performed improved photocatalytic reactions with an enhanced electron population due to a charge compensation mechanism that sensitizes the tantalate to visible light . Similarly, BiFeO 3 , NaNbO 3 , KNbO 3 , KTaO 3 , NaTaO 3 , and other tantalate-based − heterostructures have been synthesized and showed benefits compared to their bulk parts.…”

Section: Introductionmentioning

confidence: 99%

“…18 Also, LaCrO 3 −NaTaO 3 solid solutions have performed improved photocatalytic reactions with an enhanced electron population due to a charge compensation mechanism that sensitizes the tantalate to visible light. 19 Similarly, BiFeO 3 , 20 NaNbO 3 , 21 KNbO 3 , 22 KTaO 3 , 23 NaTaO 3 , 24 and other tantalate-based 25−27 heterostructures have been synthesized and showed benefits compared to their bulk parts.…”

Section: ■ Introductionmentioning

confidence: 99%

NaNbO₃/NaTaO₃ Superlattices: Cation-Ordering Improved Band-Edge Alignment for Water Splitting and CO₂ Photocatalysis

2021

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Perovskite oxide heterostructures have been extensively investigated for their excellent photocatalytic properties. Here, through hybrid density functional theory calculations, we systematically investigate the formation of NaNbO 3 −NaTaO 3 (NBO-NTO) heterostructures. The sequential cations replacement in the superlattices reveals the Nb−Ta ratio range that allows the effective formation of heterostructures, which occurs through a spontaneous polarization mechanism induced by the electrostatic potential discontinuity in the interface. The resulting cation ordering is responsible for the sawtoothlike potential distribution that spatially separates valence and conduction charges and reduces the heterostructure bandgap. The symmetric NBO 5 /NTO 5 junction has the smallest bandgap (2.50 eV) whose transitions are associated with Nb 5d xy orbitals on the interfacial plane. Such a relaxation mechanism provides the heterostructure with anisotropic optical properties and interface absorption peaks closer to the visible light spectrum. The phenomena strongly suggest the use of these heterostructures in photocatalytic reactions, supported by their coherent band-edge alignment with both water splitting and CO 2 reforming potentials.

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The atomic-scale structure of LaCrO₃–NaTaO₃ solid solution photocatalysts with enhanced electron population

Abstract: The atomic-scale structure of a NaTaO3 photocatalyst doped with La3+ and Cr3+ for visible light sensitization is successfully revealed.

Cited by 23 publications

References 25 publications

Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO₃ Photocatalysts

Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO₃ Photocatalysts

Sodium Tantalate Photocatalysts Doped with Metal Cations: Why Are They Active for Water Splitting?

NaNbO₃/NaTaO₃ Superlattices: Cation-Ordering Improved Band-Edge Alignment for Water Splitting and CO₂ Photocatalysis

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The atomic-scale structure of LaCrO3–NaTaO3 solid solution photocatalysts with enhanced electron population

Abstract: The atomic-scale structure of a NaTaO3 photocatalyst doped with La3+ and Cr3+ for visible light sensitization is successfully revealed.

Cited by 23 publications

References 25 publications

Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO3 Photocatalysts

Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO3 Photocatalysts

Sodium Tantalate Photocatalysts Doped with Metal Cations: Why Are They Active for Water Splitting?

NaNbO3/NaTaO3 Superlattices: Cation-Ordering Improved Band-Edge Alignment for Water Splitting and CO2 Photocatalysis

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The atomic-scale structure of LaCrO₃–NaTaO₃ solid solution photocatalysts with enhanced electron population

Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO₃ Photocatalysts

Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO₃ Photocatalysts

NaNbO₃/NaTaO₃ Superlattices: Cation-Ordering Improved Band-Edge Alignment for Water Splitting and CO₂ Photocatalysis