The Effects of Preparation Conditions for a BaNbO<sub>2</sub>N Photocatalyst on Its Physical Properties

Hisatomi, Takashi; Katayama, Chisato; Teramura, Kentaro; Takata, Tsuyoshi; Moriya, Yosuke; Minegishi, Tsutomu; Katayama, Masao; Nishiyama, Hiroshi; Yamada, Taro; Domen, Kazunari

doi:10.1002/cssc.201400121

Cited by 45 publications

(58 citation statements)

References 16 publications

(38 reference statements)

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“…4a). 77,87 95,96 The lower activities with respect to the tantalum materials are likely due to the presence of reduced oxidation states of niobium. [82][83][84] It can be explained in terms of maximum utilization of d orbitals in p bonding with the lone pairs of the anions (Fig.…”

Section: Perovskite Oxynitridesmentioning

confidence: 99%

Metal oxynitrides as emerging materials with photocatalytic and electronic properties

Fuertes

2015

Mater. Horiz.

139

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Oxynitrides of transition metals, alkaline earth metals and rare earth metals are intensively investigated as a group of materials to expand and tune the properties of oxides. The differences in polarizability, electronegativity and anion charge of nitrogen and oxygen induce changes in the physical and chemical properties of oxides by nitrogen introduction. The effects on properties arise from the higher covalency of the metal-nitrogen bond and the changes in the energies of electronic levels, and are important in slightly doped nitrogen metal oxides as in stoichiometric oxynitrides. More intense recent progress in oxynitride research has been made in some specific fields such as photocatalysis in water splitting and other processes as the observed small band gaps lead to activity in the visible light range. The stabilization of new perovskite oxynitrides, with the oxidation states of cations tuned by N/O stoichiometry, has led to new magnetic and dielectric materials. The lower electronegativity of nitrogen and larger crystal field splitting induced by N 3À shifts the emission wavelengths of phosphors to the red, and oxynitridosilicates have been investigated as components of white LEDs.

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Section: Perovskite Oxynitridesmentioning

confidence: 99%

Metal oxynitrides as emerging materials with photocatalytic and electronic properties

Fuertes

2015

Mater. Horiz.

139

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“…The perovskite‐type BaNbO 2 N, unlike SrNbO 2 N which can be obtained by nitridation of Sr 2 Nb 2 O 7 , does not have a crystalline oxide precursor with both a pentavalent Nb state and a stoichiometric Ba/Nb ratio of unity . This has encouraged researchers to study the preparation of stoichiometric oxide mixtures as precursors to BaNbO 2 N. Ba‐rich oxide mixtures have also been examined in an attempt to suppress the reduction of Nb species . Such mixtures have been found to effectively suppress the formation of NbO x N y , but require high‐temperature nitridation under a high flow rate of NH 3 gas that promotes nitridation.…”

Section: Introductionmentioning

confidence: 99%

Efficient Solar‐Driven Water Oxidation over Perovskite‐Type BaNbO₂N Photoanodes Absorbing Visible Light up to 740 nm

Seo

Hisatomi

Nakabayashi

et al. 2018

Advanced Energy Materials

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materials is a potential means of addressing these concerns by producing hydrogen as a clean, renewable fuel source. [1] Because visible and infrared wavelengths account for a large portion of the solar spectrum, it is necessary to develop semiconductors with longer light absorption onset wavelengths in order to achieve high solar-to-hydrogen energy conversion efficiencies.Perovskite-type oxynitrides, designated as AB(O,N) 3 (where A = La, Ca, Sr, or Ba and B = Ti, Ta, or Nb), are n-type semiconductors capable of absorbing a wide range of visible light. [2,3] Interestingly, the band gap energy for AB(O,N) 3 can be varied by employing different combinations of the A-and B-site cations. [3,4] Nb-based perovskite oxynitrides (ANb(O,N) 3 B = Nb) are of particular interest with regard to solar energy conversion because they have narrower band gap energies than Ta-or Ti-based oxynitrides. As an example, BaNbO 2 N absorbs visible light up to 740 nm, a longer wavelength than BaTaO 2 N or LaTiO 2 N, and has the potential to achieve a photocurrent density of 23.3 mA cm −2 given an incident photon-to-current efficiency (IPCE) of 100%. It is also helpful that Nb is a more abundant element than Ta. However, PEC water splitting using ANb(O,N) 3 remains relatively inefficient compared with that using Ti-and Ta-based compounds. [5][6][7] This is because the reduction of Nb species during nitridation in a NH 3 flow (i.e., from Nb 5+ to Nb 4+ or Nb 3+ ) occurs more readily than that of Ta species because of the higher electronegativity of Nb. It leads to formation of surface anion defects to compensate for charge imbalances and/or impurity phases such as NbO x N y . The surface state of ANb(O,N) 3 can therefore hinder the water oxidation reaction, unless mild synthesis conditions such as low temperature and short nitridation periods are used to suppress the reduction of Nb 5+ . Unfortunately, these conditions result in low crystallinity of the oxynitride, which enhances recombination of photoexcited holes and electrons. Thus, a synthesis method that effectively reduces the generation of inactive sites while retaining high crystallinity is required before high PEC activity can be achieved using ANb(O,N) 3 .The perovskite-type BaNbO 2 N, unlike SrNbO 2 N which can be obtained by nitridation of Sr 2 Nb 2 O 7 , does not have a crystalline oxide precursor with both a pentavalent Nb state and a Photoelectrochemical water splitting using semiconductors absorbing a wide range of visible light is a potentially attractive means of harvesting large portions of the solar spectrum. However, this is also very challenging because narrowing the semiconductor band gap lowers the driving force for photo reactions. Herein, a highly active perovskite BaNbO 2 N exhibiting photo excitation up to 740 nm for water oxidation is reported. The synthesis route, consisting of moderate nitridation and subsequent annealing in inert Ar flow, enhances the crystallinity of the BaNbO 2 N surface without inducing the reduction of the Nb species. As a result, a parti...

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“…Regarding the oxidation part (i.e. photocatalytic oxygen evolution), a certain number of metal oxides such as TiO 2 , WO 3 and BiVO 4 and nitrides or oxynitrides (Ta 3 N 5 , TaON, LaTiO 2 N) [3][4][5][6] have been proposed in Z-Schemes with materials suitable for H 2 generation (reduction part) as SrTiO 3 . 7,8 These photocatalysts should fulfil two necessary requirements: suitable band position for attaining the O 2 /H 2 O reaction (Eº= 1.23V RHE ) 3 and acceptable band gap values for solar-light activity.…”

Section: Introductionmentioning

confidence: 99%

Insights into the Performance of Co_xNi_1–xTiO₃ Solid Solutions as Photocatalysts for Sun-Driven Water Oxidation

Murcia-López

Moschogiannaki

Binas

et al. 2017

ACS Appl. Mater. Interfaces

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CoNiTiO systems evaluated as photo- and electrocatalytic materials for oxygen evolution reaction (OER) from water have been studied. These materials have shown promising properties for this half-reaction both under (unbiased) visible-light photocatalytic approach in the presence of an electron scavenger and as electrocatalysts in dark conditions in basic media. In both situations, CoNiTiO exhibits the best performance and is proved to display high faradaic efficiency. A synergetic effect between Co and Ni is established, improving the physicochemical properties such as surface area and pore size distribution, besides affecting the donor density and the charge carrier separation. At higher Ni content, the materials exhibit behavior more similar to that of NiTiO, which is a less suitable material for OER than CoTiO.

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The Effects of Preparation Conditions for a BaNbO₂N Photocatalyst on Its Physical Properties

Cited by 45 publications

References 16 publications

Metal oxynitrides as emerging materials with photocatalytic and electronic properties

Metal oxynitrides as emerging materials with photocatalytic and electronic properties

Efficient Solar‐Driven Water Oxidation over Perovskite‐Type BaNbO₂N Photoanodes Absorbing Visible Light up to 740 nm

Insights into the Performance of Co_xNi_1–xTiO₃ Solid Solutions as Photocatalysts for Sun-Driven Water Oxidation

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The Effects of Preparation Conditions for a BaNbO2N Photocatalyst on Its Physical Properties

Cited by 45 publications

References 16 publications

Metal oxynitrides as emerging materials with photocatalytic and electronic properties

Metal oxynitrides as emerging materials with photocatalytic and electronic properties

Efficient Solar‐Driven Water Oxidation over Perovskite‐Type BaNbO2N Photoanodes Absorbing Visible Light up to 740 nm

Insights into the Performance of CoxNi1–xTiO3 Solid Solutions as Photocatalysts for Sun-Driven Water Oxidation

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The Effects of Preparation Conditions for a BaNbO₂N Photocatalyst on Its Physical Properties

Efficient Solar‐Driven Water Oxidation over Perovskite‐Type BaNbO₂N Photoanodes Absorbing Visible Light up to 740 nm

Insights into the Performance of Co_xNi_1–xTiO₃ Solid Solutions as Photocatalysts for Sun-Driven Water Oxidation