Achieving photocatalytic water oxidation on LaNbON 2 under visible light irradiation

Wan, Lipeng; Xiong, Fengqiang; Zhang, Bingxue; Che, Ruxin; Li, Yue; Yang, Minghui

doi:10.1016/j.jechem.2018.01.004

Cited by 24 publications

(17 citation statements)

References 20 publications

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“…The absorption edge wavelength as estimated from the onset of light absorption was approximately 700 nm. This wavelength was somewhat shorter than the value of 750 nm reported for LaNbN 2 O and the light absorption onset observed for the nitridation product obtained from LaNbO 4 [17,18]. Notably, the nitridation product resulting from La 0.6 Na 0.4 Zn 0.4 Nb 0.6 O 3 exhibited a brighter color than that produced by LaNbO 4 .…”

Section: Resultsmentioning

confidence: 59%

“…This is primarily because it is difficult to synthesize LaNbN 2 O having suitable semiconducting characteristics. LaNbN 2 O is typically obtained by heating oxides containing La and Nb under an NH 3 flow [7,17]. During this nitridation process, Nb 5+ ions are more readily reduced to Nb 4+, and Nb 3+ than are their Ta analogs, such that anion defects are generated [6].…”

Section: Introductionmentioning

confidence: 99%

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Oxygen Evolution Activity of LaNbN2O-Based Photocatalysts Obtained from Nitridation of a Precursor Oxide Structurally Modified by Incorporating Volatile Elements

2021

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The perovskite-type oxynitride LaNbN2O is a photocatalyst that can evolve oxygen from aqueous solutions in response to long-wavelength visible light. However, it is challenging to obtain active LaNbN2O because of the facile reduction of Nb5+ during the nitridation of the precursor materials. The present study attempted to synthesize a perovskite-type oxide La0.6Na0.4Zn0.4Nb0.6O3, containing equimolar amounts of La3+ and Nb5+ in addition to volatile Na+ and Zn2+, followed by the nitridation of this oxide to generate LaNbN2O. The obtained oxide was not the intended single-phase material but rather comprised a cuboid perovskite-type oxide similar to La0.5Na0.5Zn0.33Nb0.67O3 along with spherical LaNbO4 particles and other impurities. A brief nitridation was found to form a LaNbN2O-like shell structure having a light absorption onset of approximately 700 nm on the cuboid perovskite-type oxide particles. This LaNbN2O-based photocatalyst, when loaded with a CoOx cocatalyst, exhibited an apparent quantum yield of 1.7% at 420 nm during oxygen evolution reaction from an aqueous AgNO3 solution. This was more than double the values obtained from the nitridation products of LaNbO4 and LaKNaNbO5. The present work demonstrates a new approach to the design of precursor oxides that yield highly active LaNbN2O and suggests opportunities for developing efficient Nb-based perovskite oxynitride photocatalysts.

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Section: Resultsmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Oxygen Evolution Activity of LaNbN2O-Based Photocatalysts Obtained from Nitridation of a Precursor Oxide Structurally Modified by Incorporating Volatile Elements

2021

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“…As a result, the crystalline LaNbON 2 was prepared by the thermal ammonolysis of LaNbO 4 in Lewis basic La-excess atmosphere. In the previous reports, hard nitridation conditions, e.g., a high temperature of 1223 K, high flow rate of NH 3 , and addition of molten salts, were necessary to synthesize the crystalline LaNbON 2 , because the nitridation process is accompanied by the structural transition between scheelite and perovskite structures. ,, It is thus remarkable that, in this study, the excess La caused the complete nitridation in mild conditions that included lower temperature, shorter time, and absence of the additives.…”

Section: Resultsmentioning

confidence: 66%

“…There was also no activity for hydrogen evolution using the synthesized pure LaNbON 2 . Wan et al prepared LaNbON 2 by the nitridation of LaNbO 4 and La 3 NbO 7 , calcinated with NaCl and KCl flux in air. , The nitridation of La 3 NbO 7 , followed in order by acid treatment to remove a La 2 O 3 impurity phase, and by annealing treatment in Ar at 973 K for 15 min, caused low-defect LaNbON 2 particles. Nevertheless, the amount of O 2 gas evolved over the CoO x -loaded LaNbON 2 during the visible light water oxidation using a Xe lamp (λ > 400 nm) was low at 5.4 μmol h –1 .…”

Section: Introductionmentioning

confidence: 99%

Visible-Light-Driven Water Splitting over Particulate LaNbON₂ Prepared from La-Rich Lanthanum Niobium Oxides

Seo

Jeong

Kim

2021

ACS Appl. Energy Mater.

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A LaNbON2 semiconductor is capable of absorbing long light wavelengths up to 750 nm, which indicates a promising n-type material for solar water splitting to produce hydrogen. In this study, we present enhanced photocatalytic and photoelectrochemical activities over the particulate LaNbON2 during visible-light-driven water oxidation. La-rich oxide mixtures, prepared by the calcination of La2O3–Nb2O5 with La/Nb ratios greater than 1.00, were proposed as a starting precursor for the synthesis of less-defective LaNbON2. The La-rich condition caused the synthesis of smaller LaNbON2 particles with larger BET surface areas, which were favorable for the complete nitridation under mild conditions. The LaNbON2 particles prepared from the La/Nb ratio of 1.20, which were capable of absorbing a wide range of visible light up to approximately 750 nm and above, completed the nitridation at 1123 K for 15 h. The La-rich condition promoted reduced bulk defect density of LaNbON2 and suppressed the formation of Nb3+ species at the oxynitride surface during nitridation. These differences led to water oxidation photocurrent over the particulate LaNbON2 photoanode under AM 1.5 G simulated sunlight, which has never previously been reported. Therefore, the synthesis strategy using La-rich oxide was effective at preparing less-defective LaNbON2, thus improving the photoactivity.

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“…Water oxidation using the oxynitride has rarely been studied, despite its narrow band gap energy of 1.7 eV. The starting oxides such as amorphous oxide mixture, 11 LaNbO 4 , 12–13 La 3 NbO 7 , 14–15 and LaKNaNbO 5 16 were introduced for the synthesis of LaNbON 2 . The LaNbON 2 photocatalyst, prepared from scheelite‐type LaNbO 4 with a La/Nb ratio of 1 stoichiometric to that of oxynitride, exhibited almost negligible water oxidation activity under visible light using a 300 W Xe lamp 11–13 .…”

Section: Introductionmentioning

confidence: 99%

Size Control of LaNbON₂ Particles for Enhanced Photocatalytic Water Oxidation Under Visible Light Irradiation

Seo

2021

Bulletin Korean Chem Soc

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Perovskite‐type LaNbON2 has the longest wavelength onset of visible light absorption—up to approximately 740 nm—among (oxy)nitrides based on transition metals Ti, Ta, and Nb. Water oxidation using visible‐light‐responsive LaNbON2 is challenging because the synthesis of the oxynitride has rarely been studied. Herein, we report the synthesis of small LaNbON2 particles and their size effect on photocatalytic water oxidation under visible light illumination. The small scheelite‐type LaNbO4, prepared by a polymerized complex method, was transformed into less‐defective LaNbON2 during nitridation as compared with that nitrided from LaNbO4 via a solid‐state reaction method. The small LaNbON2 particles, capable of absorbing intense visible light 700 nm above, improved the O2 evolution during 5 h of water oxidation under 300 W Xe light irradiation (λ > 420 nm). This enhancement was attributed to the size reduction of LaNbON2 particles, leading to increased surface area and encouragement of mild nitridation.

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Achieving photocatalytic water oxidation on LaNbON 2 under visible light irradiation

Cited by 24 publications

References 20 publications

Oxygen Evolution Activity of LaNbN2O-Based Photocatalysts Obtained from Nitridation of a Precursor Oxide Structurally Modified by Incorporating Volatile Elements

Oxygen Evolution Activity of LaNbN2O-Based Photocatalysts Obtained from Nitridation of a Precursor Oxide Structurally Modified by Incorporating Volatile Elements

Visible-Light-Driven Water Splitting over Particulate LaNbON₂ Prepared from La-Rich Lanthanum Niobium Oxides

Size Control of LaNbON₂ Particles for Enhanced Photocatalytic Water Oxidation Under Visible Light Irradiation

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Achieving photocatalytic water oxidation on LaNbON 2 under visible light irradiation

Cited by 24 publications

References 20 publications

Oxygen Evolution Activity of LaNbN2O-Based Photocatalysts Obtained from Nitridation of a Precursor Oxide Structurally Modified by Incorporating Volatile Elements

Oxygen Evolution Activity of LaNbN2O-Based Photocatalysts Obtained from Nitridation of a Precursor Oxide Structurally Modified by Incorporating Volatile Elements

Visible-Light-Driven Water Splitting over Particulate LaNbON2 Prepared from La-Rich Lanthanum Niobium Oxides

Size Control of LaNbON2 Particles for Enhanced Photocatalytic Water Oxidation Under Visible Light Irradiation

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Resources

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Visible-Light-Driven Water Splitting over Particulate LaNbON₂ Prepared from La-Rich Lanthanum Niobium Oxides

Size Control of LaNbON₂ Particles for Enhanced Photocatalytic Water Oxidation Under Visible Light Irradiation