Black nanostructured Nb<sub>2</sub>O<sub>5</sub> with improved solar absorption and enhanced photoelectrochemical water splitting

Cui, Houlei; Zhu, Guangshan; Xie, Yijun; Zhao, Wei; Yang, Chengliang; Lin, Tianquan; Gu, Hui; Huang, Fu Qiang

doi:10.1039/c5ta01544h

Cited by 88 publications

(48 citation statements)

References 51 publications

(58 reference statements)

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“…Large amount of black TiO 2– x was achieved from one batch by the Al‐reduction route (Figure b) and the Al‐reduced TiO 2– x samples extend the photoresponse from UV light to visible and infrared light region (Figure c) . This aluminum reduction method has been applied to prepare other black nanooxides with high optical absorption, such as black brookite TiO 2 ,] Nb 2 O 5 and SrTiO 3 , TiO 2 nanotube and gray TiO 2 nanowire . The Al‐reduction generated black titania had a crystalline‐disordered core‐shell structure, TiO 2 @TiO 2– x .…”

Section: Synthetic Approaches For Black Titaniamentioning

confidence: 99%

Progress in Black Titania: A New Material for Advanced Photocatalysis

Liu

Zhu

Wang

et al. 2016

Advanced Energy Materials

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279

190

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excited charges should separate from each other and migrate to the surface to perform photocatalytic reactions, before they are annihilated in the recombination process. [ 3,17,18 ] Nevertheless, TiO 2 has a wide bandgap of 3.0−3.2 eV for the three common natural polymorphs -anatase, rutile and brookite. [ 8 ] That limits the optical absorption of TiO 2 in the ultraviolet (UV) region of the solar spectrum, resulting in insuffi cient utilization of solar energy (less than 5%). Another hurdle for TiO 2 material in the photo-chemical applications is its low quantum effi ciency that results from its high recombination of photo-generated electron-hole pairs. [ 16,18 ] Therefore, improving the optical absorption properties and reducing electron-hole recombination of TiO 2 are expected to be signifi cant for superior photoactivity.Various strategies have been adopted to tune TiO 2 's optical and electronic properties to improve its visible-light photoactivity. For example, metal ions (Co, Ni, Mn, Fe, Cr, …) or non-metal ions (N, S, C, I, …) are doped in the titania matrix to induce mid-gap states or to narrow the bandgap of TiO 2 , aiming to enhance its visible-light response. [ 3,17 ] Doping with open-shell metals is claimed to be benefi cial for red-shifting TiO 2 photochemistry into the visible, while closed shell cation dopants have no photochemical benefi t. Some d -block transition metal doping often generates deeply localized d -states in the forbidden bandgap of TiO 2 and results in recombination centers for carriers. [ 3,19 ] For the incorporation of non-metal ions, heavy doping is always diffi cult due to the large differences in chemistry between the alien ions and O 2− in titania, thus the visible light absorption is not signifi cantly enhanced. [ 20 ] Dye-sensitized or noble metal nanodots decorated TiO 2 nanostructures have been largely designed to enhanced its optical properties and to improve the charge separation effi ciency. [ 6,9,15,17,21 ] Additionally, charge separation in TiO 2 is believed to be effi ciently improved by forming heterojunctions with other semiconductors, such as metal oxides and chalcogenides. [ 6,22 ] In 2011, a hydrogenated black titania with a narrowed bandgap of ≈1.5 eV was reported to boost the full spectrum sunlight absorption and the photocatalytic activity. [ 23 ] This discovery has triggered world-wide scientifi c interests in black TiO 2 nanomaterials. [ 8 ] Black TiO 2 is featured by selfstructural modifi cations, involving self-doped Ti 3+ /oxygen vacancy, or incorporation of H-doping. [ 5,8 ] Owing to these modifi cations, their crystal and electronic structures as well as the surface property are signifi cantly changed, and the most marked effect is the color changing. The intrinsic TiO 2The photocatalytic activity of TiO 2 has aroused a broad range of research effort since 1972. Although TiO 2 has a very high effi ciency in utilizing ultraviolet light, its overall solar activity is very limited due to its wide bandgap (≈3.0−3.2 eV). This is a bottleneck for TiO 2 to...

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Section: Synthetic Approaches For Black Titaniamentioning

confidence: 99%

Progress in Black Titania: A New Material for Advanced Photocatalysis

Liu

Zhu

Wang

et al. 2016

Advanced Energy Materials

Self Cite

279

190

View full text Add to dashboard Cite

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“…In addition to stoichiometric phases, several phases with oxygen deficiency such as monoclinic Nb 12 O 29 10 and Nb 22 O 54 exist. 11 Niobium pentoxide can be applied successfully as photocatalyst, 12−16 photodetector, 15 electrode material for photo-electrochemical water splitting 17 and in dye-sensitized solar cells. 18−21 Recently another class of niobium oxides, Nb 3 O 7 (OH) 22 , has attracted attention as very promising photochemical properties are discovered for this phase, 23−28 and its performance as electrode material in dye-sensitized solar cells exceeds Nb 2 O 5 .…”

Section: ■ Introductionmentioning

confidence: 99%

Heat-Induced Phase Transformation of Three-Dimensional Nb₃O₇(OH) Superstructures: Effect of Atmosphere and Electron Beam

Betzler

Harzer

Ciston

et al. 2016

Crystal Growth & Design

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Nanostructured niobium oxides and hydroxides are potential candidates for photochemical applications due to their excellent optical and electronic properties. In the present work the thermal stability of Nb 3 O 7 (OH) superstructures prepared by a simple hydrothermal approach is investigated at the atomic scale. Transmission electron microscopy and electron energy-loss spectroscopy provide insights into the phase transformation occurring at elevated temperatures and probe the effect of the atmospheric conditions. In the presence of oxygen, H 2 O is released from the crystal at temperatures above 500 °C, and the crystallographic structure changes to H-Nb 2 O 5 . In addition to the high thermal stability of Nb 3 O 7 (OH), the morphology was found to be stable, and first changes in the form of a merging of nanowires are not observed until 850 °C. Under reducing conditions in a transmission electron microscope and during electron beam bombardment, an oxygen-deficient phase is formed at temperatures above 750 °C. This transformation starts with the formation of defects in the crystal lattice at 450 °C and goes along with the formation of pores in the nanowires which accommodate the volume differences of the two crystal phases.

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“…Consequently, the electronic band gap decreases from 3.2 (anatase) to ~1 eV 14 15 . The concept of introduction of defects was also used for other metal oxides to improve their optical properties 24 25 26 27 28 29 30 .…”

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confidence: 99%

Oxygen-Deficient Zirconia (ZrO2−x): A New Material for Solar Light Absorption

Sinhamahapatra

Jeon

Kang

et al. 2016

Sci Rep

271

166

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Here, we present oxygen-deficient black ZrO2−x as a new material for sunlight absorption with a low band gap around ~1.5 eV, via a controlled magnesiothermic reduction in 5% H2/Ar from white ZrO2, a wide bandgap(~5 eV) semiconductor, usually not considered for solar light absorption. It shows for the first time a dramatic increase in solar light absorbance and significant activity for solar light-induced H2 production from methanol-water with excellent stability up to 30 days while white ZrO2 fails. Generation of large amounts of oxygen vacancies or surface defects clearly visualized by the HR-TEM and HR-SEM images is the main reason for the drastic alteration of the optical properties through the formation of new energy states near valence band and conduction band towards Fermi level in black ZrO2−x as indicated by XPS and DFT calculations of black ZrO2−x. Current reduction method using Mg and H2 is mild, but highly efficient to produce solar light-assisted photocatalytically active black ZrO2−x.

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Black nanostructured Nb₂O₅ with improved solar absorption and enhanced photoelectrochemical water splitting

Abstract: Oxygen-deficient black Nb2O5 nanochannels are successfully prepared, and studied as efficient photoanodes for photoelectrochemical water splitting for the first time.

Cited by 88 publications

References 51 publications

Progress in Black Titania: A New Material for Advanced Photocatalysis

Progress in Black Titania: A New Material for Advanced Photocatalysis

Heat-Induced Phase Transformation of Three-Dimensional Nb₃O₇(OH) Superstructures: Effect of Atmosphere and Electron Beam

Oxygen-Deficient Zirconia (ZrO2−x): A New Material for Solar Light Absorption

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Black nanostructured Nb2O5 with improved solar absorption and enhanced photoelectrochemical water splitting

Abstract: Oxygen-deficient black Nb2O5 nanochannels are successfully prepared, and studied as efficient photoanodes for photoelectrochemical water splitting for the first time.

Cited by 88 publications

References 51 publications

Progress in Black Titania: A New Material for Advanced Photocatalysis

Progress in Black Titania: A New Material for Advanced Photocatalysis

Heat-Induced Phase Transformation of Three-Dimensional Nb3O7(OH) Superstructures: Effect of Atmosphere and Electron Beam

Oxygen-Deficient Zirconia (ZrO2−x): A New Material for Solar Light Absorption

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Product

Resources

About

Black nanostructured Nb₂O₅ with improved solar absorption and enhanced photoelectrochemical water splitting

Heat-Induced Phase Transformation of Three-Dimensional Nb₃O₇(OH) Superstructures: Effect of Atmosphere and Electron Beam