Electrospun Black Titania Nanofibers: Influence of Hydrogen Plasma-Induced Disorder on the Electronic Structure and Photoelectrochemical Performance

Lepcha, Ashish; Maccato, Chiara; Mettenbörger, Andreas; Andreu, Teresa; Mayrhofer, Leonhard; Walter, Michael; Olthof, Selina; Ruoko, Tero‐Petri; Klein, Axel; Moseler, Michael; Meerholz, Klaus; Morante, J. R.; Barreca, Davide; Mathur, Sanjay

doi:10.1021/acs.jpcc.5b02767

Cited by 74 publications

(53 citation statements)

References 39 publications

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“…A broad and remarkable EPR resonance at low‐field with a “ g ” factor of 2.097 was observed (Figure A), which was attributed to the active oxygen species sitting on the O vac . However, the asymmetric resonance, peculiarly at a higher field, implies the presence of Ti 3+ ( g ≈1.97) or Ti cations with a lower valence state, which is caused by the hydrogenation treatment and is essential to maintain the neutral charge of the deficient NHTA . However, only a small amount of Ti 3+ species was identified by X‐ray photoelectron spectroscopy (XPS), indicating that Ti 3+ mainly exist in the bulk because the Ti 3+ species are not stable on the surface and easily oxidized in air .…”

Section: Resultsmentioning

confidence: 99%

“…[17,35] However,t he asymmetric resonance, peculiarly at ah igher field, implies the presence of Ti 3 + (g % 1.97) or Ti cationswithal ower valence state, which is caused by the hydrogenation treatment andi se ssential to maintain the neutral chargeo ft he deficientN HTA. [36] However, only as mall amount of Ti 3 + species was identified by X-ray photoelectron spectroscopy (XPS), indicating that Ti 3 + mainly exist in the bulk because the Ti 3 + speciesa re not stable on the surfacea nd easily oxidized in air. [34] The above analysis indicates that the Ti 3 + exists in the bulk of NHTAa nd O vac dominate the disordered NHTAsurface.…”

Section: Resultsmentioning

confidence: 99%

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Black N/H‐TiO₂ Nanoplates with a Flower‐Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

Zhang

Zhou

et al. 2016

ChemSusChem

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A facile two‐step strategy was used to prepare black of hydrogenated/nitrogen‐doped TiO2 nanoplates (NHTA) with a flower‐like hierarchical architecture. In situ nitriding and self‐assembly was realized by hydrothermal synthesis using tripolycyanamide as a N source and as a structure‐directing agent. After thorough characterization, it was found that the hydrogenation treatment did not damage the flower‐like architecture but distorted the anatase crystal structure and significantly changed the band structure of NHTA owing to the increased concentration of oxygen vacancies, hydroxyl groups, and Ti3+ cations. Under AM 1.5 illumination, the photocatalytic H2 evolution rate on the black NHTA was approximately 1500 μmol g−1 h−1, which was much better than the N‐doped TiO2 nanoplates (≈690 μmol g−1 h−1). This improvement in the hydrogen evolution rate was attributed to a reduced bandgap, enhanced separation of the photogenerated charge carriers, and an increase in the surface‐active sites.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Black N/H‐TiO₂ Nanoplates with a Flower‐Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

Zhang

Zhou

et al. 2016

ChemSusChem

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“…[ 71 ] Additionally, black anatase TiO 2 nanoparticles, [ 72 ] blue (111)facet exposed TiO 2 nanosheets with Exposed (001), [ 73,74 ] hydrogenate TiO 2 fi lm [ 75 ] and black TiO 2 nanofi ber [ 76 ] were also successfully obtained by H 2 plasma treatment. [ 71 ] Additionally, black anatase TiO 2 nanoparticles, [ 72 ] blue (111)facet exposed TiO 2 nanosheets with Exposed (001), [ 73,74 ] hydrogenate TiO 2 fi lm [ 75 ] and black TiO 2 nanofi ber [ 76 ] were also successfully obtained by H 2 plasma treatment.…”

Section: Wileyonlinelibrarycommentioning

confidence: 96%

“…[ 70 ] First-principle calculations by Lu et al suggested that the H adatoms induced mid-gap states located close to the VBM for the (101) and (100) surfaces of anatase phase TiO 2 . [ 128,129 ] With the increase of oxygen vacancy/Ti 3+ concentration, the Ti 3d band shifts deeper and exhibits multiple bands with a width of 0.5−1.5 eV below the CB minimum, [ 16,27,39,48,62,76,109,130 ] as shown in Figure 28 a−e. [ 126 ] However, Sotoudeh suggested that H-doping in the oxygen defective TiO 2x system could remove the O-vacancy mid-gap and created an empty mid-gap state below the conduction band.…”

Section: Electronic Structure Of Black Titaniamentioning

confidence: 99%

Progress in Black Titania: A New Material for Advanced Photocatalysis

Liu

Zhu

Wang

et al. 2016

Advanced Energy Materials

278

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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“…Hydrogen plasma technology has attracted increasing interest owing to its effectiveness in engineering surface-disordered TiO 2 nanomaterials with a typical crystalline/amorphous core/shell structure [33,39,57,60]. Ti 3+ species and oxygen vacancies were reported to be the primary defects in some cases [57,58], while Ti-H groups and oxygen vacancies were believed to be the dominant defects in other cases [33,39].…”

Section: Black Tio 2 Nanomaterials As Visible Light-active Photocatalmentioning

confidence: 99%

Black Titanium Dioxide Nanomaterials in Photocatalysis

Yan

Xia

2017

International Journal of Photoenergy

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Titanium dioxide (TiO 2 ) nanomaterials are widely considered to be state-of-the-art photocatalysts for environmental protection and energy conversion. However, the low photocatalytic efficiency caused by large bandgap and rapid recombination of photoexcited electrons and holes is a challenging issue that needs to be settled for their practical applications. Structure engineering has been demonstrated to be a highly promising approach to engineer the optical and electronic properties of the existing materials or even endow them with unexpected properties. Surface structure engineering has witnessed the breakthrough in increasing the photocatalytic efficiency of TiO 2 nanomaterials by creating a defect-rich or amorphous surface layer with black color and extension of optical absorption to the whole visible spectrum, along with markedly enhanced photocatalytic activities. In this review, the recent progress in the development of black TiO 2 nanomaterials is reviewed to gain a better understanding of the structure-property relationship with the consideration of preparation methods and to project new insights into the future development of black TiO 2 nanomaterials in photocatalytic applications.

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Electrospun Black Titania Nanofibers: Influence of Hydrogen Plasma-Induced Disorder on the Electronic Structure and Photoelectrochemical Performance

Cited by 74 publications

References 39 publications

Black N/H‐TiO₂ Nanoplates with a Flower‐Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

Black N/H‐TiO₂ Nanoplates with a Flower‐Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

Progress in Black Titania: A New Material for Advanced Photocatalysis

Black Titanium Dioxide Nanomaterials in Photocatalysis

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Electrospun Black Titania Nanofibers: Influence of Hydrogen Plasma-Induced Disorder on the Electronic Structure and Photoelectrochemical Performance

Cited by 74 publications

References 39 publications

Black N/H‐TiO2 Nanoplates with a Flower‐Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

Black N/H‐TiO2 Nanoplates with a Flower‐Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

Progress in Black Titania: A New Material for Advanced Photocatalysis

Black Titanium Dioxide Nanomaterials in Photocatalysis

Contact Info

Product

Resources

About

Black N/H‐TiO₂ Nanoplates with a Flower‐Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

Black N/H‐TiO₂ Nanoplates with a Flower‐Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution