Conducting Interface in Oxide Homojunction: Understanding of Superior Properties in Black TiO<sub>2</sub>

Lu, Xiaofeng; Chen, Aiping; Lü, Xujie; Lu, Ping; Dai, Y. M.; Enriquez, Erik; Dowden, P. C.; Xu, Hongwu; Kotula, Paul Gabriel; Azad, Abul K.; Yarotski, D. A.; Prasankumar, R. P.; Taylor, Antoinette J.; Thompson, J. D.; Jia, Q. X.

doi:10.1021/acs.nanolett.6b02454

Cited by 100 publications

(44 citation statements)

References 36 publications

(66 reference statements)

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“…ii) The bandgap narrowing and the increased visible absorption will increase the efficiency of e–h pair generation η e–h . iii) The properly enhanced donor density will increase the efficiency of charge transport η trans . iv) Due to the low‐temperature treatment of HWA, the typical hydrogenation issues such as TiO 2 structure destruction and degradation of FTO will be avoided .…”

Section: Resultsmentioning

confidence: 99%

“…Specifically, the black TiO 2 with disordered shell delivered superior properties to overcome the limitations of the large bandgap (rutile 3.0 eV; anatase 3.2 eV) and lower conductivity of pristine TiO 2 , and improve visible light absorption, charge separation, and electron transport in the photo‐electrochemical (PEC) process. Recently, Lü et al fabricated TiO 2 homojunction films with an oxygen‐deficient amorphous layer on top of a highly crystalline layer to simulate the similar structural and functional configuration of H–TiO 2 nanoparticles, and found that metallic conduction could be realized at the crystalline–amorphous homointerface via electronic interface reconstruction, which could explain the enhanced electron transport of black TiO 2 . Wang et al reported the visible‐light photocatalytic and PEC properties of aluminum‐reduced black TiO 2 .…”

Section: Introductionmentioning

confidence: 99%

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Facile and Efficient Atomic Hydrogenation Enabled Black TiO₂ with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

Wang

Mayrhofer

Hoefer

et al. 2019

Advanced Energy Materials

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Black TiO2 has demonstrated a great potential for a variety of renewable energy technologies. However, its practical application is heavily hindered due to lack of efficient hydrogenation methods and a deeper understanding of hydrogenation mechanisms. Here, a simple and straightforward hot wire annealing (HWA) method is presented to prepare black TiO2 (H–TiO2) nanorods with enhanced photo‐electrochemical (PEC) activity by means of atomic hydrogen [H]. Compared to conventional molecular hydrogen approaches, the HWA shows remarkable effectiveness without any detrimental side effects on the device structure, and simultaneously the photocurrent density of H–TiO2 reaches 2.5 mA cm−2 (at 1.23 V vs reversible hydrogen electrode (RHE)). Due to the controllable and reproducible [H] flux, the HWA can be developed as a standard hydrogenation method for black TiO2. Meanwhile, the relationships between the wire temperatures, structural, optical, and photo‐electrochemical properties are systematically investigated to verify the improved PEC activity. Furthermore, the density functional theory (DFT) study provides a comprehensive insight not only into the highly efficient mechanism of the HWA approach but also its favorably low‐energy‐barrier hydrogenation pathway. The findings will have a profound impact on the broad energy applications of H–TiO2 and contribute to the fundamental understanding of its hydrogenation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Facile and Efficient Atomic Hydrogenation Enabled Black TiO₂ with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

Wang

Mayrhofer

Hoefer

et al. 2019

Advanced Energy Materials

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“…4 nm range of disordered shell. Recently Lü et al prepared TiO 2 homo-junction films consisting of an oxygen-deficient amorphous layer on top of a highly crystalline layer in order to simulate the crystalline core-disordered shell configuration of black TiO 2 nanoparticles [24]. They observed that metallic conduction was achieved at the crystalline − amorphous homo-interface via electronic interface reconstruction, which may be the main reason for the enhanced electron transport of black H-TiO 2 .…”

Section: Resultsmentioning

confidence: 99%

Enhanced Photoelectrochemical Behavior of H-TiO2 Nanorods Hydrogenated by Controlled and Local Rapid Thermal Annealing

et al. 2017

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Recently, colored H-doped TiO2 (H-TiO2) has demonstrated enhanced photoelectrochemical (PEC) performance due to its unique crystalline core—disordered shell nanostructures and consequent enhanced conduction behaviors between the core-shell homo-interfaces. Although various hydrogenation approaches to obtain H-TiO2 have been developed, such as high temperature hydrogen furnace tube annealing, high pressure hydrogen annealing, hydrogen-plasma assisted reaction, aluminum reduction and electrochemical reduction etc., there is still a lack of a hydrogenation approach in a controlled manner where all processing parameters (temperature, time and hydrogen flux) were precisely controlled in order to improve the PEC performance of H-TiO2 and understand the physical insight of enhanced PEC performance. Here, we report for the first time a controlled and local rapid thermal annealing (RTA) approach to prepare hydrogenated core-shell H-TiO2 nanorods grown on F:SnO2 (FTO) substrate in order to address the degradation issue of FTO in the typical TiO2 nanorods/FTO system observed in the conventional non-RTA treated approaches. Without the FTO degradation in the RTA approach, we systematically studied the intrinsic relationship between the annealing temperature, structural, optical, and photoelectrochemical properties in order to understand the role of the disordered shell on the improved photoelectrochemical behavior of H-TiO2 nanorods. Our investigation shows that the improvement of PEC performance could be attributed to (i) band gap narrowing from 3.0 to 2.9 eV; (ii) improved optical absorption in the visible range induced by the three-dimensional (3D) morphology and rough surface of the disordered shell; (iii) increased proper donor density; (iv) enhanced electron–hole separation and injection efficiency due to the formation of disordered shell after hydrogenation. The RTA approach developed here can be used as a suitable hydrogenation process for TiO2 nanorods/FTO system for important applications such as photocatalysis, hydrogen generation from water splitting and solar energy conversion.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-2105-x) contains supplementary material, which is available to authorized users.

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“…The high photoactivity was attributed to the Ti 3+ defects and disordered surface layer which resulted in a narrowed bandgap of 2.2 eV [93]. Recently, black amorphous TiO 2 film was achieved by pulsed laser deposition at 100°C for 10 min under vacuum condition using a commercial TiO 2 target and a KrF excimer laser at a repetition rate of 2 Hz with a laser fluence of 2 J·cm −2 [94]. This black amorphous TiO 2 film was deposited on a predeposited crystalline TiO 2 film to construct a bilayer structure similar to the crystalline/amorphous core/shell structure of black TiO 2 nanoparticles in order to create a simpler model to elucidate the working mechanism of black TiO 2 nanomaterials in many applications [94].…”

Section: Magnesium Reductionmentioning

confidence: 99%

“…This black amorphous TiO 2 film was deposited on a predeposited crystalline TiO 2 film to construct a bilayer structure similar to the crystalline/amorphous core/shell structure of black TiO 2 nanoparticles in order to create a simpler model to elucidate the working mechanism of black TiO 2 nanomaterials in many applications [94]. Metallic conduction was achieved at the crystalline/amorphous homointerface via electronic interface reconstruction [94]. This points to a research direction that may partly eluciate the high performance of black TiO 2 in many applications.…”

Section: Magnesium Reductionmentioning

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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Conducting Interface in Oxide Homojunction: Understanding of Superior Properties in Black TiO₂

Cited by 100 publications

References 36 publications

Facile and Efficient Atomic Hydrogenation Enabled Black TiO₂ with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

Facile and Efficient Atomic Hydrogenation Enabled Black TiO₂ with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

Enhanced Photoelectrochemical Behavior of H-TiO2 Nanorods Hydrogenated by Controlled and Local Rapid Thermal Annealing

Black Titanium Dioxide Nanomaterials in Photocatalysis

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Conducting Interface in Oxide Homojunction: Understanding of Superior Properties in Black TiO2

Cited by 100 publications

References 36 publications

Facile and Efficient Atomic Hydrogenation Enabled Black TiO2 with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

Facile and Efficient Atomic Hydrogenation Enabled Black TiO2 with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

Enhanced Photoelectrochemical Behavior of H-TiO2 Nanorods Hydrogenated by Controlled and Local Rapid Thermal Annealing

Black Titanium Dioxide Nanomaterials in Photocatalysis

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Product

Resources

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Conducting Interface in Oxide Homojunction: Understanding of Superior Properties in Black TiO₂

Facile and Efficient Atomic Hydrogenation Enabled Black TiO₂ with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

Facile and Efficient Atomic Hydrogenation Enabled Black TiO₂ with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway