Microwave-assisted preparation of self-doped TiO<sub>2</sub> nanotube arrays for enhanced photoelectrochemical water splitting

Li, Hui; Chen, Jiangqiong; Xia, Zhengbin; Xing, Junheng

doi:10.1039/c4ta05021e

Cited by 71 publications

(40 citation statements)

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“…In addition, the H-TiO2/SrTiO3 porous microspheres show a much smaller slope in the Mott-Schottky plot compared to that of TiO2/SrTiO3. The charge-carrier densities of TiO2, SrTiO3, TiO2/SrTiO3, and H-TiO2/SrTiO3 calculated from their slopes according to the Mott-Schottky equation [40] are 2.76 × 10 17 , 2.96 × 10 17 , 6.75 × 10 17 , and 7.78 × 10 17 cm −3 , respectively. This reveals the further enhancement of carrier densities upon hydrogenation treatment, which contributes to an improvement in photocatalytic performance.…”

Section: Resultsmentioning

confidence: 99%

Hydrogenated TiO2/SrTiO3 porous microspheres with tunable band structure for solar-light photocatalytic H2 and O2 evolution

et al. 2016

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The production of H2 and O2 from solar-light photocatalytic water splitting has attracted significant research attention as a clean and renewable source of energy. In this study, hydrogenated TiO2/SrTiO3 porous microspheres were prepared as a high-performance photocatalyst. Titanium glycerolate and then strontium complex precursors were first prepared via a two-step solvothermal process, then, after calcination in air and subsequent H2/Ar reduction treatments, hydrogenated TiO2/SrTiO3 porous microspheres with controllable defects and band positions were prepared. Several characterization techniques were used to demonstrate that the catalyst heterostructures, the oxygen-vacancy content, and the unique porous structures synergistically enhanced the visible-light harvesting abilities and photogenerated charge separation, and resulted in improved photocatalytic efficiency for H2 and O2 evolution. As expected, the optimum treatment conditions provided hydrogenated TiO2/SrTiO3 porous microspheres that showed excellent photocatalytic activity with H2 and O2 evolution rates of 239.97 and 103.79 μmol h −1 (50 mg catalyst, under AM 1.5 irradiation), respectively, which were ca. 5.9 and 6.6 times higher, respectively, than those of solid TiO2/SrTiO3 materials. Thus, this type of hydrogenated TiO2/SrTiO3 porous microsphere catalyst shows great potential as a photocatalyst for solar-energy conversion applications.

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Section: Resultsmentioning

confidence: 99%

Hydrogenated TiO2/SrTiO3 porous microspheres with tunable band structure for solar-light photocatalytic H2 and O2 evolution

et al. 2016

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“…The black TiO 2 is considered as a promising candidate for PEC water splitting due to its appropriate band structure. [ 65 ] Based on this effect, improved PEC water-splitting performances were widely seen in black TNT arrays prepared by other reduction methods, [ 56,57,79,83 ] as well reduced black TiO 2 nanowires [ 45,141 ] or nanorods. [ 65 ] The applied bias photon-to-current effi ciency (ABPE) of B-TNT achieved 1.20% at a higher bias of 0.68 V (vs. Pt), impressively higher than that of TNT, 0.25% at 0.49 V (vs. Pt), as shown in Figure 32 e. [ 65 ] The incident-photon-to-current-conversion effi ciency (IPCE) of B-TNT was also largely enhanced in comparison to TNT, along both UV and visible light regions (Figure 32 f).…”

Section: Wileyonlinelibrarycommentioning

confidence: 93%

Progress in Black Titania: A New Material for Advanced Photocatalysis

Liu

Zhu

Wang

et al. 2016

Advanced Energy Materials

288

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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“…An efficient way for promoting the separation rate of electron-hole pairs is the combination of PC and electrochemical technologies via PEC technique [3]. In the PEC process, an electrical bias potential applied between the anode and cathode, which can increase charge separation and restrict their recombination [3,4]. In addition, the formation of heterojunction can efficiently reduce the recombination of carrier, thus, increased the PC and PEC efficiency [4,5].…”

Section: Introductionmentioning

confidence: 99%

Enhanced photocatalytic and photoelectrochemical activities of reduced TiO2−x/BiOCl heterojunctions

Fu¹,

Zeng²,

Ma³

et al. 2016

Journal of Power Sources

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A key issue to design highly efficient photoelectrodes for hydrogen production is how to prohibit the rapid carrier recombination. In order to use the visible light and reduce the recombination of electrons and holes, reduced TiO 2-x /BiOCl heterojunctions are successfully synthesized and the photoelectrodes are assembled in this work. The effects of various Bi/Ti molar ratios on the structural, morphological, optical, photoelectrochemical and photocatalytic activities of the resultant samples are investigated systematically. The TiO 2-x nanoparticles contain Ti 3+ , Ti 2+ , and oxygen vacancies (Ov), while the BiOCl nanosheets exposed {001} facet. Ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) results indicate that the existence of Ti 3+ , Ti 2+ and Ov expand the light-response range. Linear scan voltammetry and electrochemical impedance spectroscopy results indicate that more efficient electron transportation is presented in the heterojunctions with the appropriate Bi/Ti molar ratio. Consequently, the reduced TiO 2-x /BiOCl heterojunction with the most appropriate Bi/Ti molar ratio exhibits a high

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Microwave-assisted preparation of self-doped TiO₂ nanotube arrays for enhanced photoelectrochemical water splitting

Abstract: Bulk abundant Ti3+ self-doped TiO2 nanotube arrays are prepared by a microwave-assisted chemical reduction method with NaBH4.

Cited by 71 publications

References 41 publications

Hydrogenated TiO2/SrTiO3 porous microspheres with tunable band structure for solar-light photocatalytic H2 and O2 evolution

Hydrogenated TiO2/SrTiO3 porous microspheres with tunable band structure for solar-light photocatalytic H2 and O2 evolution

Progress in Black Titania: A New Material for Advanced Photocatalysis

Enhanced photocatalytic and photoelectrochemical activities of reduced TiO2−x/BiOCl heterojunctions

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Microwave-assisted preparation of self-doped TiO2 nanotube arrays for enhanced photoelectrochemical water splitting

Abstract: Bulk abundant Ti3+ self-doped TiO2 nanotube arrays are prepared by a microwave-assisted chemical reduction method with NaBH4.

Cited by 71 publications

References 41 publications

Hydrogenated TiO2/SrTiO3 porous microspheres with tunable band structure for solar-light photocatalytic H2 and O2 evolution

Hydrogenated TiO2/SrTiO3 porous microspheres with tunable band structure for solar-light photocatalytic H2 and O2 evolution

Progress in Black Titania: A New Material for Advanced Photocatalysis

Enhanced photocatalytic and photoelectrochemical activities of reduced TiO2−x/BiOCl heterojunctions

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Microwave-assisted preparation of self-doped TiO₂ nanotube arrays for enhanced photoelectrochemical water splitting