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SCIENCE CHINA Materials, Volume 61, Issue 6: 822-830(2018) https://doi.org/10.1007/s40843-018-9222-4

Engineering oxygen vacancy on rutile TiO2 for efficient electron-hole separation and high solar-driven photocatalytic hydrogen evolution

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  • ReceivedJan 2, 2018
  • AcceptedJan 28, 2018
  • PublishedFeb 13, 2018

Abstract

Oxygen vacancy (VO) plays a vital role in semiconductor photocatalysis. Rutile TiO2 nanomaterials with controllable contents of VO (0–2.18%) are fabricated via an in-situ solid-state chemical reduction strategy, with color from white to black. The bandgap of the resultant rutile TiO2 is reduced from 3.0 to 2.56 eV, indicating the enhanced visible light absorption. The resultant rutile TiO2 with optimal contents of VO (~2.07%) exhibits a high solar-driven photocatalytic hydrogen production rate of 734 μmol h−1, which is about four times as high as that of the pristine one (185 μmol h−1). The presence of VO elevates the apparent Fermi level of rutile TiO2 and promotes the efficient electron-hole separation obviously, which favor the escape of photogenerated electrons and prolong the life-time (7.6×103 ns) of photogenerated charge carriers, confirmed by scanning Kelvin probe microscopy, surface photovoltage spectroscopy and transient-state fluorescence. VO-mediated efficient photogenerated electron-hole separation strategy may provide new insight for fabricating other high-performance semiconductor oxide photocatalysts.


Funded by

the Key Program Projects of the National Natural Science Foundation of China(21631004)

the National Natural Science Foundation of China(51672073)


Acknowledgment

This work was supported by the Key Program Projects of the National Natural Science Foundation of China (21631004) and the National Natural Science Foundation of China (51672073).


Interest statement

These authors declared no conflict of interest.


Contributions statement

Xiao F conducted the experiments; Zhou W, Zhao X and Fu H designed and engineered the work; Sun B, Li H, Qiao P and Ren L performed the characterization; Xiao F wrote the paper with support from Zhou W, Zhao X and Fu H. All authors contributed to the general discussion.


Author information

Fang Xiao received her BSc degree in 2015 from Datong University, China. Her research interests are focused on rutile TiO2 nanomaterials for photocatalysis.


Wei Zhou received his PhD degree in 2009 from Jilin University, China. Afterwards, he joined Prof. Honggang Fu’s group at Heilongjiang University, and became a full professor in 2015. His research interests include mesoporous materials, semiconductor nanomaterials for solar energy conversion, photocatalysis, and their photothermal and photoelectrochemical performance.


Xiaojun Zhao received his BSc degree in 1982 from Tianjin Normal University, China. He received his MSc degree in 2001 and PhD degree in 2004 from Nankai University, China. Currently, he is a full professor at Tianjin Normal University. His research interests focus on inorganic-organic hybrid functional material.


Honggang Fu received his BSc degree in 1984 and MSc degree in 1987 from Jilin University, China. Then, he joined Heilongjiang University as an assistant professor. In 1999, he received his PhD degree from Harbin Institute of Technology, China. He became a full professor in 2000. Currently, he is also Cheung Kong Scholar Professor. His interests focus on oxide-based semiconductor nanomaterials for solar energy conversion and photocatalysis, and crystalline carbon-based nanomaterials for energy conversion and storage.


Supplement

Supplementary information

Supplementary data are available in the online version of the paper.


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  • Figure 1

    Typical XRD patterns (a) and Raman spectra (b) of pristine rutile TiO2 (i) and hydrogenated rutile TiO2 under 250°C (ii), 300°C (iii), and 350°C (iv), respectively.

  • Figure 2

    SEM (a), TEM (b), HRTEM images (c) and the corresponding selected-area electron diffraction pattern (d) of the hydrogenated rutile TiO2 (300°C).

  • Figure 3

    The UV/vis absorption spectra (a), the corresponding optical bandgaps (b), N2 adsorption-desorption isotherms (c), XPS of valence band spectra (d), O 1s (e) and Ti 2p (f) of the pristine rutile TiO2 (i) and the hydrogenated rutile TiO2 under 250°C (ii), 300°C (iii), and 350°C (iv), respectively. The inset of (a) is the digital photos of sample i–iv.

  • Figure 4

    (a) Photocatalytic hydrogen evolution rates, (b) cycling tests of photocatalytic hydrogen generation under AM 1.5 irradiation, (c) the single-wavelength photocatalytic hydrogen evolution rates, (d) transient-state fluorescence spectrum, (e) surface photovoltage spectroscopy, (f) scanning Kelvin probe maps of pristine rutile TiO2 (i) and hydrogenated rutile TiO2 under 250°C (ii), 300°C (iii), and 350°C (iv), respectively. The inset of (c) enlarges the AQE of single-wavelength light at 420 and 520 nm.

  • Figure 5

    Photoelectrochemical properties of the pristine rutile TiO2 (sample i) and the hydrogenated rutile TiO2 (sample iii). (a) Linear sweeps voltammograms in the dark and under AM 1.5 irradiation, (b) the chronoamperometry, (c) the Nyquist plots of electrochemical impedance in the dark and under AM 1.5 irradiation, and (d) the Mott-Schottky plots.

  • Figure 6

    Schematic illustration of oxygen vacancy-mediated efficient photogenerated electron-hole separation in hydrogenated rutile TiO2 photocatalytic hydrogen production.

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