Qingyao Wang

In-Situ-Reduced Synthesis of Ti3+ Self-Doped TiO2/g-C3N4 Heterojunctions with High Photocatalytic Performance under LED Light Irradiation

A simple one-step calcination route was used to prepare Ti(3+) self-doped TiO2/g-C3N4 heterojunctions by mixture of H2Ti3O7 and melamine. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) technologies were used to characterize the structure, crystallinity, morphology, and chemical state of the as-prepared samples. The absorption of the prepared Ti(3+) self-doped TiO2/g-C3N4 heterojunctions shifted to a longer wavelength region in comparison with pristine TiO2 and g-C3N4. The photocatalytic activities of the heterojunctions were studied by degrading methylene blue under a 30 W visible-light-emitting diode irradiation source. The visible-light photocatalytic activities enhanced by the prepared Ti(3+) self-doped TiO2/g-C3N4 heterojunctions were observed and proved to be better than that of pure TiO2 and g-C3N4. The photocatalysis mechanism was investigated and discussed. The intensive separation efficiency of photogenerated electron-hole in the prepared heterojunction was confirmed by photoluminescence (PL) spectra. The removal rate constant reached 0.038 min(-1) for the 22.3 wt % Ti(3+) self-doped TiO2/g-C3N4 heterojunction, which was 26.76 and 7.6 times higher than that of pure TiO2 and g-C3N4, respectively. The established heterojunction between the interfaces of TiO2 nanoparticles and g-C3N4 nanosheets as well as introduced Ti(3+) led to the rapid electron transfer rate and improved photoinduced electron-hole pairs separation efficiency, resulting in the improved photocatalytic performance of the Ti(3+) self-doped TiO2/g-C3N4 heterojunctions.

Fabrication of Ti3+ self-doped TiO2(A) nanoparticle/TiO2(R) nanorod heterojunctions with enhanced visible-light-driven photocatalytic properties

Ti3+ self-doped TiO2(A)/TiO2(R) heterojunctions comprising anatase TiO2 (TiO2(A)) nanoparticles and rutile TiO2 (TiO2(R)) nanorods were synthesized by a simple hydrothermal method using Zn as the reductant. The structure, crystallinity, morphology, and chemical state of the as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The heterojunction architectures and Ti3+ contents could be controlled by adjusting the temperature of the hydrothermal treatment. Zn acts as a reducing agent and Zn2+ stabilizes the oxygen vacancies. Meanwhile, the generated ZnO clusters promote phase transformation from TiO2(A) to TiO2(R). The visible-light photocatalytic degradation of dyes was analyzed. The Ti3+ self-doped TiO2(A)/TiO2(R) heterojunctions exhibited an extended visible light absorption and higher visible-light photocatalytic activity than that of commercial P25 TiO2 in the photodegradation of Methylene blue and Rhodamine B under visible-light irradiation (λ ≥ 400 nm). Ti3+ self-doping expanded the light-response range, and the formed heterojunctions at the interface of TiO2(A) nanoparticles and TiO2(R) nanorods efficiently reduced the recombination of photoinduced electron–hole pairs. This self-doping increased the lifetime of charge carriers by 15 times that of P25 TiO2 and enhanced the corresponding photocatalytic activity of the self-doped heterojunctions.

Ultrasonic-assisted pyrolyzation fabrication of reduced SnO2–x /g-C3N4 heterojunctions: Enhance photoelectrochemical and photocatalytic activity under visible LED light irradiation

Novel SnO2–x/g-C3N4 heterojunction nanocomposites composed of reduced SnO2–x nanoparticles and exfoliated g-C3N4 nanosheets were prepared by a convenient one-step pyrolysis method. The structural, morphological, and optical properties of the as-prepared nanocomposites were characterized in detail, indicating that the aggregation of g-C3N4 nanosheets was prevented by small, well-dispersed SnO2–x nanoparticles. The ultraviolet–visible spectroscopy absorption bands of the nanocomposites were shifted to a longer wavelength region than those exhibited by pure SnO2 or g-C3N4. The charge transfer and recombination processes occurring in the nanocomposites were investigated using linear scan voltammetry and electrochemical impedance spectroscopy. Under 30-W visible-light-emitting diode irradiation, the heterojunction containing 27.4 wt.% SnO2–x exhibited the highest photocurrent density of 0.0468 mA·cm–2, which is 33.43 and 5.64 times larger than that of pure SnO2 and g-C3N4, respectively. The photocatalytic activity of the heterojunction material was investigated by degrading rhodamine B under irradiation from the same light source. Kinetic study revealed a promising degradation rate constant of 0.0226 min−1 for the heterojunction containing 27.4 wt.% SnO2–x, which is 32.28 and 5.79 times higher than that of pure SnO2 and g-C3N4, respectively. The enhanced photoelectrochemical and photocatalytic performances of the nanocomposite may be due to its appropriate SnO2–x content and the compact structure of the junction between the SnO2–x nanoparticles and the g-C3N4 nanosheets, which inhibits the recombination of photogenerated electrons and holes.

Facile synthesis of S-doped reduced TiO 2- x with enhanced visible-light photocatalytic performance

Abstract A different approach to synthesize visible-light-active sulfur (S)-doped reduced titania (S-TiO 2- x ) using thiourea dioxide as both the S source and reductant was developed. The structure, morphology, and optical and electronic properties of the as-prepared S-TiO 2- x samples were examined by multiple techniques, such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, Brunauer-Emmett-Teller and photocurrent measurements, and electrochemical impedance spectroscopy. The photocatalytic activity of S-TiO 2- x was evaluated by photodegradation of organic Rhodamine B under visible-light irradiation. The degradation rate of Rhodamine B by S-TiO 2- x obtained by calcination was about 31, 2.5, and 3.6 times higher than those of pure TiO 2 , pristine TiO 2- x , and S-doped TiO 2 , respectively. In addition, the as-prepared S-TiO 2- x exhibited long-term stable photocatalytic performance in the degradation of Rhodamine B under visible-light illumination. This report reveals a new approach to prepare stable and highly efficient solar light-driven photocatalysts for water purification.

Sb Nanoparticles Anchored on Nitrogen-Doped Amorphous Carbon-Coated Ultrathin CoSx Nanosheets for Excellent Performance in Lithium-Ion Batteries

Compared to single-component materials, hybrid materials with various components display superior electrochemical performance. In this work, two-dimensional CoSx@NC@Sb nanosheets assembled by ultrathin CoSx nanosheets (∼4 nm) and a thin layer of N-doped amorphous carbon (NC) combined with colloidlike Sb nanoparticles are designed and synthesized via a solvothermal route accompanied by a carbonization and Sb deposition procedure. If applied in lithium-ion batteries (LIBs), the hybrids exhibit a specific capacity of 960 mA h g-1 at the 100th cycle at 0.1 A g-1. Moreover, the reversible capacity still maintains at 494 mA h g-1 after 500 cycles at a high rate of 10 A g-1. All enhanced electrochemical properties of the hybrids are attributed to the synergistic effect of the two components and their unique structural features, which can effectively increase the electrical conductivity, shorten the pathway of Li+ diffusion, accommodate the volume variation, and inhibit the aggregation and pulverization of the electrode. We believe that the current work can provide a new strategy for designing and fabricating high-performance anode materials for LIBs.

Z-Scheme NiTiO3/g-C3N4 Heterojunctions with Enhanced Photoelectrochemical and Photocatalytic Performances under Visible LED Light Irradiation

Direct Z-scheme NiTiO3/g-C3N4 heterojunctions were successfully assembled by using simple calcination method and the photoelectrochemical and photocatalytic performance were investigated by light emitting diode (LED). The photoanode composed by the heterojunction with about 50 wt % NiTiO3 content exhibits the best photoelectrochemical activity with photoconversion efficiency up to 0.066%, which is 4.4 and 3.13 times larger than NiTiO3 or g-C3N4. The remarkably enhanced photoelectrochemical and photocatalytic activity of the heterojunction can be due to the efficiently photogenerated electron-hole separation by a Z-scheme mechanism.

In Situ Synthesis of Ti3+ Self-Doped TiO2/N-Doped Carbon Nanocomposites and its Visible Light Photocatalytic Performance

Ti3+ self-doped TiO2 (TiO2−x)/N-doped carbon nanostructure composites were prepared via a facile one-step hydrothermal method to optimize the use of visible light and reduce recombination of photogenerated electrons and holes. The composites were characterized by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The amounts of carbon and nitrogen sources affect the morphology and photocatalytic performance. At low amounts of the sources, the N-doped carbon nanostructure is an amorphous film and is well-combined with TiO2−x nanoparticles through surface carbon–oxygen groups. At high amounts of the sources, N-doped carbon quantum dots (NCQDs) were obtained, and carbon atoms could substitute for oxygen atoms in the TiO2 lattice to form Ti–C structures, which are responsible for the high photocatalytic activity under visible light illumination. Transient photocurrent response and electrochemical impeda...

Transformation from Ag@Ag3PO4 to Ag@Ag2SO4 hybrid at room temperature: preparation and its visible light photocatalytic activity

In the present study, Ag/Ag2SO4 hybrid photocatalysts were obtained via a facile redox–precipitation reaction approach by using Ag@Ag3PO4 nanocomposite as the precursor and KMnO4 as the oxidant. Multiple techniques, such as X-ray diffraction pattern (XRD), transmission electron microscope (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS) and Brunauer–Emmett–Teller (BET), photocurrent and electrochemical impedance spectroscopy (EIS), were applied to investigate the structures, morphologies, optical, and electronic properties of as-prepared samples. The photocatalytic activities were evaluated by photodegradation of organic rhodamine B (RhB) and methyl orange (MO) under visible light irradiation. It was found that pure Ag2SO4 can partially transform into metallic Ag during the photocatalytic degradation of organic pollutants, but the Ag/Ag2SO4 hybrids can maintain its structure stability and show enhanced visible light photocatalytic activity because of the surface plasma resonance effect of the metallic Ag.