6 research outputs found

    New Type Photocatalyst PbBiO<sub>2</sub>Cl: Materials Design and Experimental Validation

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    A new kind of nanostructured photocatalyst, PbBiO<sub>2</sub>Cl is synthesized by a simple hydrothermal method. The proposed formation mechanism of PbBiO<sub>2</sub>Cl is carried out by analyzing the XRD patterns and SEM images of the products prepared under different conditions. The PbBiO<sub>2</sub>Cl nanostructure behaves as a truncated bipyramid, exposed with {002} and {103} facets. Moreover, theoretical calculation and absorption spectrum indicate the PbBiO<sub>2</sub>Cl shows strong absorption in the visible region with a band gap of 2.53 eV. The obtained PbBiO<sub>2</sub>Cl nanostructures exhibit significantly enhanced photocatalytic activity on degradation of methyl orange (MO) and 4-chlorophonel (4-CP). This work may offer a paradigm on designing and synthesizing visible photocatalyst exposed with reactive facets, which can be applied in many fields

    Modification of Pd and Mn on the Surface of TiO<sub>2</sub> with Enhanced Photocatalytic Activity for Photoreduction of CO<sub>2</sub> into CH<sub>4</sub>

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    The novel Pd- and Mn-comodified TiO<sub>2</sub> photocatalyst (TiO<sub>2</sub>–Pd–Mn) was prepared via a simple sol–gel method. The introduced Pd and Mn existed as the −O–Pd–O– and −O–Mn–O– species on the surface of the photocatalyst. The band structure and density of states are studied by theoretical calculations, which is demonstrated by the experimental results. The modification with Pd and Mn ions results in the strong visible response and efficient separation of photogenerated carriers. Thus, the TiO<sub>2</sub>–Pd–Mn exhibit improved photocatalytic activity compared with pure TiO<sub>2</sub>, TiO<sub>2</sub>–Pd, and TiO<sub>2</sub>–Mn for photoreduction of CO<sub>2</sub> and H<sub>2</sub>O into CH<sub>4</sub>. It is an effective method on developing the highly active TiO<sub>2</sub>-based materials by modification with double elements on the surface

    Structure of Nitrogen and Zirconium Co-Doped Titania with Enhanced Visible-Light Photocatalytic Activity

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    Nitrogen and zirconium co-doped TiO<sub>2</sub> (TiO<sub>2</sub>–N–<i>x</i>%Zr) photocatalysts were synthesized via a sol–gel method. The existing states of the dopants (N and Zr) and their corresponding band structures were investigated via XRD, Raman, BET, XPS, TEM, FT-IR, UV–vis DRS, and PL techniques. It was found that N existed only as a surface species (NO<sub><i>x</i></sub>) and Zr<sup>4+</sup> was doped in a substitutional mode; the doping of Zr<sup>4+</sup> ions and modification of N extended the absorption into the visible region and inhibited the recombination of electrons and holes. Moreover, the excess Zr<sup>4+</sup> ions existed as the ZrTiO<sub>4</sub> phase when the content of Zr was sufficiently high, which could also contribute to the separation of the charge carriers. Therefore, the TiO<sub>2</sub>–N–<i>x</i>%Zr samples show enhanced visible-light photocatalytic activity compared with single-doped TiO<sub>2</sub>. These results offer a paradigm for the design and fabrication of optoelectronic functional materials such as solar cells and photocatalysts

    Doping Behavior of Zr<sup>4+</sup> Ions in Zr<sup>4+</sup>-Doped TiO<sub>2</sub> Nanoparticles

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    TiO<sub>2</sub> nanoparticles doped with different concentrations of Zr<sup>4+</sup> ions were prepared by the sol–gel method and annealed at different temperatures. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high resolution transmission electron microscopy (HRTEM) techniques were used to investigate the existing states and doping mechanism of dopants as well as the phase transition of the Zr<sup>4+</sup>-doped TiO<sub>2</sub> samples. It was revealed that the doping behavior of introduced Zr<sup>4+</sup> ions was closely related to the doping concentration. The Zr<sup>4+</sup> ions would replace the lattice Ti<sup>4+</sup> ions directly in substitutional mode at a certain annealing temperature. Moreover, if the concentration of doped Zr<sup>4+</sup> ions is high enough, excess Zr<sup>4+</sup> ions would form ZrTiO<sub>4</sub> on the surface of TiO<sub>2</sub>. In addition, the phase transition temperature from anatase to rutile increases significantly after doping Zr<sup>4+</sup> ions, due to their larger electropositivity and radius than those of Ti<sup>4+</sup> ions. Our results may afford a better understanding on the doping mechanism and aid in the preparation of Zr-doped TiO<sub>2</sub> with high photoelectric performance

    Adjustment and Matching of Energy Band of TiO<sub>2</sub>‑Based Photocatalysts by Metal Ions (Pd, Cu, Mn) for Photoreduction of CO<sub>2</sub> into CH<sub>4</sub>

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    A series of the metal ions (Pd, Cu, and Mn) modified TiO<sub>2</sub> photocatalysts are synthesized via simple sol–gel method. Characterized by X-ray diffraction, Raman, UV–vis absorption spectra, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, time-resolved photoluminescence (PL) decay curves, and PL, it was revealed these introduced metal ions existed as O–Me–O species (Me: Pd, Cu, and Mn) on the surface of TiO<sub>2</sub>. The corresponding theory calculation is used to investigate the electronic density of states and band structure of the metal ions (Pd, Cu, and Mn) modified TiO<sub>2</sub>. The modified TiO<sub>2</sub> photocatalysts exhibit an improved photocatalytic performance on reduction of CO<sub>2</sub> and H<sub>2</sub>O into methane (CH<sub>4</sub>), attributed to the contribution of surface species by enhancing the visible absorption efficiently, separating charge carriers, and matching of the redox potential on the photoreduction of CO<sub>2</sub> into CH<sub>4</sub>. This article could provide a wider understanding about the adjustment and matching of the energy level for the synthesis and design of functional materials with excellent photocatalytic performance

    The Design of TiO<sub>2</sub> Nanostructures (Nanoparticle, Nanotube, and Nanosheet) and Their Photocatalytic Activity

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    Density functional theory (DFT) calculation is carried out to access the band structure and density of states (DOS) based on the models of TiO<sub>2</sub> nanoparticle, nanotube, and nanosheet, predicting the order of the photocatalytic activity for three different nanostructures. Sol–gel method and hydrothermal method are used to achieve desired morphologies: nanoparticles, nanotubes, and nanosheets (fragmentized nanotubes). The photocatalytic activity ranks in the order of nanosheets > nanotubes > nanoparticles, which is consistent with theoretical prediction. It was revealed that the enlargement of band gap is caused by the quantum confinement effect; the prolonged lifetime of photogenerated electrons and increased specific surface areas are dependent on the morphology of the nanostructure. All these factors contribute to the improvement of the photocatalytic activity for nanostructures. Our results can guide the design and selection of low-dimensional nanomaterials with desired morphology and improved photoelectric functional properties, which can be used in many fields, such as solar cells, photocatalysis, and photosynthesis
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