Dongbo Xu

Fabrication of a Ag/Bi3TaO7 Plasmonic Photocatalyst with Enhanced Photocatalytic Activity for Degradation of Tetracycline

A novel Ag/Bi3TaO7 plasmonic photocatalyst has been prepared by a simple photoreduction process. The as-prepared Ag/Bi3TaO7 photocatalyst exhibited an enhanced photocatalytic activity for the degradation of tetracycline (TC) compared to that of a bare Bi3TaO7 catalyst. The 1 wt % Ag-loaded Bi3TaO7 sample showed the highest photocatalytic efficiency for TC degradation (85.42%) compared with those of the other samples. The enhanced photocatalytic activity could be ascribed to the synergistic effect of the surface plasmon resonance caused by Ag nanoparticles. Electrochemical impedance spectroscopy demonstrated that the incorporation of silver nanoparticles onto the Bi3TaO7 surface promoted the separation of photogenerated carriers. In addition, an electron spin resonance (ESR) and trapping experiment revealed that the photoinduced active species hydroxyl radical and superoxide radical were the main active species in the photocatalytic process of TC degradation. The photocatalytic reaction mechanism was discussed by active species trapping and ESR analysis.

Ag-Decorated ATaO3 (A = K, Na) Nanocube Plasmonic Photocatalysts with Enhanced Photocatalytic Water-Splitting Properties

Tantalate semiconductor nanocrystals have been at the forefront of the photocatalytic conversion of solar energy to supply hydrogen owing to their favorable and tunable optical and electronic properties as well as advances in their synthesis. However, a narrow band gap is required for response to improve the efficiency of the photocatalysts. Here we propose an efficient enhancement of the H2 generation under simulated sunlight and visible light irradiation by a dispersion of Ag-decorated KTaO3 and NaTaO3 nanocubes. X-ray diffraction and UV-vis diffuse reflectance spectra are used to characterize the products. Transmission electron microscope (TEM) and high-resolution high-angle annular dark-field scanning TEM (HAADF-STEM) images show that the Ag nanoparticles (NPs) are uniformly loaded on the surfaces of KTaO3 and NaTaO3. The photocatalytic water-splitting results over Ag-decorated KTaO3 and NaTaO3 show that the rate for H2 evolution from aqueous CH3OH solutions is up to 185.60 and 3.54 μmol/h·g under simulated sunlight and the rate for H2 evolution is more than 2 times than that of pure NaTaO3 and KTaO3 materials. However, under purely visible light illumination the highest H2 evolution of 25.94 and 0.83 μmol/h·g is observed in the case of Ag-decorated KTaO3 and NaTaO3 nanocubes. To the best of our knowledge, this is the first time that the photocatalytic water-splitting activity of the prepared Ag-decorated KTaO3 and NaTaO3 nanocubes has been reported.

Fabrication of MgFe2O4/MoS2 Heterostructure Nanowires for Photoelectrochemical Catalysis

A novel one-dimensional MgFe2O4/MoS2 heterostructure has been successfully designed and fabricated. The bare MgFe2O4 was obtained as uniform nanowires through electrospinning, and MoS2 thin film appeared on the surface of MgFe2O4 after further chemical vapor deposition. The structure of the MgFe2O4/MoS2 heterostructure was systematic investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and Raman spectra. According to electrochemical impedance spectroscopy (EIS) results, the MgFe2O4/MoS2 heterostructure showed a lower charge-transfer resistance compared with bare MgFe2O4, which indicated that the MoS2 played an important role in the enhancement of electron/hole mobility. MgFe2O4/MoS2 heterostructure can efficiently degrade tetracycline (TC), since the superoxide free-radical can be produced by sample under illumination due to the active species trapping and electron spin resonance (ESR) measurement, and the optimal photoelectrochemical degradation rate of TC can be achieved up to 92% (radiation intensity: 47 mW/cm(2), 2 h). Taking account of its unique semiconductor band gap structure, MgFe2O4/MoS2 can also be used as an photoelectrochemical anode for hydrogen production by water splitting, and the hydrogen production rate of MgFe2O4/MoS2 was 5.8 mmol/h·m(2) (radiation intensity: 47 mW/cm(2)), which is about 1.7 times that of MgFe2O4.

Visible-light-drived high photocatalytic activities of Cu/g-C3N4 photocatalysts for hydrogen production

Cu/g-C3N4 photocatalysts have been synthesized using a facile method. The composition and morphology of the prepared samples were characterized by a variety of analytical methods. The results indicate that the Cu nanoparticles were uniformly loaded onto the surface of g-C3N4. In addition, photocatalytic activity experiments were carried out by investigating H2 production under visible light irradiation. The results reveal that the composites exhibited excellent performance for H2 evolution in the absence of a cocatalyst, which demonstrates that Cu nanoparticles could trap photogenerated electrons and act as a cocatalyst effectively. Thus, it was effective in transferring the interfacial photogenerated charge carriers and efficiently enhanced the photocatalytic activity.

Enhanced photocatalytic degradation activity for tetracycline under visible light irradiation of Ag/Bi3.84W0.16O6.24 nanooctahedrons

In this work, a Ag/Bi3.84W0.16O6.24 nanooctahedron composite photocatalyst was successfully synthesized via a green method at room temperature using silver nitrate (AgNO3) as the silver source. Furthermore, the photocatalytic degradation of TC under visible light was conducted to investigate the effect of Ag. In particular, the Ag/Bi3.84W0.16O6.24 nanooctahedron composite photocatalyst showed the highest photocatalytic activity when the content of Ag was 10% (molar ratio R = 0.1). Electron spin resonance examination confirmed that photoinduced active species (˙OH and O2˙−) were involved in the photocatalytic degradation of TC. The high-efficiency photocatalytic activity of the as-prepared Ag/Bi3.84W0.16O6.24 photocatalyst could be ascribed to the SPR absorption of silver nanoparticles as well as fast generation, separation and transportation of photogenerated carriers.

The synthesis of a novel Ag–NaTaO3 hybrid with plasmonic photocatalytic activity under visible-light

In this work, a visible-light-driven plasmonic Ag–NaTaO3 nanocomposite photocatalyst is prepared by a photochemical reduction process. The structure analyses of the Ag–NaTaO3 reveal that the Ag nanoparticles (5–10 nm) are uniformly loaded on the surface of the cube NaTaO3 nanocrystals. The plasmonic Ag–NaTaO3 nanocomposite showed an enhanced photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation. In particular, the Ag–NaTaO3 nanocomposite shows the highest photocatalytic activity at the nominal atomic ratio of silver to tantalum as 0.6, which is more than 3 times that of pure NaTaO3. The enhancement of the photocatalytic activity was attributed to the effective charge transfer from the plasmon-excited Ag nanoparticles to NaTaO3, which suppresses the charge recombination during the photocatalytic process. This work may provide a new insight into the design and preparation of the advanced NaTaO3-based visible-light photocatalytic materials.

Controllable TiO2 heterostructure with carbon hybrid materials for enhanced photoelectrochemical performance

In TiO2 both advantages (stability and low cost) and disadvantages (large bandgap) coexist, so how to optimize a bare TiO2 electrode is a continuous hot topic for the construction of suitable photoelectrochemical (PEC) devices based on TiO2 for water splitting. This paper reports a facile and simple fabrication of a TiO2/RGO/C3N4 photoelectrode for PEC splitting of water. Its heterostructure configuration has been characterized and confirmed by XRD, Raman spectroscopy, XPS, TEM and STEM. The introduction of both RGO and C3N4 film onto the surface of TiO2 is mainly due to the fact that C3N4 has a strong photoelectric ability to respond to visible light and RGO plays an important role in the fast transfer of photogenerated charges across interfaces. Photocurrent and monochromatic incident photon-to-photocurrent efficiency (IPCE) of the titled heterostructure have been obviously improved, and the IPCE value (0.5 V vs. AgCl/Ag) of TiO2/RGO/C3N4 was estimated to be up to 28% at a wavelength of 400 nm.

Boosting Water Splitting Performance of BiVO4 Photoanode through Selective Surface Decoration of Ag2S

The unsatisfactory of solar absorption and charge separation is the main loss limiting the conversion efficiency in photoelectrochemical water splitting system. Here, Ag2S/BiVO4 heterostructure have been fabricated for the first time to PEC splitting water, achieving efficient solar‐to‐chemical energy conversion. The Ag2S nanoparticles evenly distributing on the surface of BiVO4 not only promotes the charge separation, but also greatly facilitates the surface hole injection. The results show that the optimal Ag2S/BiVO4 heterostructure reach a remarkable photocurrent density of 1.91 mA/cm2 at 1.23 V (vs RHE) under 100 mW/cm2 irradiation, which is approximately 3.2‐fold higher than that of bare BiVO4. The incident photon‐to‐current efficiency (IPCE) of Ag2S/BiVO4 heterostructure have been enhanced up to 23 % in visible region (Vbias=1.23 V, 460 nm). In addition, Ag2S/BiVO4 shows the attracting stability during photoelectrochemical process, since its photocurrent density can keep for 92 % after 2 h. The charges transfer mechanism for Ag2S/BiVO4 heterostructure were also proposed. This work provides a new insight for constructing efficient and stable photoanodes based on BiVO4.

catena-Poly[[[diaqua­(1,10-phenanthroline-κ2N,N′)cobalt(II)]-μ-1H-benzimidazole-5,6-dicarboxyl­ato-κ2N3:O6] sesquihydrate}

In the title compound, {[Co(C9H4N2O4)(C12H8N2)(H2O)2]·1.5H2O}n, the CoII atom is hexacoordinated by one N atom and one O atom from two symmetry-related 1H-benzimidazole-5,6-dicarboxylate ligands, two N atoms from one 1,10-phenanthroline ligand (phen) and two water molecules. The dihedral angle between the 1H-benzimidazole-5,6-dicarboxylate and 1,10-phenanthroline ligands is 74.41 (4)°. The crystal packing is governed by intermolecular O—H⋯O and N—H⋯O hydrogen-bonding interactions. All water (coordinating and lattice) molecules take part in the hydrogen-bonding interactions. In addition, there are π–π stacking interactions between inversion-related phen ligands, the shortest centroid–centroid distance being 3.7536 (16) Å. One of the two lattice water molecules shows half-occupancy.