Changlin Yu

Sonochemical fabrication of novel square-shaped F doped TiO2 nanocrystals with enhanced performance in photocatalytic degradation of phenol

A sonochemical method was developed for the fabrication of novel square-shaped TiO(2) nanocrystals doped with different F contents. The prepared samples were characterized by some physicochemical characterizations like X-ray diffraction (XRD), N(2) physical adsorption, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy and UV-vis diffuse reflectance spectra (DRS). Phenol, as a hazardous chemical in water, was chosen to evaluate the photocatalytic degradation performance of the prepared TiO(2) nanocrystals under UV light irradiation. Results show that under ultrasonic irradiation conditions, F can easily be doped into TiO(2) and the obtained pure and F doped TiO(2) nanocrystals show mesoporous structures which were formed by the role of ultrasound-induced aggregation. Moreover, the doping of optimal content of F (1.3 mol%) gives 5.3 times increase in the phenol degradation rate. The high photocatalytic degradation activity of the doped TiO(2) could be attributed to the factor that F doping increases the surface hydroxyl groups over TiO(2) and effectively reduces the recombination rate of photo-generated electron/hole pairs, then producing more OH radicals to decompose the phenol molecules.

Design and fabrication of heterojunction photocatalysts for energy conversion and pollutant degradation

Photocatalysis has attracted much attention for its promise in converting solar energy to chemical energy and in degrading various pollutants. Many recent investigations have demonstrated photocatalysts with well-defined junctions between two semiconductors with matched electronic band structures. Such structures effectively facilitate charge transfer and suppress recombination of photogenerated electrons and holes, leading to extremely high activity and stability. In this review, we focus on the influence of the heterojunction on the performance of semiconductor photocatalysts, including TiO2-based, ZnO-based, and Ag-based semiconductor photocatalysts. We also investigate fabrication methods for heterojunctions and attempt to understand the mechanisms behind photocatalysis. Finally, we propose challenges to design and clarify the mechanism for enhancing the effect of the heterojunction on photocatalyst performance.

Preparation, characterization and photocatalytic performance of Mo-doped ZnO photocatalysts

A series of Mo-doped ZnO photocatalysts with different Mo-dopant concentrations have been prepared by a grinding-calcination method. The structure of these photocatalysts was characterized by a variety of methods, including N2 physical adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, photoluminescence (PL) emission spectroscopy, and UV-vis diffuse reflectance spectroscopy (DRS). It was found that Mo6+ could enter into the crystal lattice of ZnO due to the radius of Mo6+ (0.065 nm) being smaller than that of Zn2+ (0.083 nm). XRD results indicated that Mo6+ suppressed the growth of ZnO crystals. The FT-IR spectroscopy results showed that the ZnO with 2 wt.% Mo-doping has a higher level of surface hydroxyl groups than pure ZnO. PL spectroscopy indicated that ZnO with 2 wt.% Mo-doping also exhibited the largest reduction in the intensity of the emission peak at 390 nm caused by the recombination of photogenerated hole-electron pairs. The activities of the Mo-doped ZnO photocatalysts were investigated in the photocatalytic degradation of acid orange II under UV light (λ = 365 nm) irradiation. It was found that ZnO with 2 wt.% Mo-doping showed much higher photocatalytic activity and stability than pure ZnO. The high photocatalytic performance of the Mo-doped ZnO can be attributed to a great improvement in the surface properties of ZnO, higher crystallinity and lower recombination rate of photogenerated hole-electron (e−/h+) pairs. Moreover, the undoped Mo species may exist in the form of MoO3 and form MoO3/ZnO heterojunctions which further favors the separation of e−/h+ pairs.

Growth of single-crystalline SnO2 nanocubes via a hydrothermal route

Single-crystalline nanocubes of SnO2 have been fabricated by oxidation of SnF2 with (NH4)2S2O8 under proper hydrothermal conditions.

A sonochemical route to fabricate the novel porous F, Ce-codoped TiO2 photocatalyst with efficient photocatalytic performance

A novel F, Ce-codoped TiO2 photocatalyst with mesoporous structure was successfully fabricated by ultrasound irradiation. The obtained catalysts were characterized by X-ray diffraction, Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, photoluminescence spectroscopy, and N2 adsorption. The photocatalytic activity of the samples was evaluated by degradation of acid orange II under UV light irradiation. Results showed that F and Ce can be successfully doped into TiO2 under ultrasonic irradiation conditions. All the single F or Ce-doped TiO2 and F, Ce-codoped TiO2 have shown good mesoporous structures, and this can be contributed to the ultrasound-induced aggregation effect. The F, Ce-codoped TiO2 photocatalyst exhibits much higher photocatalytic activity than that of pure, single F or Ce-doped TiO2, which could be attributed to that F, Ce-codoping increases its surface hydroxyl groups and effectively reduces the photo-generated electron/hole pair recombination rate.

Novel hybrid Sr-doped TiO2/magnetic Ni0.6Zn0.4Fe2O4 for enhanced separation and photodegradation of organics under visible light

Titanium dioxide (TiO2) has been intensively used as a photocatalyst for the degradation of organic pollutants in water, but is typically obstacle by a low efficiency, costly separation, limited visible light response, and poor recyclability. Herein, we provided a reliable method to simultaneously tackle these four obstacles by developing an integrated and multifunctional hybrid photocatalyst/magnetic material, i.e., Sr–TiO2/Ni0.6Zn0.4Fe2O4. This novel hybrid not only demonstrated a high efficiency (90–100%) and a good cycling performance (90% maintenance) for photodegradation of bisphenol A (BPA) under both UV and visible light irradiation, but it can also efficiently work at a wide pH range (4–10) and can be easily separated from water for reuse only by introducing an external magnetic field. The materials structure-to-activity correlation has also been investigated. It was found that doping Sr2+ and a coupling magnetic material with TiO2 could extend the visible light response and create active defects in TiO2, which were responsible for the nearly three times higher activity than that of commercial TiO2(P25) under visible light. On the other hand, doping excessive Sr2+ lowered the surface area, enlarged the crystalline size and caused particle aggregation; thus, leading to a decrease in photocatalytic activity of the hybrid. These further modifications in the hybrid materials can provide a competitive alternative to control the organic pollutants in waste water.

One-pot synthesis of Au144(SCH2Ph)60 nanoclusters and their catalytic application

Here, we report the one-pot synthesis of atomically precise gold nanoclusters – Au144(SCH2Ph)60 with moderate efficiency (ca. 20% yield based on HAuCl4). The Au144(SCH2Ph)60 nanoclusters are obtained from the polydispersed Aun(SG)m nanoclusters in the presence of excess H–SCH2Ph ligands via a combination of “ligand-exchange” and “size-focusing” processes. The as-obtained Au144(SCH2Ph)60 nanoclusters are well determined by UV-vis spectroscopy and electrospray ionization (ESI) mass spectrometry, and in conjunction with matrix-assisted laser desorption ionization (MALDI) mass spectrometry and thermal gravimetric analysis (TGA). The purity of the Au144(SCH2Ph)60 nanoclusters is further characterized by size exclusion chromatography (SEC) and elemental analysis. The powder X-ray diffraction (PXRD) analysis implies that the Au144(SCH2Ph)60 nanoclusters do not adopt the face-centered cubic (fcc) structure, as the diffraction angle (2θ = 50.5°) is only observed in the Au144(SCH2Ph)60 nanoclusters. Further, the Au144(SCH2Ph)60/TiO2 catalyst exhibits excellent catalytic performance (92% conversion of methyl phenyl sulfide with 99% selectivity for sulfoxide) in the selective sulfoxidation; size-dependence of the gold nanocluster catalyst is observed in the catalytic reactions: Au144(SCH2Ph)60 > Au99(SPh)42 > Au38(SCH2CH2Ph)24 > Au25(SCH2CH2Ph)18.

Ruthenium–nickel–nickel hydroxide nanoparticles for room temperature catalytic hydrogenation

Improving the utilization of metals in heterogeneous catalysts with excellent catalytic performance, high selectivity and good stability represents a major challenge. Herein a new strategy is disclosed by enabling a nanoscale synergy between a transition metal and a noble metal. A novel Ru/Ni/Ni(OH)2/C catalyst, which is a hybrid of Ru nanoclusters anchored on Ni/Ni(OH)2 nanoparticles (NPs), was designed, prepared and characterized. The Ru/Ni/Ni(OH)2/C catalyst exhibited a remarkable catalytic activity for naphthalene hydrogenation in comparison with existing Ru/C, Ni/Ni(OH)2/C and Ru–Ni alloy/C catalysts. This is mainly attributed to the interfacial Ru, Ni and Ni(OH)2 sites of Ru/Ni/Ni(OH)2/C, where hydrogen is adsorbed and activated on Ru while Ni transfers the activated hydrogen species (as a “bridge”) to the activated naphthalene on Ni(OH)2 sites, producing decalin through a highly effective pathway.

In situ synthesis, crystal structures, and luminescence of two new tetrazole complexes

The synthesis, crystal structures, and luminescent properties of two new complexes containing tetrazolyl ligands are described. Refluxing a mixture of fipronil (fipronil = (±)-5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-carbonitrile), sodium azide, and CuCl2 in ethanol and water gives complex 1, [M(L)2](H2O)2] ⋅ 2H2O (HL = (±)-5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-tetrazole, M = Cu). Hydrothermal reaction of fipronil, sodium azide, and Cd(ClO4)2 in the presence of water and ethanol (Demko–Sharpless tetrazole synthesis) yields 2, [M(L)2](H2O)2] ⋅ 2H2O (M = Cd). The metals in both complexes are six coordinate from two water molecules, two nitrogens from different tetrazolyl groups, and two nitrogens from pyrazolyl groups. Photoluminescence studies reveal that 2 exhibits strong blue fluorescent emission at λ max = 451 nm in solid state at room temperature.

Nitrogen-doped graphene/tungsten oxide microspheres as an electro-catalyst support for formic acid electro-oxidation

Tungsten trioxide (WO3) spheres decorated with nitrogen-doped graphene (NRGO–WO3) were synthesized by applying the spray-drying procedure and characterized for their ability to serve as an electro-catalyst support for formic acid electro-oxidation. A possible mechanism for the formation of NRGO–WO3 was proposed based on the results of tunneling electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Pd nanoparticles with dimensions of 4.8 nm were loaded onto the surface of NRGO–WO3 using a conventional sodium borohydride reduction method. The electrocatalytic performances of Pd/NRGO–WO3 for formic acid oxidation were investigated by using cyclic voltammetry and chronoamperometry. Due to the decrease in the resistance to electron transfer resulting from the modification of N-doped graphene, which produced an excellent electrical conductor, as well as due to the hydrogen spill-over effect, which accelerated the dehydrogenation of formic acid on Pd active sites, a great enhancement of the electrochemical performances was achieved.