Xiaohong Yin

Photocatalytic reduction of CO2 in methanol to methyl formate over CuO-TiO2 composite catalysts.

Photocatalytic reduction of CO(2) on CuO-TiO(2) composite catalysts in the presence of methanol to prepare methyl formate had been investigated. Methanol was used as sacrificial reagent to react with the photo-generated holes in the valence band, and CO(2) was reduced by the electrons in the conduction band. CuO-TiO(2) was optimized for CuO loading, preparation method and calcination temperature. The catalyst of 1.0CuO-TiO(2), calcined at 450°C and CTAB as a dispersant showed the highest overall activity. The heterojunction between CuO and TiO(2) demonstrated with HRTEM played an important role in enhancing the photocatalytic activity.

Photocatalytic reduction of carbon dioxide over ZnFe2O4/TiO2 nanobelts heterostructure in cyclohexanol.

A series of ZnFe2O4/TiO2 heterostructure photocatalysts with different mass percentages of ZnFe2O4 were synthesized through hydrothermal deposition method. The photocatalysts were characterized by SEM, TEM, XRD, XPS, and UV-vis DRS techniques. It is observed that ZnFe2O4 nanoparticles grew on the TiO2 nanobelts, and the obtained nanocomposites have ordered nanobelt structure with a high crystallinity. The photocatalytic activities of the nanocomposites were tested by photocatalytic reduction of CO2 in cyclohexanol under UV light (main wave length at 360nm) irradiation. The experimental results showed that the main products were cyclohexanone (CH) and cyclohexyl formate (CF). Compared with pure TiO2 and ZnFe2O4 samples, the obtained ZnFe2O4/TiO2 nanocomposites showed much higher photocatalytic performance. The loading amount of ZnFe2O4 was an important factor affecting the generation yields of the products. When the loading amount of ZnFe2O4 reached 9.78%, the ZnFe2O4/TiO2 heterostructure sample displayed the highest activity. The Z-scheme system reaction mechanism was proposed to explain the photocatalytic activity of the ZnFe2O4/TiO2 heterostructure sample.

Synthesis of hexagonal and cubic ZnIn2S4 nanosheets for the photocatalytic reduction of CO2 with methanol

ZnIn2S4 nanosheets with hexagonal and cubic structures have been prepared through a liquid ultrasonic exfoliation method and another strategy involving a lamellar hybrid, respectively. The structure, morphology, and composition properties of the as-prepared samples were characterized using X-ray powder diffraction, UV-vis spectrophotometry, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The photocatalytic activities of the as-prepared ZnIn2S4 samples were evaluated by methyl formate formation from CO2 photoreduction in methanol as a solution of absorbing CO2 and reducing agent, and the activity over hexagonal ZnIn2S4 was better than over cubic ZnIn2S4. In addition, both hexagonal and cubic ZnIn2S4 nanosheets displayed much higher reactivity than ZnIn2S4 microspheres prepared by the hydrothermal method. The electronic structures of the two phases of ZnIn2S4 were investigated in the light of density functional theory.

Selective photocatalytic reduction of CO2 to methanol in CuO-loaded NaTaO3 nanocubes in isopropanol

Summary A series of NaTaO3 photocatalysts were prepared with Ta2O5 and NaOH via a hydrothermal method. CuO was loaded onto the surface of NaTaO3 as a cocatalyst by successive impregnation and calcination. The obtained photocatalysts were characterized by XRD, SEM, UV–vis, EDS and XPS and used to photocatalytically reduce CO2 in isopropanol. This worked to both absorb CO2 and as a sacrificial reagent to harvest CO2 and donate electrons. Methanol and acetone were generated as the reduction product of CO2 and the oxidation product of isopropanol, respectively. NaTaO3 nanocubes loaded with 2 wt % CuO and synthesized in 2 mol/L NaOH solution showed the best activity. The methanol and acetone yields were 137.48 μmol/(g·h) and 335.93 μmol/(g·h), respectively, after 6 h of irradiation. Such high activity could be attributed to the good crystallinity, morphology and proper amount of CuO loading, which functioned as reductive sites for selective formation of methanol. The reaction mechanism was also proposed and explained by band theory.

Preparation of TiO2/Polyacrylic Acid and Application in Photocatalytic Degradation of Methyl Orange

TiO2 (P25) fine particles were loaded in a polyacrylic acid (PAA), which possessed a unique absorption characteristic and was synthesised by aqueous solution polymerization. The TiO2/PAA composite was taken as a photocatalyst to degrade methyl orange (MO), the degradability resistance and reproducibility of the photocatalyst were investigated experimentally. The results showed that the TiO2/PAA photocatalyst had a good activity and stability in degradability of organic compound.

ZnFe 2 O 4 deposited on BiOCl with exposed (001) and (010) facets for photocatalytic reduction of CO 2 in cyclohexanol

ZnFe2O4-BiOCl composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were then used as catalysts for the photocatalytic reduction of CO2 in cyclohexanol under ultraviolet irradiation to give cyclohexanone (CH) and cyclohexyl formate (CF). The photocatalytic CO2 reduction activities over the hydrothermally prepared ZnFe2O4-BiOCl composites were higher than those over the directly-precipitated composites. This is because compared to the directprecipitation sample, the ZnFe2O4 nanoparticles in the hydrothermal sample were smaller and more uniformly distributed on the surface of BiOCl and so more heterojunctions were formed. Higher CF and CH yields were obtained for the pure BiOCl and BiOCl composite samples with more exposed (001) facets than for the samples with more exposed (010) facets. This is due to the higher density of oxygen atoms in the exposed (001) facets, which creates more oxygen vacancies, and thereby improves the separation efficiency of the electron-hole pairs. More importantly, irradiation of the (001) facets with ultraviolet light produces photo-generated electrons which is helpful for the reduction of CO2 to ∙CO2-. The mechanism for the photocatalytic reduction of CO2 in cyclohexanol over ZnFe2O4-BiOCl composites with exposed (001) facets involves electron transfer and carbon radical formation.

Block Copolymer as a Surface Modifier to Monodisperse Patchy Silica Nanoparticles for Superhydrophobic Surfaces

Monodisperse patchy silica nanoparticles (PSNPs) less than 100 nm are prepared based on the seed-regrowth method using a poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-PEO-type block copolymer as a surface modifier. Well-defined patches are controllably synthesized through area-selective deposition of silica onto the surface of seeds. After colloidal PSNPs are further modified with trimethylchlorosilane, the advancing and receding contact angles of water for PSNPs are 168 ± 2° and 167 ± 2°, respectively. The superhydrophobic and transparent coatings on the various types of substrates are obtained by a simple drop-casting procedure. Additionally, almost the same superhydrophobicity can be achieved by using colloidal PSNPs via redispersing the powder of superhydrophobic PSNPs in ethanol.

Nanoheterostructures of potassium tantalate and nickel oxide for photocatalytic reduction of carbon dioxide to methanol in isopropanol

Cubic perovskite-type and octahedral pyrochlore-type powders of potassium tantalate (KTaO3) were selectively synthesized by a single-step hydrothermal method under different concentrations of potassium hydroxide (KOH). The obtained photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectra (EDS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and UV-vis absorption spectra (UV-vis). The photocatalytic activities of the KTaO3 samples for reduction of carbon dioxide to methanol under UV light irradiation were investigated. The results showed that the KOH concentration played a significant role in determining the phases of the resultant products. Compared with the cubic crystalline structure, the octahedral crystalline structure exhibited the higher photocatalytic activity. In addition, the photocatalytic activities of KTaO3 were obviously increased when a small amount of nickel oxide (NiO) was loaded as a co-catalyst. The highest rate of methanol formation was 1815 μmol/g/h when 2 wt% of NiO was loaded.

Block copolymer-assisted synthesis of monodisperse colloidal patchy nanoparticles

Amphiphilic block copolymers are able to assemble into spherical micelles in an aqueous solution. Spherical micelles are expected to adsorb on the surface of colloidal nanoparticles (NPs) through hydrogen-bonding interaction. Hence, it should be possible to guide the area-selective deposition of precursors onto the exposed surface of colloidal seeds, where no micelles are adsorbed. Using colloidal silica and polydopamine nanospheres as seeds, block copolymer F127 and P123 are used as surface modifiers to guide the controlled solution-phase deposition of precursors on a selectively exposed surface of seed NPs, leading to the formation of patchy NPs. Effects of the addition amount of tetraethoxysilane (TEOS), types of block copolymers, and the volume fraction of miscible organic solvents on the size and morphology of patchy silica NPs are investigated systematically through electron microscopic imaging. Block copolymer micelles adsorption model for the formation of colloidal patchy NPs is first proposed. Our study suggests that the shape and size of patchy silica NPs are determined by the amount of TEOS and dielectric constant of solution.

Fabrication of nano copper oxide evenly patched on cubic sodium tantalate for oriented photocatalytic reduction of carbon dioxide

A synthetic process was exploited to fabricate patchy CuO evenly planted on cubic NaTaO3 for photocatalytically reducing CO2 in isopropanol. The nano patches of CuO with about 15 nm in size were uniformly distributed on the surface of NaTaO3 via a phase-transfer protocol and solvothermal synthesis. The crystal phase, morphology, composition, optical absorption and charge separation of as-prepared CuO-NaTaO3 were characterized by XRD, SEM, TEM, EDX, XPS, UV-Vis and PL. The results of photocatalytic reduction of CO2 confirmed that the CuO patched NaTaO3 possessed better ability to separate charge carriers and selectively reduce CO2 to methanol than CuO directly loaded NaTaO3 using the traditional liquid phase reduction procedure after comparing the methanol yields. Furthermore, 5 wt% CuO patched NaTaO3 led to the highest methanol yield of 1302.22 μmol g-1 h-1. A redox mechanism was proposed and illustrated in a schematic diagram.