Microwave Hydrothermally Synthesized Metal-Organic Framework-5 Derived C-doped ZnO with Enhanced Photocatalytic Degradation of Rhodamine B.

C-doped ZnO particles have been successfully prepared by the calcination using microwave hydrothermally prepared metal-organic framework-5 (MOF-5) as the precursor. MOF-5 was turned into C-doped ZnO through calcination at 500 °C, and its cubic shape was well-maintained. X-ray photoelectron spectroscopic studies confirmed the C-doping in the ZnO. The as-prepared C-doped ZnO demonstrated a Rhodamine B (RhB) degradation efficiency of 98% in 2 h under an solar-simulated light irradiation, much higher than that of C-doped ZnO derived from MOF-5 synthesized by the ordinary hydrothermal method. The trapping experiment revealed that the crucial factors in the RhB removal were photogenerated h+ and •O2-.

Advances in Template Prepared Nano-Oxides and their Applications: Polluted Water Treatment, Energy, Sensing and Biomedical Drug Delivery.

The nano-oxide materials with special structures prepared by template methods have a good dispersion, regular structures and high specific surface areas. Therefore, in some areas, improved properties are observed than conventional bulk oxide materials. For example, in the treatment of dye wastewater, the treatment efficiency of adsorbents and catalytic materials prepared by template method was about 30 % or even higher than that of conventional samples. This review mainly focuses on the progress of inorganic, organic and biological templates in the preparation of micro- and nano- oxide materials with special morphologies, and the roles of the prepared materials as adsorbents and photocatalysts in dye wastewater treatment. The characteristics and advantages of inorganic, organic and biological template are also summarized. In addition, the applications of template method prepared oxides in the field of sensors, drug carrier, energy materials and other fields are briefly discussed with detailed examples.

Research Progress in the Field of Adsorption and Catalytic Degradation of Sewage by Hydrotalcite-Derived Materials.

With the rapid development of industry and agriculture and the greatly improved living conditions, the resultant gradually deteriorated environments threaten the human beings. Refractory or even toxic pollutants, which are from different industries such as printing and dyeing, pesticides, chemicals, petrochemicals, plastics and rubber, seriously threat the ecosystems and human health. Having the advantages of flexible composition, unique structure, high stability, memory effect, easy preparation and low cost, hydrotalcite compounds have a great potential in sewage degradation and environmental protection. This study focuses on the adsorption and catalytic properties (such as photocatalysis, electrocatalysis and photoelectrocatalysis) of hydrotalcite-derived materials for treating organic, inorganic and heavy metal ion sewage. The types of adsorption and catalysis, and the effects of various influencing factors on the degradation efficiency were discussed as well.

One-pot microwave-hydrothermally synthesized carbon nanotube-cerium oxide nanocomposites for enhanced visible photodegradation of acid orange 7.

Carbon nanotubes (CNT)-cerium oxide (CeO2) nanocomposites were fabricated successfully by one-pot microwave hydrothermal growth of regular CeO2 nanoparticles with a size of 8 nm on hydroxyl-functionalized multi-walled CNTs. These nanocomposite photocatalysts demonstrated an acid orange (AO7) photocatalytic degradation efficiency of above 90% under solar-simulated light irradiation for 3 h, which was much higher than that of the pure CeO2 nanoparticles. The enhanced photocatalytic activity was observed to mainly originate from the ˙O2- and hole traps, while the hydroxyl radical ˙OH played a secondary role.

3D Porous Amorphous γ-CrOOH on Ni Foam as Bifunctional Electrocatalyst for Overall Water Splitting.

The development of novel and highly efficient bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an ongoing challenge. The Cr3+ cation has a special electronic configuration (t32ge0g), which facilitates charge transfer and electron capture. However, Cr-based materials applied on water-splitting electrocatalysis is still a research void up to now. Herein, a novel amorphous γ-CrOOH was developed as a bifunctional electrocatalyst toward overall water splitting for the first time. It shows extraordinary HER activity with an ultralow overpotential of only 149 mV at 50 mA cm-2. Meantime, there is a small overpotential of 334 mV at 50 mA cm-2 for the OER. Importantly, the bifunctional electrocatalyst for overall water-splitting electrocatalysis can work with a cell voltage of merely 1.56 V at 10 mA cm-2. Amorphous γ-CrOOH has effectively enhanced the intrinsic electrochemical activity via density functional theoretical calculations. Therefore, this work not only provides a new method for preparation of amorphous γ-CrOOH but also expands the types of catalysts for water splitting.

Synthesis and Visible-Light Photocatalytic Activity of CeO2 Nanoboxes Based on Pearson's Principle.

The CeO2 nanoboxes with well-defined hollow structure were fabricated by template-engaged coordinating etching of Cu2O cubes based on Pearson's hard and soft acid-base principle. The morphologically uniform CeO2 nanoboxes have an average edge length of 400 nm and shell thickness of around 60 nm. The strong chemical affinity between Cu+ and S2O(2− 3) was the driving force for the etching of Cu2O templates and the formation of shells. A possible formation mechanism of CeO2 nanoboxes was proposed. The synthesized CeO2 nanoboxes exhibit good photocatalytic activity for photodegradation of acid orange 7 (AO 7) under visible light irradiation.

Bacteria-Directed Construction of ZnO/CdS Hollow Rods and Their Enhanced Photocatalytic Activity.

Zinc oxide (ZnO) hollow rods were fabricated by precipitation method with Bacillus subtilis as template. CdS nanoparticles were then decorated on the surface of the ZnO rods through hydrothermal method. The as-prepared samples were characterized using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscope and ultraviolet-visible spectroscopy techniques. The ZnO/CdS composite hollow rods copied the morphology of Bacillus subtiis. A possible formation mechanism of the rods was proposed. The photocatalytic activity of the samples was further evaluated through the photodegradation of Rhodamine B under a simulated solar-light irradiation. Results indicated that the photocatalytic activity of the rods improved greatly.

Preparation and photocatalytic property of porous CuO hollow microspheres via carbon sphere templates.

Porous copper oxide (CuO) hollow microspheres have been successfully fabricated by using carbon spheres as templates. The products were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). The influences of different experimental parameters on the morphology of CuO structures have been investigated in detail and the possible formation mechanism of porous CuO hollow microspheres has also been proposed. The specific surface area of the hollow spheres with 74.805 m2/g is measured by BET method. Barrett-Joyner-Halenda (BJH) calculations for the pore size distribution, derived from desorption data, reveal that the average pore radius is 8.56 nm, and the total pore volume (r = 1686.1 A, P/P0 = 0.994296) is 0.107257 cc/g. UV-vis absorption spectrum shows quantum size effect of porous CuO hollow microspheres. Furthermore, the porous CuO hollow microspheres exhibit high efficiency for photodegradation of a sample organic dye, Rhodamine B (RhB), under UV light.

Metal organic framework-derived C-doped ZnO/TiO2 nanocomposite catalysts for enhanced photodegradation of Rhodamine B.

A series of C-doped ZnO/TiO2 composites with various molar ratios of ZnO to TiO2 were synthesized by one-step controllable pyrolysis of Zn/Ti bimetallic metal-organic frameworks (Zn/Ti-MOF). The Zn/Ti-MOF was prepared using a facile microwave hydrothermal method. Electron microscopic analysis proved that the composites presented regularity cubic morphology with an edge length of about 1 µm and the C atoms were successfully doped into ZnO/TiO2 composites. X-ray photoelectron spectroscopy (XPS) measurement results confirmed the C-doping in the ZnO/TiO2. Comparative experimental studies showed that 2% ZnO/TiO2 composites prepared with the calcination temperature of 600℃ displayed the best photocatalytic degradation efficiency (94%) of RhB under the simulated sunlight irradiation. Cyclical experiment indicated the high stability and reusability of 2% ZnO/TiO2 composites. Electron spin resonance (ESR) and trapping experiments illustrated that the produced O2- served as the main active species for the efficient RhB removal. This work provides an efficient way for preparing C-doped bimetal oxides composites, which would have an important application prospect in the photocatalytic degradation of organic pollutants in environmental water.

N self-doped ZnO derived from microwave hydrothermal synthesized zeolitic imidazolate framework-8 toward enhanced photocatalytic degradation of methylene blue.

The precursor particles were successfully prepared by a facile microwave hydrothermal method. Compared with solvothermal and precipitation method, microwave hydrothermal method can greatly shorten the reaction time and increase the product yields. Nitrogen (N) doped zinc oxide (ZnO) nanoparticles were derived via one-step controllable pyrolysis of zeolitic imidazolate framework-8 (Zif-8) precursors under 550 °C. The powder X-ray diffraction (XRD) analysis, elemental mapping image, energy dispersive spectrometry (EDS) spectra and X-ray photoelectron spectroscopy (XPS) analysis proved that Zif-8 particles were converted to ZnO and the N atoms were successfully doped into ZnO lattice. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results demonstrated that N doped ZnO retained the morphology of Zif-8 with a particle size of approximately ~70 nm and the UV-visible diffuse reflectance spectra (UV-vis DRS) showed that the as-prepared N doped ZnO possessed a lower band gap (3.16 eV) than commercial ZnO (3.26 eV). The photocatalytic activities of the as-prepared samples were evaluated by the degradation rate of methylene blue (MB) upon irradiation with solar-simulated light. The photocatalytic degradation efficiency of N doped ZnO was 95.3% after 80 min illumination, which was much higher than that of other samples prepared by other methods. Quenching tests proved that the photo-generated holes (h+) played a main role in the photodegradation of MB under solar-simulated light irradiation.

Dichlorido-2κCl-{µ-6,6'-dimeth-oxy-2,2'-[propane-1,3-diylbis(nitrilo-methyl-idyne)]diphenolato-1κO,N,N',O:2κO,O}copper(II)zinc(II).

In the title compound, [CuZnCl(2)(C(19)H(20)N(2)O(4))], the Cu(II) ion exhibits a slightly distorted square-planar coordination geometry defined by two N atoms and two O atoms of the 6,6'-dimeth-oxy-2,2'-[propane-1,3-diylbis(nitrilo-methyl-idyne)]diphenolate Schiff base ligand. The Zn(II) ion is also four-coordinated by the two phenolate O atoms of the Schiff base ligand and by two cis-coordinated chloride anions.

Engineering borate modified NiFe layer double hydroxide nanoarrays as "hydroxyl ions hungry" electrocatalysts for enhanced oxygen evolution.

NiFe layered double hydroxides (NiFe-LDHs) have been regarded as significant electrocatalysts for the oxygen evolution reaction (OER). However, their overpotential must still be further reduced to enable commercial applications. Herein, a promising and highly effective "hydroxyl ions hungry" electrode structure was prepared for the first time via a two-step hydrothermal reaction procedure to enhance the surface adsorption kinetics to obtain an ultralow overpotential. The electrode exhibits OER activity with ultralow overpotentials of 203 mV and 293 mV at the current densities of 10 mA cm-2 and 100 mA cm-2, respectively, in 1.0 M KOH. These results reveal an important way to improve the catalytic performance in an alkaline medium.

Synthesis and photoelectrocatalytic activity of In2O3 hollow microspheres via a bio-template route using yeast templates.

Indium oxide (In2O3) hollow microspheres were prepared using yeast as a bio-template with the aid of a precipitation method. The yeast provided a solid frame for the deposition of In(OH)3 to form the precursor. The resulting In2O3 hollow microspheres were obtained by calcining the precursor at 650 °C. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms and UV-Vis diffuse reflectance spectroscopy. The results showed that the diameter of the In2O3 hollow microspheres was about 2.0-3.0 µm and the spherical shells were composed of In2O3 nanoparticles with a size of ∼20 nm. The BET specific surface area of the sample was 19.23 m2 g-1. The photoelectrocatalytic test results showed that the photoelectrocatalytic degradation efficiency of methylene blue (MB) using In2O3 hollow microspheres as catalysts under visible light irradiation and a certain voltage could reach above 95% after 4 hours, much higher than that of only photodegradation. The enhanced photoelectrocatalytic activity could be attributed to the hydroxyl radicals HO˙ produced by the light irradiation reaction process which could oxidize the electron donors and were beneficial to reducing the recombination of electrons and holes.

Synthesis, characterization and photocatalytic activity of mixed-metal oxides derived from NiCoFe ternary layered double hydroxides.

Ternary NiCoFe mixed-metal oxides (NCF-MMOs) with different Ni/Co/Fe ratios were successfully synthesized through a hydrotalcite-like precursor route by co-precipitation of appropriate amounts of metal salts from homogeneous solution, followed by calcination at 600 °C. X-ray diffraction (XRD) patterns revealed the formation of well crystalline layered double hydroxides (LDHs), particularly at the M2+/M3+ ratio of 3 : 1. Brunauer-Emmett-Teller (BET) analysis revealed that the resulting NiCoFe LDHs possessed large specific surface areas (66.9-93.8 m2 g-1). The NCF-MMO (1 : 2 : 1) samples were demonstrated to be formed by the aggregation of regular cubes with an edge length of about 2 µm, and each cube was accumulated with many fine particles with a size of ∼130 nm. UV-vis diffuse reflection spectroscopy (DRS) confirmed that the samples showed a broad absorption in the visible-light region (450-750 nm), with a low band gap of 2.33-2.77 eV. The calcined samples with a Ni/Co/Fe molar ratio of 1 : 2 : 1 possessed the best photocatalytic activity with 96.8% degradation of methylene blue (MB) dye under visible light irradiation for 4 h, which exceeded those of commercial P25 TiO2, binary NiFe mixed-metal oxides and pure Fe2O3, CoO and NiO particles under the same conditions. NCF-MMO (1 : 2 : 1) also had a strong degradation effect on the non-dye pollutant phenol as well. Kinetic studies suggested that the degradation of MB followed a pseudo-first-order kinetic behavior. The photodegradation mechanism of NCF-MMOs was also discussed.

Yeast-template synthesized Fe-doped cerium oxide hollow microspheres for visible photodegradation of acid orange 7.

Fe-doped cerium oxide (CeO2) hollow microspheres were successfully synthesized by a simple co-precipitation route using yeast asa bio-template and nitrate as the oxide precursor. The products were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption-desorption isotherms and UV-Vis diffuse reflectance spectroscopy. It was found that the products had a well-defined ellipsoidal morphology and the size of the hollow microspheres was about 1.5-2.5µm. The formation mechanism of Fe-doped CeO2 hollow microspheres was proposed and discussed as well. The photocatalytic test results showed that the Fe-doped CeO2 hollow microspheres exhibited a higher photocatalytic activity in the degradation of acid orange 7 (AO7) aqueous solutions containing H2O2 under visible irradiation compared with CeO2 hollow microspheres and Fe-doped CeO2 nanoparticles, which was attributed to their more oxygen vacancies, higher specific surface area and lower band gap. The degradation rate of the Fe-doped CeO2 hollow microspheres was found to be 93% after 80min and the degradation reaction followed pseudo-first-order kinetics.

Solvothermal synthesis, characterization and photocatalytic property of zirconium dioxide doped titanium dioxide spinous hollow microspheres with sunflower pollen as bio-templates.

Zirconium dioxide (ZrO2) doped titanium dioxide (TiO2) spinous hollow microspheres were successfully prepared through a facile solvothermal method using sunflower pollen as bio-templates. The products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption-desorption isotherms and UV-Vis diffuse reflectance spectroscopy. It was found that the products have spinous microsphere morphology with an approximate diameter of 12 µm. The ZrO2 doped TiO2 hollow microspheres exhibited a higher photocatalytic activity in the degradation of Rhodamine B (RhB) in aqueous solutions under UV-light irradiation compared with TiO2 hollow microspheres and ZrO2-doped TiO2 particles. In particular, the removal of RhB followed pseudo-first-order kinetics, and 96.3% of RhB was degraded in 60 min under UV-light irradiation when ZrO2 doped TiO2 spinous hollow microspheres were used as the photocatalysts. Neutral and alkaline conditions were found to favor over acidic conditions for the photocatalytic degradation of RhB. Furthermore, scavenging experiments indicated that photogenerated holes (h+) and radicals (OH and O-2) were the main reactive species in the photocatalytic process using ZrO2 doped TiO2 hollow microspheres as the catalysts under UV light irradiation.

ZnFeAl-layered double hydroxides/TiO2 composites as photoanodes for photocathodic protection of 304 stainless steel.

A series of ZnFeAl-layered double hydroxides/TiO2 (ZnFeAl-LDHs/TiO2) composites are synthesized by a combined anodization and hydrothermal method. The structure, surface morphology, photo absorption and photocathodic protection properties of these samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) and electrochemical tests. The unique structure of the ZnFeAl-LDHs reduces the charge carriers recombination, and the visible photoresponse property increase the light harvesting. The XPS study reveals that the electrons in the ZnFeAl-LDHs travel to TiO2, and the ZnFeAl-LDHs/TiO2 composites generate and transfer more electrons to 304 stainless steel (304SS), and exhibits a better photocathodic protection performance than pure TiO2. In addition, after intermittent visible-light illumination for four days, the photoanode still exhibits good stability and durability.