Overwhelming low ammonia escape and low temperature denitration efficiency via MnOx-decorated two-dimensional MgAl layered double oxides

Low temperature catalysts are attracting increasing attention in the selective catalytic reduction(SCR)of NO with NH3.Mn Ox-decorated Mg Al layered double oxide(Mn/Mg Al-LDO)was synthesized via a facile fast pour assisted co-precipitation(FP-CP)process.Compared to the Mn/Mg Al-LDO obtained via slow drop assisted coprecipitation(SD-CP)method,the Mn/Mg Al-LDO(FP-CP)has excellent activity.The Mn/Mg Al-LDO(FP-CP)catalyst was shown to possess a high NO conversion rate of 76%-100%from 25 to 150℃,which is much better than the control Mn/Mg Al-LDO(SD-CP)(29.4%-75.8%).In addition,the Mn/Mg Al-LDO(FP-CP)offered an enhanced NO conversion rate of 97%and a N2selectivity of 97.3%at 100℃;the NO conversion rate was 100%and the N2selectivity was 90%at 150℃with a GHSV of 60,000 h^-1.The Mn/Mg Al-LDO(FP-CP)catalyst exhibited a smaller fragment nano-sheet structure(sheet thickness of 7.23 nm).An apparent lattice disorder was observed in the HRTEM image confirming the presence of many defects.The H2-TPR curves show that the Mn/Mg Al-LDO(FP-CP)catalyst has abundant reducing substances.Furthermore,the enhanced surface acidity makes the NH3concentration of the Mn/Mg Al-LDO(FP-CP)catalyst lower than 100 ml·m^-3after the reaction from 25 to 400℃.This can effectively reduce the ammonia escape rate in the SCR reaction.Thus,the Mn/Mg Al-LDO(FP-CP)catalyst has potential applications in stationary industrial installations for environmentally friendly ultra-low temperature SCR.

Preparation of birnessite-supported Pt nanoparticles and their application in catalytic oxidation of formaldehyde

Flaky and nanospherical birnessite and birnessite-supported Pt catalysts were successfully prepared and characterized by means of Xray diffraction （XRD）,transmission electron microscopy （TEM）,energy dispersive spectroscopy （EDS） and N2 adsorption-desorption.Effects of the birnessite morphology and Pt reduction method on the catalytic activity for the complete oxidation of formaldehyde （HCHO） were investigated.It was found that flaky birnessite exhibited higher catalytic activity than nanospherical birnessite.The promoting effect of Pt on the birnessite catalyst indicated that the reduction method of the Pt precursor greatly influenced the catalytic performance.Flaky birnessite-supported Pt nanoparticles reduced by KBH 4 showed the highest catalytic activity and could completely oxidize HCHO into CO2 and H2O at 50℃,whereas the sample reduced using H2-plasma showed lower activity for HCHO oxidation.The differences in catalytic activity of these materials were jointly attributed to the effects of pore structure,surface active sites exposed to HCHO and the dispersion of Pt nanoparticles.

Broadband Antireflective Superhydrophilic Thin Films with Outstanding Mechanical Stability on Glass Substrates

A facile approach was developed to fabricate visible/near-infrared antireflective(AR),superhydrophilic and anti-fogging thin films on glass substrates.Glass substrate was first etched by H_(2)SiF_(6)-based vapor and then dip-coated sequentially in a base-catalyzed 20 nm SiO_(2)nanoparticles sol and an acid-catalyzed SiO_(2)sol.After an-nealing,the prepared thin film(named E/BSiO_(2)/ASiO_(2))not only showed good optical and wetting properties,but also exhibited excellent mechanical properties.The thin film has enhanced transmittance in the spectral range of UV to near-infrared.The maximum transmittance of E/BSiO_(2)/ASiO_(2)thin film coated glass substrate is 98.4%in 400-1200 nm and 96.1%in 1200-2500 nm,respectively.Comparing with blank glass substrate,the average transmittance increases by 5%in the wavelength range of 300-2500 nm.Meanwhile,the film showed good anti-fogging performance.SEM and AFM were employed to characterize the morphology of the thin film.The pre-pared thin film has potential application in various areas,like solar cells,windowpanes and eyeglasses,and may also find applications in membrane-based separation,selective catalysis and sensors.

An Advance in Complete Oxidation of Formaldehyde at Low Temperatures

Editor＇s comments Formaldehyde （HCHO） emitted from chemical manufacturing plants including methanol-gasoline/diesel fuel vehicles and the construction and decoration materials is one of the major air pollutions, which induces photochemical pollution and hazards human health. Great efforts have been made for the reduction or control of the emission of HCHO to satisfy the stringent environmental regulations. Now, a new study supported by the National Natural Science Foundation of China reports mesoporous manganese oxide with novel nanostructures for the decomposition of HCHO. The obtained manganese oxide nanomaterials showed high catalytic activities for oxidative decomposition of HCHO at low temperatures. Complete conversion of HCHO to CO2 and H2O were achieved, and no harmful by- products were detected in effluent gases. The catalytic activities of these nanomaterials are significantly higher than those of previously reported manganese oxide octahedral molecular sieve （OMS-2） nanorods , MnO x powders, and alumnina-supported mangnaese-palladium oxide catalysts. These results provide a new route for the removal of HCHO and other air pollutions.

Rapid assessment of DNA damage induced by polystyrene nanosphere suspension using a photoelectrochemical DNA sensor

Nanomaterials have been used increasingly in a wide variety of applications, and some of them have shown toxic effects on experimental animals and cells. In this study, a previously established photoelectrochemical DNA sensor was employed to rapidly detect DNA damage induced by polystyrene nanosphere （PSNS） suspensions. In the sensor, a double-stranded DNA film was assembled on a semiconductor electrode, and a DNA intercalator, Ru（bpy）2（dppz）2＋ （bpy = 2,2＇-bipyridine, dppz = dipyrido[3,2-a：2＇,3＇-c]phenazine） was used as the photoelectrochemical signal indicator. After the DNA-modified electrode was exposed to 2.0 mg/mL PSNS suspension, photocurrent of DNA-bound Ru（bpy）2（dppz）2＋ decreased by about 20%. The decrease is attributed to the chemical damage of DNA and consequently less binding of Ru（bpy）2（dppz）2＋ molecules to the electrode. Gel electrophoresis of DNA samples incubated with PSNS suspension confirmed DNA damage after the chemical exposure. However, in both photoelectrochemical and gel electrophoresis experiments, extensively washed PSNS did not induce any DNA damage, and the supernatant of PSNS suspension exhibited comparable DNA damage as the unwashed PSNS suspension. Furthermore, UV-visible absorption spectrum of the supematant displayed a pattern very similar to that of styrene oxide （SO）, a compound which has been shown to induce DNA damage by forming covalent DNA adducts. It is therefore suggested that styrene oxide and other residual chemicals in the PSNS may be responsible for the observed DNA damage. The results highlight the importance of full characterization of nanomaterials before their toxicity study, and demonstrate the utility of photoelectrochemical DNA sensors in the rapid assessment of DNA damage induced by chemicals and nanomaterials.

Design and roles of RGO-wrapping in charge transfer and surface passivation in photoelectrochemical enhancement of cascade-band photoanode

Fast charge transfer and anti-photocorrosion are two crucial factors for developing efficient, durable photoanodes for photoelectrochemical （PEC） cells. Reduced graphene oxide （RGO） is a promising photoanode element that can provide both of these. In this study, we elucidated the roles of RGO in the charge transfer and surface passivation of photoanodes by the precise design of a RGO-wrapped photoanode and examination of its PEC properties. Arrays of hetero-nanorods （HNRs） with three different designs were fabricated as photoanodes using RGO, CdSe nanoparticles （NPs）, and ZnO nanorods （NRs） as building blocks. CdSe@ZnO HNRs were prepared by decorating ZnO NRs with CdSe NPs. Finite-element analysis and experimental studies demonstrated that in the CdSe@ZnO HNRs, if only the ZnO NRs were wrapped by RGO, the conductivity between CdSe and ZnO was enhanced by RGO to shuttle charges. If RGO only surrounded the outside of the CdSe@ZnO HNRs, the corrosion was slowed owing to the passivation effect of RGO, which increased the electron lifetime of the photoanode. If both CdSe and ZnO were fully wrapped by RGO, the advantages of the two aforementioned cases were both obtained. RGO-wrapped CdSe@ZnO HNRs with position-controlled designs are promising photoanode materials with a high PEC efficiency, and the developed synthesis process can be applied to explore the design and fabrication of next-generation photoanodes using RGO as a buildin~ block.

Giant electrorheological effects of aluminum-doped TiO_2 nanoparticles

Titania nanoparticles doped with cations have been synthesized via a modified hydrolysis method. The X-ray diffraction analyses, scanning electron microscopy and other characteristics measurements, were used to study the structure of the nanoparticles. The results showed interesting electrorheological （ER） effect with titania nanoparticles modified by aluminum ions, and different cations on ER effect were determined by ionic potential and resistance of the particle aggregates in the electric field. The doping ratio of aluminum ions was dominated by the appropriate sites of the particle surface and the ER effect strongly depends on the doping ratio.