Self-Assembly of Surface-Functionalized Ag1.8 Mn8 O16 Nanorods with Reduced Graphene Oxide Nanosheets as an Efficient Bifunctional Electrocatalyst for Rechargeable Zinc-Air Batteries.

Bifunctional electrocatalysts play a key role in the performance of rechargeable metal-air batteries. Herein, we report a hybrid catalyst, Ag1.8 Mn8 O16 /rGO, self-assembled by Ag1.8 Mn8 O16 nanorods and reduced graphene oxide (rGO) nanosheets through electrostatic attraction. The hybrid catalyst exhibits a better oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity than commercial Pt/C in alkaline medium. When employed as an air-cathode catalyst in Zn-air cells, the hybrids enabled higher and more stable output voltage and better durability of the cells, benefitting from the improved electrode conductivity, larger surface area, and synergetic coupling as a result of its high structural integrity.

Co@Co3 O4 @PPD Core@bishell Nanoparticle-Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction.

Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high-performance primary zinc-air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co3 O4 core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co3 O4 @PPD core@bishell structure, obtained via a three-step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co3 O4 NPs encapsulated by ultrathin highly graphitized N-doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N-doped graphitic carbon outer shell and ultrathin nanocrystalline Co3 O4 inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co3 O4 @PPD in air-cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm(-2) .

Mussel-inspired one-pot synthesis of transition metal and nitrogen co-doped carbon (M/N-C) as efficient oxygen catalysts for Zn-air batteries.

Transition metal and nitrogen co-doping into carbon is an effective approach to promote the catalytic activities towards the oxygen reduction reaction (ORR) and/or oxygen evolution reaction (OER) in the resultant electrocatalysts, M/N-C. The preparation of such catalysts, however, is often complicated and in low yield. Herein we report a robust approach for easy synthesis of M/N-C hybrids in high yield, which includes a mussel-inspired polymerization reaction at room temperature and a subsequent carbonization process. With the introduction of selected transition metal salts into an aqueous solution of dopamine (DA), the obtained mixture self-polymerizes to form metal-containing polydopamine (M-PDA) composites, e.g. Co-PDA, Ni-PDA and Fe-PDA. Upon carbonization at elevated temperatures, these metal-containing composites were converted into M/N-C, i.e. Co-PDA-C, Ni-PDA-C and Fe-PDA-C, respectively, whose morphologies, chemical compositions, and electrochemical performances were fully studied. Enhanced ORR activities were found in all the obtained hybrids, with Co-PDA-C standing out as the most promising catalyst with excellent stability and catalytic activities towards both ORR and OER. This was further proven in Zn-air batteries (ZnABs) in terms of discharge voltage stability and cycling performance. At a discharge-charge current density of 2 mA cm(-2) and 1 h per cycle, the Co-PDA-C based ZnABs were able to steadily cycle up to 500 cycles with only a small increase in the discharge-charge voltage gap which notably outperformed Pt/C; at a discharge current density of 5 mA cm(-2), the battery continuously discharged for more than 540 h with the discharge voltage above 1 V and a voltage drop rate of merely 0.37 mV h(-1). With the simplicity and scalability of the synthetic approach and remarkable battery performances, the Co-PDA-C hybrid catalyst is anticipated to play an important role in practical ZnABs.

Influence of organic loading rate on integrated bioreactor treating hypersaline mustard wastewater.

Mustard tuber wastewater is characterized by high salinity and high organic content that is potentially detrimental to the biological treatment system and affects the treatment efficiency accordingly. The experiment used the integrated bioreactor to reduce much of the organics in mustard tuber wastewater, and found the influence of organic loading rate on effluent chemical oxygen demand (COD) and phosphate (PO4 (3-) -P). Results showed that under the condition of 10-15 °C, 6 mg/L of dissolved oxygen, the reduction value of COD removal rate in anaerobic and aerobic area was 14.5% and 31.7% when the organic loading rate increased from 2.0 to 4.0 kg COD/m(3) /day. Therefore, an integrated bioreactor should take 2.0 kg COD/m(3) /day organic loading rate in mustard wastewater treatment if the effluent is expected to meet the third level of "Integrated Wastewater Discharge Standard" (GB 8978-1996).

Development of Cobalt Hydroxide as a Bifunctional Catalyst for Oxygen Electrocatalysis in Alkaline Solution.

Co(OH)2 in the form of hexagonal nanoplates synthesized by a simple hydrothermal reaction has shown even greater activity than cobalt oxides (CoO and Co3O4) in oxygen reduction and oxygen evolution reactions (ORR and OER) under alkaline conditions. The bifunctionality for oxygen electrocatalysis as shown by the OER-ORR potential difference (ΔE) could be reduced to as low as 0.87 V, comparable to the state-of-the-art non-noble bifunctional catalysts, when the Co(OH)2 nanoplates were compounded with nitrogen-doped reduced graphene oxide (N-rGO). The good performance was attributed to the nanosizing of Co(OH)2 and the synergistic interaction between Co(OH)2 and N-rGO. A zinc-air cell assembled with a Co(OH)2-air electrode also showed a performance comparable to that of the state-of-the-art zinc-air cells. The combination of bifunctional activity and operational stability establishes Co(OH)2 as an effective low-cost alternative to the platinum group metal catalysts.

Co3O4 nanoparticles decorated carbon nanofiber mat as binder-free air-cathode for high performance rechargeable zinc-air batteries.

An efficient, durable and low cost air-cathode is essential for a high performance metal-air battery for practical applications. Herein, we report a composite bifunctional catalyst, Co3O4 nanoparticles-decorated carbon nanofibers (CNFs), working as an efficient air-cathode in high performance rechargeable Zn-air batteries (ZnABs). The particles-on-fibers nanohybrid materials were derived from electrospun metal-ion containing polymer fibers followed by thermal carbonization and a post annealing process in air at a moderate temperature. Electrochemical studies suggest that the nanohybrid material effectively catalyzes oxygen reduction reaction via an ideal 4-electron transfer process and outperforms Pt/C in catalyzing oxygen evolution reactions. Accordingly, the prototype ZnABs exhibit a low discharge-charge voltage gap (e.g. 0.7 V, discharge-charge at 2 mA cm(-2)) with higher stability and longer cycle life compared to their counterparts constructed using Pt/C in air-cathode. Importantly, the hybrid nanofiber mat readily serves as an integrated air-cathode without the need of any further modification. Benefitting from its efficient catalytic activities and structural advantages, particularly the 3D architecture of highly conductive CNFs and the high loading density of strongly attached Co3O4 NPs on their surfaces, the resultant ZnABs show significantly improved performance with respect to the rate capability, cycling stability and current density, promising good potential in practical applications.

Mesoporous spherical Li4Ti5O12 as high-performance anodes for lithium-ion batteries.

Porous microspherical Li4Ti5O12 aggregates (LTO-PSA) can be successfully prepared by using porous spherical TiO2 as a titanium source and lithium acetate as a lithium source followed by calcinations. The synthesized LTO-PSA possess outstanding morphology, with nanosized, porous, and spherical distributions, that allow good electrochemical performances, including high reversible capacity, good cycling stability, and impressive rate capacity, to be achieved. The specific capacity of the LTO-PSA at 30 C is as high as 141 mA h g(-1), whereas that of normal Li4Ti5O12 powders prepared by a sol-gel method can only achieve 100 mA h g(-1). This improved rate performance can be ascribed to small Li4Ti5O12 nanocrystallites, a three-dimensional mesoporous structure, and enhanced ionic conductivity.

Co3O4 nanoparticle-modified MnO2 nanotube bifunctional oxygen cathode catalysts for rechargeable zinc-air batteries.

We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone.

[Between Hengshanhuangqi and Chuanhuangqi based on metabolomics and ITS2 sequences].

To compare the differences between Hengshanhuangqi (HH) and Chuanhuangqi (CH) at molecular level, 1H NMR based plant metabolomics approach was used to reveal the chemical difference between HH and CH. Then, the contents of astragaloside IV and calycosin-7-O-beta-D-glucoside, the marker compounds specified in China Pharmacopoeia, were determined. In addition, the ITS2 fragments of HH and CH were sequenced. Twenty-three metabolites were identified in the 1H NMR spectrum, and the principal component analysis showed CH and HH could be separated clearly. HH contained more aspartic acid, GABA, citric acid, astragaloside IV and calycosin-7-O-beta-D-glucoside, while CH contained more threonine, alanine, acetic acid, choline, arginine, fructose and sucrose. And the astragaloside IV is almost undetectable in CH. In addition, the ITS2 fragment sequences of HH and CH were different at eight bases. Thus, the HH and CH showed significant differences chemically and genetically.

Nanopaper based on Ag/TiO2 nanobelts heterostructure for continuous-flow photocatalytic treatment of liquid and gas phase pollutants.

The Ag/TiO(2) nanobelt heterostructures were prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The photocatalytic activity of TiO(2) nanobelts was evidently enhanced by the heterostructures between Ag nanoparticles and TiO(2) nanobelts. The nanopapers based on Ag/TiO(2) nanobelt heterostructures were fabricated via a modified paper-making process. A novel continuous photocatalytic reactor was designed, and MO removal rate of Ag/C-TiO(2) nanopaper was achieved to 100% in 40 min for single layer and only in 6 min for three layers. The self-supported TiO(2) nanopapers with porous structures also showed an excellent continuous photocatalytic performance for toluene gas under UV light irradiation, and the corresponding degradation rate was 69.5% in 184 min. Moreover, the Ag/TiO(2) nanobelts nanopaper showed a good antibacterial effect. The multifunctional TiO(2) nanopapers modified by the heterostuctures could have potential applications in the environmental and biomaterial fields.

Interface dominated high photocatalytic properties of electrostatic self-assembled Ag(2)O/TiO(2) heterostructure.

Electrostatic self-assembled Ag(2)O/TiO(2) nanobelts heterostructure was synthesized via simple physical mixing of Ag(2)O nanoparticles and TiO(2) nanobelts. The morphologies and microstructures of Ag(2)O/TiO(2) nanobelt heterostructure were characterized by high resolution transmission electron microscopy. The interface dominated high UV photocatalytic activity and degraded photoluminescence strength of composite catalyst confirmed the heterostructure effect between Ag(2)O nanoparticles and TiO(2) nanobelts. X-ray photoelectron spectroscope provided direct evidence of charge transfer on the heterostructures between them.

Enhancement of ethanol vapor sensing of TiO2 nanobelts by surface engineering.

TiO(2) nanobelts were prepared by a hydrothermal process, and the structures were manipulated by surface engineering, including surface coarsening by an acid-corrosion procedure and formation of Ag-TiO(2) heterostuctures on TiO(2) nanobelts surface by photoreduction. Their performance in the detection of ethanol vapor was then examined and compared by electrical conductivity measurements at varied temperatures. Of the sensors based on the four nanobelt samples (TiO(2) nanobelts, Ag-TiO(2) nanobelts, surface-coarsened TiO(2) nanobelts, and surface-coarsened Ag-TiO(2) nanobelts), they all displayed improved sensitivity, selectivity, and short response times for ethanol vapor detection, in comparison with sensors based on other oxide nanostructures. Importantly, the formation of Ag-TiO(2) heterostuctures on TiO(2) nanobelts surface and surface coarsening of TiO(2) nanobelts were found to lead to apparent further enhancement of the sensors sensitivity, as well as a decrease of the optimal working temperature. That is, within the present experimental context, the vapor sensor based on surface-coarsened Ag-TiO(2) composite nanobelts exhibited the best performance. The sensing mechanism was interpreted on the basis of the surface depletion model, and the improvement by oxide surface engineering was accounted for by the chemical sensitization mechanism. This work provided a practical approach to the enhancement of gas sensing performance by one-dimensional oxide nanomaterials.

Ag2O/TiO2 nanobelts heterostructure with enhanced ultraviolet and visible photocatalytic activity.

Ag(2)O/TiO(2) heterostructure with high photocatalytic activity both in ultraviolet and visible-light region was synthesized via a simple and practical coprecipitation method by using surface-modified TiO(2) nanobelts as substrate materials. The as-prepared heterostructure composite included Ag(2)O nanoparticles assembled uniformly on the rough surface of TiO(2) nanobelts. Comparing with pure TiO(2) nanobelts and Ag(2)O nanoparticles, the composite photocatalyst with a wide weight ratio between TiO(2) and Ag(2)O exhibited enhanced photocatalytic activity under ultraviolet and visible light irradiation in the decomposition of methyl orange (MO) aqueous solution. On the basis of the characterization by X-ray diffraction, photoluminescence and UV-vis diffuse reflectance spectroscopies, two mechanisms were proposed to account for the photocatalytic activity of Ag(2)O/TiO(2) nanobelts' heterostructure.

A photocatalytic reduction method for the preparation of TiO2 nanobelt supported noble metals (Ag, Au).

TiO2 nanobelts, with typical widths of 50 to 200 nm, thicknesses of 20-50 nm, supported noble metals (Ag, Au) are prepared by the photocatalytic reduction method. The as-made samples were characterized by Transmission electron microscopy (TEM), Field-emission scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS). The results show that silver particles, with the grain size of about 10 nm, deposited on the surface of nanobelts are uniform. And the grain size of Au on the surface of nanobelts is about 30 nm. In this method, the as-made TiO2 nanobelt is not only used as support, but also as photocatalyst to reduce the noble metal ions.