[en] Carbon cryogel (CC) has been prepared through sol-gel polycondensation of resorcinol (R) with formaldehyde (F) followed by freeze-drying and carbonization in this work. The characteristics and lithium-ion insertion-extraction property have been investigated for the first time. Based on the results that CC has very excellent cycling stability but very limited lithium-ion charge-discharge capacity, SiO is employed to synthesize CC-SiO composite by high energy mechanical ball-milling to improve the applicability. The results showed that, CC-SiO is composed of active carbon, graphite, SiO and dispersed Si crystal, while CC is composed of active carbon and graphite. CC-SiO has smaller and much more uniform particles than CC. SiO can greatly improve discharge capacity of CC with an acceptable sacrifice of cycling stability, and the charge-discharge capacity of CC-SiO comes mainly from lithium insertion-extraction in Si-SiO in the sample. CC-SiO has excellent high-rate discharge ability and is promising anode material of lithium-ion battery for use of high power density purpose

[en] The selective catalytic reduction (SCR) of NO by hydrocarbon is an efficient way to remove NO emission from lean-burn gasoline and diesel exhaust. In this paper, a thermally and hydrothermally stable Al-Ce-pillared clay (Al-Ce-PILC) was synthesized and then modified by SO₄^2-, whose surface area and average pore diameter calcined at 773 K were 161 m²/g and 12.15 nm, respectively. Copper-impregnated Al-Ce-pillared clay catalyst (Cu/SO₄^2-/Al-Ce-PILC) was applied for the SCR of NO by C₃H₆ in the presence of oxygen. The catalyst 2 wt% Cu/SO₄^2-/Al-Ce-PILC showed good performance over a broad range of temperature, its maximum conversion of NO was 56% at 623 K and remained as high as 22% at 973 K. Furthermore, the presence of 10% water slightly decreased its activity, and this effect was reversible following the removal of water from the feed. Py-IR results showed SO₄^2- modification greatly enhanced the number and strength of Broensted acidity on the surface of Cu/SO₄^2-/Al-Ce-PILC, which played a vital role in the improvement of NO conversion. TPR and XPS results indicated that both Cu⁺ and isolated Cu²⁺ species existed on the optimal catalyst, mainly Cu⁺, as Cu content increased to 5 wt%, another species CuO aggregates which facilitated the combustion of C₃H₆ were formed. (author)

[en] A highly stable perovskite cathode material, Ba_0.5Sr_0.5(Co_0.6Zr_0.2)Fe_0.2O_3-δ (BSCZF) for intermediate temperature solid-oxide fuel cells (IT-SOFCs) was synthesized via the improved EDTA-citric acid complexing technique combined with high-temperature sintering. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectra (EIS) measurements. An electrolyte-supported BSCZF/SDC/Ni-SDC fuel cell was fabricated to evaluate the performance of the material. The XRD study indicates that the sintering temperature higher than 950 deg. C is sufficient to the formation of clean single BSCZF perovskite phase. Due to the incorporation of Zr ions, BSCZF perovskite exhibit lower electrical conductivity with higher activation energy but higher structural stability than the Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) parent oxide. The maximum electrical conductivity of BSCZF attains 16.9 S cm^-1 at around 540 deg. C. Impedance spectra showed that the ASRs of BSCZF cathode on samaria doped ceria (Ce_0.8Sm_0.2O_1.9, SDC) electrolyte are low but are still slightly larger than those of BSCF at similar conditions. The BSCZF/SDC/Ni-SDC cell exhibited a stable output with the maximum power densities of 30, 75, 139 and 241 mW cm^-2 at 550, 600, 650 and 700 deg. C, respectively. Due to the high electrochemical performances as well as the excellent stability, BSCZF perovskite may be an attractive cathode material for IT-SOFCs.

[en] Yttria-stabilized zirconia (YSZ) nanotubes were synthesized by the sol-gel method using porous anodic alumina oxide (AAO) as the templates. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersion X-ray (EDX) spectrum and selected area electron diffraction (SAED) techniques were used to characterize the morphology and crystalline structure of the prepared YSZ nanotubes. The length and the diameter of the YSZ nanotubes are 50 μm and 200 nm, respectively, which are in good agreement with the dimensions of the template pores, while the wall thickness of the nanotubes depends on the impregnation time. XRD and SAED measurements indicate that the obtained YSZ nanotubes after sintering at 1073 K possess a polycrystalline structure and a cubic crystal phase. Brunauer-Emmett-Teller (BET) measurement shows that the YSZ nanotubes have a surface specific area of around 40.5 m² g^-1 that is higher than that corresponding to the YSZ nanopowders

[en] CoTMPP-TiO₂NT/BP composites have been synthesized by preparing CoTMPP and depositing CoTMPP on carbon-supported titania nanotube (TiO₂NT/BP) using microwave irradiation method at the same time, followed by heat-treatment from 300 to 900 deg. C in N₂ atmosphere. The catalytic activity for oxygen reduction was evaluated by rotating disc electrode technique in half cells with 0.5 M H₂SO₄. The number of electrons exchanged during ORR and the percentage of peroxide (%H₂O₂) produced by the reaction were evaluated for catalysts by rotating ring disk electrode (RRDE) measurements. The influences of TiO₂NT doping, the heat-treating temperature and the different ratios of BP:TiO₂NT on the activity of electrocatalysts for oxygen reduction were investigated. The stability of the CoTMPP-TiO₂NT/BP electrocatalysts was studied with potentialstatic-polarization measurements in 0.5 M H₂SO₄ + 0.5 M CH₃OH. CoTMPP-TiO₂NT/BP composites show higher catalytic activity and better stability than CoTMPP/BP. The mechanism for the enhanced catalytic activity of CoTMPP-TiO₂NT/BP is discussed

[en] A promising non-precious metal FeCoTETA/C catalyst has been easily synthesized, by chelating Fe and Co with triethylenetetramine (TETA) in ethanol followed by pyrolyzing in an Ar atmosphere, as electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). The catalyst has been characterized with various physicochemical techniques as well as electrochemical analysis and single cell performance measurement. The results showed that nano-intermetallic FeCo particles and several types of N and O species are present on carbon matrix. The catalyst delivers better electrocatalytic activity toward ORR compared with CoTETA/C catalyst, the %H₂O₂ is about 10% with an electron-transfer number of around 3.8. The PEMFC with this catalyst in cathode reaches a maximum power density of 256 mW cm⁻² and has a current density of 514 mA cm⁻² at 500 mV.

[en] ZnS/C composites were synthesized by a combined precipitation with carbon coating method. Morphology and structure of the as-prepared ZnS/C composite materials with carbon content of 4.6 wt%, 9.3 wt% and 11.4 wt% were characterized using TEM and XRD technique. TEM observation demonstrated that the ZnS/C (9.3 wt% C) composite showed excellent microstructure with 20-30 nm ZnS nanoparticles uniformly dispersed in conductive carbon network. Electrochemical tests showed that the ZnS/C (9.3 wt% C) composite presented superior performance with initial charge and discharge capacity of 1021.1 and 481.6 mAh/g at a high specific current of 400 mA/g, after 300 cycles, the discharge capacity of ZnS/C electrode still maintained at 304.4 mAh/g, with 63.2% of its initial capacity. The rate capability and low temperature performance of the ZnS/C (9.3 wt% C) composite were compared with commercial MCMB anode. The results showed that the ZnS/C (9.3 wt%) composite exhibited much better cycle capability and low temperature performance than MCMB anode. ZnS/C composite seems to be a promising anode active material for lithium ion batteries. Intercalation mechanism of the ZnS/C composites for lithium ion insertion-extraction is proposed based on the ex situ X-ray diffraction analysis incorporating with its electrochemical characteristics.

[en] Olivine compounds LiFe_1-xMn_xPO₄ (0.0 ≤ x ≤ 0.3) for cathodes of secondary lithium-ion batteries were synthesized via a mechanoactivation-assisted solid-state reaction. The optimal manganese content and electrochemical performance of the as-synthesized powders were investigated by XRD, EDX mapping, cyclic voltammetry, and charge-discharge characterizations. According to XRD and EDX mapping results, phase-pure compounds with olivine structure were formed after the calcination under nitrogen atmosphere at 700 ^oC for 20 h. Among the various LiFe_1-xMn_xPO₄ under test, LiFe_0.8Mn_0.2PO₄ showed the highest electrical conductivity, which reached a value of 3.49 x 10^-5 S cm^-1 at room temperature, more than 5 orders higher than that of pristine LiFePO₄ (1.08 x 10^-10 S cm^-1). Without the carbon coating, pristine LiFe_0.8Mn_0.2PO₄ showed discharge capacity of ∼123 and 100 mAh g^-1 at 0.1 and 1 C rates, respectively. It means about 91% and 74% of the Fe²⁺ in LiFe_0.8Mn_0.2PO₄ is electrochemically utilizable correspondingly. For a comparison, they are only 65% and 15% for the pristine LiFePO₄ prepared by a similar process. LiFe_1-xMn_xPO₄ also showed stable cycling performance within the 50 cycles under test. It suggests manganese lightly doped LiFePO₄ could be practical cathode materials for high-rate lithium-ion batteries.

[en] Highlights: • A facile and mass-producible strategy was developed to modify the surface of Cu foils with carbon. • The modified carbon is robust and strong. • Overall performances of lithium ion batteries were improved by the surface carbon modification on Cu current collector. • Full-cell systems were used to evaluate the effects of Cu surface modification. - ABSTRACT: We have developed a facile and mass-producible strategy named electric discharge method to successfully improve the surface properties of Cu foils with rough carbon layer. Electrochemical tests in half-cells demonstrate that the coated carbon layer can significantly reduce the polarization resistance and enhance the reversible capacity of graphite anode when utilizing the Cu foils as current collector for lithium ion batteries. More importantly, the developed carbon coated Cu anode current collector can also improve the overall performances of LiFePO_4 full cells in terms of enhanced rate capability (from 887.9 to 946.3 mAh at 4C rate), reduced polarization voltage (11.7 mV lower at 4C rate), longer cycle life (about 650 increased cycles if taking 80 % capacity retention as the end of cycle life when used at 1 C rate) as well as improved low-temperature performance (capacity retention: 42.87% vs. 38.85% at -20 °C)

[en] A series of red-emitting Eu³⁺-doped K₂LaNb₅O₁₅ niobate phosphors with tetragonal tungsten bronze-type structure were synthesized by the solid state reaction method. The structure of new tungsten bronze-type K₂EuNb₅O₁₅ was identified by Rietveld refinements to crystallize in the tetragonal space group P4bm, which is isostructural to K₂LaNb₅O₁₅. The relative intensity of the emission from both ⁵D₀→⁷F₂ and ⁵D₀→⁷F₁ increases with increasing Eu³⁺ ion concentration. The quenching mechanism of the K₂La_1−xNb₅O₁₅:xEu system was investigated in detail. The relationship between Photoluminescence properties and the TTB-type structure was discussed. The quantum efficiency of K₂EuNb₅O₁₅ excited under near-UV light (399 nm) is 132% of that of commercial Y₂O₃:Eu³⁺ (394 nm). The results demonstrated K₂EuNb₅O₁₅ phosphor as a potential candidate for white light emitting diode pumped by near-UV or blue chip. -- Highlights: • KLa_1−xNb₅O₁₅:xEu³⁺ phosphors were synthesized by the solid state reaction method. • K₂EuNb₅O₁₅ was identified to have a tetragonal tungsten bronze-type structure. • Compared with Y₂O₃:Eu³⁺, K₂EuNb₅O₁₅ performed better luminescence properties