Graphene/polyaniline composite sponge of three-dimensional porous network structure as supercapacitor electrode

As a supercapacitor electrode, the graphene/polyaniline(PANI) composite sponge with a three-dimensional(3D)porous network structure is synthesized by a simple three-step method. The three steps include an in situ polymerization,freeze-drying and reduction by hydrazine vapor. The prepared sponge has a large specific surface area and porous network structure, so it is in favor of spreading the electrolyte ion and increasing the charge transfer efficiency of the system.The process of preparation is simple, easy to operate and low cost. The composite sponge shows better electrochemical performance than the pure individual graphene sponge while PANI cannot keep the shape of a sponge. Such a composite sponge exhibits specific capacitances of 487 F·g~(-1) at 2mV/s compared to pristine PANI of 397 F·g~(-1).     

Explanation of Effect of Added Water on Dye-Sensitized Nanocrystalline TiO2 Solar Cell： Correlation between Performance and Carrier Relaxation Kinetics

Time-resolved mid-IR transient absorption spectroscopy is employed to explore the mechanism of improving the performance of dye-sensitized TiO2 solar cell （DSSC） when a certain amount of H2 0 is added into the electrolyte. The relaxation kinetics of dye-sensitized TiO2 nanocrystalline film and the corresponding DSSC performance are investigated under different conditions. It is found that the interracial charge recombination is retarded and electron injection efficiency is increased in the water vapour and in the electrolyte when D20 is added. The values of open-circuit photovoltage Voc and the short-circuit photocarrent Jsc of the cells are linearly correlated to the product of the two decay time constants. We also observed that Voc well correlates with electron injection efficiency. It provides a preliminary microscopic account for the function of the added water in improving the performance of DSSCs.     

Dielectric properties of electrospun titanium compound/polymer composite nanofibres

Poly(vinylpyrrolidone)/tetrabutyl titanate (PVP/ [CH3(CH2)3O]4Ti) composite nanofibres are prepared by elec- trospinning. After calcining parts of composite nanofibres in air at 700 C, petal-like TiO2 nanostructures are obtained. The characterizations of composite nanofibres and TiO2 nanostructures are carried out by a scanning electron micro- scope, an x-ray diffractometer, and an infrared spectrometer. Electrospun nanofibres are pressed into pellets under different pressures in order to explore their dielectric properties. It is found that the dielectric constants decrease with frequency increasing. The dielectric constant of the composite nanofibre pellet increases whereas its dielectric loss tangent decreases due to the doped titanium ions compared with those of pure PVP nanofibre pellets. In addition, it is observed that the dielectric constant of the composite nanofibre pellet decreases with the increase of the pressure applied in pelletization.     

Production of CH （A2△） by multi-photon dissociation of （CH3）2CO,CH3NO2, CH2Br2, and CHBr3 at 213 nm

In order to realize electrostatic Stark deceleration of CH radicals and study cold chemistry, the fifth harmonic of a YAG laser is used to prepare CH(A2△) molecules through using the multi-photon dissociation of(CH3)2CO, CH3NO2, CH2Br2,and CHBr3 at ～ 213 nm. The CH product intensity is measured by using the emission spectrum of CH(A2△→ X2Π). The dependence of fluorescence intensity on laser power is studied, and the probable dissociation channels are analyzed. The relationship between the fluorescence intensity and some parameters, such as the temperature of the beam source, stagnation pressure, and the time delay between the opening of pulse valve and the photolysis laser, are also studied. The influence of three different carrier gases on CH signal intensity is investigated. The vibrational and rotational temperatures of the CH(A2△) product are obtained by comparing experimental data with the simulated ones from the LIFBASE program.     

Instability of lithium bis(fluorosulfonyl)imide(LiFSI)–potassium bis(fluorosulfonyl)imide(KFSI) system with LiCoO_2 at high voltage

The cycling performance, impedance variation, and cathode surface evolution of the Li/LiCoO2 cell using Li FSI–KFSI molten salt electrolyte are reported. It is found that this battery shows poor cycling performance, with capacity retention of only about 67% after 20 cycles. It is essential to understand the origin of the instability. It is noticed that the polarization voltage and the impedance of the cell both increase slowly upon cycling. The structure and the properties of the pristine and the cycled LiCoO2 cathodes are investigated by x-ray diffraction(XRD), scanning electron microscopy(SEM), Raman spectroscopy, x-ray photoelectron spectroscopy(XPS), and transmission electron microscopy(TEM). It is found that the LiCoO2 particles are corroded by this molten salt electrolyte, and the decomposition by-product covers the surface of the LiCoO2 cathode after 20 cycles. Therefore, the surface side reaction explains the instability of the molten salt electrolyte with LiCoO2.     

A low cost composite quasi-solid electrolyte of LATP,TEGDME,and LiTFSI for rechargeable lithium batteries

The composite quasi solid state electrolytes(CQSE) is firstly synthesized with quasi solid state electrolytes(QSE) and lithium-ion-conducting material Li_(1.4)Al_(0.4)Ti_(1.6)(PO_4)_3(LATP), and the QSE consists of [LiG4][TFSI] with fumed silica nanoparticles. Compared with LATP, CQSE greatly improves the interface conductance of solid electrolytes. In addition,it has lower liquid volume relative to QSE. Although the liquid volume fraction of CQSE is droped to 60%, its conductivity can also reach 1.39 × 10~(-4)S/cm at 20℃. Linear sweep voltammetry(LSV) is conducted on each composite electrolyte.The results show the possibility that CQSE has superior electrochemical stability up to 5.0 V versus Li/Li+. TG curves also show that composite electrolytes have higher thermal stability. In addition, the performance of Li/QSE/Li Mn_2O_4 and Li/CQSE/Li Mn_2O_4 batteries is evaluated and shows good electrochemical characteristics at 60℃.     

Effect of Poly（Ether Urethane） Introduction on the Performance of Polymer Electrolyte for All-Solid-State Dye-Sensitized Solar Cells

The introduction of poly（ether urethane） （PEUR） into polymer electrolyte based on poly（ethylene oxide）, LiI and I2, has significantly increased the ionic conductivity by nearly two orders of magnitudes. An increment of I3- diffusion coefficient is also observed. All-solid-state dye-sensitized solar cells are constructed using the polymer electrolytes. It was found that PEUR incorporation has a beneficial effect on the enhancement of open circuit voltage VOC by shifting the band edge of TiO2 to a negative value. Scanning
electron microscope images indicate the perfect interfacial contact between the TiO2 electrode and the blend electrolyte.     

Optical Design of Dye-Sensitized Nanocrystalline Solar Cells

In nanocrystalline dye-sensitized solar cells (DSSCs) the absorption of a large fraction of the incident solar radiation is important for achieving high efficiencies. We develop a model to include both the optical process and the electrochemical process. This model allows us to calculate the performance of the different optical designs (for example the different scattering layers and the different reflecting plane). It is found that appropriate optical designs can improve the performance of DSSCs greatly.     

Adsorption of propylene carbonate on the Li Mn_2O_4 (100) surface investigated by DFT+U calculations

Understanding the mechanism of the interfacial reaction between the cathode material and the electrolyte is a significant work because the interfacial reaction is an important factor affecting the stability,capacity,and cycling performance of Li-ion batteries.In this work,spin-polarized density functional theory calculations with on-site Coulomb energy have been employed to study the adsorption of electrolyte components propylene carbonate(PC)on the LiMn2O4(100)surface.The findings show that the PC molecule prefers to interact with the Mn atom on the LiMn2O4(100)surface via the carbonyl oxygen(Oc),with the adsorption energy of?1.16 eV,which is an exothermic reaction.As the adsorption of organic molecule PC increases the Mn atoms coordination with O atoms on the(100)surface,the Mn3+ions on the surface lose charge and the reactivity is substantially decreased,which improves the stability of the surface and benefits the cycling performance.     

Photoelectrocatalytic oxidation of methane into methanol and formic acid over ZnO/graphene/polyaniline catalyst

ZnO/graphene/polyaniline(PANI) composite is synthesized and used for photoelectrocatalytic oxidation of methane under simulated sun light illumination with ambient conditions. The photoelectrochemical(PEC) performance of pure ZnO, ZnO/graphene, ZnO/PANI, and ZnO/graphene/PANI photoanodes is investigated by cyclic voltammetry(CV),chronoamerometry(J–t) and electrochemical impedance spectroscopy(EIS). The yields of methane oxidation products,mainly methanol(CH_3OH) and formic acid(HCOOH), catalysed by the synthesized ZnO/graphene/PANI composite are 2.76 and 3.20 times those of pure ZnO, respectively. The mechanism of the photoelectrocatalytic process converting methane into methanol and formic acid is proposed on the basis of the experimental results. The enhanced photoelectrocatalytic activity of the ZnO/graphene/PANI composite can be attributed to the fact that graphene can efficiently transfer photo-generated electrons from the inner region to the surface reaction to form free radicals due to its superior electrical conductivity as an inter-media layer. Meanwhile, the introduction of PANI promotes solar energy harvesting by extending the visible light absorption and enhances charge separation efficiency due to its conducting polymer characteristics.In addition, the PANI can create a favorable π-conjunction structure together with graphene layers, which can achieve a more effective charge separation. This research demonstrates that the fabricated ZnO/graphene/PANI composite promises to implement the visible-light photoelectrocatalytic methane oxidation.     

Recombination Reduction in Dye-Sensitized Solar Cells by Screen-Printed TiO2 Underlayers

In dye-sensitized solar cells （DSSCs）, the TiO2 underlayer can block the electron recombination at the FTO （fluorine doped SnO2） glass/electrolyte interface. This underlayer was traditionally prepared by spray-pyrolysis or spin coating. In this study, we develop an alternative method based on screen-printing. The quality of the screen-printed underlayers is characterized by SEM, XPS and the photoelectrochemistry measurements. The prepared underlayers are smooth and effective. The screen-printing technique is cheap and easy to handle and can produce films with different patterns. These advantages will facilitate applications of the screen-printed underlayer.     

Comparison of optical properties of Cu-Al_2O_3 and Ag-Al_2O_3 nano-array composite structure

Cu-Al2O3 (Ag-Al2O3) nano-array composite structures were obtained by alternating current (AC) elec-trodeposition Cu (Ag) into the pores of anodic alumina. Their transmitted spectra and polarized properties were investigated in detail. Experimental results indicate that the transmittance of Cu-Al2O3 is superior to that of Ag-Al2O3 in visible and infrared wavebands, and the extinction ratio is better than that of Ag-Al2O3 in near infrared waveband.     

LIF diagnostics of hydroxyl radical in a methanol containing atmospheric-pressure plasma jet

In this paper, a pulsed-dc CH_3OH/Ar plasma jet generated at atmospheric pressure is studied by laser-induced fluorescence(LIF) and optical emission spectroscopy(OES). A gas–liquid bubbler system is proposed to introduce the methanol vapor into the argon gas, and the CH3OH/Ar volume ratio is kept constant at about 0.1%. Discharge occurs in a 6-mm needle-to-ring gap in an atmospheric-pressure CH_3OH/Ar mixture. The space-resolved distributions of OH LIF inside and outside the nozzle exhibit distinctly different behaviors. And, different production mechanisms of OH radicals in the needle-to-ring discharge gap and afterglow of plasma jet are discussed. Besides, the optical emission lines of carbonaceous species, such as CH, CN, and C_2 radicals, are identified in the CH_3OH/Ar plasma jet. Finally, the influences of operating parameters(applied voltage magnitude, pulse frequency, pulsewidth) on the OH radical density are also presented and analyzed.     

Low platinum loading PtNPs/graphene composite catalyst with high electrocatalytic activity for dye-sensitized solar cells

Platinum nanoparticles(PtNPs)/graphene composite materials are synthesized by a controlled chemical reduction of H2PtCl6 on graphene sheets.The electrocatalytic activity of a PtNPs/graphene composite counter electrode for a dye-sensitized solar cell(DSSC) is investigated.The results demonstrate that the PtNPs/graphene composite has high electrocatalytic activity for the dye-sensitized solar cell.The cell employing PtNPs(1.6 wt%)/graphene counter electrode reaches an conversion efficiency(η)of 3.89% upon the excitation of 100 mW/cm2 AM 1.5 white light,which is comparable to that of the cell with a Pt-film counter electrode(η=3.76%).It suggests that one can use only 14% Pt content of the conventional Pt-film counter electrode to obtain a comparable conversion efficiency.It may be possible to obtain a high performance DSSC using the PtNPs/graphene composite with a very low Pt content as a counter electrode due to its simplicity,low cost,and large scalability.     

Preparation techniques and materials for long term stable SOFC - Single cell membranes

Chemical reactions and thermal expansion mismatch between electrodes and electrolyte may reduce the long term stability of SOFC-single cells and can cause undesirable thermomechanical stresses. In solid electrolyte cells the formation of MnAl₂O₄ was detected between the air electrode (La_0.5Ca_0.5MnO₃) and the electrolyte (YSZ/Al₂O₃) in a 5 μm diffusion zone within the electrolyte. The electronically conducting spinel MnAl₂O₄ is thought to be the main factor for delamination of the air electrode under anodic current (electrolysis). The performance and long term stability of the air electrode/electrolyte interface can be improved for electrolysis conditions by an additional intermediate YSZ-layer made by sol-gel technique. The mismatch in thermal expansion between the electrode materials and the electrolyte have been eliminated via optimized doping and by adding small amounts of a silicate-based substituent with a very low thermal expansion co-efficient for the cathode and anode, respectively. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

High Thermoelectric Properties of PbTe Doped with Bi2Te3 and Sb2Te3

The composition-dependent thermoelectric properties of lead telluride (PbTe) doped with bismuth telluride (Bi2Te3), antimony telluride (Sb2Te3) and (BiSb)2Te3 have been studied at room temperature. All the sampies exhibit small thermal conductivity. The figures of merit, 7.63, 1.03 and 8.97 x 10-4, have been obtained in PbTe with these dopants, respectively. These values are several times higher than those of PbTe containing other dopants with small grain sizes. The high thermoelectric performance is explained by electronic topological transition induced by alloying. The results indicate that these dopants are effective to enhance the thermoelectric performance of PbTe.     

Influence of fluoroethylene carbonate on the solid electrolyte interphase of silicon anode for Li-ion batteries:A scanning force spectroscopy study

Silicon is an important high capacity anode material for the next generation Li-ion batteries.The electrochemical performances of the Si anode are influenced strongly by the properties of the solid electrolyte interphase(SEI).It is well known that the addition of flouroethylene carbonate(FEC)in the carbonate electrolyte is helpful to improve the cyclic performance of the Si anode.The possible origin is suggested to relate to the modification of the SEI.However,detailed information is still absent.In this work,the structural and mechanical properties of the SEI on Si thin film anode in the ethylene-carbonate-based(EC-based)and FEC-based electrolytes at different discharging and charging states have been investigated using a scanning atomic force microscopy force spectroscopy(AFMFS)method.Single-layered,double-layered,and multi-layered SEI structures with various Young’s moduli have been visualized three dimensionally at nanoscale based on the hundreds of force curves in certain scanned area.The coverage of the SEI can be obtained quantitatively from the two-dimensional(2D)project plots.The related analysis indicates that more soft SEI layers are covered on the Si anode,and this could explain the benefits of the FEC additive.     

Polymer-Sandwich Ultra-Thin Silicon(100) Platform for Flexible Electronics

As a potential flexible substrate for flexible electronics,a polymer-sandwiched ultra-thin silicon platform is studied.SU-8 photoresist coated on the silicon membrane improves its flexibility as shown by an ANSYS simulation.Using the plasma enhanced chemical vapor deposited SiO_2/Si_3N_4 composite film as an etching mask,a 4" silicon-(100) wafer is thinned to 26 μm without rupture in a 30 wt.%KOH solution.The thinned wafer is coated on both sides with 20 μm of SU-8 photoresist and is cut into strips.Then the strips are bent by a caliper to measure its bending radius.A sector model of bending deformation is adopted to estimate the radius of curvature.The determined minimal bending radius of the polymer-sandwiched ultra-thin sihcon layer is no more than 3.3mm.The fabrication process of this sandwich structure can be used as a post-fabrication process for high performance flexible electronics.     

Enhanced hyperthermia performance in hard-soft magnetic mixed Zn0.5CoxFe2.5−xO4/SiO2 composite magnetic nanoparticles

High quality Zn0.5CoxFe2.5?xO4(x=0,0.05,0.1,0.15)serial magnetic nanoparticles with single cubic structures were prepared by the modified thermal decomposition method,and Zn0.5CoxFe2.5?xO4/SiO2 composite magnetic nanoparticles were prepared by surface modification of SiO2.The magnetic anisotropy of the sample increases with the increase of the doping amount of Co2+.When the doping amount is 0.1,the sample shows the transition from superparamagnetism to ferrimagnetism at room temperature.In the Zn0.5CoxFe2.5?xO4/SiO2 serial samples,the maximum value of specific loss power(SLP)with 1974 W/gmetal can also be found at doping amount of x=0.1.The composite nanoparticles are expected to be an excellent candidate for clinical magnetic hyperthermia.     

Time-Dependent Quantum Dynamics of Dissociation for CH4 on an Ni（100） Surface

The semirigid vibrating rotor target (SVRT) model proposed by Zhang [J.Chem. Phys. 111 (1999) 3929] is applied to study the dynamics of dissociative adsorption for CH4 on a fiat and static Ni(100) surface. The molecule CH4 is treated as a semirigid vibrating rotor CH3-H, and the London-Eyring-Polanyi-Sato potential