A novel polyhedral oligomeric silsesquioxane (POSS) composite polyacrylonitrile (PAN)-based porous structure gel polymer electrolyte (GPE) is prepared by phase inversion method. The POSS additive filler is firstly obtained in the dehydration condensation reaction of vinyltrimethoxysilane (VTMS) and 3-methacryloxypropyltrimethoxysilane (MPTMS). The composition and structure of synthetic POSS and the prepared POSS composite PAN-based GPEs are investigated. It is found that compared with pure PAN-based GPE, the POSS composite PAN-based GPE with 8 wt.% POSS presents the homogeneous pore distribution and abundant electrolyte uptake (540.4 wt.%), which endows GPE-8% with the excellent comprehensive performances: the highest ionic conductivity of 2.62?×?10?3 S cm?1 at room temperature, the higher lithium ion transference number of 0.38, the good compatibility with lithium anode, and the higher electrochemical stability window of 5.7 V (vs. Li/Li+). At 0.2 C, the GPE-8%-based lithium ion battery produces a satisfactory discharge capacity of 140 mAh g?1.
The paper reports the effect of SiO2 nano-filler on structural, thermal, and ion transport properties of polymer electrolyte system comprising polyvinyl alcohol (PVA) and 1-butyl-3-methylimidazolium hydrogen sulfate [C4C1Im][HSO4] ionic liquid. The addition of SiO2 nano-filler results into enhancement in amorphicity and thermal stability and lowering of glass transition temperature of the membranes. A detailed investigation of possible interactions among the constituents PVA, [C4C1Im][HSO4] and SiO2, and cation–anion and anion–anion pairs of [C4C1Im][HSO4] in the polymer electrolyte and their dissociation due to SiO2 filler has been carried out in the membranes using Fourier transform infra-red (FTIR) and Raman spectroscopy. The membranes show maximum room temperature ionic conductivity as 9.9?×?10?3 S cm?1 for 6 wt.% of the nano-filler which is about four times higher than the membrane without nano-filler and an order higher than pure [C4C1Im][HSO4]. With temperature, the ionic conductivity shows VTF behavior in the temperature range 40–120 °C. On the basis of FTIR and ion transport results, a model for ion transport in the membranes is proposed.
The electrocatalytic mechanism of Cr(III) reduction in the presence of diethylenetriaminepentaacetic acid (DTPA) and nitrate ions is studied theoretically and experimentally by using stripping square-wave voltammetry (SWV). Experimental curves are in excellent agreement with theoretical profiles corresponding to a catalytic reaction of second kind. This type of mechanism is equivalent to a CE mechanism, where the chemical reaction produces the electroactive species. Accordingly, the reaction of Cr(III)–H2O–DTPA and \( {\mathrm{NO}}_3^{-} \) would produce the electroactive species Cr(III)–NO3–DTPA and this last species would release \( {\mathrm{NO}}_2^{-} \) to the solution during the electrochemical step. In this regard, the complex of Cr(III)–DTPA would work as the catalyzer that allows the reduction of \( {\mathrm{NO}}_3^{-} \) to \( {\mathrm{NO}}_2^{-} \). Furthermore, it was found that the electrochemical reaction is quite irreversible, with a constant of ks?=?9.4?×?10?5 cm s?1, while the constant for the chemical step has been estimated to be kchem?=?1.3?×?104 s?1. Considering that the equilibrium constant is K?=?0.01, it is possible to estimate the kinetic constants of the chemical reaction as k1?=?1?×?102 s?1 and k?1?=?1.29?×?104 s?1. These values of k1 and k?1 indicate that the exchange of water molecules by nitrate is fast and that the equilibrium favors the complex with water. Also, a value for the formal potential E°’?≈??1.1 V was obtained. The model used for simulating experimental curves does not consider the adsorption of reactants yet. Accordingly, weak adsorption of reagents should be expected. 相似文献
Free-standing and flexible NiMoO4 nanorods/reduced graphene oxide (rGO) membrane with a 3D hierarchical structure was successfully synthesized by a general approach including vacuum filtration followed by thermal reduction. NiMoO4 nanorods with about 50–100 nm diameter were embedded homogenously into the 3D rGO sheets and assembled with rGO to form a membrane about 10 μm in thickness. The NiMoO4/rGO membrane could be directly evaluated as anode materials for lithium-ion batteries (LIBs) without using binder. The 3D layer stacked graphene hierarchical architecture can not only offers a continuous conducting framework for efficient diffusion and transport of ion/electron but also accommodates the large volume expansion of NiMoO4 nanorod changes during cycling. Moreover, our results show that the NiMoO4/rGO membrane exhibited excellent electrochemical performance with a high reversible capacity of 945 mAh g?1 at a current density of 0.25 A g?1 as anode materials in LIBs.
A biodegradable composite polymer membrane is fabricated by synthesizing polyvinylpyrrolidone (PVP) on the matrix of lignin, and then the corresponding gel polymer electrolyte (LP-GPE) is further prepared by absorbing the liquid electrolyte. The morphology, mechanical property, and thermal stability of the composite lignin-PVP membrane and the electrochemical properties of LP-GPE are investigated. The results of the investigation present that the mechanical property of the membrane is remarkable improved (670%) and the composite membrane exhibits a better thermal security. For electrochemical properties, a high ionic conductivity of 2.52 × 10?3 S cm?1 at room temperature, excellent lithium-ion transference number of 0.56, and outstanding electrochemical stability of LP-GPE are confirmed. Moreover, the C-rate performance and capacity retention based on Li/LP-GPE/LiFePO4 cell are superior to that of the commercial Celgard 2730 cell. Consequently, all these results demonstrate that LP-GPE can be applied as a novel electrolyte for lithium ion battery with high-performance, low-cost, and environment-friendly properties.
Biomass-derived carbon (BMC) materials have attracted much attention due to their high performance and properties of abundant source. Herein, biomass carbon sheets (BMCS) from wheat straws had been successfully synthesized via a facile high temperature carbonization and expansion processes. The morphology of BMCS keeps the natural honeycomb-like shape of the cross section and the hollow tubular array structure of the vertical section with rich pores, which provides low-resistant ion channels to support fast diffusion. The (002) crystal plane reveals that the intercalation distance of carbon sheets is 0.383 nm larger than that graphite (0.335 nm), which benefits the larger sodium ion de/intercalation. By comparing different carbonization temperatures, wheat straws carbonized at 1200 °C (BMCS-1200) with well graphite microcrystallites show more excellent sodium ion storage performance than that of 900 °C (BMC-900). BMCS-1200 shows a stable reversible capacity of 221 mAh g?1 after 200 cycles at 0.05 A g?1, while BMC-900 is 162 mAh g?1 after 100 cycles. And it also exhibits better rate capability (220, 109 mAh g?1) than that of BMC-900 (125, 77 mAh g?1) at 0.2 and 1 A g?1, respectively. Finally, it delivers 89 mAh g?1 stable capacity after 1400 cycles at 1 A g?1 to prove its excellent long-term cycling stability.
Graphical abstract High temperature carbon sheets with well graphite microcrystallites synthesized from wheat straw forexcellent sodium ion storage performance
In the current work, the effect of aniline concentration on the polymerization process and supercapacitive behavior of graphene oxide/multiwalled carbon nanotubes/polyaniline (GMP) nanocomposites were studied. Based on the obtained results, GMP nanocomposite with 0.5 M aniline (GMP5) was selected as the optimum concentration in terms of high current density and high specific capacitance. Nafion-based ionic polymer-free metal composite (IPFMC) supercapacitor was fabricated for the GMP5 nanocomposite. Solid-state symmetric supercapacitor was made after spraying of GMP5 in. on both sides of Nafion membrane. The electrochemical properties were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD), and electrochemical impedance spectroscopy (EIS) techniques in 0.5 M Na2SO4.The specific capacitance of 383.25 F g?1 (326 mF cm?2) and 527.5 F g?1 (42 mF cm?2) was obtained for the GMP5 in solid-state supercapacitor and three-electrode cell at a scan rate of 10 mV s?1, respectively. The maximum energy and power densities of 53.64 and 1777.4 W kg?1 were obtained for the IPFMC-based supercapacitor.
Lithium ion capacitor (LIC) is a novel hybrid capacitor technology that possesses a better performance than the conventional supercapacitor, such as EDLC and lithium ion battery. However, the overall performance of LIC is limited by activated carbon’s capacity as its cathode. This work is focused on synthesize of activated carbon from Indonesian local orange peel waste for LIC cathode and its modification to perform a good electrochemical performances. Activated carbon was synthesized by ZnCl2 as impregnant with mass ratio of orange peel to ZnCl2 1:2 for 1 h at 500 °C. The obtained activated carbon possessed large surface area (1200 m2 g ?1), higher than commercial activated carbon (Merck-p.a.) with surface area of 775.6 m2 g?1. Modification was done using wet oxidation method by utilizing HNO3 65 %, H2SO4 98 %, and H2O2 30 %, with ratio 1:1 (w/w). Electrochemical properties were studied by using half cell test pouch with Li metal as reference electrode and 1 M LiPF6 (EC:EMC:DMC = 1:1:1) as electrolyte. Modification had successfully increased oxygen atoms in activated carbon samples. Surface-modified cells demonstrated a higher capacitance (almost twice in the galvanostatic test) than that of the unmodifed one due to the pseudocapacitance effect of oxygen functional groups. However, its electrochemical performance was unstable. The unmodified cell showed a stable performance with 56.3 F g?1 at current density of 0.3 mA g?1 and voltage window 2.5–4 V.
B-Nb2O5 was recrystallized from commercially available oxide, and XRD analyses indicated that it is stable in contact with solutions over the pH range 0 to 9, whereas solid polyniobates such as Na8Nb6O19?13H2O(s) appear to predominate at pH>9. Solubilities of the crystalline B-Nb2O5 were determined in five NaClO4 solutions (0.1≤Im/mol?kg?1≤1.0) over a wide pH range at (25.0±0.1)?°C and at 0.1 MPa. A limited number of measurements were also made at Im=6.0 mol?kg?1, whereas at Im=1.0 mol?kg?1 the full range of pH was also covered at (10, 50 and 70)?°C. The pH of these solutions was fixed using either HClO4 (pH≤4) or NaOH (pH≥10) and determined by mass balance, whereas the pH on the molality scale was measured in buffer mixtures of acetic acid?+?acetate (4≤pH≤6), Bis-Tris (pH≈7), Tris (pH≈8) and boric acid?+?borate (pH≈9). Treatment of the solubility results indicated the presence of four species, \(\mathrm{Nb(OH)}_{n}^{5-n}\) (where n=4–7), so that the molal solubility quotients were determined according to:
and were fitted empirically as a function of ionic strength and temperature, including the appropriate Debye-Hückel term. A Specific Interaction Theory (SIT) approach was also attempted. The former approach yielded the following values of log?10Ksn (infinite dilution) at 25?°C: ?(7.4±0.2) for n=4; ?(9.1±0.1) for n=5; ?(14.1±0.3) for n=6; and ?(23.9±0.6) for n=7. Given the experimental uncertainties (2σ), it is interesting to note that the effect of ionic strength only exceeded the combined uncertainties significantly in the case of log?10Ks6 to Im=1.0 mol?kg?1, such that these values may be of use by defining their magnitudes in other media. Values of ΔfGo, ΔfHo, So and \(C_{p}^{\mathrm{o}}\) (298.15 K, 0.1 MPa) for each hydrolysis product were calculated and tabulated.
In operando quantification of field-assisted ion release during high-voltage anodisation (up to 100 V SHE) of Nb in 0.1 M sulphuric acid was performed. Electrochemical high-field oxide formation under both potential and current control was studied separately. The quantification of in situ ion release via ICP-MS revealed an increase of the oxide dissolution factor (from 337 to 422 fm V?1) when decreasing the potential scan rate from 200 to 100 mV s?1. Dissolution rates measured during galvanostatic oxide formation allowed measuring oxide dissolution factors of 719 and 837 fm V?1 for current densities of 1.0 and 0.5 mA cm?2, respectively. As compared to the potentiodynamic case, higher dissolution rates and oxide dissolution factors were measured for galvanostatic anodisation. The overall fraction of the charge used for generation of soluble Nb species was below 0.4% for all oxide growth regimes. Cross-sectional SEM imaging proofs an oxide formation factor of 2.1 nm V?1. The surface of anodised films was extremely smooth and featureless without any cracks or voids. Based on X-ray diffraction, the films were found to be amorphous, indicating that no field crystallisation is occurring under the applied oxide growth conditions even at higher voltages.
A porous, hollow, microspherical composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) was prepared using hollow MnO2 as the sacrificial template. The resulting composite was found to be mesoporous; its pores were about 20 nm in diameter. It also delivered a reversible discharge capacity value of 220 mAh g?1 at a specific current of 25 mA g?1 with excellent cycling stability and a high rate capability. A discharge capacity of 100 mAh g?1 was obtained for this composite at a specific current of 1000 mA g?1. The high rate capability of this hollow microspherical composite can be attributed to its porous nature.
Hydrothermally synthesized Co3O4 microspheres were anchored to graphite oxide (GO) and thermally reduced graphene oxide (rGO) composites at different cobalt weight percentages (1, 10, and 100 wt%). The composite materials served as the active materials in bulk electrodes for two-electrode cell electrochemical capacitors (ECCs). GO/Co3O4–1 exhibited a high energy density of 35 W kg?1 with a specific capacitance (Csp) of 196 F g?1 at a maximum charge density of 1 A g?1. rGO/Co3O4-100 presented high specific power output values of up to 23.41 kW h kg?1 with linear energy density behavior for the charge densities applied between 0.03 and 1 A g?1. The composite materials showed Coulombic efficiencies of 96 and 93 % for GO/Co3O4–1 and rGO/Co3O4–100 respectively. The enhancement of capacitive performance is attributed to the oxygenated groups in the GO ECC and the specific area in the rGO ECC. These results offer an interesting insight into the type of carbonaceous support used for graphene derivative electrode materials in ECCs together with Co3O4 loading to improve capacitance performance in terms of specific energy density and specific power.
Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111) is a promising alternative to LiCoO2, as it is less expensive, more structurally stable, and has better safety characteristics. However, its capacity of 155 mAh g?1 is quite low, and cycling at potentials above 4.5 V leads to rapid capacity deterioration. Here, we report a successful synthesis of lithium-rich layered oxides (LLOs) with a core of LiMO2 (R-3m, M?=?Ni, Co) and a shell of Li2MnO3 (C2/m) (the molar ratio of Ni, Co to Mn is the same as that in NCM 111). The core–shell structure of these LLOs was confirmed by XRD, TEM, and XPS. The Rietveld refinement data showed that these LLOs possess less Li+/Ni2+ cation disorder and stronger M*–O (M*?=?Mn, Co, Ni) bonds than NCM 111. The core–shell material Li1.15Na0.5(Ni1/3Co1/3)core(Mn1/3)shellO2 can be cycled to a high upper cutoff potential of 4.7 V, delivers a high discharge capacity of 218 mAh g?1 at 20 mA g?1, and retains 90 % of its discharge capacity at 100 mA g?1 after 90 cycles; thus, the use of this material in lithium ion batteries could substantially increase their energy density.
Graphical Abstract Average voltage vs. number of cycles for the core–shell and pristine materials at 20 mA g?1 for 10 cycles followed by 90 cycles at 100 mA g?1
A series of PANI-CNTs/TiO2 nanotubes/Ti electrodes were fabricated via pulse current co-electrodeposition of polyaniline and functionalized carbon nanotubes onto TiO2 nanotubes/Ti electrodes. FT-IR spectrometry, X-ray photoelectron spectroscopy, and scanning electron microscopy were applied in order to characterize the modified TiO2 nanotubes/Ti electrodes. The morphology studies showed that the PANI-CNTs/TiO2 nanotubes/Ti nanocomposite electrode has many interlaced PANI-CNTs nanorods on the surface of TiO2 nanotubes. The electrochemical measurements of the modified electrodes confirmed that the CNTs in the composite can significantly improve the capacitive behavior as well which have been compared with that of PANI/TiO2 nanotubes/Ti electrodes. The modified electrode exhibited much higher specific capacitance (190 mF cm?2 with 90% retention after 1000 cycles) compared to the PANI/TiO2 nanotubes/Ti (70 mF cm?2 with 77% retention after 1000 cycles) at a current density of 0.85 mA cm?2, indicating its great potential for supercapacitor applications.
The oxidation of nanomolar levels of iron(II) with oxygen has been studied in NaCl solutions as a function of temperature (0 to 50?°C), ionic strength (0.7 to 5.6 mol?kg?1), pH (6 to 8) and concentration of added NaHCO3 (0 to 10 mmol?kg?1). The results have been fitted to the overall rate equation: $$\mathrm{d}\mbox{[Fe(II)]}/\mathrm{d}t=-k_{\mathrm{app}}\mbox{[Fe(II)]}[\mbox{O}_{2}]$$ The values of kapp have been examined in terms of the Fe(II) complexes with OH? and CO32?. The overall rate constants are given by: $$k_{\mathrm{app}}=\alpha_{\mathrm{Fe}2+}k_{\mathrm{Fe}}+\alpha_{\mathrm{Fe(OH)}+}k_{\mathrm{Fe(OH)}+}+\alpha_{\mathrm{Fe(OH)}2}k_{\mathrm{Fe(OH)}2}+\alpha_{\mathrm{Fe(CO3)}2}k_{\mathrm{Fe(CO3)}2}$$ where αi is the molar fraction and ki is the rate constant of species i. The individual rate constants for the species of Fe(II) interacting with OH? and CO32? have been fitted by equations of the form: $$\begin{array}{l}\ln k_{\mathrm{Fe}2+}=21.0+0.4I^{0.5}-5562/T\\[6pt]\ln k_{\mathrm{FeOH}}=17.1+1.5I^{0.5}-2608/T\\[6pt]\ln k_{\mathrm{Fe(OH)}2}=-6.3-0.6I^{0.5}+6211/T\\[6pt]\ln k_{\mathrm{Fe(CO3)}2}=31.4+5.6I^{0.5}-6698/T\end{array}$$ These individual rate constants can be used to estimate the rates of oxidation of Fe(II) over a large range of temperatures (0 to 50?°C) in NaCl brines (I=0 to 6 mol?kg?1) with different levels of OH? and CO32?. 相似文献
Hollow titanium dioxide (TiO2) microspheres were synthesized in one step by employing tetrabutyl orthotitanate (TBOT) as a precursor through a facile solvothermal method in the presence of NH4HCO3. XRD analysis indicated that anatase TiO2 can be obtained directly without further annealing. TiO2 hollow microspheres with diameters in the range of 1.0–4.0 μm were confirmed through SEM and TEM measurements. The specific surface area was measured to be 180 m2 g?1 according to the nitrogen adsorption–desorption isotherms. Superior photocatalytic performance and good lithium storage properties were achieved for resultant TiO2 samples. The H2 evolution rate of the optimal sample is about 0.66 mmol h?1 after loaded with 1 wt.% Pt (20 mg samples). The reversible capacity remained 143 mAh g?1 at a specific current of 300 mA g?1 after 100 charge–discharge cycles. This work provides a facile strategy for the preparation of hollow titanium dioxide microspheres and demonstrates their promising photocatalytic H2 evolution and the lithium storage properties.
Graphical abstract Hollow titanium dioxide spheres are directly synthesized via a facile template-free solvothermal method with the presence of NH4HCO3 based on inside-out Ostwald ripening (see picture), and demonstrated both as a photocatalyst for water splitting and a promising anode material for lithium-ion batteries. Superior photocatalytic performance and excellent lithium storage properties are achieved for resultant TiO2 hollow microspheres.
We obtained Tannin-4-azobenzoic acid (azo dye) by the conventional method of diazotization and coupling of aromatic amines. The properties of the azo dye were characterized via ultraviolet-visible (UV–vis), infrared (IR), and nuclear magnetic resonance (NMR) spectroscopy. Nanocrystalline titanium dioxide (TiO2) thin films were deposited by hydrothermal method onto fluorine-doped tin (IV) oxide (FTO)-coated glass substrate at 353 K for 4 h. The as-deposited and annealed films were characterized for structural, morphological, optical, thickness, and wettability properties. The synthesized metal free azo dye was used to sensitize the prepared TiO2 thin film with thickness of 26 μm. The photoelectrochemical (PEC) performance of TiO2 sensitized with the azo dye was evaluated in polyiodide (0.1 M KI + 0.01 M I2 + 0.1 M KCl) electrolyte at 40 mW cm?2 illumination intensity. The cell yielded a short circuit current of 2.82 mA, open circuit voltage of 314.3 mV, a fill factor of 0.30, and a photovoltaic conversion efficiency value of 0.64%.
Tin (Sn) has been considered as an attractive anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity (847 mAh g?1). Nevertheless, its low conductivity and large volume change during cycling essentially prevent the possibility of high capacity and long-term cycle for SIBs. In this work, Sn nanoparticles are well embedded into the highly ordered mesoporous carbon (CMK-3) matrix (Sn@CMK-3) using a facile sonochemical method combined with heat treatment. The resultant Sn@CMK-3 nanohybrid electrode delivers an initial charge capacity of 412 mAh g?1 at 100 mA g?1. A reversible capacity of 337 mAh g?1 is obtained after 200 cycles, indicating the good cycle stability of the nanohybrid structure. The electrode also shows a potential rate capability, which maintains a capacity of 228 mAh g?1 at 1000 mA g?1. When the current density returns to 50 mA g?1, the capacity goes back to 381 mAh g?1, with a capacity retention of 86.9%. The enhanced sodium storage performance of Sn@CMK-3 nanohybrid can be related to the synergistic effect between CMK-3 and Sn.
Graphical abstract Sn@CMK-3 nanohybrid with Sn nanoparticles uniformly distributed into the highly ordered mesoporous carbon matrix exhibited good cycling performance and rate capability.
A new zinc-layered hydroxide-L-phenylalanate (ZLH-LP)-modified multiwalled carbon nanotube (MWCNT) was prepared as a new material of paste electrode for the detection of paracetamol (PCM) in 1.0?×?10?1 M phosphate buffer solution and at pH 7.5. The electrochemical characterization of the MWCNTs/ZLH-LP paste electrode was characterized by square wave voltammetry, electrochemical impedance spectroscopy, and cyclic voltammetry while the morphology properties of the MWCNTs, ZLH-LP, and MWCNTs/ZLH-LP were investigated using transmission electron microscopy and scanning electron microscopy. Under optimized conditions, the MWCNTs/ZLH-LP paste electrode demonstrated an excellent electrocatalytic activity towards oxidation of PCM in the linear responses’ ranges from 7.0?×?10?7 M to 1.0?×?10?4 M (correlation coefficient, 0.996) with the limit of detection obtained at 8.3?×?10?8 M. As a conclusion, the MWCNTs/ZLH-LP paste electrode revealed good repeatability, reproducibility, and stability, and was found to be applicable for use in pharmaceutical tablet samples.
The three-dimensional porous Li3V2(PO4)3/nitrogen-doped reduced graphene oxide (LVP/N-RGO) composite was prepared by a facile one-pot hydrothermal method and evaluated as cathode material for lithium-ion batteries. It is clearly seen that the novel porous structure of the as-prepared LVP/N-RGO significantly facilitates electron transfer and lithium-ion diffusion, as well as markedly restrains the agglomeration of Li3V2(PO4)3 (LVP) nanoparticles. The introduction of N atom also has positive influence on the conductivity of RGO, which improves the kinetics of electrochemical reaction during the charge and discharge cycles. It can be found that the resultant LVP/N-RGO composite exhibits superior rate properties (92 mA h g?1 at 30 C) and outstanding cycle performance (122 mA h g?1 after 300 cycles at 5 C), indicating that nitrogen-doped RGO could be used to improve the electrochemical properties of LVP cathodes for high-power lithium-ion battery application.
Graphical abstract The three-dimensional porous Li3V2(PO4)3/nitrogen-doped reduced graphene oxide composite with significantly accelerating electron transfer and lithium-ion diffusion exhibits superior rate property and outstanding cycle performance.
