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1.
《Electrochemistry communications》2008,10(11):1792-1796
Manganese oxide nanowires with β-MnOOH in core and Mn3O4 in shell were successfully plated onto various conductive substrates from a Mn(CH3COO)2 solution by anodic deposition under a two-electrode, pulse-rest mode. The aspect ratio of uniform nanowire morphologies in cm2 scale is controllable by varying the deposition variables. Patterned MnOx nanowire arrays were obtained by combining lithographic and electroplating techniques demonstrated to be a powerful method for preparing MnOx nanowires in the field emission (FE) array cathodes with a low turn-on voltage (∼3.4 V/μm at 1 μA/cm2). 相似文献
2.
Cathode reactions in Zn/MnO2 batteries using aqueous electrolytes have been usually interpreted by the reduction of Mn4 + to Mn3 + while protons and/or cations penetrate inside the cathode. However, until now, the MnO2 storage charge mechanism using a non-aqueous gel polymer electrolyte (GPE) has not been investigated. In this work, ionic liquid-based GPEs including BMIM Tf and ZnTf2 have been employed in Zn/MnO2 batteries. Different states of charge of MnO2 cathodes used in Zn/IL-GPE/MnO2 batteries have been analyzed by XPS and EDX techniques. XPS analysis showed that Mn4 + is reduced during the discharge process at the same time as Zn2 + cations are incorporated into the cathode. Besides, Zn2 + cations insertion is accompanied by triflate anions. 相似文献
3.
《Electrochemistry communications》2007,9(2):262-268
A series of lithium–manganese–nickel-oxide compositions that can be represented in three-component notation, xLi[Mn1.5Ni0.5]O4 · (1 − x){Li2MnO3 · Li(Mn0.5Ni0.5)O2}, in which a spinel component, Li[Mn1.5Ni0.5]O4, and two layered components, Li2MnO3 and Li(Mn0.5Ni0.5)O2, are structurally integrated in a highly complex manner, have been evaluated as electrodes in lithium cells for x = 1, 0.75, 0.50, 0.25 and 0. In this series of compounds, which is defined by the Li[Mn1.5Ni0.5]O4–{Li2MnO3 · Li(Mn0.5Ni0.5)O2} tie-line in the Li[Mn1.5Ni0.5]O4–Li2MnO3–Li(Mn0.5Ni0.5)O2 phase diagram, the Mn:Ni ratio in the spinel and the combined layered Li2MnO3 · Li(Mn0.5Ni0.5)O2 components is always 3:1. Powder X-ray diffraction patterns of the end members and the electrochemical profiles of cells with these electrodes are consistent with those expected for the spinel Li[Mn1.5Ni0.5]O4 (x = 1) and for ‘composite’ Li2MnO3 · Li(Mn0.5Ni0.5)O2 layered electrode structures (x = 0). Electrodes with intermediate values of x exhibit both spinel and layered character and yield extremely high capacities, reaching more than 250 mA h/g with good cycling stability between 2.0 V and 4.95 V vs. Li° at a current rate of 0.1 mA/cm2. 相似文献
4.
《Electrochemistry communications》2007,9(1):103-108
The whole range of solid solutions Li(Li(1−x)/3CoxMn(2−2x)/3)O2 (0 ⩽ x ⩽ 1) was firstly synthesized by an aqueous solution method using poly-vinyl alcohol as a synthetic agent to investigate their structure and electrochemical properties. X-ray diffraction results indicated that the synthesized solid solutions showed a single phase without any detectable impurity phase and have a hexagonal structure with some additional peaks caused by monoclinic distortion, especially in the solid solutions with a low Co amount. In the electrochemical examination, the solid solutions in the range between 0.2 ⩽ x ⩽ 0.9 showed higher discharge capacity and better cyclability than LiCoO2 (x = 1) on cycling between 2.0 and 4.6 V with 100 mA g−1 at 25 °C. For example, Li(Li0.2Co0.4Mn0.4)O2 (x = 0.4) exhibited a high discharge capacity of 180 mA h g−1 at the 50th cycle. By synthesizing the solid solution between Li2MnO3 and LiCoO2, the electrochemical properties of the end members were improved. 相似文献
5.
We present a binder-free catalytic anode for highly efficient and stable oxygen evolution reaction in alkaline media. The catalyst consists of a thin film of buserite-type layered manganese dioxide (MnO2) intercalated with Co2 + ions, resulting from electrodeposition of the layered MnO2 film with tetrabutylammonium (Bu4N+) ions on a carbon cloth, followed by ion-exchange of the initially incorporated Bu4N+ with Co2 + in solution. The electrode is capable to produce a current density of 10 mA cm− 2 at an overpotential (η) of 377 mV with a Tafel slope of 48 mV dec− 1, much superior to the layered MnO2 without Co2 +. 相似文献
6.
《Solid State Sciences》2007,9(2):196-204
Rietveld refinement of the crystal and magnetic structures of LixMnO2 (x = 0.98, 1.00, 1.02) are performed using neutron and X-ray measurements. A significant structural disorder due to the presence of manganese ions in lithium positions (MnLi) and lithium ions in manganese ones (LiMn) is found to be a common feature of Li0.98MnO2, Li1.00MnO2, and Li1.02MnO2.An essential anisotropy of the thermal-expansion coefficients of the lithium manganese oxides is observed in the temperature range of 1.5–300 K. Furthermore, the distortion of the oxygen octahedral environment around the manganese ions decreases when the temperature lowers. This is attributed to the strong exchange interactions between parallel exchange-coupled Mn chains. First-principles calculations of the effective exchange-interaction parameters in Li16Mn16O32 confirm the essential antiferromagnetic interactions between the chains. In addition, a hypothetical (Li15Mn)Mn16O32 structure where a lithium atom located between the Mn double layers is replaced by a manganese atom is considered. The calculations reveal that the presence of such defects results in appearance of a ferromagnetic component that agrees with the magnetic measurements. 相似文献
7.
《Electrochemistry communications》2007,9(10):2611-2616
An interesting mode of reactivity of MnO2 nanoparticles modified electrode in the presence of H2O2 is reported. The MnO2 nanoparticles modified electrodes show a bi-direction electrocatalytic ability toward the reduction/oxidation of H2O2. Based on this property, a choline biosensor was fabricated via a direct and facile electrochemical deposition of a biocomposite that was made of chitosan hydrogel, choline oxidase (ChOx) and MnO2 nanoparticles onto a glassy carbon (GC) electrode. The biocomposite is homogeneous and easily prepared and provides a shelter for the enzyme to retain its bioactivity. The results of square wave voltammetry showed that the electrocatalytic reduction currents increased linearly with the increase of choline chloride concentration in the range of 1.0 × 10−5 –2.1 × 10−3 M and no obvious interference from ascorbic acid and uric acid was observed. Good reproducibility and stability were obtained. A possible reaction mechanism was proposed. 相似文献
8.
The corrosion behaviors of Ti40Zr25Ni12 -xNbxCu3Be20 (x = 0, 4, 8, and 12 at.%) alloys in 0.5 mol/L H2SO4 solution were studied, aiming to establish the relationship between Nb content and corrosion resistance. The addition of Nb element gives rise to a clear microstructural evolution, from a completely amorphous structure for the alloys without Nb and with 4% Nb alloys to an amorphous/crystalline composite structure for the alloys with 8% and 12% Nb. The alloy with higher Nb content exhibits better corrosion resistance, which can be attributed to the formation of Ti4 +-, Zr4 +-, and Nb5 +-enriched highly protective surface film in corrosive solutions. 相似文献
9.
Zhan-Ping Feng Gao-Ren Li Jin-Hui Zhong Zi-Long Wang Yan-Nan Ou Ye-Xiang Tong 《Electrochemistry communications》2009,11(3):706-710
MnO2 multilayer nanosheet clusters were prepared via electrochemical deposition route, which shows simpleness and high efficiency. The growth process of MnO2 multilayer nanosheet clusters was investigated in this paper. The deposited MnO2 films were characterized by XRD, SEM, TEM, and XPS. In addition, it was also electrochemically characterized by cyclic voltammetry in 1.0 M Na2SO4 electrolyte. The MnO2 multilayer nanosheet clusters show a big specific capacitance, and it can be achieved about 521.5 F g?1 at 5 mV s?1. These materials also have a high electrochemical stability. 相似文献
10.
Mi Liu Gui-Jun Zhang Zhu-Rui Shen Ping-Chuan Sun Da-Tong Ding Tie-Hong Chen 《Solid State Sciences》2009,11(1):118-128
Hierarchically structured mesoporous MnO2 with high surface area was prepared by a facile precursor route. Well-defined morphological manganese oxalate, synthesized by adding l-lysine via a hydrothermal method, was used as precursor. Mesoporous amorphous MnO2 with high Brunauer–Emmett–Teller (BET) surface area (340 m2/g) and mesoporous Mn2O3 composed of nano-crystals (BET surface area 188 m2/g) were obtained by selective calcination of the oxalate precursor at 330 °C and 400 °C, respectively. Thermogravimetric and differential thermal analyses (TG–DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2-sorption analysis and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure and property of products. Cyclic voltammetry (CV) and charge–discharge measurements were used to preliminarily study the electrochemical performance of the products. The range of pH value (about 5.0–7.0) in the synthesis process is apt to prepare the hierarchical structured manganese dioxide. Other types of amino acids were also employed as the crystallization modifiers and different morphologies of manganese dioxides were obtained. 相似文献
11.
PbO2 thin films were prepared by pulse current technique on Ti substrate from Pb(NO3)2 plating solution. The hybrid supercapacitor was designed with PbO2 thin film as positive electrode and activated carbon (AC) as negative electrode in the 5.3 M H2SO4 solution. Its electrochemical properties were determined by cyclic voltammetry (CV), charge–discharge test and electrochemical impedance spectroscopy (EIS). The results revealed that the PbO2/AC hybrid supercapacitor exhibited large specific capacitance, high-power and stable cycle performance. In the potential range of 0.8–1.8 V, the hybrid supercapacitor can deliver a specific capacitance of 71.5 F g?1 at a discharge current density of 200 mA g?1(4 mA cm?2) when the mass ratio of AC to PbO2 was three, and after 4500 deep cycles, the specific capacitance remains at 64.4 F g?1, or 32.2 Wh Kg?1 in specific energy, and the capacity only fades 10% from its initial value. 相似文献
12.
《Solid State Sciences》2012,14(7):782-788
First principles calculations have been performed to study the effects of the La3+ and Mn3+ substitutions in the multiferroic BiFeO3. The real compositions Bi1−xLaxFeO3 and BiFe1−xMnxO3 with x = 0.0, 0.1, 0.2, 0.3 were modeled by substitution of one, two and three Bi3+ or Fe3+ by La3+ or Mn3+ in the orthorhombic BiFeO3 structure, respectively. Density functional theory within the generalized gradient approximation with Hubbard correction of Dudarev (GGA + U) and plane wave pseudo-potential approach has been used to track the changes that occur in the structural parameters, electronic structure, magnetic, optical and polarization properties of the modified BiFeO3. The substitution of one Bi3+ with La3+ increases the band gap energy whereas the augmentation of La3+ substitutes decreases it. The substitutions of Fe3+ with Mn3+ do not change the band gap energy. The calculations predicted larger polarization of the modified BiFeO3, antiferromagnetism for Bi1−xLaxFeO3 and small ferrimagnetism for BiFe1−xMnxO3. Better multiferroic properties are expected for BiFe1−xMnxO3 materials (x = 0.1, 0.2) due to the increasing polarization and ferrimagnetic behavior. The optical properties were estimated by the calculated imaginary and real parts of the dielectric function. The increase of La3+ and Mn3+ substitutes lead to lower absorption intensity at energy range 2–7 eV. 相似文献
13.
Dawei Feng Cheng Wang Wentai Cheng Guobao Li Shujian Tian Fuhui Liao Ming Xiong Jianhua Lin 《Solid State Sciences》2009,11(4):845-851
A new layered compound, K4Mn3(HPO4)4(H2PO4)2 (1), has been synthesized under hydrothermal conditions. It crystallizes in the monoclinic space group P21/n with a = 8.874(2) Å, b = 6.554(1) Å, c = 18.075(4) Å, and β = 93.39(3)°. The structure consists of zigzag [Mn3O14]n chains of edge-sharing MnO6 octahedrons and MnO7 pentagonal bi-pyramids, which form layers of formula [Mn3(HPO4)4(H2PO4)2]4? in the ab plane via H2PO4 and HPO4 units with vertex-sharing. Potassium ions lie between these layers. Magnetic measurements indicate Curie–Weiss behavior above 6 K for 1. A Heisenberg model, with alternating exchange interactions J1J1J2… within the chain and exchange interactions J3J3… between the chains, is proposed to describe the magnetic behavior. 相似文献
14.
The redox reaction between TiCl3 and NaNO3 to form Ti(IV) and NO2? prior to deposition in a specially designed TiCl3 + NaNO3 solution is the key step effectively promoting the cathodic deposition of porous TiO2 films. The continuous reduction of NO2? to N2 and NH3 generates extensive OH?, enhancing the deposition rate of TiO2. The linear sweep voltammetric (LSV) and electrochemical quartz crystal microbalance (EQCM) studies reveal the electrocatalytic effect of oxy-hydroxyl-titanium already deposited onto the substrate for the NO2? and N2 reduction. The porous and crystalline structures of as-deposited and annealed TiO2 films are examined by field-emission scanning electron microscopic (FE-SEM), transmission electron microscopic (TEM) and selected area electron diffraction (SAED) analyses. 相似文献
15.
In the series La2/3?xTbxCa1/3MnO3, it is known that the compositions are ferromagnetic for smaller values of x and show spin glass characteristics at larger values of x. Our studies on the magnetic properties of various compositions in the La2/3?xTbxCa1/3MnO3 series show that the cross over from ferromagnetic to spin glass region takes place above x ≈ 1/8. Also, a low temperature anomaly at 30 K, observed in the ac susceptibility curves, disappears for compositions above this critical value of x. A mixed phase region coexists in the narrow compositional range 0.1 ≤ x ≤ 0.125, indicating that the ferromagnetic to spin glass cross over is not abrupt. 相似文献
16.
Kuang-Tsin Lee Chung-Bo Tsai Wen-Hsien Ho Nae-Lih Wu 《Electrochemistry communications》2010,12(7):886-889
One common dilemma encountered in designing a supercapacitor electrode is that the specific capacitance (Cs) of the active material decreases significantly as the active-material loading (mass area? 1) increases. As a result, the geometric capacitance density (GCD; Farad area? 1) of the electrode does not scale up linearly but gradually levels off with increasing loading. For MnO2 supercapacitors, this problem has been solved to a great extent by introducing a superabsorbent polymer (SAP) binder, namely polyacrylic acid (PAA), to form composite particles with MnO2. Other than acting as a binder to bound together MnO2 particles, the SAP is believed to facilitate distribution of electrolyte throughout the active layer owing to its electrolyte-absorbing and swelling behaviors. The Cs of MnO2 remains almost unchanged as the oxide loading varies over a wide range (1.5–6.5 mg cm? 2) of heavy active-material loading. In addition, putting PAA throughout the entire active layer helps to magnify the specific interaction between PAA and MnO2 that is known to enhance the capacitance of individual MnO2 particles. The success in combining both high Cs and high active-material loading results in GCD of ca. 1.8–1.4 F cm? 2 even under very high current densities (ca. 35–260 mA cm? 2 or 5–40 A g? 1-MnO2). 相似文献
17.
《Electrochemistry communications》2008,10(10):1617-1620
Novel core–shell SDC (Ce0.8Sm0.2O1.9)/amorphous Na2CO3 nanocomposite was prepared for the first time. The core–shell nanocomposite particles are smaller than 100 nm with amorphous Na2CO3 shell of 4–6 nm in thickness. The nanocomposite electrolyte shows superionic conductivity above 300 °C, where the conductivity reaches over 0.1 S cm−1. Such high conductive nanocomposite has been applied in low-temperature solid oxide fuel cells (LTSOFCs) with an excellent performance of 0.8 W cm−2 at 550 °C. A new potential approach of designing and developing superionic conductors for LTSOFCs was presented to develop interface as ‘superionic highway’ in two-phase materials based on coated SDC. 相似文献
18.
Xiangpeng Fang Xia Lu Xianwei Guo Ya Mao Yong-Sheng Hu Jiazhao Wang Zhaoxiang Wang Feng Wu Huakun Liu Liquan Chen 《Electrochemistry communications》2010,12(11):1520-1523
Nanorods of MnO2, Mn3O4, Mn2O3 and MnO are synthesized by hydrothermal reactions and subsequent annealing. It is shown that though different oxides experience distinct phase transition processes in the initial discharge, metallic Mn and Li2O are the end products of discharge, while MnO is the end product of recharge for all these oxides between 0.0 and 3.0 V vs. Li+/Li. Of these 4 manganese oxides, MnO is believed the most promising anode material for lithium ion batteries while MnO2 is the most promising cathode material for secondary lithium batteries. 相似文献
19.
《Electrochemistry communications》2008,10(7):1035-1037
Nanostructured amorphous RuO2 · xH2O/C composite materials are prepared via a modified sol–gel process using glycolic acid. The glycolate anion, which dissociates from glycolic acid at pH 7, behaves as a stabilizer by adsorbing onto the RuO2 · xH2O surface, thus resulting in particles with a size of about 2 nm. As evidenced by zeta potential measurements, the surface charge of RuO2 · xH2O becomes more electronegative as the amount of glycolic acid increases. After heat treatment at 160 oC to remove the stabilizer, RuO2 · xH2O/C is found to exhibit an amorphous structure. The specific capacitance of RuO2 · xH2O/C particles (40 wt% Ru) prepared in the presence of glycolic acid (0.3 g L−1) is 462 F g−1, which is 30% higher than that of the material prepared in the absence of glycolic acid. Both the nanosized particles and the amorphous structure mainly contribute to this increase in the specific capacitance. 相似文献
20.
《Electrochemistry communications》2008,10(11):1724-1727
MnO2 nanowires were electrodeposited onto carbon nanotube (CNT) paper by a cyclic voltammetric technique. The as-prepared MnO2 nanowire/CNT composite paper (MNCCP) can be used as a flexible electrode for electrochemical supercapacitors. Electrochemical measurements showed that the MNCCP electrode displayed specific capacitances as high as 167.5 F g−1 at a current density of 77 mA g−1. After 3000 cycles, the composite paper can retain more than 88% of initial capacitance, showing good cyclability. The CNT paper in the composite acted as a good conductive and active substrate for flexible electrodes in supercapacitors, and the nanowire structure of the MnO2 could facilitate the contact of the electrolyte with the active materials, and thus increase the capacitance. 相似文献