Electrochemical surface properties of Co3O4 electrodes

The electrochemical behaviour of Co₃O₄ layers deposited by thermal decomposition of Co(NO₃)₂ at 200–500°C on titanium supports with and without an interlayer of RuO₂ has been studied by cyclic voltammetry, chronopotentiometry and potential step experiments in alkaline solutions. Such variables as the calcination temperature, the solution pH, the potential sweep rate and the oxide loading have been investigated in detail to determine their influence on voltammetric peaks and voltammetric charge. Insight has been gained into the relevance of the latter to surface area determination and to proton diffusion into the oxide layer. The role of the support-active layer interface and especially that of the RuO₂ interlayer has been scrutinized. The importance of surface studies for the understanding of the electrocatalytic behaviour of Co₃O₄ electrodes has been analysed.Presented at the 37th Meeting of the International Society of Electrochemistry, Vilnius, USSR, 25–29 August 1986.     

微波辅助金属有机骨架材料制备无定形Co3O4花球及其电化学性能

以六水合硝酸钴(Co(NO3)2?6H2O)、苯甲酰丙酮（C10H10O2）为原料, 利用微波法合成了前体。前体在500℃空气条件下锻烧得到无定形Co3O4花球。通过 XRD、 SEM、TEM对目标产物进行了表征 , 研究了无定形Co3O4花球的微观结构、表面形貌。电化学测试结果表明,无定形Co3O4花球负极材料 在100mA/g的电流密度下,首次充电比容量达到826mAh/g;循环100圈后,容量保持率为89.2％,具有高的比容量、良好的循环性能和广泛的应用前景。     

Electrochemical supercapacitor material based on manganese oxide: preparation and characterization

A novel class of electrochemical supercapacitor electrode material has been electrochemically synthesized from a manganese halide complex in water-containing acetonitrile electrolyte at room temperature. This material has been physically and chemically characterized by scanning electron microscopy, X-ray photoelectron microscopy (XPS), FT-Raman microscopy and cyclic voltammetry. XPS and FT-Raman characterization suggest that this material is composed of manganese oxide with a chemical composition of Mn₃O₄ and containing a moderate amount of carbon. Cyclic voltammetric characterization indicates that this material has higher electronic conductivity than usually seen for manganese oxide and that it shows fast kinetics for the charge-discharge process in both aqueous and acetonitrile electrolytes. The material provides a large pseudocapacitance over a potential window of about 1 V in aqueous electrolyte and about 2 V in acetonitrile electrolyte. It is therefore a good candidate as a material for an electrochemical supercapacitor electrode.     

Porous Co3O4 column as a high-performance Lithium anode material

Journal of Porous Materials - Co3O4 has been widely investigated as a promising candidate anode material for lithium-ion batteries. We report on the porous Co3O4 column synthesized via a simple...     

Fabrication of CuFe2O4@g-C3N4@GNPs nanocomposites as anode material for supercapacitor applications

The aim of this study was to synthesize CuFe₂O₄ together with g-C₃N₄ and GNPs in various combinations on the surface of Ni foam for use as anode materials in supercapacitors. The fabricated electrodes were investigated by XRD, FTIR, XPS, BET, SEM and TEM for content and by CV, GCD and EIS analysis for electrochemistry. The characterization results showed that CuFe₂O₄ was successfully synthesized together with g-C₃N₄ and GNPs in a nanosponge-like geometry. The highest value of specific capacitance was found to be 989 mF/cm² at 2 mA measurement in the triple combination. Moreover, the stability of this electrode was measured to be 70% after 1500 cycles at 16 mA, while the energy and power densities were calculated to be 27.8 mWh/cm² and 300 mW/cm², respectively. The EIS results show that the carbon-based component increased the Cs value by decreasing the charge transfer and diffusion resistances of the electrodes. Compared to its counterparts in the literature, its Cs value is quite high, but its stability is low, so it can be used in low-cycle applications.     

Ni@NiCo2O4 core/shells composite as electrode material for supercapacitor

A novel Ni@NiCo₂O₄ core/shells structure consisting of the Ni microspheres skeletons and nanosheet-like NiCo₂O₄ skins was designed and investigated as the electrochemical electrode for supercapacitor. Due to the unique architecture with Ni microspheres as the highly conductive cores improving the electrical conductivity of electrode and external nanosheet-like NiCo₂O₄ shells as the efficient electrochemical active materials facilitating the contact between the electrode and electrolyte, the as-prepared Ni@NiCo₂O₄ exhibited excellent electrochemical performance with high specific capacity of 597 F g⁻¹ (1 A g⁻¹) as well as remarkable capacitance retention of 96% (3000 cycles). These impressive results pave the way to design high-performance electrode materials for energy storage.     

Fabrication and electrochemical evaluation of polyhedral PANI-coated Co3O4 electrode for supercapacitor application

In this work, conducting polymer modification on metal oxide surfaces was targeted to improve the composite conductivity and stability for electrochemical energy storage applications. Polyhedral cobalt oxide (Co₃O₄) was prepared using a molten salt combustion method and coated with polyaniline (PANI). The composite (PANI-CoM) was characterized using XRD, TGA, FTIR, FESEM, TEM, and BET. From cyclic voltammetry analysis in 6 M KOH, PANI-CoM shows a high C_S (985 F/g) compared to bare Co₃O₄ (278 F/g), indicating that PANI coating has improved pseudocapacitive charge storability of the electrode. The electrolyte diffusion on the internal active surfaces has increased from 11% to 31%, contributed by the reduction of internal resistance by 29%. Activated carbon and ordered mesoporous carbon (OMC) were used to manufacture two sets of asymmetrical supercapacitor devices, and PANI-CoM/OMC functioned the best performance with an E_D of 22 Wh/kg at a P_D of 400 W/kg.     

Magnetic properties of Co3O4 polycrystal powder

The results of investigations of magnetic properties of Co₃O₄ polycrystals in powder morphology with average crystallite size of 10 µm are presented. The temperature dependence of the magnetic susceptibility, measured in a wide temperature interval (1.5≤T≤400 K) using SQUID magnetometer, as well as electron spin resonance (ESR) spectra measured at X-band and Q-band frequency ranges have been studied. Antiferromagnetism with a Néel temperature T_N at about 39 K was observed from the analysis of evolution of molar magnetic susceptibility and ESR intensity as a function of temperature. ESR parameters namely g-factor, intensity (I_ESR), g-value, and linewidth ΔH for powder Co₃O₄ have been obtained. Some deviations from the expected values of some magnetic properties were determined and discussed.     

Porous Co3O4 nanorods as superior electrode material for supercapacitors and rechargeable Li-ion batteries

Porous aggregated nanorods of Co₃O₄ with a surface area of ~100 m² g^?1 synthesized without using any templates or surfactants give very high specific capacitance of ~780 F g^?1 when used as electrode in a faradaic supercapacitor, with a cycle life of more than 1,000 cycles. Further, in Li-ion batteries when used as an anode, the Co₃O₄ nanorods achieved a capacity of 1155 mA h g^?1 in the first cycle and upon further cycling it is stabilized at 820 mA h g^?1 for more than 25 cycles. Detailed characterization indicated the stability of the material and the improved performance is attributed to the shorter Li-insertion/desertion pathways offered by the highly porous nanostructures. The environmentally benign and easily scalable method of synthesis of the porous Co₃O₄ nanorods coupled with the superior electrode characteristics in supercapacitors and Li-ion batteries provide efficient energy storage capabilities with promising applications.     

Electrochemical and magneto-optical properties of cobalt molybdate nano-catalyst as high-performance supercapacitor

Nanorod shaped cobalt molybdate (CoMoO₄) electro-catalysts synthesized by microwave combustion route using urea as the fuel. The formation of monoclinic nanocrystalline structure, metal-oxygen (M–O) and chemical bonding was confirmed by X-ray powder diffractometry (XRD), Fourier transform infrared (FT-IR) and Raman spectroscopy, respectively. Scanning electron microscope (SEM) associated with energy dispersive X-ray (EDX) and high-resolution transmission electron microscope (HR-TEM) were used to confirm the morphology, elemental composition and particle size of the samples, respectively. The optical and defects were confirmed by the UV–vis. absorption and photoluminescence (PL) spectroscopy at room temperature (RT). The room temperature magnetic behaviors of product were investigated by vibrating sample magnetometer (VSM). Surface binding energy and element confirmation were examined by X-ray Photoelectron spectroscopy (XPS). The electrochemical (EC) performance was studied by cyclic voltammetry (CV), galvanostatic charge-discharge analysis (GCD) and electrochemical impedance spectroscopy (EIS) analysis. The CV curve proved the existence of redox pairs and the supercapacitor nature exhibited by the EIS (Nyquist plots). The GCD studies provided the non-symmetrical discharge curves and the highest specific capacitance (Csp) of ~ 133?F/g were acquired at a constant discharge current density (1?mA/cm^?2). The cyclic stability investigations revealed capacitance retention of about 100% after 1000 cycles, proposing the prospective usage of CoMoO₄ in energy-storage devices.     

Polyaniline grafted chitosan/GO-CNT/Fe3O4 nanocomposite as a superior electrode material for supercapacitor application

Developing appropriate stable electroactive electrode materials for supercapacitor application is the challenging issue, which attracts enormous attention in recent decades. In this regard, Fe₃O₄ nanoparticles are firstly synthesized on chitosan/graphene oxide-multiwall carbon nanotubes (CS/GM/Fe₃O₄). Then, polyaniline (PANI) is grafted on it via in situ chemical polymerization and named as CS/GM/Fe₃O₄/PANI. The as-prepared nanocomposites are characterized by Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. The capacitive properties of the electrodes are investigated in a three electrode configuration in 0.5 M Na₂SO₄ electrolyte by various electrochemical techniques. The specific capacitance of CS/GM/Fe₃O₄/PANI electrode is 1513.4 Fg⁻¹ at 4 Ag⁻¹ which is 1.9 times higher than that of CS/GM/Fe₃O₄ (800 Fg⁻¹). Meanwhile, the electrodes exhibit appropriate cycle life along with 99.8% and 93.95% specific capacitance at 100 Ag⁻¹ for chitosan/GO-CNT/Fe₃O₄ and polyaniline grafted chitosan/GO-CNT/Fe₃O₄, respectively.     

ZIF-derived wrinkled Co3O4 polyhedra supported on 3D macroporous carbon sponge for supercapacitor electrode

Co₃O₄/melamine-derived carbon sponge (MCS) nanocomposite in which wrinkled ball-in-dodecahedral Co₃O₄ nanoparticles derived from ZIF-67 were homogeneously dispersed on the interconnected MSC was fabricated via a simple immersion and thermolysis route. As-prepared ultralight Co₃O₄/MCS possessed mechanically robust characteristic and unique 3D macroporous framework anchored with corrugated Co₃O₄ dodecahedra. Utilized as a pseudocapacitor electrode, Co₃O₄/MCS hybrid exhibited a great specific capacitance of 1409.5 F g⁻¹ at the current density of 0.5 A g⁻¹ and excellent long-term cycling stability of 93.2% after 1000 charge/discharge cycles, which might be ascribed to the synergistic effect of the inherent high redox activity from Co₃O₄ polyhedra combined with excellent electrical conductivity of MCS. This work demonstrates that tunable structure design and rational morphology control are efficient approaches for manufacturing novel electrode materials with extraordinary electrochemical performance.     

Uniform and porous Mn-doped Co3O4 microspheres: Solvothermal synthesis and their superior supercapacitor performances

Uniform and porous Mn-doped Co₃O₄ microspheres (Mn@Co₃O₄ MSs) assembled with many nanoparticles (NPs) were prepared through an initially solvothermal reaction and subsequent annealing treatment at 550 ^oC in air. These Mn@Co₃O₄ MSs had an average diameter of about 9?μm and possessed a BET specific surface area of 70.4?m²/g. The pore diameter was mainly centered at 12.3?nm and the mean pore size was measured to be 15?nm. When the Mn@Co₃O₄ MSs were used as electrode material for supercapacitors, the electrochemical performances were assessed in 2?M KOH aqueous solution using a typical three-electrode configuration. Such Mn@Co₃O₄-MSs-modified electrode exhibited a highly specific capacitance of 773?F/g at 1 A/g, 62.7% rate capability at 16 A/g, and 73.9% capacitance retention of its original value after 5000 cycles at 5 A/g. The excellently electrochemical behaviors indicate that such Mn-doped Co₃O₄ MSs can be used as a superior electrode material for advanced supercapacitors in the future. The current synthesis strategy is facile and can be further employed to prepare other electrode materials with outstanding electrochemical performances.     

Co3O4-Bi2O2CO3催化剂的制备及其光催化性能

以Bi(NO₃)₃·5H₂O、Co(CH₃COO)₂·4H₂O为原料,采用化学沉淀-水热法制备了Co₃O₄-Bi₂O₂CO₃异质结构复合半导体光催化剂,并通过X射线衍射仪（XRD）、扫描电镜（SEM）、X射线光电子能谱（XPS）、紫外可见漫反射光谱（DRS）、荧光光谱（PL）等手段对所合成的复合型催化剂进行了理化性能表征。研究结果表明：引入Co₃O₄没有改变Bi₂O₂CO₃物相结构,但促进了Bi₂O₂CO₃ 对可见光的吸收能力,提高了Bi₂O₂CO₃表面吸附氧物种的数量,抑制了光生载流子复合。复合光催化剂对罗丹明B（RhB）的光催化脱色实验显示引入Co₃O₄能够明显提高Bi₂O₂CO₃催化剂的光催化脱色能力。尤其是Co₃O₄引入量为0.6%的Co₃O₄-Bi₂O₂CO₃样品对罗丹明B染料的光催化脱色率可达到97%（模拟日光照射30min）。本文为复合型光催化剂制备提供了简单易行的技术路线,制备的新型半导体复合光催化剂Co₃O₄-Bi₂O₂CO₃在环境净化方面表现出了较好的应用前景。     

Comparison between unsupported mesoporous Co3O4 and supported Co3O4 on mesoporous silica as catalysts for N2O decomposition

Mesoporous Co₃O₄ (meso-Co₃O₄) and Co₃O₄ nanoparticles supported on mesoporous silica SBA-15 (Co/SBA-15) were prepared by hydrothermal synthesis and an impregnation method, respectively. Although the as-prepared meso-Co₃O₄ had mesopores and a higher surface area comparable to that of Co/SBA-15, its catalytic activity for N₂O decomposition was much lower than that of Co₃O₄/SBA-15. The low catalytic activity of meso-Co₃O₄ mainly stems from the drastic decrease of the meso-Co₃O₄ surface area under the reaction condition used. On the other hand, Co/SBA-15 maintained its high surface area and mesopores with the aid of a robust silica support. This finding indicates that Co₃O₄ supported by a support is much more stable and efficient than meso-Co₃O₄ under N₂O decomposition reaction conditions.     

纳米多孔Fe_2O_3–Fe_3O_4/Ni复合材料作为锂离子电池负极材料的电化学性能

通过在NH4F+H2O的乙二醇溶液中阳极氧化铁箔,制备了纳米多孔结构的铁氧化物(Fe2O3–Fe3O4),然后在纳米多孔中电沉积镍,再经过400°C退火0.5 h,获得了镍与纳米多孔氧化铁的复合材料(Fe2O3–Fe3O4/Ni)。考察了电流密度和时间对镍沉积的影响。用扫描电镜、能谱仪、X射线衍射仪表征了复合材料的表面形貌、元素组成和物相,测试了其电化学性能并与未经电沉积镍的纳米多孔氧化铁(Fe2O3–Fe3O4)比较。结果表明,氧化铁由Fe2O3和Fe3O4组成。镀镍的最佳电流密度为2.0 m A/dm2,时间30 s。该纳米多孔Fe2O3–Fe3O4/Ni复合材料作为锂离子电池负极材料表现出更好的电化学性能──经过50次充放电循环后的放电比容量仍有438.3 m A·h/g,而Fe2O3–Fe3O4电极的放电比容量仅为110.6 m A·h/g。Fe2O3–Fe3O4/Ni电极的循环稳定性和倍率性能优异。     

纳米锰氧化物超级电容器电极材料的制备与性能

采用模板和液相沉淀两种方法制备了锰的氧化物,XRD的测试结果表明,两种方法制备的锰氧化物分别为MnO2和Mn3O4。从TEM图可以看出,模板法制备的MnO2为直径为5~8nm左右的颗粒,而用液相沉淀制备的Mn3O4形貌为直径约为10nm左右的纤维棒。循环伏安和充放电测试结果都表明MnO2是更好的超电容器的电极材料。MnO2和Mn3O4在200mA·g-1电流密度下的放电比电容分别为157.5和145.0F·g-1,经过500次充放电后比电容分别为132.5和125.0F·g-1,充放电效率分别为64.9%和63.7%。     

Electrochemical performance of quaternary (1-x)ZnMn2O4/(x)MgFe2O4 solid solution as supercapacitor electrode

Novel nano quaternary metals solid solutions from MgFe₂O₄ and ZnMn₂O₄ were synthesized using a sol-gel procedure. The development of a solid solution and the formed phase were examined by phase analysis utilizing the X'Pert High Score Plus program and Fourier transform infrared (FTIR) spectroscopy technique. Rietveld analysis of X-ray diffraction data (XRD), scanning electron microscope (SEM/EDS) and transmission electron microscope (TEM) were applied to determine the lattice parameters, crystallite size, different cations distribution and elemental analysis of the formed solid solutions. The measured dielectric properties of obtained solid solutions are found to be affected by the composition ratio (x). The solid solution (1-x)ZnMn₂O₄/(x)MgFe₂O₄ samples exhibited a ferroelectric–paraelectric transition at ferroelectric Curie temperature (T_c). The different hopping mechanisms in the different samples were also examined. The electrochemical performance was tested and influence of composition ratio (x) on the cathodic and anodic potential was investigated. The specific capacitance (C_s) value of electrodes depended on the composition ratio (x) beside the type of cations forming oxides. The (0.9)MgFe₂O₄/(0.1)ZnMn₂O₄ sample showed the best performance as a supercapacitor material. The outstanding electrochemical property of the (0.9)MgFe₂O₄/(0.1)ZnMn₂O₄ electrode was further confirmed by EIS inspection. The super stability of MgFe₂O₄/ZnMn₂O₄ solid solution could be attributed to the activation of the solid solution materials during the CV cycling and the synergistic effects.     

A new strategy for porous carbon synthesis: Starch hydrogel as a carbon source for Co3O4@C supercapacitor electrodes

A novel Co₃O₄@C composite with a three-dimensional (3D) interconnected network morphology was successfully fabricated by anchoring cobalt oxide nanocrystals onto porous carbon originating from starch hydrogels via freeze drying, precarbonization and thermal treatment in an aqueous system. Benefiting from unique structural features, the optimized electrode delivers an excellent capacitance of 1314.0 F g^?1 (1 A g^?1) and outstanding durability in terms of capacity preservation (93.5% over 10,000 cycles). In addition, an asymmetric supercapacitor consisting of DF-2 and active carbon exhibits an energy density of 149.1 Wh?kg^?1 at 800 W kg^?1 while maintaining great stability. The observed excellent performance is attributed to the unique 3D network, good conductivity and high surface-to-volumetric ratio of the carbon skeleton derived from the starch gel, which has wide scope for applications.