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Synthesis and Electrochemical Performance of LiMnPO4 by Hydrothermal Method  [PDF]
Daichi Fujimoto,Yu Lei,Zheng-Hong Huang,Feiyu Kang,Junichi Kawamura
International Journal of Electrochemistry , 2014, DOI: 10.1155/2014/768912
Abstract: LiMnPO4 with olivinestructure which is the promising candidate for high voltage cathode material was synthesized by hydrothermal method. In order to synthesize high purity and well-defined LiMnPO4, several precursors for Li, Mn, and P sources and hydrothermal reaction parameters including temperature and [H2O]/[Mn] value are optimized. By analyzing the structure, Mn valence, morphology, and chemical ratio via XRD, XPS, Raman, SEM, and ICP LiMnPO4 synthesized from manganese acetate tetrahydrate have single phase of LiMnPO4 without impurity and showed charge and discharge reaction caused by Mn2+/Mn3+ redox. Specific capacity of synthesized LiMnPO4 grew up during cycling. Moreover, when hydrothermal temperature was set at 150°C and [H2O]/[Mn] value was set at 15, discharge capacity as high as 70?mAh/g was obtained at rate. 1. Introduction Lithium-ion batteries are used widely as mobile devices like cellphone and notebook. Recently, researchers are actively devoted into the lithium-ion battery research for high energy conversion system, such as electric vehicle. Most of present lithium-ion batteries have used LiCoO2 as cathode which was discovered in 1980 [1]. However, LiCoO2 which includes rare-metal Co has irreversible structure shift at discharging over 0.6 Li from LiCoO2 that cause discharge capacity limited to 120~130?mAh/g instead of theoretical capacity of 270?mAh/g [2]. Several alternative materials are proposed as cathode materials. In 1997, Padhi et al. reported that phospho-olivine can work as promising cathode materials for lithium-ion battery [3, 4]. Among phospho-olivine LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4 are considered to be possible candidates for lithium-ion battery. Compared to LiFePO4 and LiCoPO4, LiMnPO4 is a cathode material with high redox potential which can be used with presently available liquid electrolyte so that LiMnPO4 exceeds the energy density of LiFePO4 which is the most investigated electrode among LiMPO4 family [5]. The characteristic of this olivine structure is an inductive effect which appears due to a strong covalent bond of to rise up redox potential [3]. However, the strong covalent bond causes poor conductivity, decelerating the charge and discharge processes. So far, several approaches have been used to solve this problem, such as controlling the particle size, morphology, and carbon coating [6]. Solid state reaction is generally used to prepare LiMnPO4 [7, 8]. Besides this, other approaches such as sol-gel method [9, 10], precipitation [11–13], hydrothermal [10, 14–19], solvothermal method [14, 20–22], spray
Sol-Gel Synthesis and Electrochemical Performance of LiMnPO4/C Cathode Material
WANG Yan-Ming, WANG Fei, WANG Guang-Jian
无机材料学报 , 2013, DOI: 10.3724/sp.j.1077.2013.12268
Abstract: LiMnPO4/C composite as a cathode material for lithium ion batteries was synthesized via a Sol-Gel method using tributyl phosphate as both chelating agent and phosphor source while lauric acid as a carbon source. Crystalline structure and morphology of the composite were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results indicate that the LiMnPO4/C composite is well crystallized as an olivine structure without any detectable impurity phase at annealing temperature of 700 . The spherical-like LiMnPO4/C microparticles are composed of large numbers of nanoparticles with the size ranging from 50 nm to 100 nm, which are covered with a thin carbon layer. Cyclic voltammetry and galvanostatic charge-discharge tests reveal that LiMnPO4/C composite has superior electrochemical performance. The initial discharge capacities of LiMnPO4/C are 141 and 113 mAh/g at rates of 0.05C and 0.5C under room temperature, respectively, along with high cyclic stability and good charge-discharge performances under high and low temperatures.
Controlled Growth of Zinc Oxide Nano Structures by Electrochemical Synthesis and Their Photoluminescence Properties  [PDF]
ZHANG Wen, HE Yong-Ning, ZHOU Cheng-Bo, CUI Wu-Yuan
无机材料学报 , 2011, DOI: 10.3724/sp.j.1077.2011.00602
Abstract: Different types of zinc oxide (ZnO) nanostructures were prepared by electrochemical synthesis on an indium tin oxide (ITO) glass substrate by adjusting the concentration of the electrolyte, deposition time and temperature. X―ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM) and photoluminescence (PL) spectrum were to determine the characteristics of these ZnO nano structures. The results show that ZnO films is formed quickly at the voltage over a threshold. The ZnO films morphologies are determined by the concentration of the electrolyte. Nanobuds, nanorods, flakes can be obtained in turn with the concentration of Zn(NO3)2·6H2O increasing. Such different morphology formation mechanisms are discussed on the basis of crystal growth theory. The PL spectra of the samples show that the flake ZnO films have a significant widen near edge emission peak with the depressed visible emission, which may have potential applications on optoelectronic devices and sensors.
Synthesis and Electrochemical Properties of Porous SnO2 Agglomerates
LI Fang, ZHU Ying-Chun
无机材料学报 , 2012, DOI: 10.3724/sp.j.1077.2011.11557
Abstract: Porous SnO2 agglomerates with crystalline pore walls were obtained by employing CTAB and trimethyl phosphate (TMP) as molecular co―templates via hydrothermal method. Tin (IV) chloride dihydrate was used as the inorganic precursor at high molar ratio of surfactant/Sn4+. The resulting samples were characterized by SEM, (HR)TEM, XRD, thermal analysis and nitrogen adsorption―desorption to examine the structural and morphological characters. The results indicate that the addition of small co―template TMP can facilitate the assembling of tin ions near the CTAB micelles, which can increase the specific surface area and improve the thermal stability of the resulted sample. The electrochemical properties of porous SnO2 as the anode materials of lithium―ion battery (LIB) are further investigated by using galvanostatic method. The porous SnO2 calcined at 300 displays a much higher reversible capacity of 962.4 mAh/g, which can be ascribed to the incomplete combustion of the organic materials and the unique nanostructure itself. The addition of bigger counter ions with large electric negativity might give an alternative approach to improve the properties of porous metal oxides synthesized by soft template method.
Use of Dendrimers during the Synthesis of Pt-Ru Electrocatalysts for PEM Fuel Cells: Effects on the Physical and Electrochemical Properties  [PDF]
J. C. Calderón,L. Calvillo,M. J. Lázaro,E. Pastor
International Journal of Electrochemistry , 2011, DOI: 10.4061/2011/564828
Abstract: In this work, Pt-Ru catalysts were synthesized by a novel methodology which includes the use as encapsulating molecules of dendrimers of different generation: zero (DN-0), one (DN-1), two (DN-2), and three (DN-3). Synthesized catalysts were heat-treated at 350°C, and the effects of this treatment was established from the physical (X-ray dispersive energy (XDE) and X-ray diffraction (XRD)) and electrochemical characterization (cyclic voltammetry and chronoamperometry). Results showed that the heat-treatment benefits the catalytic properties of synthesized materials in terms of CO and methanol electrochemical oxidation. The curves for CO stripping were more defined for heat-treated catalysts, and methanol oxidation current densities were higher for these materials. These changes are principally explained from the removal of organic residues remaining on the surface of the Pt-Ru nanoparticles after the synthesis procedure. After the activation of the catalysts by heating at 350°C, the real importance of the use of these encapsulating molecules and the effect of the generation of the dendrimer become visible. From these results, it can be concluded that synthesized catalysts are good catalytic anodes for direct methanol fuel cells (DMFCs). 1. Introduction Direct methanol fuel cells (DMFCs) are a promising power source for automotive and portable power applications. This versatility is related to ease in fuel handling, simple system design, high efficiency, and low emissions [1, 2]. Nevertheless, the use of DMFCs is limited by the reaction kinetics for methanol electro-oxidation on platinum, which possesses a slow rate and involves steps like methanol adsorption with their respective dissociation, water adsorption also with its activation, and CO oxidation as intermediate of this reaction [3]. In fact, the presence of CO and HCOO? intermediates is determinant in slow reaction kinetics due to the strong adsorption of these species on Pt, blocking the electroactive sites. As an alternative for solving this problem, Pt-Ru alloys have been suggested [4, 5] because of their higher activity for methanol electro-oxidation, stability, and ability of Ru for providing OHads species, which are able to weaken and accelerate CO adsorption and oxidation [3]. These reasons motivate the implementation of novel Pt-Ru nanoparticles synthesis procedures, with controlled metal loading, Pt?:?Ru atomic proportions, particle size, and homogeneous dispersion on a determined support. Typical wet impregnation and incipient wetness methods do not allow controlling these properties
Fabrication, Modification, and Emerging Applications of TiO2 Nanotube Arrays by Electrochemical Synthesis: A Review  [PDF]
Jian-Ying Huang,Ke-Qin Zhang,Yue-Kun Lai
International Journal of Photoenergy , 2013, DOI: 10.1155/2013/761971
Abstract: Titania nanotube arrays (TNAs) as a hot nanomaterial have a unique highly ordered array structure and good mechanical and chemical stability, as well as excellent anticorrosion, biocompatible, and photocatalytic performance. It has been fabricated by a facile electrochemical anodization in electrolytes containing small amounts of fluoric ions. In combination with our research work, we review the recent progress of the new research achievements of TNAs on the preparation processes, forming mechanism, and modification. In addition, we will review the potential and significant applications in the photocatalytic degradation of pollutants, solar cells, water splitting, and other aspects. Finally, the existing problems and further prospects of this renascent and rapidly developing field are also briefly addressed and discussed. 1. Introduction Nanostructured materials with peculiar properties are not expected in bulk phase and have already led to a breakthrough in various fields of science and technology. Moreover, much of the current interest in one-dimensional nanostructures, such as nanotube, nanowire, nanorod, and nanobelts, was initiated by the discovery of carbon nanotubes by Iijima et al. in 1991 [1]. Within these nanostructure materials, TiO2-based nanotubes attracted engrossing interest and intensive researches due to their merits of high specific surface area, ion-changeable ability, and photocatalytic ability. Over the past decades, nanostructured materials derived from TiO2 have extensively been investigated for many promising applications, including solar cells/batteries, self-cleaning coatings, electroluminescent hybrid devices, and photocatalysis, owing to their peculiar chemical and physical behaviors. Currently, developed methods of fabricating TiO2-based nanotubes comprise the assisted-template method [2, 3], hydrothermal treatment [4–6], and electrochemical anodic oxidation [7–10]. Each fabrication method has unique advantages and functional features and comparisons among these approaches. Regarding the template-assisted method, anodic aluminum oxide (AAO) nanoporous membrane, which consists of an array of parallel straight nanopores with controllable diameter and length, is usually used as template. However, the template-assisted method often encounters difficulties of prefabrication and postremoval of the previous templates and usually results in impurities. Concerning hydrothermal treatment, the self-assembled TiO2 nanotubes are based on the treatment of Ti foils or TiO2 powders in a tightly closed vessel containing highly concentrated
Electrodeposition of nanostructured coatings and their characterization-a review
Injeti Gurrappa and Leo Binder
Science and Technology of Advanced Materials , 2008,
Abstract: Nanostructured materials have gained importance in recent years due to their significantly enhanced properties. In particular, electrochemistry has a special role in producing a variety of nanostructured materials. In the current review, we discuss the superiority of electrochemical deposition techniques in synthesizing various nanomaterials that exhibit improved characteristics compared with materials produced by conventional techniques, as well as their classification, synthesis routes, properties and applications. The superior properties of a nanostructured nickel coating produced by electrochemical deposition are outlined. The properties of various nanostructured coating materials produced by electrochemical techniques are also described. Finally, the importance of nanostructured coatings in industrial applications as well as their potential in future technologies is emphasized.
Synthesis and Electrochemical Properties of Highly Dispersed Li4Ti5O12 Nanocrystalline as Anode Material for Lithium Secondary Batteries  [PDF]
无机材料学报 , 2010, DOI: 10.3724/sp.j.1077.2010.00235
Abstract: Nano-sized Li4Ti5O12 powder with high dispersivity was prepared by a novel solgel route using lauric acid as surfactant. The crystal structure, microstructure and the electrochemical properties of samples were characterized by XRD, FESEM, TGDSC, laser particle size analysis, A.C. impedance and galvanostatically chargedischarge experiments. The results demonstrated that the crystallization, microstructure and electrochemical properties were influenced significantly by heattreatment temperature. Li4Ti5O12 powders calcined at 800℃ for 10h were comprised of crystallites with the particle size in the range of 120-275nm, revealing high dispersivity almost without any agglomerates, and exhibiting an excellent electrochemical performance. Its discharge capacities at 0.5C and 1C rates were 174.7mAh/g and 163.3mAh/g, respectively. After 50 cycles, fairly stable cycling performance was achieved without obvious capacity fading. Electrochemical impedance spectroscopy tests demonstrated that the surface reaction kinetics of Li4Ti5O12 was improved significantly from the state of the complete charge to the state of the complete discharge. The charge and discharge results of samples demonstrated that the route to synthesis highly dispersed nanocrystalline was appropriate for preparing Li4Ti5O12 with high electrochemical performance.
Synthesis, structural study and electrochemical properties of copper(II) complexes derived from benzene- and p-toluenesulphonylhydrazones
Journal of the Serbian Chemical Society , 2003,
Abstract: The synthesis and characterization of benzene- and p-toluenesulphonylhydrazones derived from salicylaldehyde and 2-hydroxy-1-naphthaldehyde and their Cu(II) complexes are reported. The compounds were characterized on the basis of elemental analyses, electronic and IR spectra, magnetic moments, and conductance measurements. The electrochemical behavior of the Cu(II) complexes was investigated in DMSO by cyclic voltammetry (CV), rotating disc electrode (RDE) and coulometry. The oxidative polymerization of the copper complexes on a glassy carbon electrode was carried out in DMSO.
Synthesis, Characterization, Spectral Properties and Electrochemical of Compounds trans-[Ru(NH)3L(bpa)]2+  [PDF]
Wagner Batista dos Santos, Marcio Adriano Sousa Chagas, K.M.D. de Sousa, Daniel Tizo Costa, Luiz Alfredo Pavanin
Open Journal of Inorganic Chemistry (OJIC) , 2016, DOI: 10.4236/ojic.2016.62009
Abstract: n this work, we present synthesis of the compounds trans-[Ru(NH3)4L(bpa)]2+ where L is pyridine ligands: pyridine (py), isonicotinamide (isn), 4-acetylpyridine (4-acpy) and 4-picoline (4-pic) and 1,2-bis (4-pyridyl) ethane (bpa), their characterization by UV-visible spectroscopy and electrochemical properties. This series shows intense bands in the region between 400 and 515 nm, allocated bands charge transfer (MLCT), the influence of substituents on the pyridine ring (4-acpy and isn), and the interaction between the ligand and the metal, causing a second MLCT band, which is lighter and has more energy. The compound is characterized by spectroscopy by Fourier transform infrared spectroscopy (FTIR). The displacement observed in the symmetrical stretching of νs(CCN) group in the complex compared with the νs(CCN) group in the free ligand is indicative of coordination of the pyridine group to the Ruthenium (II) metallic center. The electrochemical data (cyclic voltammetry) show that reversibility criteria are well defined and formal Ef potential, indicating the influence of the pyridine ring substituent.
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