Search

We have developed a template-free, easily controllable, and simple method for the mass production of hydrogenated iron oxide nanoparticles (NPs). These NPs were formed with a regular spherical shape by underwater plasma discharge treatment at room temperature and atmospheric pressure. The various phases of well-crystallized iron oxide NPs were carefully monitored by controlling the amount of hydrazine. Further, the obtained Brunauer–Emmett–Teller surface area of 67.86 m2/g was much larger than that of a commercial sample (32.40 m2/g), which was further increased to 85.07 m2/g by adjusting the amount of hydrazine. The removal efficiency for heavy metal and organic dyes was obtained to be ~100%, which was 10 times faster than that of the commercial sample. Furthermore, ~100% flocculation efficiency was obtained by using only 6 g/g microalgal cell of the prepared iron oxide, whereas no significant change was observed for commercial iron oxide irrespective of the amount of flocculant. These excellent efficiencies for the removal of pollutant from waste water can be originated in the high specific surface area, relatively positively charged surface, and good crystallinity of the synthesized samples. These indicate that the hydrogenated iron oxide NPs in this study are potentially useful for water purification by serving as an adsorbent, photocatalytic material, and flocculant.

Molybdenum-based compounds are considered as a potential replacement for expensive precious-metal electrocatalysts for the hydrogen evolution reaction (HER) in acid electrolytes. However, coating of thin films of molybdenum nitride or carbide on a large-area self-standing substrate with high precision is still challenging. Here, MoNx is uniformly coated on carbon cloth (CC) and nitrogen-doped carbon (NC)-modified CC (NCCC) substrates by atomic layer deposition (ALD). The as-deposited film has a nanocrystalline character close to amorphous and a composition of approximately Mo2 N with significant oxygen contamination, mainly at the surface. Among the as-prepared ALD-MoNx electrodes, the MoNx /NCCC has the highest HER activity (overpotential η≈236 mV to achieve 10 mA cm-2 ) owing to the high surface area and porosity of the NCCC substrate. However, the durability of the electrode is poor, owing to the poor adhesion of NC powder on CC. Annealing MoNx /NCCC in H2 atmosphere at 400 °C improves both the activity and durability of the electrode without significant change in the phase or porosity. Annealing at an elevated temperature of 600 °C results in formation of a Mo2 C phase that further enhances the activity (η≈196 mV to achieve 10 mA cm-2 ), although there is a huge reduction in the porosity of the electrode as a consequence of the annealing. The structure of the electrode is also systematically investigated by electrochemical impedance spectroscopy (EIS). A deviation in the conventional Warburg impedance is observed in EIS of the NCCC-based electrode and is ascribed to the change in the H+ ion diffusion characteristics, owing to the geometry of the pores. The change in porous nature with annealing and the loss in porosity are reflected in the EIS of H+ ion diffusion observed at high-frequency. The current work establishes a better understanding of the importance of various parameters for a highly active HER electrode and will help the development of a commercial electrode for HER using the ALD technique.

Transparent glass of xEu2O3-(100-x)TeO2 binary system is obtained by using the melt-quenching method and especially studied for x = 5 in xEu2O3-(100-x)TeO2 composition. Optical properties such as transmission, excitation, and emission spectra of Eu2O3-TeO2 glass-ceramics are studied and carefully compared for the samples heated at different temperatures. The one step heat-treatment affects the crystallinities as well as phase formation and yields cubic [Eu2Te6O15], orthorhombic [TeO2], and tetragonal [TeO2] phases depending on the heat treating temperature. Glass-ceramics of Eu3+-doped tetragonal [TeO2] shows stronger emission intensity at wavelength of 613 nm with an excitation wavelength of 394 nm compared with that from cubic [Eu2Te6O15] or Eu3+-doped orthorhombic [TeO2]. Enhancement of emission intensity in Eu3+-doped tetragonal [TeO2] is related to the local environment of Eu3+ ions substituted in tetragonal TeO2 lattice.

Molybdenum-based compounds are considered as a potential replacement for expensive precious-metal electrocatalysts for the hydrogen evolution reaction (HER) in acid electrolytes. However, coating of thin films of molybdenum nitride or carbide on a large-area self-standing substrate with high precision is still challenging. Here, MoN

ZnO-branched nanostructures have recently attracted considerable attention due to their rich architectures and promising applications in the field of optoelectronics. Contrary to n -type semiconducting metal oxides, cupric oxide is a p -type semiconductor which can be applied to high-critical-temperature superconductors, photovoltaic materials, field emission, and catalysis. We report the synthesis of the ZnO nanorods on the CuO nanofibers prepared by using the electrospinning method along with the hydrothermal method. As the growing time increases, emission spectra of the hetero-structured ZnO/CuO show that the observed band in the UV region is slightly increased, while the intensity of the green emission is highly enhanced. The hetero-structured ZnO/CuO is found to be a promising candidate for developing renewable devices with photoluminescent behavior and the increased surface to volume ratio.

Rare-earth-ions-doped apatite-based phosphors for near ultra-violet excitation have been studied. Ca 5 (PO 4 ) 3 Cl:Eu 3+ and Ca 5 (PO 4 ) 3 Cl:Sm 3+ phosphors are synthesized by using the solid–state reaction method sintering at 1100 °C and 1300 °C, respectively. Optical properties of these phosphors are characterized by measuring the absorption, excitation, and emission spectra at room temperature. Strong red-orange emissions corresponding to the 5 D 0 → 7 F 0 transition of Eu 3+ and the 4 G 5/2 → 6 H 7/2 transition of Sm 3+ from the near ultra-violet excitation are observed. Ca 5 (PO 4 ) 3 Cl:Eu 3+ and Ca 5 (PO 4 ) 3 Cl:Sm 3+ are red-orange emitting phosphors and the difference in emission intensity as varying the sintering temperatures is observed in both phosphors.

We investigated the correlation between the structures of 4-component glasses (B2O3–CaO–Al2O3–La2O3) and their leaching behaviors. We used a FT-IR and a MAS-NMR to analyze the structures of ground as-prepared and leached glasses for 7 and 28 days. Elemental releases represent that the leaching was incongruent. After leaching 28 days, BO4 structure dramatically decreased and AlO6 ratio increased compared to the glasses before the leaching test. That might be because these structures in the glasses were broken or released into solution during the leaching test. The addition of La3+ into the glass stabilizes the formation of BO4 and more highly charged AlO5 and AlO6.

We report the structural characteristics and the chemical bonding states of nano-sized BaTiO 3 powders before and after having been heat treatment. We prepare BaTiO 3 nanopowders by using the solvothermal method at different reaction temperatures. We anneal the prepared powders at 400 and 600 °C, respectively, for 1 h. We examine the structures of the prepared powders by using the Rietveld analysis, and the chemical bonding states of the ions by using a fitting program with an assumption that the measured spectra are Gaussian. Then, we study the morphology of the nanopowders, and measure the ferroelectric properties with frequency and reaction temperature. We show that the BaTiO 3 nanopowders prepared by using the solvothermal method at lower reaction temperature exhibit the tetragonality and are useful for the electronic device applications.

Magnesium ferrite (MgFe2O4) exhibiting a spinel phase was synthesized by using the polymerized complex and the solid-state reaction methods, and its physico-chemical properties were studied to explore the water-splitting under visible light photons. The study revealed the potential for using MgFe2O4 particles for photo-catalytic application. The structural study provided information on ferrite nano-crystallites fabricated by using the polymer complex method. The morphological studies demonstrated that, in contrast to the solid-state reaction method, a homogenous, monodispersed ferrite photocatalyst could be formed by using the polymerized complex method. The optical study revealed a larger visible-light absorption capability for the nanosized MgFe2O4 photocatalysts prepared by using the polymer complex methods, and indicated a red-shift of the bandgap by 0.06 eV as compared to the bandgap of the bulk. These nanocrystallites were highly photoactive with respect to the photodegradation and photocatalytic hydrogen evolution applications. The electrochemical analysis showed that they exhibited favorable bandedge positions suitable for photocatalytic H2 evolution. Thus, nanocrystalline MgFe2O4 is an active visible-light photocatalyst, that might be useful for the decomposition of water.

In this study, hierarchically three-dimensional (3D) nanotubular sea urchin-shaped iron oxide nanostructures (3D-Fe2O3) were synthesized by a facile and rapid ultrasound irradiation method. Additives, templates, inert gas atmosphere, pH regulation, and other complicated procedures were not required. Dense 3D-Fe2O3 with a relatively large Brunauer–Emmett–Teller (BET) surface area of 129.4 m2/g was synthesized within 23 min, and the BET surface area was further improved to 282.7 m2/g by a post heat-treatment process. In addition, this post processing led to phase changes from maghemite (γ phase) to hematite (α phase) Fe2O3. Subsequent characterization suggested that the growth mechanism of the 3D-Fe2O3 follows self-assembly and oriented attachment. The prepared 3D-Fe2O3 was applied to wastewater purification. Ultrasound-irradiated 3D-Fe2O3 can eliminate a As(V) and Cr(VI) from water with 25 times faster removal rate by using a one third smaller amount than commercial α-Fe2O3. This was attributed to the inter-particle pores and relatively positively charged surface of the nanostructure. In addition, post heat treatment on ultrasound-irradiated 3D-Fe2O3 significantly influenced the photocatalytic degradation of methylene blue and phenol, with a 25 times higher removal efficiency than that of commercial α-Fe2O3, because of both high BET surface area and good crystallization of the prepared samples.

We investigate the crystallinity and the optical properties of pure and Sm3+-doped 15K2O-15Nb2O5-70TeO2 glass ceramics after heat treatment. We prepare pure and 1 mol% Sm3+-doped 15K2O-15Nb2O5-70TeO2 glasses by using the conventional melt-quenching method. After annealing at 390 °C and 410 °C, respectively, we characterize the crystallinity of the glasses. We examine the chemical bonding states of the ions and the optical properties by taking absorption, excitation, and emission spectra. We show that Sm3+-doped 15K2O-15Nb2O5-70TeO2 glass ceramics after heat treatment are excellent red-orange-emitting phosphors under near UV excitation.

The effects of incorporated alkali metal ions on the chemical bonding states and optical properties in samarium-doped strontium orthosilicate phosphors are studied. Sr2−x M x SiO4:Sm3+ (M = Li, Na, and K) phosphors are synthesized by using tje solid-state reaction method to vary the incorporated amount of the alkali metal ions. The structures, surface morphology, and chemical bonding states of the powders are analyzed. Optical properties for varying amounts of incorporated alkali metal ions are examined by measuring absorption, excitation, and emission spectra. A red-orange emission due to the transition of Sm3+ is observed in all samples, and powders with alkali metal ions incorporated exhibit enhanced emission intensities by a factor of 1.24 to 2.16 compared with that of z pure Sr2SiO4:Sm3+ powder with the same amount of Sm3+. We have shown that Sr2−x M x SiO4:Sm3+ ceramics exhibit a red-orange emission with enhanced intensity for operation with near ultra-violet excitation.

Trivalent samarium-doped calcium-orthosilicate (Ca2SiO4:Sm3+) powder is synthesized by varying Sm2O3 amounts and the solid-state reaction method. X-ray diffraction patterns show that the obtained powders formed as orthorhombic-structured Ca2SiO4. Scanning electron microscope images show that the powders have uniform structures of a few micrometers in size. Photophysical features are analyzed by taking absorption, excitation, and emission spectra. Emission spectra exhibit a red-orange luminescence from the 4G5/2 → 6H7/2 transition of Sm3+ in all synthesized phosphors. Both the physical and the optical properties show that Ca2SiO4:Sm3+ is an encouraging red-orange emitting phosphor applicable to photonics operating with near ultra-violet excitation.

A simple conversion process of inulin polymer into hydroxymethylfurfural (HMF) was developed using Bronsted acid catalyst (HCl) in the presence of an ionic liquid, 1-octyl-3-methylimidazolium chloride ([OMIM]Cl). In addition, the physicochemical properties of inulin particle and its depolymerixation products were scrutinized. FESEM and XRD diffraction frequency showed that inulin particles are clustered in a granulated formation and their molecular structure is highly amorphous. FT-IR analysis identified five characteristic frequency regions: Region 1; 700–900, Region 2; 900–1,200, Region 3; 1,200–1,350; Region 4; 1,350–1,500, and Region 5; 1,530–1,800 cm−1. HPLC analysis confirmed that the major composition of inulin consists of fructose and glucose. The synthesis of HMF was significantly affected by the Bronsted catalyst and its concentration. Its highest yield (63.1±5.1 dwt%) was achieved at 0.3M HCl in the presence of [OMIM]Cl. No presence of the Bronsted catalyst exhibited negligible HMF yield (2.3±1.1 dwt%). Our results demonstrate that the Bronsted catalyst plays a pivotal role in the catalytic process of HMF synthesis from inulin polymer.

A new green technology was developed using citrus peel waste to produce hydroxymethylfurfual (HMF). FT-IR analysis of the waste showed 4 characteristic vibration modes (C H, C O, C OH, and C O/COO−), contributing to sugars. XRD and FESEM elucidated that the waste and its hydrolysate consist of highly amorphous clusters. HCl increased HMF yield by 1.4-fold. CrF3 increased its yield by 1.7-fold. At 0.2 of the stoichiometric ratio value, HMF yield was highest. The highest HMF yield was achieved in the reaction mixture of 4 g [OMIM]Cl, 1 mL ethyl acetate, 0.1 g CrF3, 5 mL 0.3 M HCl, and 0.5 g biomass.

An eco-beneficial strategy for the production of hydroxymethylfurfural (HMF) was developed using kudzu root extract as a sustainable biomass material and the physicochemical properties of the extract characterized using FESEM, XRD, and FT-IR. The visual image of the kudzu extract and the XRD analysis revealed that the molecular structure of the extract is amorphous and its major composition would be starch. The FT-IR analysis showed 6 characteristic vibration modes contributing to starch and other sugars. The halide ligands of different types significantly affected the synthesis of HMF. The exceptional promotion effect on HMF synthesis was achieved by fluorine ligand of the chromium-based metal catalyst. The most effective stoichiometry ratio of catalyst-to-feed biomass for the synthesis of HMF from kudzu root extract was found at its ratio value of 0.2. The most optimal extraction condition for HMF synthesis from the kudzu extract occurred at 0.3 M HCl. The highest HMF production (34.8 ± 4.8 dwt%) was obtained in the reaction mixture containing 40% (w/v) ionic liquid, 10% (v/v) ethyl acetate, 1% (w/v) halide catalyst, and 50% (v/v) of 0.3 M HCl extract by undergoing the reaction at 130 °C for 12 h.

Pure and metal (Cu, Al, Sn, and V)-doped Li 4 Ti 5 O 12 powders are prepared with solid-state reaction method. The effects of dopants on the physical and electrochemical properties are characterized by using TGA, XRD, and SEM. Compared with pure Li 4 Ti 5 O 12 , metal-doped Li 4 Ti 5 O 12 powders show structural stability and enhanced lithium ion diffusivity brought by doped metal ions. Voltage characteristics and initial charge–discharge characteristics according to the C rates in pure and metal-doped Li 4 Ti 5 O 12 electrode materials are studied. Pure Li 4 Ti 5 O 12 powder shows a relatively good discharge capacity of 164 mAh/g at a rate 0.2 C , and some of metal-doped Li 4 Ti 5 O 12 powders show higher discharge capacities. Metal-doped Li 4 Ti 5 O 12 powders are promising candidates as anode materials for lithium-ion batteries.

Optical properties of samarium-doped strontium orthosilicate for near ultra-violet excitation are studied. Sr 2 SiO 4 :Sm 3+ phosphor is synthesized by using the solid-state reaction method. The structure and physical properties of the phosphor are characterized by using X-ray diffractometer, scanning electron microscope, UV–visible spectrophotometer, high-resolution secondary ion mass spectrometer, and X-ray photoelectron spectrometer. Optical properties are studied by taking excitation and emission spectra. A strong red-orange luminescence corresponding to 4 G 5/2 → 6 H 7/2 transition of Sm 3+ for near ultra-violet excitation is observed. It is found that Sr 2 SiO 4 :Sm 3+ is a red-orange emitting phosphor and has higher efficiency for the operation with near ultra-violet excitation.

Trivalent europium-ion-doped Y2SiO5 phosphors are synthesized by using the reverse micelle and the sol-gel processes. The crystallinity, morphology, and chemical states of the ions are characterized, and the photophysical properties are studied by taking absorption, excitation, and emission spectra for various concentrations of europium. Y2SiO5:Eu3+ is a red-emitting phosphor, has a higher efficiency for operation under near UV excitation, and may be a promising candidate for photonic applications.

Photoluminescent properties of samarium-doped calcium titanate for near ultra-violet excitation were studied. CaTiO 3 :Sm 3+ phosphor was synthesized by using the solid-state reaction method. The structure and properties of the phosphor were characterized by using X-ray diffractometer, scanning electron microscope, UV–visible spectrophotometer, high-resolution secondary ion mass spectrometer, and X-ray photoelectron spectrometer. The photoluminescent properties were studied by taking excitation and emission spectra. A strong red–orange luminescence corresponding to 4 G 5/2 → 6 H 7/2 transition of Sm 3+ for near ultra-violet excitation was observed. It was found that CaTiO 3 :Sm 3+ was a red–orange emitting phosphor and had higher efficiency for the operation with near ultra-violet excitation.

A simple two-step process was conducted to scrutinize new catalytic action of chromium fluoride (CrF 3 ) by evaluating its effect on the yield of hydroxylmethylfurfural (HMF) in ionic liquid (1-octyl-3-methylimidazolium chloride) using raw tapioca root biomass with high starch, and hydrolysis efficiency of the biomass extract was characterized by FT-IR spectrometry and FESEM image analysis. The FT-IR absorbance bands confirmed the presence of starch and other soluble sugars in the acidic biomass extract by presenting its frequency signals in the 950–1200 cm −1 regions. FESEM image showed that the efficiency of the biomass hydrolysis is time-dependent. The concentration of CrF 3 significantly affected the yield of HMF. Its highest yield (52.6 ± 4.8 dwt%) was achieved at 1% CrF 3 , but over 1% CrF 3 its yields began to decline. The combined addition of CrF 3 and CrBr 3 showed ca. 1.3-fold higher yield than CrF 3 alone. The reaction rates of HMF synthesis were considerably influenced by the stoichiometry ratio of CrF 3 to biomass. The highest reaction rate (0.41 g/g biomass/h) occurred at 0.2 ratio value.

The photophysical properties of europium-doped calcium titanate for near ultra-violet excitation were studied in order to investigate whether it is applicable to white light-emitting diodes. CaTiO 3 :Eu 3+ phosphors were synthesized by using the solid-state reaction method. The structures and basic properties of the phosphors were characterized by using X-ray diffractometer, scanning electron microscope, UV-visible spectrophotometer, and X-ray photoelectron spectrometer. The photophysical properties were examined by taking excitation and emission spectra. A strong red luminescence corresponding to 5 D 0 → 7 F 2 transition of Eu 3+ under near ultra-violet excitation was observed. It was found that CaTiO 3 :Eu 3+ was a red-emitting phosphor and had higher efficiency for operation under near ultra-violet excitation.

CaCO3 extracted from starfish by using the commercial protein lyase having α-amylase, β-amylase, and protease is applied to remove heavy metal ions. The extracted CaCO3 shows excellent characteristics in removing heavy metal ions such as Cu 2+ , Cd 2+ , Pb 2+ , and Cr 6+ compared with conventional materials such as crab shells, sawdust, and activated carbon except for removing Zn 2+ . SEM images reveal that the extracted CaCO3 has a good morphology and porosity. We characterize the removal efficiencies of the extracted CaCO3 for the heavy metal ions according to the concentrations, pH, temperatures, and conditions of empty bed contact times.

LiFePO4 powders were synthesized by using the sol-gel and the solid-state reaction methods. The chemical states of Fe ions were studied by using XPS, and their electrochemical properties according to the oxidation states of Fe ions were compared. The average oxidation state of Fe ions in LiFePO4 powders synthesized by using the solid-state reaction method was found to be Fe3+, on the other hand, that of Fe ions synthesized by using the sol-gel method was found to be Fe2+. The obtained discharge capacities were 50 mAh/g and 120 mAh/g at a rate 0.1 C in LiFePO4 synthesized by using the solid-state reaction and sol-gel methods, respectively. Relatively a good cycling stability was observed in sol-gel prepared powder.

Perchlorate () is a contaminant found in surface water and soil/ground water. Autotrophic perchlorate-reducing bacteria (PRB) use hydrogen gas () as an electron donor to remove perchlorate. Since iron corrosion can produce , feasibility of autotrophic perchlorate-removal using zero-valent iron (ZVI) was examined in this study using activated sludge that is easily available from a wastewater treatment plant. Batch test showed that activated sludge microorganisms could successfully degrade perchlorate in the presence of ZVI. The perchlorate biodegradation was confirmed by molar yield of as perchlorate was degraded. Scanning electron microscope revealed that rod-shaped microorganisms on the surface of iron particles used for the autotrophic perchlorate-removal, suggesting that iron particles could serve as supporting media for the formation of biofilm as well. DGGE analyses revealed that microbial profile of the inoculum (activated sludge) was different from that of biofilm sample obtained from the ZVI-added enrichment culture used for -degradation. A major band of the biofilm sample was most closely related to the class Clostridia.

Chromium halides were introduced for the sustainable production of hydroxymethylfurfural (HMF) from raw acorn biomass using an acidic ionic liquid. The free sugars (glucose and maltose) released by the acidic hydrolysis of the biomass were confirmed by the FT-IR absorption bands around 995-1014cm(-1) and HPLC. FESEM analysis showed that the acorn biomass contains various sizes of starch granules and their structures were severely changed by the acidic hydrolysis. An optimal concentration of HCl for the HMF yields was 0.3M. The highest HMF yield (58.7+1.3dwt%) was achieved in the reaction mixture of 40% [OMIM]Cl+10% ethyl acetate+50% 0.3M HCl extract containing a mix of CrBr(3)/CrF(3). The combined addition of two halide catalysts was more effective in the synthesis of HMF (1.2-fold higher on average) than their single addition. The best productivity of HMF was found at 15% concentration of the biomass and at 50%, its relative productivity declined down to ca. 0.4-fold.

The surface conditions of LiFePO4 powder were modified by adding AlF3 and Al2O3 by using the sol-gel process to improve its electrochemical properties. The surface of LiFePO4 powders was partially covered with nano-sized AlF3 and Al2O3, which is confirmed by using a transmission electron microscope image. The states of coated Al materials were examined by using X-ray photoelectron spectrometer results. The nano-sized AlF3- and Al2O3-coated LiFePO4 powders showed no difference in the bulk structure compared with the pristine one. However, the AlF3- and Al2O3-coating on LiFePO4 powders improved the overall electrochemical properties such as the discharge capacity, the cyclability, and the rate capability compared with those of a pure LiFePO4. Such enhancements were attributed to the presence of a stable AlF3 and Al2O3 layer which acts as an interfacial stabilizer on the surface of LiFePO4 powders.

Nanocrystalline ZnFe 2 O 4 oxide-semiconductor with spinel structure was synthesized by the polymerized complex (PC) method and investigated for its photocatalytic and photoelectric properties. The observation of a highly pure phase and a lower crystallization temperature in ZnFe 2 O 4 made by PC method is in total contrast to that was observed in ZnFe 2 O 4 prepared by the conventional solid-state reaction (SSR) method. The band gap of the nanocrystalline ZnFe 2 O 4 determined by UV-DRS was 1.90 eV (653 nm). The photocatalytic activity of ZnFe 2 O 4 prepared by PC method as investigated by the photo-decomposition of isopropyl alcohol (IPA) under visible light (≥ 420 nm) was much higher than that of the ZnFe 2 0 4 prepared by SSR as well as TiO 2-x N x . High photocatalytic activity of ZnFe 2 O 4 prepared by PC method was mainly due to its surface area, crystallinity and the dispersity of platinum metal over ZnFe 2 O 4 .

oC for 12 hours for the calcination. Then we calcined again at 800 o C for 12 hours. We characterized the synthesized compounds via the crystallinity, the valence states of iron ions, and their shapes using TGA, XRD, SEM, TEM, and XPS. We found that the synthesized powders were carbon-coated using TEM images and the iron ion is substituted from 3+ to 2+ through XPS measurements. We observed voltage characteristics and initial charge-discharge characteristics according to the C rate in LiFePO4 batteries. The obtained initial specific capacity of the chitosan added LiFePO4 powder is 110 mAh/g, which is much larger than that of LiFePO4 only powder.

Regardless of high capacity and stability during lithium extraction, LiFePO4 materials have difficulty in the applications for high electrical density because of low electrical conductivities. In order to optimize this problem, we synthesized carbon coated LiFePO4 by adding humic acid using solid state reaction method. We characterized the synthesized compounds via the crystallinity, the valence states of Fe ions, and their shapes. We found the carbon coating using X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). We also found that the iron ion is substituted from 3+ to 2+ through XPS measurement. We showed that the carbon coating increased the electrochemical behavior by measuring the charge-discharge characteristics.