Metal oxalate hydrate body having a certain shape, preparation method thereof, and metal oxide/carbon composite body prepared from the same

Abstract

The present invention relates to a metal oxalate hydrate body having a certain shape, a preparation method thereof, and a metal oxide/carbon composite body prepared by using the metal oxalate hydrate body. In the present invention, the metal oxalate body, whose shape is diversely controlled, and the metal oxide/carbon composite body therefrom are provided.

Claims

1. Metal oxalate hydrate particles having an angled polyhedron shape which are formed by carrying out a hydrothermal reaction of a mixture at a temperature in the range from 80 C. to 150 C., the mixture comprising: at least one metal hydrate salt selected from iron(III) chloride tetrahydrate, iron(II) chloride tetrahydrate, iron(III) chloride hexahydrate, iron(II) chloride tetrahydrate, iron(III) nitrate nonahydrate, iron(III) sulfate hydrate, iron(II) perchlorate hydrate, iron(II) sulfate hydrate, Cr(NO.sub.3).sub.3.9H.sub.2O, Co(NO.sub.3).sub.2.6H.sub.2O, Ni(NO.sub.3).sub.2.6H.sub.2O, Pd(NO.sub.3).sub.2.2H.sub.2O, CoCl.sub.2.6H.sub.2O, CuCl.sub.2.2H.sub.2O, CrCl.sub.3.6H.sub.2O, CaCl.sub.2.6H.sub.2O, MnCl.sub.2.4H.sub.2O, Cr.sub.2(SO.sub.4).sub.3.12H.sub.2O, CoSO.sub.4.7H.sub.2O, NiSO.sub.4.6H.sub.2O, Mg(NO.sub.3).sub.2.6H.sub.2O, Al(NO.sub.3).sub.3.9H.sub.2O, Ca(NO.sub.3).4H.sub.2O, ZnSO.sub.4.6H.sub.2O, Sr(NO.sub.3).sub.2.4H.sub.2O, Zn(NO.sub.3).sub.3.H.sub.2O, Zn(NO.sub.3).6H.sub.2O, Al.sub.2(SO.sub.4).sub.3.18H.sub.2O, and Cr.sub.2(SO.sub.4).sub.3.12H.sub.2O, polyvinylpyrrolidone as a surfactant, a saccharide, and water; wherein the average diameter of the metal oxalate hydrate particles is from 1 m to 100 m.

2. The metal oxalate hydrate particles of claim 1, which have the shape of a rectangular cuboid or a cube.

3. The metal oxalate hydrate particles of claim 1, wherein the shape of the metal oxalate hydrate particles is controlled by regulating at least one of the saccharide, the surfactant, the amount of saccharide added, or the amount of surfactant added.

4. The metal oxalate hydrate particles of claim 1, wherein a molar ratio of the surfactant is from 0.5 to 40 relative to 1 mole of the metal hydrate salt.

5. The metal oxalate hydrate particles of claim 1, wherein parts by weight of the saccharide are from 0.5 to 10 relative to 1 part by weight of the metal hydrate salt.

6. The metal oxalate hydrate particles of claim 1, wherein the hydrothermal reaction is carried out by heating the solution of step 1 to a temperature of 80 C. to 150 C., followed by reacting the solution for 30 minutes to 48 hours.

7. The metal oxalate hydrate particles of claim 1, wherein the saccharide is at least one selected from a monosaccharide, a disaccharide, and a polysaccharide.

8. The metal oxalate hydrate particles of claim 7, wherein the monosaccharide is at least one selected from glucose, fructose, and galactose, the disaccharide is at least one selected from sucrose, lactose, maltose, trehalose, melibiose, and cellobiose, and the polysaccharide is at least one selected from raffinose, stachyose, starch, dextrin, glycogen, and cellulose.

9. The metal oxalate hydrate particles of claim 1, wherein polyvinylpyrrolidone (PVP) has an average molecular weight of 10,000 to 36,000.

10. The metal oxalate hydrate particles of claim 1, wherein the at least one metal hydrate salt is selected from iron(III) chloride tetrahydrate, iron(II) chloride tetrahydrate, iron(III) chloride hexahydrate, iron(II) chloride tetrahydrate, iron(III) nitrate nonahydrate, iron(III) sulfate hydrate, iron(II) perchlorate hydrate, iron(II) sulfate hydrate, Co(NO.sub.3).sub.2.6H.sub.2O, Ni(NO.sub.3).sub.2.6H.sub.2O. CoCl.sub.2.6H.sub.2O, CoSO.sub.4.7H.sub.2O, NiSO.sub.4.6H.sub.2O.

11. A method for preparing the metal oxalate hydrate particles having an angled polyhedron shape of claim 1, comprising: preparing a mixture comprising a metal hydrate salt, a surfactant, a saccharide, and water (step 1); heating the mixture of step 1 to decompose the metal hydrate salt via a hydrothermal reaction, thereby forming metal oxalate hydrate particles having an angled polyhedron shape (step 2); and optionally cooling the product obtained in step 2 and washing the metal oxalate hydrate particles (step 3); wherein the average diameter of the metal oxalate hydrate particles is from 1 m to 100 m; and wherein the metal hydrate salt is at least one selected from iron(III) chloride tetrahydrate, iron(II) chloride tetrahydrate, iron(III) chloride hexahydrate, iron(II) chloride tetrahydrate, iron(III) nitrate nonahydrate, iron(III) sulfate hydrate, iron(II) perchlorate hydrate, iron(II) sulfate hydrate, Cr(NO.sub.3).sub.3.9H.sub.2O, Co(NO.sub.3).sub.2.6H.sub.2O, Ni(NO.sub.3).sub.2.6H.sub.2O, Pd(NO.sub.3).sub.2.2H.sub.2O, CoCl.sub.2.6H.sub.2O, CuCl.sub.2.2H.sub.2O, CrCl.sub.3.6H.sub.2O, CaCl.sub.2.6H.sub.2O, MnCl.sub.2.4H.sub.2O, Cr.sub.2(SO.sub.4).sub.3.12H.sub.2O, CoSO.sub.4.7H.sub.2O, NiSO.sub.4.6H.sub.2O, Mg(NO.sub.3).sub.2.6H.sub.2O, Al(NO.sub.3).sub.3.9H.sub.2O, Ca(NO.sub.3).4H.sub.2O, ZnSO.sub.4.6H.sub.2O, Sr(NO.sub.3).sub.2.4H.sub.2O, Zn(NO.sub.3).sub.3.H.sub.2O, Zn(NO.sub.3).6H.sub.2O, Al.sub.2(SO.sub.4).sub.3.18H.sub.2O, and Cr.sub.2(SO.sub.4).sub.3.12H.sub.2O.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an illustration showing the step-by-step shapes of the active iron oxalate hydrate body synthesized such that the shape is controlled, and the carbon-based iron oxide/carbon composite body obtained therefrom according to an embodiment of the present invention.

(2) FIG. 2 shows the flow chart of the preparation of the carbon-based iron oxide/carbon composite body according to an embodiment of the present invention.

(3) FIG. 3 shows images and spectrum of the iron oxalate body in the form of a cube obtained via a hydrothermal reaction according to Example 1 ((a) TEM image, (b-d) SEM images, (e) XRD spectrum).

(4) FIG. 4 shows a SEM image of the iron oxalate body in the shape of a cube taken after 2 hours of the reaction according to Example 2.

(5) FIG. 5 shows images and spectrum of FeO(OH) particles obtained via a reaction excluding glucose according to Comparative Example 1, in contrast to Example 1 ((a-b) TEM images, (c) XRD spectrum).

(6) FIG. 6 shows SEM images of the iron oxalate body according to Example 3 ((a) low magnification, (b) high magnification)

(7) FIG. 7 shows a SEM image of the iron oxalate body obtained via a reaction excluding PVP according to Comparative Example 2, in contrast to Example 2.

(8) FIG. 8 shows a SEM image of the iron oxalate body obtained by reacting with sucrose, which is a disaccharide, according to Example 4.

(9) FIG. 9 shows a SEM image of the iron oxalate body obtained by reacting with starch, which is a polysaccharide, according to Example 5.

(10) FIG. 10 shows SEM images of the iron oxide/carbon composite body obtained via a high-temperature thermal decomposition of the iron oxalate body according to Example 6 ((a) low magnification, (b) high magnification)

(11) FIG. 11 shows a XRD spectrum of the iron oxide/carbon composite body obtained via a high-temperature thermal decomposition of the iron oxalate body according to Example 6.

BEST MODE

(12) Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are provided for illustrative purposes only, and the scope of the present invention should not be limited thereto in any manner.

Example 1 Synthesis of Cube-Type Iron Oxalate Body Via Hydrothermal Reaction

(13) 20 g of Fe(NO.sub.3).sub.3.9H.sub.2O salt, 16.7 g (three equivalents) of polyvinylpyrrolidone (PVP, average Mw55000), and 18 g of glucose, a monosaccharide, were placed into a flask containing 100 mL of distilled water, and the resulting mixture was stirred under the air atmosphere and then heated to 100 C. After heating, the resulting mixture underwent hydrothermal reaction at 100 C. for 26 hours, and the temperature was cooled to room temperature to terminate the reaction.

(14) A colloidal solution, which was cooled at room temperature, was washed once by pouring distilled water thereinto, and the resulting mixture was subjected to centrifugation. Then, the distilled water was discarded, and the remaining mixture was washed again by pouring ethanol thereinto, followed by centrifugation. Herein, the mixture was precipitated by centrifugation at 10000 rpm for 30 minutes. The finally-obtained iron oxalate hydrate body was washed by pouring ethanol thereinto to remove impurities.

(15) The analysis results of transmission electron microscopy (TEM) images, scanning electron microscopy (SEM) images, and X-ray diffraction (XRD) of the finally-obtained iron oxalate hydrate body having a micrometer-scale size were shown in FIGS. 3 (a), (b) to (d), and (e), respectively.

(16) From the analysis results, it was confirmed that the iron oxalate hydrate bodies in the form of a cube having a size of 10 m were produced. As shown in FIG. 3 (e), it was confirmed that the crystals of the bodies in the sample obtained were found to be iron oxalate dehydrate (FeC.sub.2O.sub.42H.sub.2O, JCPDS#22-0635) via XRD analysis.

Example 2 Synthesis of Cube-Type Iron Oxalate Hydrate Body Via Hydrothermal Reaction

(17) The iron oxalate hydrate body was prepared by the same method as in Example 1, except that 10 g of Fe(NO.sub.3).sub.3.9H.sub.2O salt, 8.35 g (three equivalent) of polyvinylpyrrolidone (PVP, average Mw55000), 9 g of glucose, and 50 mL of distilled water were used, and the hydrothermal reaction was carried out at 100 C. for 2 hours.

(18) As shown in FIG. 4, the iron oxalate hydrate body obtained was in the form of a cube. As a result, it was confirmed that the synthesis time and variation in scale did not have a significant impact on the shape of the body, compared to experimental conditions of Example 1.

Comparative Example 1 Synthesis Experiment Excluding Glucose

(19) Under the same reaction conditions as Example 1, the experiment was carried out excluding glucose as a carbon precursor. As can be seen with TEM images shown in FIGS. 5 (a) and (b), uneven particles in the form of an oval of about 500 nm were observed, and it was confirmed that the particles obtained via XRD analysis were found to have the structure of FeO(OH) (ferric oxyhydroxide, Goethite), and not the structure of the iron oxalate hydrate, as shown in FIG. 5(c).

Example 3 Synthesis of Iron Oxalate Hydrate Body in the Presence of Excess PVP

(20) The iron oxalate hydrate body was prepared by the same method as in Example 1, except that 5 g of Fe(NO.sub.3).sub.3.9H.sub.2O salt, 41.8 g (thirty equivalents) of polyvinylpyrrolidone (PVP, average Mw55000), 4.5 g of glucose, and 25 mL of distilled water were used, and the hydrothermal reaction was carried out at 100 C. for 2 hours.

(21) The low magnification and high magnification SEM analysis results of the finally-obtained iron oxalate hydrate body revealed that the particles in the shape of a rectangular cuboid with a length of 20 m in the longitudinal direction seemed to be formed in the low magnification SEM image shown in FIG. 6 (a), but it was confirmed in the high magnification SEM image shown in FIG. 6 (b) that the cross-section of the ends thereof were slightly sunken.

Comparative Example 2 Synthesis of Iron Oxalate Hydrate Body without PVP

(22) Under the same reaction conditions as Example 2, the experiment was carried out without PVP as a surfactant. As a result, the ends of the cubic-type particles having a size of about 10 m were not properly formed as shown in the SEM image of FIG. 7.

Example 4 Synthesis of Iron Oxalate Hydrate Body Using Sucrose, a Disaccharide

(23) 5 g of Fe(NO.sub.3).sub.3.9H.sub.2O salt, 4.18 g (three equivalent) of polyvinylpyrrolidone (PVP, average Mw55000), and 18 g of sucrose, a disaccharide, were placed into a flask containing 25 mL of distilled water, and the resulting mixture was stirred under the air atmosphere and then heated to 100 C. After heating, the resulting mixture underwent a hydrothermal reaction at 100 C. for 2 hours, and the mixture was cooled to room temperature to terminate the reaction. A colloidal solution, which was cooled at room temperature, was washed once by pouring distilled water thereinto, and the resulting mixture was subjected to centrifugation. The distilled water was discarded, and the remaining mixture was washed again by pouring ethanol thereinto, followed by centrifugation. Herein, the mixture was precipitated by centrifugation at 10000 rpm for 30 minutes. The finally-obtained iron oxalate hydrate body was washed by pouring ethanol thereinto to remove impurities.

(24) As shown in FIG. 8, the iron oxalate hydrate body obtained using sucrose, a disaccharide, was in the shape of a long rod-like rectangular cuboid in which crystals thereof are biased in one direction, unlike when glucose was used as a carbon source in Examples 1 to 3.

Example 5 Synthesis of Iron Oxalate Hydrate Body Using Starch, a Polysaccharide

(25) 10 g of Fe(NO.sub.3).sub.3.9H.sub.2O salt, 8.35 g (three equivalent) of polyvinylpyrrolidone (PVP, average Mw55000), and 9 g of starch, a polysaccharide, were placed into a flask containing 50 mL of distilled water, and the resulting mixture was stirred under the air atmosphere and then heated to 100 C.

(26) After heating, the resulting mixture underwent hydrothermal reaction at 100 C. for 2 hours, and the mixture was cooled to room temperature to terminate the reaction. A colloidal solution which was cooled at room temperature was washed once by pouring distilled water thereinto, and the mixture was subjected to centrifugation. The distilled water was discarded, and the remaining mixture was washed again by pouring ethanol thereinto, followed by centrifugation. Herein, the mixture was precipitated by centrifugation at 10000 rpm for 30 minutes. The finally-obtained iron oxalate hydrate body was washed by pouring ethanol thereinto to remove impurities.

(27) The SEM analysis results of the iron oxalate hydrate body obtained above revealed that many bodies in the shape of a small, irregular rectangular cuboid with a size of several hundred nanometers were formed, confirming the deterioration of the quality of the bodies.

Example 6 Synthesis of Iron Oxide/Carbon Composite Body Via High-Temperature Heat Treatment of Iron Oxalate

(28) The iron oxalate hydrate body in the form of a powder obtained in Example 2 was introduced to a tubular calcinator, and was subjected to heat treatment at 400 C. for 4 hours under an inert gas atmosphere (atmospheric pressure, velocity at 100 mL/min to 200 mL/min) to obtain the iron oxide/carbon composite body.

(29) As a result, the overall shape of the composite body was in the form of a cube, as shown in the low magnification SEM image of FIG. 10 (a), and the high magnification SEM image of FIG. 10 (b) showed that small grains of several tens of nanometers were generated in the inside of cubic structure. Also, the small grain particles were found to be iron oxide (Fe.sub.2O.sub.3) via XRD analysis shown in FIG. 11 (c).

Example 7 Synthesis of Cube-Type Iron-Nickel Oxalate Hydrate Body and Cube-Type Iron-Cobalt Oxalate Hydrate Body by Hydrothermal Reaction

(30) For the synthesis of nickel-iron oxalate hydrate particles, the mixture of PVP (8.3 g, 75 mmol) and glucose (9 g, 50 mmol) was dissolved in 50 mL of distilled water, and then slowly heated to 100 C. for 20 minutes under inert conditions. Thereafter, the mixed solution of Fe(NO.sub.3).sub.3.9H.sub.2O (5.1 g, 12.5 mmol) and Ni(NO.sub.3).sub.2.6H.sub.2O (3.6 g, 12.5 mmol), melted at 323 K, was injected into the hot PVP-glucose mixture solution at 373 K; the mixture solution was refluxed for 1 hour at the same temperature. After 1 hour, the colloidal dispersion was cooled to room temperature, and separated by centrifugation at 8,000 rpm for 10 minutes. Finally, the precipitates were washed with distilled water and ethanol several times by centrifugation at 8,000 rpm for 10 minutes; precipitates were dried in an oven at 333 K.

(31) To prepare the iron-cobalt oxalate hydrate particles, Co(NO.sub.3).sub.2.6H.sub.2O (3.6 g, 12.5 mmol) was employed with Fe(NO.sub.3).sub.3.9H.sub.2O (5.1 g, 12.5 mmol). The procedures and conditions were identical to those used in the synthesis of iron-nickel oxalate hydrate particles.

(32) Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.