KR20160087963A - Composite catalyst for fuel cell and its preparing method - Google Patents

Abstract

The present invention relates to a composite catalyst for polymer electrolyte membrane fuel cells (PEMFCs). According to the present invention, the composite catalyst for the PEMFCs wherein a spacer is induced to a graphene sheet wherein boron supporting a metal catalyst substance is doped to prevent other graphene sheets from being placed on the graphene sheet is provided. Thus, the effects of reducing resistance to an electron transfer by using the graphene sheet with the doped boron as a support element and maintaining high electron density are obtained. In addition, a specific surface area of the graphene sheet is highly maintained by inducing the spacer capable of preventing other graphene sheets from being place on the graphene sheet. Thus, an effect of manufacturing the PEMFC capable of providing excellent performance is obtained.

Description

TECHNICAL FIELD [0001] The present invention relates to a composite catalyst for a fuel cell,

The present invention relates to a composite catalyst for polymer electrolyte membrane fuel cells (PEMFCs), and more particularly to a polymer electrolyte membrane fuel cell (PEMFCs) composite catalyst for supporting a metal catalyst material on a graphene sheet doped with boron, And a method of manufacturing the composite catalyst. The present invention relates to a composite catalyst for a fuel cell.

Various carbon materials such as carbon nanotubes, fullerenes, carbon molecular sieve, carbon fiber, and graphene are attracting attention due to their high durability, excellent electrical conductivity, low cost, high mechanical strength and large specific surface area. Of the various carbon materials, graphene has a two-dimensional structure that is different from the three-dimensional structure of other carbon materials, which has very good physical properties. Graphene consists of hexagonal arranged carbon atoms with a single molecule thickness, which is the basic structure of the graphite carbon material. Graphene requires physicochemical coordination to be used for various purposes. One of the methods for improving the electrochemical properties is atom doping, which is one of the methods of making silicon into semiconductors. Two general methods of element doping are known. One is a method commonly used in the process of making semiconductors by chemical vapor deposition. The other is element doping which utilizes thermal decomposition. It is a method of doping different kinds of elements into existing pure matter by a quick and simple method compared to the former method. Various types of elements have been doped into graphene sheets to alter the electrochemical properties of graphene. These studies have confirmed that doped graphene has great potential in various fields. However, when using graphene as a catalyst support for electrochemical applications, there is a serious problem of returning graphene sheets to graphite.

On the other hand, Korean Patent Publication No. 10-2011-0051584 (a method for producing graphene using a catalyst alloy) and Korean Patent No. 10-1148844 (method for producing graphene using a metal catalyst) However, with respect to the composite catalyst for a fuel cell in which a spacer is introduced to support a metal catalyst material on a graphene sheet doped with boron and to prevent re-deposition of the graphene sheet bearing the metal catalyst material It has not been disclosed at all.

The present inventors have found that by introducing a spacer to prevent re-deposition of the graphene sheet after carrying the metal catalyst material on the graphene sheet doped with boron, the specific surface area of the graphene sheet can be kept high In addition, the present inventors have completed the present invention by experimentally confirming that the performance of a polymer electrolyte fuel cell including such a composite catalyst is improved.

It is an object of the present invention to provide a composite catalyst for a fuel cell, in which a spacer is introduced into a boron-doped graphene sheet carrying a metal tendon to prevent re-deposition of the graphene sheet.

Another object of the present invention is to provide a method of manufacturing a composite catalyst for a fuel cell in which a spacer is introduced into a boron-doped graphene sheet carrying a metal-attracting substance to prevent re-deposition of the graphene sheet.

In order to achieve the above object, the present invention provides a fuel cell comprising a graphene sheet doped with boron on which a metal catalyst material is supported, a fuel injected with a spacer to prevent re- Thereby providing a composite catalyst for a battery.

Wherein the metal catalyst material comprises at least one metal selected from the group consisting of Pt, Pd, Ag, Cu, Ni, Co, Mo, Ru, Re, Rb, Pb and La and a metal oxide comprising the metal And at least one selected from the above.

The spacer is selected from a carbon nano tube, carbon black (CB), and the like.

The spacer is carbon black (CB), and is contained in an amount of 1 wt% to 30 wt%.

The present invention also provides a fuel cell including an electrode including the composite catalyst for a fuel cell.

The present invention also provides a method for preparing graphene oxide, comprising: (1) preparing graphene oxide; (2) doping the graphene oxide with boron; and (3) (4) a step of injecting a spacer into the graphene oxide on which the metal catalyst material is supported. The present invention also provides a method for manufacturing a composite catalyst for a fuel cell, comprising the steps of:

The metal catalyst material may be at least one metal selected from the group consisting of Pt, Pd, Ag, Cu, Ni, Co, Mo, Ru, Re, Rb, Pb and La, And an oxide of at least one selected from the group consisting of.

In the step (4), the spacer is selected from a carbon nano tube, a carbon molecular sieve, and carbon black.

In the step (4), the spacer is carbon black (CB) and is contained in an amount of 1 wt% to 30 wt%.

The present invention also provides a composite catalyst for a fuel cell produced by the above-described method.

According to the present invention as described above, it is possible to provide a fuel cell composite fuel cell in which a spacer is introduced into a graphene sheet doped with boron on which a metal catalyst material is supported, By providing a catalyst, boron-doped graphene sheets can be used as a support to reduce the electron mobility and maintain a high electron density, as well as to provide a spacer for preventing recoating of the graphene sheet, It is possible to manufacture a polymer electrolyte fuel cell which can maintain a high surface area and exhibit excellent performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of platinum (Pt) -boron (B) -graffin (Gr) synthesis and carbon black insertion.
2 is an XRD pattern graph of graphite (a), graphene oxide (b), and B-Gr (c).
3 is an XRD pattern graph of platinum (Pt) -boron (B) -graffin (Gr).
Fig. 4 is a graph showing the C 1s main wavelength (a) of graphene oxide, the C 1s major wavelength of B-Gr (b) / B- (E) of the O 1s of Pt-B-Gr, and the major wavelength (f) dp of Pt 4f of Pt-B-Gr.
5 is a scanning electron micrograph of graphite (a), graphene oxide (b) and B-Gr (c).
6 is a TG / DTA graph of graphene oxide (a), Pt-B-Gr.
7 is an FT-IR wavelength graph of graphite (a), graphene oxide (b), B-Gr (c) and Pt-B-Gr (d).
8 is a graph showing the Raman spectral wavelength of graphene oxide (a), B-Gr (b), and Pt-B-Gr (c)
9 is a TEM photograph (a) of Pt-B-Gr, a particle size analysis graph (b) of platinum particles in Pt-B-Gr, and a TEM photograph (c) of carbon black inserted between graphen sheets.
Pt-B-Gr / CB0.2, Pt-B-Gr / CB0.3, (*) Pt- CV curve graph of B-Gr / CB0.4.
Pt-B-Gr / CB0.2, Pt-B-Gr / CB0.3, (*) Pt- B-Gr / CB0.4 electrochemically active area graph according to the number of circulating current measurements.
FIG. 12 is a graph showing the relationship between the IV curve (empty symbol), () Pt-C, () Pt-B-Gr for battery performance at 100% humidified condition at 80 ° C., (*) Pt-B-Gr / CB0.2, Pt-B-Gr / CB0.3,
FIG. 13 is a graph showing the electrochemical resistance graphs (() Pt-C, () Pt-B-Gr, () Pt-B-Gr of the membrane electrode assembly prepared using catalysts having four different carbon black contents / CB 0.2, () Pt-B-Gr / CB 0.3, () Pt-B-Gr / CB 0.4).

The present invention provides a composite catalyst for a fuel cell in which a spacer is introduced into a graphene sheet doped with boron on which a metal catalyst material is supported to prevent reattachment of the graphene sheet. Wherein the metal catalyst material comprises at least one metal selected from the group consisting of Pt, Pd, Ag, Cu, Ni, Co, Mo, Ru, Re, Rb, Pb and La and a metal oxide comprising the metal At least one selected may be selected, and it is preferable to select Pt having an average particle size of 2 to 5 nm. On the other hand, the thickness of the graphene sheet is preferably 0.3 to 0.4 nm. In addition, a spacer may be introduced to prevent the re-deposition of the metal catalyst material from the graphene sheet, and the spacer may be made of a carbon material, preferably a carbon nano tube, carbon Carbon molecular sieve , carbon black , and the like. Further, it is preferable to select carbon black (CB) as a spacer, and more preferably carbon black is contained in an amount of 1 wt% to 30 wt%. When the carbon black (CB) is contained in an amount of 30 wt.% Or more, the performance of the fuel cell deteriorates.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which: FIG. You can do it. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1. Synthesis of graphene oxide

Graphene oxide was synthesized by the optimized Hummers method. Graphite powder was used as a base material. Graphite (E-NanoTech. Co., Korea ) of 4g, of _{5g K 2 S 2 O 8 (} YakuriPureChemicalsCo., Japan) and 5g of _{P 2 O 5 (SamchunChemicalCo.,} Korea) the 80㎖ of H ₂ SO ₄ ( Samchun Chemical Co., Korea) and heated in an oil bath at 80 ° C for 2 hours. The mixture of black gray was slowly cooled at room temperature for 10 hours.

The mixture was washed with 500 ml of deionized water three times to remove residual impurities such as acids. The resultant was dried in a vacuum oven at 80 캜. The pre-oxidized graphite in the form of a large lump was pulverized and put into 80 ml of H ₂ SO ₄ and stirred at 4 ° C in an ice bath. When mixing was completed, 12 g of KMnO ₄ (Samchun Chemical Co., Korea) was slowly added to the mixture, and the mixture was stirred for 30 minutes and kept at a temperature of 4 ° C or lower in the ice bath. When the slurry became a dark color, it was heated to 35 DEG C, stirred for 30 minutes, and diluted with 200 mL of deionized water. In the course of the process, the slurry of a blue color turns into a bright yellow color. The mixture is heated to 80 < 0 > C and stirred for 30 minutes. Thereafter, 400 ml of deionized water, 20 ml of H ₂ O ₂ (Junsei, Japan) and 100 ml of 10 wt.% HCl solution are added to give a lighter color and little bubbles. The mixture was ultrasonically dispersed for 2 hours so that the laminated layer was easily peeled off. The mixture was rinsed with deionized water to remove residual metal ions and acid until the pH was neutral. This was carried out using centrifugation, and after completion of washing, graphene oxide in powder form was obtained by vacuum oven drying at 60 DEG C for 12 hours.

Example 2. Synthesis of Boron Doping Graphene (B-Gr) by Pyrolysis

Boron doping graphene was synthesized by thermal solid phase reaction method. 300 mg of graphene oxide and 900 mg of H ₃ BO ₄ (Yakuri Pure Chemical Products Co., Japan) were dissolved in water, thoroughly mixed, and then dried to remove water. The dried graphene oxide / H ₃ BO ₄ mixture was transferred to a ceramic crucible and placed in a tubular reactor. Before the heat treatment, the reactor was filled with argon in a tubular reactor for 30 minutes. The graphene oxide / H ₃ BO ₄ mixture was heated to 700 ° C at a rate of 5 ° C min ^-1 and then thermally decomposed for 2 hours. Thereafter, the reactor was slowly cooled naturally to room temperature while maintaining argon filling. After the heat treatment, the product was washed three times with 100 ml of ethanol and 500 ml of deionized water to completely remove residual ions. The product was dried in a vacuum oven at 6O < 0 > C for 12 hours.

Example 3 Carrying of platinum (Pt) nanoparticles on boron (B) -graffin (Gr) sheet

Platinum particles were supported on boron graphene by microwave method. 100 mg of boron doping graphene was placed in a mixed solution of 48 ml of ethylene glycol (EG, Samchun Chemical Co., Korea) and 12 ml of isopropyl alcohol (IPA, Samchun Chemical Co., Korea) Lt; / RTI > 160 mg of H ₂ PtCl ₆ (Aldrich Co.) As a platinum precursor was dispersed in 4 ml of ethylene glycol and dispersed in a solution in which boron doping graphene was dispersed for 2 hours. 1 M NaOH solution was added dropwise to the mixture little by little to adjust the pH to 12. The mixture was placed in a typical domestic microwave oven (Samsung, RE-C21AW, operating frequency: 2450 MHz) and heated to 700 W power for 3 minutes. After cooling the mixture heated to room temperature, 0.5 M HNO ₃ solution was gradually added to adjust the pH to 4 to adjust the size of the platinum particles. The Pt-B-Gr was subjected to 500 ml deionized water washing and filtration three times and then dried in a vacuum oven at 60 DEG C for 12 hours.

Example 4. Insertion of carbon black into platinum (Pt) -boron (B) -graffin (Gr)

To insert carbon black in Pt-B-Gr, carbon black was inserted into 24 mg of Pt-B-Gr at a ratio of 20, 30, 40 wt%, and 169 mg of a 5 wt. gave. Each sample was named Pt-B-Gr / CB0.2, Pt-B-Gr / CB0.3 and Pt-B-Gr / CB0.4. 1 ml IPA was used as a catalyst dispersing agent and ultrasonic dispersion was performed at 50 캜 for 1 hour.

The Pt-B-Gr synthesis and the carbon black insertion process are summarized in FIG.

Experimental Example 1. Measurement of physical properties

(1) XRD pattern identification and SEM analysis

Powder X-ray diffraction analysis (XRD, Rigaku Model D / Max 2200) using Cu K? Radiation was performed to obtain an XRD pattern. At 40kV 30mA, the scan rate was 5 ㅀ min ^-1 and the resolution was 0.04 당 per 2 罐.

As a result, the XRD pattern of Pt-B-Gr prepared in Example 4 is as shown in Fig. 3, and the XRD patterns of graphite (a), graphene oxide (b) and B- , It was confirmed that an abrupt phase change occurred when graphite was synthesized from graphene oxide and B-Gr. The major peak at C (002) was found at 26.5 ^o at 2 theta due to the lamination of graphite. The C (002) peak of graphite was shifted from 2? To 11 ^o due to the chemical oxidation of graphite through the Hummer's method because of the oxidative groups such as epoxy, carboxyl, hydroxyl groups, to be. The B-Gr was synthesized by the thermal decomposition method described in the experimental method, and it was confirmed that the 11 ^o peak disappears at 2 ?. In order to clarify this phase change, a scanning electron microscope (SEM, JEOL JSM-6308) analysis was performed and the results are shown in Fig. As can be seen from Fig. 5, it was confirmed that the peeling progressed in graphite and the surface morphology largely changed. Fig. 5 (a) shows the shape of the graphite laminate in the bulk state. 5 (b), unlike graphite, it was possible to confirm that the graphene sheets were peeled off due to the oxidizing groups. The B-Gr was synthesized through the thermal decomposition described in the experimental method, and it was confirmed through the corrugated graphene sheet form as shown in FIG. 5 (c).

As described in the above-mentioned experimental procedure, it was confirmed by XRD whether Pt particles were included in the boron-doped graphene sheet (B-Gr) and successfully contained. As can be seen in FIG. 3, the major peaks of Pt (111), Pt (200), Pt (220) and Pt (311) are clearly shown at 40, 46, 67.5 and 81.4 Platinum particles are well supported on the B-Gr surface.

The average size of the Pt particles was obtained from the Pt peak using the following Scherrer equation.

[Equation 1]

In Schrrer's equation, L is the average particle size, the constant 0.94 is the constant when the crystal structure is an octahedron, λ _k is the wavelength of the X-ray (1.54056 nm), and B _2θ is the radian of full width at half maximum (FWHM) Value, and [theta] _B is the angular position of the Pt (220) peak. When the FWHM value of Pt (220) was calculated and the Scherrer equation was calculated, the average size of Pt particles supported on B-Gr was 2.37 nm.

(2) XPS spectrum analysis

To further clarify the surface functional group analysis of graphene oxide and B-Gr, and to clarify the oxidation state of platinum particles supported on Pt-B-Gr, XPS analysis was carried out. The results are shown in FIG.

4 (a), the peaks are divided into four different types of carbon in graphene oxide. This is sp ² hybridization CC at 284.5 eV, C-OH at 285.2 eV, COC at 286.4 eV, and HO-C = O at 288.1 eV, summarized in Table 1 below.

[Table 1]

Figures 4 (b), (c), (d) and (e) show the XPS wavelengths of B-Gr synthesized using thermal decomposition of graphene oxide and boric acid. FIG. 4 (b) shows the C 1s and O 1s in B-Gr and the B 1s peak of weak intensity at 284.5, 533 and 192 eV, respectively. FIG. 4 (c) shows the major wavelength of C 1s, which is divided into five types of peaks. This is CB at 283.7 eV, C = C at 284.5 eV, CO at 285.4 eV, OCO at 286.1 eV, and C = O at 287 eV. The XPS wavelengths of B 1s and O 1s in B-Gr are divided into Fig. 4 (d) and (e). Figure 4 (d) shows the wavelength for B 1s in B-Gr divided by BC ₃ (BsuboundsintohexagonalCofgraphene) at 188.9 eV, BC ₂ O at 190.7 eV, and BCO ₂ at 192.1 eV, respectively. Fig. 5 (e) shows the wavelength for O1s in B-Gr, divided by OC at 531.5 eV, O = C at 532.5 eV, and OB at 533.1 eV, respectively. The bond energies and their relative intensities are summarized in Table 2 below. Table 2 shows that 3.4% of the boron introduced by substituting the carbon and the oxidation groups remain.

[Table 2]

5 (f) shows the XPS wavelength of Pt 4f doublet (4f _7/2 , 4f _5/2 ) measured at 71.2 and 74.3 eV of platinum nanoparticles in Pt-B-Gr, It was slightly lower than Pt 4f _{7/2 and} 4f _5/2 [44] of Pt (0). This is because graphene and boron have a work function lower than that of Pt (5.65 eV) at 4.45 and 4.48 eV, which means that the pi electrons in graphene are activated by bonding with the boron- Is transferred to boron in B-Gr. In other words, the electron transport to the boron in the B-Gr could increase the amount of platinum in the metal state in the oxidized state, which is summarized in Table 3. Compared with the previous results, the relative strength of Pt (0) increased by 8% in Pt-B-Gr. The increase of Pt (0) content is a very important factor in the increase of catalytic activity. It can reduce the expensive platinum content and improve the slow oxygen reduction reaction (ORR) of cathode which plays the most important role in fuel cell performance Therefore, it is very important to improve battery performance.

[Table 3]

(2) Thermogravimetric analysis (TGA)

Through TGA, O and platinum contents in graphene oxide and Pt-B-Gr were confirmed. FIG. 6 (a) shows that graphene oxide was reduced by 6.5% at 100 ° C. and then decreased by 29% at 200 ° C. due to the elimination of oxidizing functional groups, as water molecules that were absorbed were removed. In contrast to the graphene oxide of FIG. 6 (a), in FIG. 6 (b), only 1% reduction in weight due to the removal of water molecules at 100.degree. C. was confirmed, Weight loss was confirmed. As a result, the platinum content in Pt-B-Gr was measured to be 39.0 wt.%.

(3) Fourier transform ultraviolet ray analysis (FT-IR)

FT-IR was performed to identify the surface functional groups of graphene oxide, B-Gr, and Pt-B-Gr, and the results are shown in FIG. In the case of the graphene oxide synthesized by the oxidation of ^{graphite, 3400 cm -1 hydroxyl (OH)} , carbonyl / carboxyl (C = O) at ^{1728 cm -1, aromatics (C =} C) at 1625 cm ^-1, at 1384 in cm ^-1 at the carboxyl (CO), 1262 cm ^-1 in the epoxy (CO), 1088 cm ^-1 had to read alkoxy (CO), respectively, which are also shown in 7 (b). When boron was doped with a dopant, it was confirmed that the intensity of the oxidizing group was significantly reduced as compared with that of graphene oxide in FIG. 7 (c). This shows that in the process of doping graphene oxide with boron through thermal decomposition, It happened at the same time. At 1105 cm ^-1 , the weak wavelengths of BC and CO were overlapped and measured. It was confirmed that the intensity of the wavelength was reduced due to the progress of the further reduction of the remaining oxidizing functional groups during the reduction of the platinum precursor during the platinum loading.

(4) Raman spectroscopy analysis

The Raman spectroscopic results of graphene oxide, B-Gr and Pt-B-Gr show two distinct peaks, D-band and G-band, measured at 1345 and 1590 cm ^-1 . The G-band is generated by E _2g phonons in which the sp ² -C atom is an extension of the plane-coupled tangent. The D-band ("D = disordered" band) is caused by the interaction of the sp ² -rings in the graphene layer due to bonding angles, bond length disorder, hybridization, etc., . This is shown in FIG. 8, which means that as the relative intensity ratio I _D / I _G is greater than 1, the doped atomic defect sites are more numerous.

(5) TEM analysis and particle size distribution analysis

9 (a) is a TEM photograph showing the particle size distribution of Pt-B-Gr. As a result, it was confirmed that the platinum nanoparticles having a size of 2 to 3 nm were uniformly dispersed and partially agglomerated, and the particle size analysis results were summarized through FIG. 9 (b). In the case of Fig. 9 (c), carbon black particles of 10 nm to 50 nm in size are inserted between graphene nanosheets. The average particle size of the measured platinum nanoparticles was 2.40 nm, which is similar to the result calculated using the Scherrer equation.

Experimental Example 2. Measurement of electrochemical characteristics

(1) CV measurement result

The electrochemical activity area of various Pt-B-Gr / CBx (x = 0.0, 0.2, 0.3, 0.4) catalysts was measured and compared with Pt-C. The results are shown in FIG.

As described in the experimental method, different contents of carbon black were inserted in the Pt-B-Gr to prevent re-deposition. The electrochemical active area of Pt-B-Gr / CBx (x = 0.0, 0.2, 0.3, 0.4) was calculated by the following equation through hydrogen adsorption area and double layer charge current.

[Equation 2]

The electrochemically active areas of Pt-C, Pt-B-Gr, Pt-B-Gr and CB0.2, Pt-B-Gr and CB0.3, and Pt- 77.9, 91.7, 51.1 m < ² > g < ^{-1 &} gt ;. As a result, it was confirmed that the electrochemically active area increases as the carbon black insertion amount increases to 30 wt.% (Ie, Pt-B-Gr / CB0.3). At 30 wt.% Or more, the electrochemically active area decreased. This is presumed to be the result of relatively large carbon black particles partially blocking the platinum particles. In addition, the results of measuring the durability of various catalysts by measuring the circulation currents of 400, 800, and 1200 cycles are shown in FIG.

From these results, it was confirmed that the insertion of carbon black improved the catalyst durability. In the Pt-B-Gr / CB0.2 and Pt-B-Gr / CB0.3 of FIG. 11, electrochemically active areas after 1200 cycles of circulating current measurement were reduced by only 10.2 and 9.8%, respectively. It is presumed that carbon black inhibited the aggregation of platinum nanoparticles. In contrast, the electrochemically active area decreased by 45.3% in Pt-B-Gr and decreased by 21.8% in Pt-B-Gr / CB0.4. In the case of Pt-B-Gr / CB0.4, the electrochemically active area reduction is presumably the result of the relatively large carbon black particles being trapped by platinum. The electrochemically active area of the initial Pt-C was 46.6 m ² g ^{-1 which} was slightly larger than Pt-B-Gr, but smaller than Pt-B-Gr after 1200 circulating current measurements.

(2) Measurement of electrochemical active area according to the number of times of circulating current measurement

The anode and cathode catalyst inks were prepared using commercial Pt-C and Pt-B-Gr / CBx (x = 0.0, 0.2, 0.3, 0.4) catalysts as described in the previous experimental method. A variety of membrane electrode assemblies were fabricated to evaluate cell performance at 100% relative humidity. This is shown in FIG. 12, and it was confirmed that the battery performance was improved remarkably by carbon black insertion. The voltage densities at 0.6 V were 0.37, 0.70, 0.83 and 0.40 A cm ^-2 , respectively, when using Pt-B-Gr / CBx (x = 0.0, 0.2, 0.3 and 0.4) , A current density of 0.6 A to 0.05 A cm ^-2 was measured. However, when the amount of the carbon black particles exceeds a certain amount, the carbon black particles block the platinum particles between the graphene sheets. This partial shrinkage of the carbon black reduces the active area of the platinum nanoparticles and degrades the negative electrode reaction. The reason why the decrease in the electrochemical active area of Pt-B-Gr / CB0.4 is greatly different from the decrease in the active area of Pt-B-Gr / CB0.2 and Pt-B-Gr / CB0.3 have. In addition, the performance of Pt-B-Gr / CB0.4 is lower than that of Pt-B-Gr / CB0.2 at low current density because the active area of platinum particles is not utilized properly for the cathode reaction . However, Pt-B-Gr / CB0.4 shows higher cell performance than Pt-B-Gr / CB0.2 at high current density. This is presumably because more carbon black content provides larger pores to facilitate mass transfer.

To confirm the effect of boron doping, the cell performance using Pt-B-Gr and the previous cell performance results using Pt-G were compared at 0.6 V current density. In the case of using Pt-B-Gr, the current density was 0.37 A cm ^-2 at 0.6 V, whereas the previous experiment showed a current density of 0.036 A cm ^-2 . Each MEA was fabricated to compare cell performance differences with the doping amount of boron.

As a result of the analysis of the overall results, it was estimated that the enhancement of the performance was due to the transfer of electrons from the graphene electron to the boron, boron to the platinum nanoparticle, and the expansion of the active area through the insertion of carbon black.

Meanwhile, FIG. 13 shows the resistance of a single cell in a Nyquist plot, where Z ' _{real, which} is the width of the high frequency region, represents the total resistance. The diameter of the semicircle is the charge transfer resistance, which is measured due to the characteristics of the anode catalyst and the oxygen reduction reaction of the cathode. This means that a smaller diameter semicircular cathode catalyst has a smaller resistance and the results are summarized in Table 4 below. As shown in the table, the charge transfer resistance of Pt-B-Gr / CBx catalyst tends to decrease while x increases from 0.0 to 0.3, while resistance to Pt-B-Gr / CB0.4 increases . This is consistent with the cell performance results of FIG. Referring to FIG. 12, the Pt-B-Gr / CB0.4 catalyst exhibits a low current density at low voltage, presumably due to a slow cathodic reaction, but the overall cell performance has the second highest storage density. This is presumably due to the smooth transfer of the substance.

[Table 4]

Experimental Example 3. Experimental Result

Summarizing the above experimental results, it was confirmed that boron was effectively doped into graphene through FT-IR, Raman spectroscopy, and XPS analysis. The XPS analysis showed that the Pt 4f peak shifted to a slightly lower binding energy due to graphene and boron having a lower work function than platinum, as a result of electron transfer from graphene to boron and from boron to platinum . The electrochemically active area of Pt-B-Gr, Pt- B-Gr / CB0.2, Pt-B-Gr / CB0.3 for, respectively, while the amount of carbon black increased ^{41.6, 77.9, 91.7 m 2 g} - ¹ , but in the case of Pt-B-Gr / CB0.4, platinum particles were blocked due to too much carbon black particles and a smaller electrochemically active area was measured at 51.1 m ² g ^-1 . The electrochemically active area measured by cyclic currents of 400, 800 and 1200 cycles for various catalysts (Pt-B-Gr / CBx, x = 0.0, 0.2, 0.3 and 0.4) As shown in FIG. This is because carbon black can prevent aggregation of platinum particles and reattachment of graphene nanosheets. As a result of the measurement of the cell performance, it was confirmed that the effects of boron doping and carbon black insertion were improved and the performance was improved. Particularly, when the amount of carbon black was 30 wt.% Or less, the performance was remarkably improved by Pt-B-Gr / CBx (ie, x = 0.2, 0.3). In addition, when an excessive amount of carbon black is inserted (that is, Pt-B-Gr / CB0.4), carbon black interferes with platinum to reduce the active area, thereby slowing the oxygen reduction reaction. However, .

Having described specific portions of the present invention in detail, it will be apparent to those skilled in the art that this specific description is only a preferred embodiment and that the scope of the present invention is not limited thereby. It will be obvious. Accordingly, the actual scope of the invention will be defined by the appended claims and their equivalents.

Claims (10)

A composite catalyst for a fuel cell, wherein a spacer is introduced into a graphene sheet doped with boron on which a metal catalyst material is supported, to prevent re-deposition of the graphene sheet.
The method according to claim 1,
Wherein the metal catalyst material comprises at least one metal selected from the group consisting of Pt, Pd, Ag, Cu, Ni, Co, Mo, Ru, Re, Rb, Pb and La and a metal oxide comprising the metal Wherein the catalyst is at least one member selected from the group consisting of a catalyst and a catalyst.
The method according to claim 1,
Wherein the spacer is selected from a carbon nano tube, a carbon black, and a carbon molecular sieve.
The method according to claim 1,
Wherein the spacer is carbon black (CB), and is contained in an amount of 1 wt% to 30 wt%.
A fuel cell comprising an electrode comprising the composite catalyst of any one of claims 1 to 4.
(1) preparing graphene oxide; and
(2) doping the graphene oxide with boron,
(3) supporting the metal catalyst material on the boron-doped graphene oxide,
(4) a step of injecting a spacer into the graphene oxide carrying the metal catalyst material.
The method according to claim 6,
The metal catalyst material may be at least one metal selected from the group consisting of Pt, Pd, Ag, Cu, Ni, Co, Mo, Ru, Re, Rb, Pb and La, Wherein the catalyst is at least one selected from the group consisting of oxides, nitrides, and oxides.
The method according to claim 6,
In the step (4), the spacer is selected from a carbon nano tube, carbon black, and CB.
The method according to claim 6,
In the step (4), the spacer is carbon black (CB) and is contained in an amount of 1 wt% to 30 wt%.
A composite catalyst for a fuel cell produced by the production method of any one of claims 6 to 9.

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