KR100866311B1 - Method for preparing n-rich nanoporous graphitic carbon nitride structure - Google Patents

Abstract

A method of manufacturing nanoporous carbon nitride having nitrogen-rich structure is provided to arrange regularly spherical pores having macro size and to improve electrocatalyst activity which can be used as a supporter to the electrocatalyst of a fuel battery because nitrogen atoms are included in the structure. A method of manufacturing nanoporous carbon nitride having nitrogen-rich structure comprises steps of: preparing a colloidal silica mold in which spherical silica having macro size is laminated; heating the colloidal silica mold at 500 - 700 °C for 1 - 3 hours; injecting molecules precursors for the carbon nitride in the colloidal silica mold; stabilizing the colloidal silica mold infused by the molecules precursors at 60-80°C for 1-3 hours; carbonizing a mixture; and removing the silica colloidal mold. The colloidal silica mold is manufactured by laminating the spherical silica having macro size of 100 - 600 nm using a sedimentation method, a centrifugation method, a filtration method or a pressing method.

Description

Method for preparing nitrogen-rich nanoporous graphite carbon nitride structure {Method for Preparing N-Rich Nanoporous Graphitic Carbon Nitride Structure}

1 is a SEM photograph of a cross section of a nanoporous graphite carbon nitride structure according to an embodiment of the present invention.

2 is a view showing an XRD pattern of the nanoporous graphite carbon nitride structure according to an embodiment of the present invention.

3 is an XPS spectrum of a nanoporous graphite carbon nitride structure according to an embodiment of the present invention.

4 is an FT-IR spectrum of a nanoporous graphite carbon nitride structure according to an embodiment of the present invention.

5 is a nitrogen adsorption-desorption isotherm of a nanoporous graphite carbon nitride structure according to an embodiment of the present invention.

6 is a TEM photograph of a Pt-Ru / C ₃ N ₄ catalyst according to an embodiment of the present invention.

FIG. 7 illustrates the use of a Pt-Ru / C ₃ N ₄ catalyst obtained from an embodiment of the present invention and a commercially available E-TEK catalyst as an anode, and an O ₂ -supplied cathode, and 30 ° C. of a direct methanol fuel cell. It is a graph comparing the performance in 60 degreeC.

8 is a 30-degree C of a direct methanol fuel cell using a Pt-Ru / C ₃ N ₄ catalyst obtained from one embodiment of the present invention and a commercially available E-TEK catalyst as an anode and an air-breathing mode cathode; It is a graph comparing the performance in 60 degreeC.

9 is a Pt-Ru / C ₃ N ₄ catalyst obtained from one embodiment of the present invention, Pt-Ru / OMC catalyst and E-TEK catalyst obtained from a comparative example using an O ₂ -feeding cathode This is a graph comparing the performance at 60 ℃ of direct methanol fuel cell.

The present invention relates to a nitrogen-rich nanoporous graphite carbon nitride, a method for preparing the same, and a fuel cell using the same. More specifically, the present invention relates to a nitrogen-rich nanoporous graphite carbon nitride having a structure in which macroscopic spherical pores are regularly arranged and connected by connecting pores to have a three-dimensional interconnected structure, a method for preparing the same, and a fuel cell using the same.

High surface area and well-developed fully interconnected pores are essential to the catalyst support. Carbon materials are mainly used as catalyst supports because of their high stability, good electrical conductivity and high specific surface area in both their acidic and basic media.

High surface area carbon black, one side Vulcan XC-72, is the most widely used to prepare supported catalysts. In fact, a commercially available E-TEK catalyst is a Pt-Ru alloy catalyst supported on Vulcan XC-72.

In recent decades, several other carbon materials such as carbon nanotubes, graphite carbon nanofibers, nanoporous carbon and mesocarbon microbeads have been reported as new supports.

The new structure of carbon support has made significant progress as it is synthesized using mesoporous molecular sieves and self-assembled colloidal silica as a template.

Divinylbenzene, sucrose, phenolic resin, perfuryl alcohol, and polyacrylonitrile are generally used as carbon precursors for preparing such carbon supports, but carbon obtained by pyrolysis in a relatively low temperature range of 700 to 1000 ° C Graphite is inadequate and mostly amorphous.

There are several records of regularly arranged porous graphitized carbon, but this can generally be synthesized by heating at high temperatures in excess of 2000 ° C.

Pitch-based graphitized carbon with highly ordered nanopores is synthesized by first preparing highly ordered porous carbon with a colloidal crystalline template, followed by heating the template-free porous carbon at 2500 ° C. Graphitization increases electron conductivity due to the unlocalized π-orbital of sp ² hybrid carbons formed on hexagonal aromatic rings.

Recently, there has been a great interest in carbon materials containing heteroatoms such as N, B or Si due to the expectation of new properties such as improved hardness, oxidation resistance and chemical resistance. The most surprising of these is the carbon nitride phase. In particular, graphite-C ₃ N ₄ is a new material with particular expectations in the field of catalysts and hard coatings.

Recently, melamine (2,4,6-triamino-s-triazine), C ₃ N ₃ (NH ₂ ) ₃ and other s-triazine (cyanuric; -C ₃ N ₄ ) ring compounds, for example C ₃ N ₃ X ₃ (X = Cl, F, OH, NHCl, N or NCNH) is being used as molecular precursor for the synthesis of the graphite form of C ₃ N ₄ .

Carbon nitride films, hollow carbon nitride spheres and carbon nitride nanotubes with a C ₃ N ₄ structure have been successfully synthesized using various molecular precursors and synthetic methods. Recently, hexagonally ordered mesoporous carbon nitrides have been described in Vinu et al. [A. Vinu, K. Ariga, T. Mori, T. Nakanishi, S. Hishita and D. Golberg, Adv . Mater ., 2005, 17, 1648 have been reported to synthesize using an inorganic template. However, the carbon nitrides obtained by Vinu's method have an N / C atomic ratio of approximately 0.2, i.e. a relatively very low nitrogen content, and have been found to be very low graphite despite the highly ordered mesopore arrangement.

To date, there have been no reports claiming the synthesis of highly ordered C ₃ N ₄ nanostructures with uniform pore arrangements with high nitrogen content. Despite the high interest in high surface area carbon nitrides, it has generally been considered difficult to produce nitrogen rich carbon nitrides having highly ordered nanoporous structures.

The present inventors have studied using a colloidal silica as a template, using a molecular precursor such as cyanamide, while studying a method for producing a graphite carbon nitride rich in nitrogen while having a highly ordered macropore. When produced by condensation, it has been found that graphite carbon nitrides rich in nitrogen while having a highly ordered pore arrangement can be obtained, which has also been found to be used as a catalyst support material for fuel cells and has completed the present invention.

Accordingly, the first technical problem of the present invention is to provide a nanoporous graphite carbon nitride structure having a highly ordered macropore and at the same time rich in nitrogen.

In addition, a second technical problem of the present invention is to provide a method for producing a nanoporous graphite carbon nitride structure having a highly ordered macropore and at the same time rich in nitrogen.

In addition, a third technical problem of the present invention is to provide a fuel cell catalyst using a nanoporous graphite carbon nitride structure.

In order to achieve the first technical problem, the present invention is a nitrogen-rich nanoporous graphite having a macro-sized spherical pore is arranged regularly, the macro-sized spherical pore has a three-dimensional interconnected form with a meso-sized connection pore It provides a carbon nitride structure.

The macro-sized spherical pore of the nanoporous graphite carbon nitride structure may be sized according to the intended use, for example, suitable diameter of the silica sphere of the colloidal silica template used in the manufacture of the nanoporous graphite carbon nitride structure Can be chosen. Preferably, the macro-sized spherical pore has a diameter of 40 to 600 nm, the meso-sized pore has a size of 10 to 100 nm, and more preferably the macro-sized spherical pore has a diameter of 200 to 300 nm. The meso-sized pores have a size of 60 to 80 nm.

In addition, the nanoporous graphite carbon nitride structure has a C ₃ N ₄ structural formula, it is preferable that the N / C atomic ratio is 1.34 to 1.38.

In order to achieve the second technical problem of the present invention, the present invention

a) preparing a silica colloidal mold in which macro-sized spherical silica is laminated;

b) injecting molecular precursors for carbon nitride into a colloidal silica template;

c) stabilizing the molecular precursor injected colloidal silica template at 60-80 ° C. for 1 hour to 3 hours;

d) carbonizing the mixture; And

e) providing a method for preparing a nitrogen-rich nanoporous graphite carbon nitride structure comprising the step of removing the silica colloidal template.

In step a) of the production method according to the present invention, the silica colloidal template is described in GS Chai, SB Yoon, JS Yu, JH Choi and YE Sung, J. Phys. Chem . B, 2004, 108, 7074 can be prepared according to the method, for example, sedimentation, centrifugation, filtration, or the like of spherical silica having a macrosize diameter, or It is preferably produced by aligning and laminating using pressing. Depending on the size of the silica sphere, the size of the macropores of the finally obtained nanoporous graphite nitride structure can be obtained small or large.

In step b) of the manufacturing method according to the present invention, a molecular precursor for carbon nitride is injected into the pores of the silica colloidal template formed in step a).

The molecular precursors include cyanamide (CN-NH ₂ ), melamine (2,4,6-triamino-s-triazine), C ₃ N ₃ (NH ₂ ) and s-triazine ring compounds (C ₃ N ₃ X ₃ (X = Cl, F, OH, NHCl, N or NCNH)), ethylenediamine (NH ₂ CH ₂ CH ₂ NH ₂ ) or ammonium chloride (NH ₄ Cl) -carbon tetrachloride (CCl ₄ ) compound, hexa Chlorobenzene (C ₆ Cl ₆ ) -sodium azide (NaN ₃ ) compound, C ₃ N ₃ Cl ₃ -NaN ₃ (or NaNH ₂ ) and melem (2,5,8-triamino-tris-s- Triazine) compounds, which may be injected in liquid form. Most preferred is cyanamide with a low melting point (45 ° C.) capable of carrying out nanocasting at relatively low temperatures.

The method of injecting the molecular precursor into the pores of the silica colloidal template may be used a variety of methods commonly used in the art, for example, by immersing the silica colloidal template in the liquid precursor solution of the molecule into the pores of the mold An impregnation method for filling the precursor solution may be used.

Step c) of the manufacturing method according to the present invention is to stabilize the silica colloidal template injected with the molecular precursor. The stabilization can be carried out by maintaining for 1 hour to 3 hours at a temperature of 60 to 80 ℃, and through this sufficient stabilization step can enrich the nitrogen content in the final product.

Step d) of the manufacturing method according to the present invention is to carbonize the silica colloidal template into which the molecular precursor is injected. Condensation of molecular precursors occurs through high temperature heat treatment, and when the temperature exceeds 600 ° C. or when no inert gas is used, the molecular precursors are completely pixelated without condensation, and thus 3 to 5 hours at 500 to 600 ° C. in the presence of inert gas. It is preferably carried out, in which argon or nitrogen gas may be used as the inert gas, and the temperature increase rate is in the range of 1 ° C / min to 10 ° C / min.

Through the carbonization reaction, replication occurs by reaction / condensation of molecular precursors and graphite carbon nitride is formed. For example, in the case of cyanamide, the C ₃ N ₄ network structure is obtained through the following reaction scheme.

The C ₃ N ₄ network structure obtained through this reaction is also considered to have an increased nitrogen content since it is mostly terminated densely with the outer uncondensed amine group (NH ₂ or = NH group).

In the step (e) of removing the silica mold in the manufacturing method according to the present invention, a method of removing spherical silica without modifying mesopores is used. There is an etching method or a firing method in this manner, for example, the etching method is etched with aqueous HF or NaOH solution.

On the other hand, it is preferable to further include the step of slightly sintering the silica colloidal mold by heating for 1 to 3 hours at 500 to 700 ℃ to provide pore connectivity prior to the step of injecting the molecular precursor into the silica colloidal mold Do.

Finally, through the above method, the macro-sized spherical pores are regularly arranged, and the macro-sized spherical pores are nitrogen-rich nanoporous graphite carbon nitride structures having three-dimensionally interconnected forms with meso-sized connecting pores. Obtained.

Since the nitrogen-rich nanoporous graphite carbon nitride structure according to the present invention has a large surface area and a well-developed three-dimensionally interconnected pores, it can be suitably used as a catalyst support for fuel cells.

In addition, in order to achieve the third technical problem of the present invention, the present invention is a macro-sized spherical pore is arranged regularly, the macro-sized spherical pore is a nitrogen rich rich having a three-dimensional interconnected form as a meso-sized pore Provided is an electrode catalyst for a fuel cell comprising a nanoporous graphite carbon nitride structure as a support.

The electrode catalyst for a fuel cell according to the present invention is a low temperature fuel cell, specifically a fuel cell using a liquid alcohol such as a direct methanol fuel cell (DMFC) or a direct ethanol fuel cell (DEFC) as a direct fuel, as well as a polymer electrolyte membrane fuel cell. Alternatively, the present invention may also be applied to oxidation (fuel electrodes) and reduction (air electrodes) electrodes of hydrogen fuel cells.

The active metal used in the electrode catalyst for fuel cell according to the present invention may be any metal having an activity in the oxidation reaction of the fuel of the fuel cell, for example platinum (Pt), ruthenium (Ru), rhodium (Rh) , At least one metal selected from the group consisting of molybdenum (Mo), osmium (Os), iridium (Ir), rhenium (Re), palladium (Pd), vanadium (V), cobalt (Co) and tungsten (W) do. For example, well-known catalytic metals such as monocomponent systems such as platinum (Pt) or bicomponent systems such as platinum-ruthenium (Pt-Ru) alloys, as well as three-component systems such as Pt-Ru-Rh, Pt-Ru -Co, Pt-Ru-Mo alloys, four-component systems, such as Pt-Ru-Co-W alloys or Pt-Ru-Mo-W alloys, and other multicomponent catalyst metals. These metals may be supported in an amount of at least 10% of the total weight of the catalyst, and at least 90% by weight, preferably 20 to 80% by weight.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example  One

Nanoporosity Graphite  Carbon nitride ( C ₃ N ₄ ) Structure manufacturing

1000 ml of ethanol (absolute), 40 ml of 28wt% ammonia and 40 ml of distilled water were added to a 1L round bottom flask, and the mixture was thoroughly stirred and mixed uniformly. Then, 60 ml of TEOS (tetraethylorthosilicate) was added to the silicon alkoxide in the solution. Stir for about 6-7 hours to allow the ions to sufficiently hydrolyze and grow to uniform size.

After centrifuging the silica ethanol suspension at about 3000 rpm for 20 to 30 minutes to remove the ethanol solution from the colloidal silica, the colloidal silica was washed with distilled water and centrifuged two to three times, and then 70 to 80 ℃ in the oven. Dried to obtain spherical silica having an average diameter of about 250 nm.

Subsequently, 1 g of the spherical silica obtained above was laminated well using a sedimentation method to form a silica colloidal mold.

The dried silica colloidal molds were lightly sintered by heating at 600 ° C. for 2 hours at their contact points to provide pore connectivity.

In order to infiltrate the cyanamide into the pores of the colloidal silica template as the molecular precursor, 0.8 g of the colloidal silica template was added in 0.74 ml of liquid cyanamide at 70 ° C. under vacuum, and the colloidal silica template added in the cyanamide solution was 60 It stayed there for minutes. The silica template was then dried in air and then washed with ethanol solution to remove excess cyanamide. The silica template was then carbonized at 550 ° C. for 4 hours with argon gas flowing at a heating rate of 3 ° C. per minute. The obtained composite was immersed in aqueous HF to remove the silica template, and the obtained residue was filtered, washed several times with distilled water and dried in an oven at 70 ° C. to obtain 0.4 g of nanoporous graphite C ₃ N ₄ structure.

A cross section of the nanoporous graphite C ₃ N ₄ structure obtained in Example 1 was photographed by scanning electron microscopy (SEM) and is shown in FIG. 1, and the XRD pattern of the nanoporous graphite C ₃ N ₄ structure obtained in Example 1 was also obtained. Was analyzed and the results are shown in FIG. 2.

Here, Scanning Electron Microscopy (SEM) used Hitachi S-4700 operating at 10kV excitation voltage, and X-ray diffraction (XRD) pattern showed Cu Ka radiation at 4k / min scan rate at 40kV and 20mA. Were analyzed using Rigaku diffractomer.

Comparative example  One

Ruled macroporous carbon ( OMC Manufacture of Structure

After preparing the spherical silica in the same manner as in Example 1, 1 g of spherical silica having a uniform size of about 250 nm in diameter was laminated well using a sedimentation method to form a silica mold, and then 4 ml of divinylbenzene monomer. The mold was immersed in a solution mixed at a ratio of 0.1845 g of AIBN (initiator), and then injected into the pores with DVB and AIBN, followed by radical polymerization at about 70 ° C. for 12 hours, followed by argon gas in a tube furnace. A carbonaceous reaction was performed at about 1000 ° C. for 8 hours while flowing, followed by removal of the silica template using a hydrogen fluoride solution to synthesize a regularly arranged macroporous carbon structure (OMC).

The XRD pattern of the macroporous carbon (OMC) structure obtained in Comparative Example 1 was analyzed and the results are shown in FIG. 2.

Referring to FIG. 1, in the C ₃ N ₄ structure according to the present invention, macro-sized spherical pores 1 are regularly arranged, and the macro-sized spherical pores are three-dimensionally interconnected with meso-sized pores 2. It can be confirmed that it has a form. That is, the meso-sized connecting pores 2 are shown by the black dots on both sides of the macropores 1 represented by the large circles. Here, the macropores 1 have a diameter of approximately 240 nm, and the meso-sized connecting pores 2 have a size of about 60 nm.

Referring to FIG. 2, strong and sharp peaks were observed at (002), and weak peaks were observed at (100), (101), and (004) of the C ₃ N ₄ structure according to the present invention. On the other hand, the carbon structure according to Comparative Example 1 shows a similar pattern in (002), (100), (101) and (004), but showed a significant difference in the intensity of the (002) peak. (002) The peak is a measure of the degree of graphitization. It is shown that the C ₃ N ₄ structure according to the invention is more graphite than the usual polymeric carbon.

The (002) peak of the C ₃ N ₄ structure is consistent with 0.335 nm d-spacing for graphite and corresponds to 0.328 nm interlayer d-spacing. The broad (002) peak of the OMC structure of Comparative Example 1 shows d-spacing of 0.352 nm.

Test Example  One

Property evaluation

The properties of the C ₃ N ₄ structure obtained in Example 1 were evaluated using the following method.

· Survey (Survey) scan XPS Spectroscopy: using Al Kα x- rays as an excitation source, and x- ray ESCALAB 250 as measured by photo electron spectrometer indicates that the results in Fig.

Fourier- Transform Infrared (FT-IR) spectroscopy : measured with a Perkin-Elmer Fourier Transform infrared spectrometer and the results are shown in FIG. 4.

Elemental analysis : analyzed using EA 1110 elemental analyzer.

EDX analysis : analyzed using Energy Dispersive X-ray Spectrometer.

Nitrogen adsorption and desorption isotherms : measured using a gas adsorption analyzer KICT-SPA 3000S at -196 ° C and the results are shown in FIG.

Specific surface area : determined from nitrogen adsorption in the relative pressure range in the range of 0.05 to 0.15 using the Brunauer-Emmett-Teller (BET) equation.

Figure 3 showing the Survey Scan XPS spectrum shows that the C ₃ N ₄ structure obtained from Example 1 contains carbon, nitrogen and a small amount of oxygen. The C1s spectra were deconvoluted into two peaks, the peak at the main 288.1 eV showing sp ² -bonded carbon (C = N), and the weak peak at 284.7ev is a graphite carbon which is in good agreement with the literature. Indicates. The N1s spectrum shows two types of sp ² hybridized nitrogen, Nα (398.6 eV: bound to two neighboring atoms) and Nβ (400.4eV: bound to three neighboring atoms). The peak region corresponding to Nα is about three times the total region of the peak corresponding to Nβ.

Elemental analysis and EDX analysis of the C ₃ N ₄ structure according to the present invention showed N / C atomic ratios of 1.38 and 1.35, respectively. This was confirmed to have a slightly higher nitrogen content than would be expected with a theoretical value of 1.33 for C ₃ N ₄ . The higher N content of the C ₃ N ₄ structure according to the present invention is mostly terminated densely with uncondensed amine groups (NH ₂ or = NH groups) which increase the nitrogen content in the outer surface structure of the resulting nanoporous network. It seems to be because.

4 showing the FT-IR spectrum confirms the presence of the condensed aromatic CN heterocycle. The overall characteristics of the spectrum were similar to that of other graphite C ₃ N ₄ systems.

The nitrogen adsorption and desorption isotherms of FIG. 5 show Type-II with H1 hysteresis loop, due to adsorption on the macroporous material. Sharp capillary condensation in the relatively high pressure range shows the presence of relatively uniform macropores in the framework. Micropore volumes are rarely observed with very low nitrogen uptake in the low pressure range, which is a typical feature of graphite materials. In addition, the specific surface area and total pore volume of the C ₃ N ₄ structure according to the present invention were measured using the volume of the adsorbed nitrogen gas molecules, and the specific surface area was 108 m 2 / g and the total pore volume was 0.41 cm 3 / g. It turned out. This was similar to the specific surface area 115 m 2 / g of the highly graphite macroporous carbon and the total pore volume 1.12 cm 3 / g.

From the results of XPS, FT-IR and the like, it can be confirmed that the C ₃ N ₄ structure according to the present invention is a new tri-s-triazine ring (C ₆ N ₇ ) crosslinked by a triangular N atom as shown in the following formula. , Nα represents an N atom linked to two neighboring carbon atoms of the s-triazine ring, and Nβ represents a trigonal N atom that makes three-fold assignment to three neighboring atoms. The atomic ratio of Nσ / Nβ is 3, which is confirmed by XPS measurement.

Example  2

Nanoporosity C ₃ N ₄  Structure Supported  Pt- Ru  Preparation of Alloy Catalyst

1.0 g of the nanoporous C ₃ N ₄ construct obtained in Example 1 was added to 100 mL HNO ₃ (10% v / v) solution. The suspension was stirred for 48 hours at room temperature and then filtered to obtain an activated support.

Supported Pt ₅₀ -Ru ₅₀ catalysts were prepared by the surfactant-stabilization method using chloroplatinic acid and ruthenium chloride as catalyst precursor, fluoric L64 (EO ₁₃ PO ₃₀ EO ₁₃ ) as surfactant, and NaBH ₄ as reducing agent. It was.

That is, 0.58 g of equimolar H ₂ PtCl ₂ · 6H ₂ O and RuCl ₃ · xH ₂ O were dissolved in 100 mL of deionized water, and 6.7 mL of L64 was added with stirring at ambient temperature to prepare a metal salt solution.

0.388 g of the activated carbon nitride obtained in Example 1 was suspended in 200 mL of deionized water to obtain a homogeneous solution by stirring.

Next, 200 ml of this solution was mixed with 100 ml of the metal salt solution. The mixture was adjusted to pH 8 by the dropwise addition of NaOH. 50 ml of a NaBH ₄ solution (which is prepared by dissolving an appropriate amount of NaBH ₄ in deionized water) was quickly added to the Pt-Ru / support reaction mixture and stirred well for at least 4 hours for complete reduction of Pt and Ru ions. . Pt-Ru / support catalyst slurry was collected by sedimentation at the bottom of the reaction vessel. The catalyst slurry was then filtered, thoroughly washed with excess ethanol-water (50:50 = v / v) solution, deionized water and dried in a vacuum oven at 70 ° C. to 60% by weight metal loading based on the catalyst total weight. Pt ₅₀ -Ru ₅₀ catalyst was prepared.

In addition, a TEM photograph of the catalyst is shown in FIG. 6. As shown in FIG. 6, the Pt-Ru alloy nanoparticles are homogeneously dispersed in a small spherical uniform size on the surface of C ₃ N ₄ , although small aggregations of metal particles are found in the sample only once. . The particle size measured directly from the TEM photograph in the region randomly selected from the sample was found to be a size range of about 3.0 nm. This was further confirmed by the mean particle size analysis from the (220) X-ray diffraction peak of Pt Fcc lattice by the Scherrer equation.

Here, the TEM was taken with an EM 912 omega at 200 kV, and a high resolution TEM image was used with a transmission electron microscope (JEOL FE-2010) operating at 200 kV.

Comparative example  2

Using the same ordered macroporous carbon (OMC) structure obtained in Comparative Example 1 0.388g as a carbon support, the same method as in Example 2 was repeated to prepare a Pt ₅₀ -Ru ₅₀ catalyst with 60% metal loading.

Comparative example  3

A commercially available 60% metal loading of E-TEK catalyst (manufactured by E-TEK) was used.

Test Example  2

In order to evaluate the electrode catalyst activity of the electrode catalysts of Examples 2, Comparative Examples 2 and 3, a potentiometer workstation (WMPG) using a DMFC (direct methanol fuel cell) unit cell having a 2 cm 2 cross-sectional catalyst area was used. -1000) was used to measure the activity at 30 ° C and 60 ° C and the results are shown in FIGS. 7 to 9.

The membrane electrode assembly (MEA) comprises a pretreated Nafion-115 (DuPont) membrane inserted between an anode (Example 2, Comparative Example 2 or 3) and a cathode (Johnson Matthey Pt Black (5.0 mg / cm 2)). Made by hot-pressing (for 5 minutes at 135 ° C. under 200 psi pressure), the required amount of supported catalyst ink was first applied onto teflonized carbon paper (TGPH-090) and dried in an 70 ° C. oven for 1 hour. I was.

The catalyst ink was made by mixing with 100 mg of catalyst and 0.763 ml of a 5 wt% Nafion solution and stirred before use. The oxidation and reduction electrodes consist of carbon paper and a carbon-supported catalyst layer. Catalyst loading at the oxidation and reduction electrodes is 3.0 (Pt-Ru metal only) and 5.0 mg / cm 2 (Pt catalyst layer unsupported from Johnson Matthey), respectively. The Nafion-115 membrane was pretreated by first boiling in 3% by weight H ₂ O ₂ for 1 hour and then by boiling in 0.5MH ₂ SO ₄ for 1 hour. Unit cell test The unit cell consists of two steel end plates and two graphite plates with a lip-channel pattern allowing the passage of methanol to the anode and the passage of oxygen gas to the cathode. 2.0 M methanol solution is fed to the anode at a flow rate of 1.5 mL / min by Masterflex liquid micropump, while dried O ₂ is fed to the cathode at a rate of 100 cc / min via a flow meter. Another series of experiments was conducted in air-breathing mode on the reduction electrode side instead of O ₂ gas supply mode while maintaining the same conditions as DMFC.

FIG. 7 shows DMFC determined at 30 ° C. and 60 ° C. using 60 wt% Pt-Ru / C ₃ N ₄ and 60 wt% Pt-Ru / E-TEK catalysts as anodes and O ₂ -supplied cathodes. Polarity curve. Current densities measured at ₄₀₀ mV are 130 mA / cm 2 and 55 mA / cm 2 at 30 ° C. for Pt-Ru / C ₃ N ₄ and Pt-Ru / E-TEK catalysts, respectively, and 330 mA / cm 2 and 140 mA / cm 2 at 60 ° C., respectively. This shows that Pt-Ru / C ₃ N ₄ is more than doubled compared to Pt-Ru / E-TEK. Maximum power densities are 77 mW / cm 2 and 42 mW / cm 2 at 30 ° C. for Pt-Ru / C ₃ N ₄ and Pt-Ru / E-TEK catalysts, respectively, 180 mW / cm 2 and 103 mW / cm 2 at 60 ° C., respectively. The Pt-Ru / C ₃ N ₄ catalyst showed about 73-83% better performance than Pt-Ru / E-TEK under the same test conditions.

8 shows DMFC determined at 30 ° C. and 60 ° C. using 60 wt% Pt-Ru / C ₃ N ₄ and 60 wt% Pt-Ru / E-TEK catalysts as anodes and air-breathing mode cathodes. Polarity curve. In the air breathing mode, the maximum power density of Pt-Ru / C ₃ N ₄ was more than twice the maximum power density of Pt-Ru / E-TEK at both 30 ° C and 60 ° C.

FIG. 9 shows 60 wt% Pt-Ru / C ₃ N ₄ , 60 wt% Pt-Ru / OMC, and 60 wt% Pt-Ru / E-TEK catalyst as anode and O ₂ -feed cathode Polar curve of DMFC determined at 60 ° C. The maximum power density of Pt-Ru / OMC is 137mW / cm 2, which is halfway between Pt-Ru / C ₃ N ₄ and Pt-Ru / E-TEK.

All shown performance data was based on reproducibility within a number of measurements and experimental errors. In particular, the Pt-Ru / C ₃ N ₄ catalyst maintained stable and constant catalytic activity for 150 hours in a unit cell. Based on the oxidative activity observed for commercial Pt-Ru / E-TEK, the good performance of Pt-Ru / C ₃ N ₄ is judged to be due to the good supporting effect of porous C ₃ N ₄ structure. This is a significant advance in DMFC and may be related to the unique structural properties of the graphite nanoporous C ₃ N ₄ framework. This is believed to be due in part to the three-dimensional interconnected well-developed porosity, which is an open highway consisting of connected macros and mesopores formed around the active catalyst for easy diffusion of fuel and products towards or away from the catalyst. This is because it provides a network.

The structural and conductivity parameters of the respective supports, C ₃ N ₄ , OMC, Vulcan XC-72 carbon used in the electrode catalysts obtained in Examples 2, Comparative Examples 2 and 3 are summarized in Table 1 below.

Sample S _BET (㎡ / g) S _micro (㎡ / g) S _{meso / macro} (㎡ / g) V _totoal (cc / g) V _micro (cc / g) σ (S / cm) C ₃ N ₄ 108 10 98 0.41 0.01 2.5 VC 230 90 140 0.31 0.06 1.1 OMC 605 410 195 0.80 0.17 1.2

In Table 1 above, VC is Vulcan XC-72 carbon. S _BET : BET surface area, S _micro : _Micropore area, S _{meso / macro} : Meso and macropore area, V _totoal : Total pore volume, V _micro : _Micropore volume, σ is electrical conductivity.

As can be seen from Table 1 above, while ordered macroporous C ₃ N ₄ has a lower surface area than OMC with a similar ordered lattice structure, gC ₃ N ₄ is about 25-35% higher than OMC Shows catalytic activity. This is believed to be because nitrogen atoms, known as electron donors, increase electrical conductivity or reduce resistance in semiconductors or oxide ceramics. Higher performance Pt-Ru / C ₃ N ₄ can contribute to the surface properties of C ₃ N ₄ networks and framework N atoms, such as graphite, since it can promote electron transfer through the conductive layer.

The nitrogen-rich nanoporous carbon nitride structure according to the present invention is a structure in which macro-sized spherical pores are regularly arranged, and they are connected by connecting pores and interconnected three-dimensionally. It is included and used as a support for the electrode catalyst of the fuel cell to improve the activity of the electrode catalyst.

Claims (12)

delete delete delete Preparing a colloidal silica template in which macro-sized spherical silica is laminated; Heating the colloidal silica template at 500 to 700 ° C. for 1 hour to 3 hours; Injecting molecular precursors for carbon nitride into a colloidal silica template; Stabilizing the molecular precursor injected colloidal silica template at 60 to 80 ° C. for 1 to 3 hours; Carbonizing the mixture; And A method for preparing nitrogen-rich nanoporous graphite carbon nitride having a structure of C ₃ N ₄ , comprising removing the silica colloidal template, wherein the N / C atomic ratio is 1.34 to 1.38. The method of claim 4, wherein The silica colloidal mold is prepared by laminating spherical silica having a macro size of 100 to 600 nm using sedimentation, centrifugation, filtration, or compression. Process for preparing nitrogen rich nanoporous graphite carbon nitride. The method of claim 4, wherein Molecular precursors for carbon nitrides include cyanamide (CN-NH ₂ ), melamine (2,4,6-triamino-s-triazine), C ₃ N ₃ (NH ₂ ) and s-triazine ring compounds ( C ₃ N ₃ X ₃ (X = Cl, F, OH, NHCl, N or NCNH)), ethylenediamine (NH ₂ CH ₂ CH ₂ NH ₂ ) or ammonium chloride (NH ₄ Cl) -carbon tetrachloride (CCl ₄ ) compounds , Hexachlorobenzene (C ₆ Cl ₆ ) -sodium azide (NaN ₃ ) compound, C ₃ N ₃ Cl ₃ -NaN ₃ (or NaNH ₂ ), melem (Melem: 2,5,8-triamino-tris- s-triazine) compound is selected from the group consisting of nitrogen-rich nanoporous graphite carbon nitride manufacturing method. The method of claim 4, wherein Wherein the carbonization is carried out at 500 to 600 ° C. for 3 to 5 hours in the presence of an inert gas. The method of claim 4, wherein The method of producing a nitrogen-rich nanoporous carbon nitride that the silica gel template is removed by etching or calcining. delete delete delete delete

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