Platinum carbon catalysts, methods for their preparation and use

Abstract

The application relates to the technical field of electrolytic water, and discloses a platinum-carbon catalyst as well as a preparation method and application thereof. The platinum-carbon catalyst comprises a nitrogen-modified carbon carrier and metal platinum loaded thereon, the nitrogen-modified carbon carrier is nitrogen-modified conductive carbon black, the platinum-carbon catalyst does not have a Pt characteristic peak in an XRD spectrum, or the ratio of the normalized peak intensity of the unit mass platinum of a Pt (111) characteristic peak to the full width at half maximum is not greater than 1.0, and the ratio of the normalized peak intensity of the unit mass platinum of a Pt (200) characteristic peak to the full width at half maximum is not greater than 0.8, and a Pt 4f 7 / 2 characteristic peak in an XPS spectrum is located above 71.8 eV. The platinum-carbon catalyst has lower overpotential and higher mass specific activity.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis technology, specifically to a platinum-carbon catalyst, its preparation method, and its application. Background Technology

[0002] PEM (Potassium Electrolysis) water electrolysis technology, with its high electrolysis efficiency, safety, reliability, compact structure, and rapid response to renewable energy, is widely recognized as one of the most promising hydrogen production technologies. During the rapid development of hydrogen energy, PEM water electrolysis technology has a huge market potential, and the demand for catalysts will also rise rapidly. However, the anode and cathode catalysts used in PEM water electrolysis are both precious metal catalysts, resulting in high catalyst costs. Platinum-carbon catalysts are the cathode catalysts in PEM water electrolysis technology and are one of the core components of this technology. Manufacturing highly active, low-cost PEM water electrolysis cathode catalysts is a hot topic in scientific research.

[0003] Nitrogen can be doped into carbon materials in various structural forms, such as pyridine nitrogen, graphitic nitrogen, pyrrole nitrogen, and nitrogen oxides. Different doping forms result in different properties of the carbon material. To date, there are no literature reports on the effects of different nitrogen forms on the performance of platinum-supported catalysts, and even fewer reports on the effects of pyrrole nitrogen alone on platinum-carbon catalysts.

[0004] The 40% platinum-carbon catalyst is currently the most mature cathode catalyst for PEM water electrolysis. Improving the dispersion and utilization rate of Pt, thereby enhancing catalyst activity, is crucial for reducing catalyst costs and accelerating the commercialization of PEM water electrolysis technology. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of manufacturing highly active and low-cost platinum-carbon catalysts, and to provide a platinum-carbon catalyst, its preparation method and application. This invention uses a simple method to composite nitrogen in the form of pyrrole nitrogen on the surface of conductive carbon black, which has a lower overpotential and higher mass-to-carbon activity compared with catalysts with the same conductive carbon black and platinum loading.

[0006] As described above, the purpose of this invention is to provide a platinum-carbon catalyst, its preparation method, and its application. In this platinum-carbon catalyst, Pt exists in the form of atomic clusters and has high dispersion, thus exhibiting superior performance compared to commercial catalysts in terms of specific activity and overpotential.

[0007] To achieve the above objectives, the present invention provides a platinum-carbon catalyst comprising a nitrogen-modified carbon support and platinum metal supported thereon, wherein the nitrogen-modified carbon support is nitrogen-modified conductive carbon black, and the platinum-carbon catalyst exhibits the following characteristics in its XRD pattern: the absence of a Pt characteristic peak, or the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (FWHM) of the Pt(111) characteristic peak is not greater than 1.0 and the ratio of the normalized peak intensity per unit mass of platinum to FWHM of the Pt(200) characteristic peak is not greater than 0.8, and the Pt 4f 7 / 2 characteristic peak in its XPS pattern is located above 71.8 eV.

[0008] Preferably, based on the total mass of the platinum-carbon catalyst, the platinum content in the platinum-carbon catalyst is 1-20% by mass, preferably 5-15% by mass.

[0009] Preferably, when the platinum content of the platinum-carbon catalyst is less than 6% by mass, the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (WHM) of the characteristic peak of Pt(111) is not greater than 0.5 and the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (WHM) of the characteristic peak of Pt(200) is not greater than 0.4.

[0010] Preferably, the nitrogen element in the nitrogen-modified carbon support exists in the form of pyrrole nitrogen.

[0011] Preferably, the platinum-carbon catalyst exhibits N2 content measured by XPS analysis. 1s Apart from the characteristic peaks between 399 and 400.5 eV, there are no other characteristic peaks between 395 and 405 eV.

[0012] Preferably, the nitrogen-modified carbon support comprises conductive carbon black and nitrogen and oxygen elements incorporated therein.

[0013] Preferably, the conductive carbon black is one or more of EC-300J, EC-600JD, ECP600JD, VXC72, VXC72R, Blackpearls 2000, PRINTEX XE2-B, PRINTEX L6, and HIBLAXK 40B2.

[0014] Preferably, the oxygen content in the conductive carbon black, as determined by XPS analysis, is greater than 4% by mass.

[0015] Preferably, the resistivity of the conductive carbon black is less than 10 Ω·m.

[0016] Preferably, the specific surface area of ​​the conductive carbon black is 200-2000 m². 2 / g.

[0017] A second aspect of this invention provides a method for preparing a platinum-carbon catalyst, the method comprising:

[0018] (1) After contacting conductive carbon black with a nitrogen source in an aqueous solution, the water is removed, and the resulting product is subjected to high-temperature treatment under an inert atmosphere to obtain nitrogen-modified conductive carbon black.

[0019] (2) Remove the solvent from the homogeneous mixture containing nitrogen-modified conductive carbon black, platinum source and solvent to obtain the precursor material;

[0020] (3) In a reducing atmosphere, the precursor material obtained in step (2) is heat-treated to obtain a platinum-carbon catalyst.

[0021] In step (1), the high temperature treatment is 1000-1500℃ and the constant temperature time is 0.5-10h;

[0022] In step (3), the heat treatment temperature is 80-200℃ and the time is 1-4h.

[0023] Preferably, in step (1), the conductive carbon black is one or more of EC-300J, EC-600JD, ECP600JD, VXC72, VXC72R, Black Pearls 2000, PRINTEX XE2-B, PRINTEX L6 and HIBLAXK 40B2.

[0024] More preferably, the oxygen content in the XPS analysis of the conductive carbon black is greater than 4% by mass.

[0025] More preferably, the resistivity of the conductive carbon black is less than 10 Ω·m.

[0026] More preferably, the specific surface area of ​​the conductive carbon black is 200-2000 m². 2 / g.

[0027] Preferably, in step (1), the nitrogen source is ammonia and / or urea.

[0028] Preferably, in step (1), the mass ratio of the conductive carbon black to the nitrogen source (based on the mass of nitrogen element) is 30:1 to 1:2.

[0029] Preferably, in step (2), the platinum source is one or more of chloroplatinic acid, chloroplatinate, tetraammineplatinum acetate, and platinum acetylacetonate.

[0030] Preferably, in step (2), the solvent is one or more of water, alcohol solvents or ketone solvents.

[0031] Preferably, the solvent is water and / or ethanol, more preferably a mixture of water and ethanol.

[0032] Preferably, in step (2), the amount of platinum source used is 0.01-0.25g relative to 1g of nitrogen-modified conductive carbon black, calculated as platinum element.

[0033] Preferably, in step (2), after the homogeneous mixture is allowed to stand, the solvent is removed, and the standing time is more than 10 hours, preferably 15-24 hours.

[0034] Preferably, in step (2), the drying temperature during solvent removal is below 100°C.

[0035] Preferably, in step (3), the heat treatment temperature is 100-180℃ and the time is 2-3h.

[0036] Preferably, in step (3), the reducing atmosphere includes hydrogen, preferably a mixture of hydrogen and an inert gas, more preferably a mixture of hydrogen and nitrogen; preferably, hydrogen accounts for 5-30% of the total gas volume.

[0037] A third aspect of the present invention provides a platinum-carbon catalyst, which is prepared by the preparation method of the present invention described above.

[0038] The fourth aspect of the present invention provides the application of the platinum-carbon catalyst of the present invention in fuel cells or water electrolysis.

[0039] The fifth aspect of the present invention provides a PEM electrolyzer, wherein the cathode of the PEM electrolyzer uses the platinum-carbon catalyst of the present invention described above.

[0040] Compared with the prior art, the present invention has the following beneficial technical effects.

[0041] I. This invention creates a novel carbon support by doping conductive carbon black with nitrogen. Platinum-carbon catalysts made with this carbon support can significantly improve the specific activity of the catalyst and reduce the overpotential.

[0042] II. In a preferred embodiment of the present invention, nitrogen is essentially compounded on the surface of conductive carbon black in the form of pyrrole nitrogen. Using this carbon support to manufacture platinum-carbon catalysts can significantly improve the catalytic performance of platinum-carbon catalysts, for example, ECSA is 1.5-2 times that of unmodified catalysts.

[0043] Third, when the platinum loading is similar, the catalyst performance of the present invention is significantly better than that of commercial catalysts. Even when the platinum loading is much lower than that of commercial catalysts, the overpotential of the catalyst of the present invention is still lower than that of commercial catalysts. Attached Figure Description

[0044] Figure 1 The XRD patterns are of the platinum-carbon catalysts in Examples 2, 4, 5 and Comparative Examples 1-3.

[0045] Figure 2The image shows the XPS spectrum of the platinum-carbon catalyst N1s from Example 2.

[0046] Figure 3 XPS spectra of the characteristic peaks of the platinum-carbon catalyst Pt 4f 7 / 2 in Example 5 and Comparative Examples 2-3.

[0047] Figure 4 The polarization curves are for the platinum-carbon catalysts of Example 2 and Comparative Examples 1 and 3.

[0048] Figure 5 This is a STEM image of the platinum-carbon catalyst in Example 5. Detailed Implementation

[0049] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0050] The first aspect of the present invention provides a platinum-carbon catalyst comprising a nitrogen-modified carbon support and platinum metal supported thereon, wherein the nitrogen-modified carbon support is nitrogen-modified conductive carbon black, and the platinum-carbon catalyst has no Pt characteristic peak in its XRD pattern, or the ratio of the normalized peak intensity per unit mass of platinum of the Pt(111) characteristic peak to the full width at half maximum (FWHM) is not greater than 1.0 and the ratio of the normalized peak intensity per unit mass of platinum of the Pt(200) characteristic peak to the full width at half maximum (FWHM) is not greater than 0.8, and the Pt characteristic peak in its XPS pattern is above 71.9 eV.

[0051] Specifically, the statement that "no Pt characteristic peaks are present in the XRD pattern, or the ratio of the normalized peak intensity per unit mass of Pt(111) characteristic peak to the full width at half maximum (FWHM) is not greater than 1.0 and the ratio of the normalized peak intensity per unit mass of Pt(200) characteristic peak to FWHM is not greater than 0.8" indicates that platinum in the platinum-carbon catalyst of the present invention exists at least mostly in an amorphous phase, but does not exclude the presence of a small amount of crystalline phase. Thus, the presence of a small amount of crystalline phase does not affect the performance of the platinum-carbon catalyst.

[0052] The ratio of the normalized peak intensity to the full width at half maximum (FWHM) per unit mass of platinum represents the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (FWHM) and the platinum mass content in the catalyst, i.e., normalized peak intensity / (full width at half maximum * platinum mass content), hereinafter also referred to as NI / (FWHM * m PtThe calculation method is as follows: (1) Under the working conditions of the powder X-ray diffractometer (tube voltage 40kV, tube current 40mA, Cu target Kα radiation), X-ray diffraction patterns of the catalyst to be tested in the range of 2θ from 20 to 70° are collected. After deducting the background signal and Kα2, the maximum value of the intensity data in the range of 22-28° is 1 and the minimum value of the intensity data in the range of 65-70° is 0. The normalized peak intensities of the Pt(111) characteristic peak and the Pt(200) characteristic peak of the catalyst to be tested are obtained respectively. (2) The X-ray diffraction pattern after normalization is fitted by peak subdivision to obtain the full width at half maximum (in °) of the Pt(111) characteristic peak and the Pt(200) characteristic peak respectively. The above-mentioned Pt(111) characteristic peak and Pt(200) characteristic peak usually refer to the characteristic peaks of 2θ at 39.8±0.2° and 46.2±0.2° respectively. (3) The normalized peak intensities of the Pt(111) characteristic peak and the Pt(200) characteristic peak are divided by the corresponding full width at half maximum (FWHM) and the mass content of the catalyst, respectively, to obtain the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (FWHM) of the Pt(111) characteristic peak and the Pt(200) characteristic peak of the catalyst.

[0053] Aberration-corrected electron microscopy analysis showed that platinum in the platinum-carbon catalyst of the present invention exists mostly in the form of atomic clusters. Specifically, at least 40%, preferably 60-90%, of the metallic platinum particles are irregular lattice fringes.

[0054] According to the present invention, the characteristic peak of Pt 4f 7 / 2 in the XPS spectrum of the platinum-carbon catalyst is located above 71.8 eV. The aforementioned XPS spectrum refers to the XPS spectrum corrected to a C1s peak at 284.3 eV. Typically, for example, when platinum is supported on a carbon support without composite elements, the characteristic peak of Pt 4f 7 / 2 is located around 71.4 eV. This indicates that the characteristic peak of Pt 4f 7 / 2 in the XPS spectrum of the platinum-carbon catalyst of the present invention is shifted to a higher electron volt level by more than 0.4 eV, for example, 0.5-0.9 eV.

[0055] According to the present invention, preferably, the platinum-carbon catalyst in XPS analysis of N 1s Apart from the characteristic peaks between 399 and 400.5 eV, there are no other characteristic peaks between 395 and 405 eV.

[0056] In the platinum-carbon catalyst of the present invention, preferably, based on the total mass of the platinum-carbon catalyst, the platinum content in the platinum-carbon catalyst is 1-20% by mass, more preferably 1-15% by mass, more preferably 4-15% by mass, and even more preferably 5-10% by mass. Furthermore, it is preferable that the platinum-carbon catalyst of the present invention does not contain any other metal elements besides platinum.

[0057] Preferably, when the platinum content of the platinum-carbon catalyst is less than 6% by mass, the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (WHM) of the characteristic peak of Pt(111) is not greater than 0.5 and the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (WHM) of the characteristic peak of Pt(200) is not greater than 0.4.

[0058] According to the present invention, the resistivity of the platinum-carbon catalyst is less than 10.0 Ω·m, preferably less than 2 Ω·m.

[0059] In the platinum-carbon catalyst of the present invention, the nitrogen element in the nitrogen-modified carbon support exists in the form of pyrrole nitrogen. Specifically, the XPS analysis of the platinum-carbon catalyst of the present invention shows only characteristic peaks of pyrrole nitrogen, and does not exhibit characteristic peaks of other types of nitrogen.

[0060] Preferably, based on the total mass of the nitrogen-modified carbon support, the nitrogen content in the nitrogen-modified carbon support is 0.1-10% by mass, preferably 0.2-5% by mass.

[0061] According to the present invention, preferably, the nitrogen-modified carbon support comprises conductive carbon black and nitrogen and oxygen elements compounded therein. Preferably, the nitrogen-modified carbon support of the present invention does not contain any composite elements other than nitrogen. Here, "composite elements" in the present invention refers to nitrogen, phosphorus, boron, sulfur, fluorine, chlorine, bromine, and iodine. More preferably, the nitrogen-modified carbon support is composed of conductive carbon black and nitrogen and oxygen elements compounded therein.

[0062] The conductive carbon black that can be used in this invention may be one or more of ordinary conductive blacks, super conductive blacks, or extra conductive blacks, such as Ketjen black, Cabot conductive black (Cabot, Black Pearls, etc.), Orion conductive black (HIBLACK, PRINTEX, etc.), etc. Specifically, it may be one or more of EC-300J, EC-600JD, ECP600JD, VXC72, VXC72R, Black Pearls 2000, PRINTEX XE2-B, PRINTEX L6, and HIBLAXK 40B2.

[0063] This invention does not restrict the method of preparation or source of conductive carbon black. The conductive carbon black may be acetylene black, furnace black, etc.

[0064] Preferably, in the XPS analysis of the conductive carbon black, the oxygen content is greater than 4% by mass, for example, 5-12% by mass.

[0065] Preferably, the resistivity of the conductive carbon black is less than 10 Ω·m, more preferably less than 5 Ω·m, more preferably less than 3 Ω·m, and even more preferably 0.01-1 Ω·m.

[0066] Preferably, the specific surface area of ​​the conductive carbon black is 200-2000 m². 2 / g, preferably 220-1500m 2 / g.

[0067] A second aspect of this invention provides a method for preparing a platinum-carbon catalyst, the method comprising:

[0068] (1) After contacting conductive carbon black with a nitrogen source in an aqueous solution, the water is removed, and the resulting product is subjected to high-temperature treatment under an inert atmosphere to obtain nitrogen-modified conductive carbon black.

[0069] (2) Remove the solvent from the homogeneous mixture containing nitrogen-modified conductive carbon black, platinum source and solvent to obtain the precursor material;

[0070] (3) In a reducing atmosphere, the precursor material obtained in step (2) is heat-treated to obtain a platinum-carbon catalyst.

[0071] In step (1), the high temperature treatment is 1000-1500℃ and the constant temperature time is 0.5-10h;

[0072] In step (3), the heat treatment temperature is 80-200℃ and the time is 1-4h.

[0073] The preparation method of the second aspect of the present invention can be used to prepare the platinum-carbon catalyst of the first aspect. In step (1), the conductive carbon black is the same as described above, and will not be repeated here.

[0074] According to the present invention, in step (1), the nitrogen source may be ammonia and / or urea.

[0075] According to the present invention, in step (1), the mass ratio of the conductive carbon black to the nitrogen source (based on the mass of nitrogen element) is preferably 30:1 to 1:2, more preferably 25:1 to 1:1.5, and even more preferably 20:1 to 3:1.

[0076] According to the present invention, in step (1), the temperature of the high-temperature treatment is 1000-1500℃, preferably 1150-1450℃; the holding time is 0.5-10h, preferably 1-5h, more preferably 1.5-4h. In addition, the heating rate of the high-temperature treatment can be 8-15℃ / min, for example 10℃ / min.

[0077] The inert atmosphere can be at least one of nitrogen, argon, neon, and helium. The high-temperature treatment can be performed in any apparatus that provides the aforementioned high-temperature treatment conditions, such as a tube furnace.

[0078] According to the present invention, the nitrogen-modified conductive carbon black obtained in step (1) can be easily dispersed in an aqueous phase. However, for some conductive carbon blacks, such as Ketjen black, it is difficult to disperse directly in an aqueous phase, and usually ethanol or other easily dispersed substances are added to help with dispersion.

[0079] According to the present invention, in step (2), the platinum source can be one or more of chloroplatinic acid, chloroplatinate, tetraammineplatinum acetate, and platinum acetylacetonate. Chloroplatinate can be potassium chloroplatinate or sodium chloroplatinate, etc.

[0080] Preferably, relative to 1g of nitrogen-modified conductive carbon black, the amount of platinum source used is 0.01-0.25g, more preferably 0.04-0.18g, calculated as platinum element.

[0081] According to the present invention, in step (2), the precursor material is obtained by dissolving nitrogen-modified conductive carbon black and a platinum source in a solvent to form a uniform mixture, and then removing the solvent from the uniform mixture. There is no particular limitation on the type of solvent. The solvent can be one or more of water, alcohol solvents, or ketone solvents; the alcohol solvent can be, for example, ethanol, and the ketone solvent can be, for example, acetone. More preferably, the solvent is water, ethanol, or a uniform mixture of ethanol and water (the volume ratio of ethanol to water can be, for example, 0.1-10:1, preferably 1-5:1). The present invention also does not particularly limit the amount of solvent used; for example, it can be 3-20 mL relative to 1 g of nitrogen-modified conductive carbon black.

[0082] This invention involves mixing nitrogen-modified conductive carbon black, a platinum source, and a solvent to obtain the aforementioned homogeneous mixture, preferably with stirring. The invention does not impose particular limitations on the stirring rate and time, as long as the homogeneous mixture is formed. Furthermore, to further accelerate the dissolution process by heating, the homogeneous mixture can also be formed.

[0083] As a method for removing the solvent from the homogeneous mixture, evaporation can be used to remove the solvent from the homogeneous mixture. The evaporation temperature and process can adopt existing techniques known to those skilled in the art. According to the present invention, in step (2), the drying temperature for removing the solvent is below 100°C. For example, the solvent can be removed by drying in an oven at 60-95°C for 12-24 hours.

[0084] According to a preferred embodiment of the present invention, in step (2), after the homogeneous mixture is allowed to stand, the solvent is removed. The standing time is more than 10 hours, preferably 12-72 hours, and more preferably 15-24 hours.

[0085] According to the present invention, in step (3), the heat treatment is carried out in a reducing atmosphere. The reducing atmosphere preferably includes hydrogen, more preferably a mixture of hydrogen and an inert gas, wherein the inert atmosphere can be nitrogen and / or argon, specifically a mixture of hydrogen and nitrogen. Preferably, hydrogen accounts for 5-30% by volume of the total gas volume. The heat treatment can be carried out in any apparatus that provides the above-described heat treatment conditions, for example, in a tube furnace.

[0086] According to the present invention, in step (3), the temperature of the heat treatment can be 80-200℃, preferably 100-180℃, and the time of the heat treatment is 1-4h, preferably 2-3h. Furthermore, the heating rate of the heat treatment can be 4-15℃ / min, generally 5-10℃ / min.

[0087] A third aspect of the present invention provides a platinum-carbon catalyst, which is prepared by the method described in the second aspect of the present invention.

[0088] The fourth aspect of the present invention provides the application of the platinum-carbon catalyst of the present invention in fuel cells or water electrolysis.

[0089] The platinum-carbon catalyst of the present invention is suitable as an anode catalyst in fuel cells, and is not particularly limited to fuel cells. For example, it can be used in hydrogen fuel cells (e.g., proton exchange membrane hydrogen fuel cells), direct alcohol fuel cells (e.g., direct alcohol fuel cells with methanol or ethanol as anode fuel), etc.

[0090] The fifth aspect of the present invention provides a PEM electrolyzer, wherein the cathode of the PEM electrolyzer uses the platinum-carbon catalyst of the present invention described above.

[0091] In this invention, except for "conductive carbon black containing composite elements" which can be determined based on context or its own limitations, all other references to "conductive carbon black" refer to conductive carbon black that does not contain composite elements; the same applies to the subordinate concepts of conductive carbon black.

[0092] In this invention, "carbon black" and "carbon black" are interchangeable technical terms.

[0093] In this invention, "inert gas" refers to a gas that does not cause any perceptible impact on the performance of nitrogen-modified conductive carbon black in the preparation method of this invention.

[0094] In this invention, except where the meaning can be determined by the context or by its own limitations, all other references to "pore volume" refer to the total pore volume of single-point adsorption when P / P0 is at its maximum.

[0095] The present invention will be described in detail below through embodiments. The instruments and testing methods used in the embodiments and comparative examples of the present invention are as follows:

[0096] Instruments, methods and conditions for XRD analysis: X-ray diffraction (XRD) analysis was performed on a Shimadzu XRD-6000 X-ray diffractometer from Japan. The test conditions included: tube voltage 40 kV, tube current 40 mA, Cu target Kα radiation, and 2θ scan range of 10° to 70°.

[0097] NI / (FWHM*m Pt The calculation method is as follows: (1) Under the working conditions of the powder X-ray diffractometer (tube voltage 40kV, tube current 40mA, Cu target Kα radiation), X-ray diffraction patterns of the catalyst to be tested in the range of 20-70° were collected. After deducting the background signal and Kα2, the maximum value of the intensity data in the range of 22-28° was 1 and the minimum value of the intensity data in the range of 65-70° was 0. The normalized peak intensities of the Pt(111) characteristic peak at 39.8±0.2° and the Pt(200) characteristic peak at 46.2±0.2° were obtained respectively. (2) The X-ray diffraction patterns after normalization were fitted to obtain the full width at half maximum (in °) of the Pt(111) characteristic peak and the Pt(200) characteristic peak respectively. (3) The normalized peak intensities of the Pt(111) and Pt(200) characteristic peaks were divided by the corresponding full width at half maximum (FWHM) and the platinum mass content of the catalyst, respectively, to obtain the NI / (FWHM*m) ratios of the Pt(111) and Pt(200) characteristic peaks of the catalyst. Pt ).

[0098] The X-ray photoelectron spectroscopy (XPS) analyzer was a VG Scientific ESCALab220i-XL model equipped with Avantage V5.926 software. The XPS analysis conditions were as follows: excitation source was monochromatic AlKα X-rays, power was 330 W, and the baseline vacuum was 3 × 10⁻⁶. -9 mbar. In addition, the electron binding energy was corrected using the C1s peak (284.3 eV) of elemental carbon, and the subsequent peaking software was XPSPEAK.

[0099] The aberration-corrected transmission electron microscope (AC-STEM) is a JEOL ARM200F model.

[0100] Electrochemical performance was tested using Solartron Analytical EnergyLab and Princeton Applied Research (Model 636A). The methods and test conditions were as follows: the catalyst polarization curve (LSV) was measured at 2500 rpm in N2-saturated 0.5 M H2SO4, and the electrochemical active area (ECSA) was measured in N2-saturated 0.5 M H2SO4. For all tests, the catalyst was prepared as a uniformly dispersed slurry and coated onto a 5 mm diameter glassy carbon electrode. The platinum content of the catalyst on the electrode was controlled within the range of 1-4 μg. No iR correction was performed in the calculations.

[0101] Resistivity testing using a four-probe resistivity tester, instrument model KDY-1, method and test conditions: applied pressure 3.9±0.03MPa, current 500±0.1mA.

[0102] Instruments, methods, and conditions for testing the platinum mass fraction in platinum-carbon catalysts: Take 30 mg of the prepared Pt / C catalyst, add 30 mL of aqua regia, reflux at 120 °C for 12 h, cool to room temperature, take the supernatant, dilute it, and test the Pt content using ICP-AES.

[0103] The Vulcan VXC72 (manufactured by Cabot Corporation, USA) was tested using the aforementioned instrumental methods, and the results showed a specific surface area of ​​258 m². 2 / g, pore volume 0.388mL / g, I D / I G It is 1.02.

[0104] Ketjenblack ECP600JD (manufactured by Lion Corporation of Japan) was tested using the aforementioned instrumental methods, and the results showed a specific surface area of ​​1362 m². 2 / g, pore volume 2.29mL / g, I D / I G It is 1.25.

[0105] The commercial platinum-carbon catalyst (HISPEC 4000, manufactured by Johnson Matthey) was tested using the aforementioned instrumental method, and the results showed that the mass fraction of platinum was 40.2%.

[0106] Preparation Example 1

[0107] This preparation example illustrates the preparation of the nitrogen-modified carbon support of the present invention.

[0108] 1 g of Vulcan XC72 was soaked in 15 mL of 0.7 wt% urea aqueous solution for 24 h; dried in an oven at 100 °C; then placed in a tube furnace and heated to 1200 °C at a rate of 10 °C / min, and kept at that temperature for 3 h; after natural cooling, nitrogen-modified carbon support was obtained, designated as carbon support A.

[0109] Preparation Example 2

[0110] This preparation example illustrates the preparation of the nitrogen-modified carbon support of the present invention.

[0111] Add 10 mL of anhydrous ethanol to 1 g of Ketjenblack ECP600JD, then add 20 mL of 1 wt% urea aqueous solution and soak for 24 h; dry in an oven at 100 °C; then place in a tube furnace and heat the tube furnace to 1300 °C at a rate of 10 °C / min, and keep at that temperature for 3 h; after natural cooling, obtain nitrogen-modified carbon support, designated as carbon support B.

[0112] Example 1

[0113] This embodiment illustrates the preparation of the platinum-carbon catalyst of the present invention.

[0114] With a ratio of 0.27 mmol chloroplatinic acid per gram of carbon support, chloroplatinic acid was first dissolved in 5 ml of water. 1 g of carbon support A was then dispersed in the chloroplatinic acid solution until uniformly dispersed. After standing for 16 h, the solution was dried in an oven at 60 °C to obtain the catalyst precursor. The precursor was then ground and placed in a tube furnace, heated to 160 °C, and reduced for 2 h under an atmosphere of N2:H2 = 4:1. The temperature was then lowered under the N2 atmosphere to obtain a platinum-carbon catalyst with a loading of 5% by mass.

[0115] Example 2

[0116] This embodiment illustrates the preparation of the platinum-carbon catalyst of the present invention.

[0117] The platinum-carbon catalyst was prepared according to the method of Example 1, except that 0.57 mmol of chloroplatinic acid was added per gram of carbon support, and the heat treatment temperature was 140°C, to obtain a platinum-carbon catalyst with a loading of 10% by mass.

[0118] Example 3

[0119] This embodiment illustrates the preparation of the platinum-carbon catalyst of the present invention.

[0120] The platinum-carbon catalyst was prepared according to the method of Example 1, except that 1.28 mmol of chloroplatinic acid was added per gram of carbon support, and the heat treatment temperature was 100°C, to obtain a platinum-carbon catalyst with a loading of 20% by mass.

[0121] Example 4

[0122] This embodiment illustrates the preparation of the platinum-carbon catalyst of the present invention.

[0123] The platinum-carbon catalyst was prepared according to the method of Example 1, except that the carbon support B prepared in Preparation Example 2 was used, 0.27 mmol of chloroplatinic acid was added per gram of carbon support, and the heat treatment temperature was 140°C to obtain a platinum-carbon catalyst with a loading of 5% by mass.

[0124] Example 5

[0125] This embodiment illustrates the preparation of the platinum-carbon catalyst of the present invention.

[0126] The platinum-carbon catalyst was prepared according to the method of Example 2, except that the carbon support B prepared in Example 2 was used, 0.57 mmol of chloroplatinic acid was added per gram of carbon support, and the heat treatment temperature was 120°C to obtain a platinum-carbon catalyst with a loading of 10% by mass.

[0127] Example 6

[0128] This embodiment illustrates the preparation of the platinum-carbon catalyst of the present invention.

[0129] The platinum-carbon catalyst was prepared according to the method of Example 2, except that the heat treatment temperature was 180°C, and a platinum-carbon catalyst with a loading of 10% by mass was obtained.

[0130] Example 7

[0131] This embodiment illustrates the preparation of the platinum-carbon catalyst of the present invention.

[0132] The platinum-carbon catalyst was prepared according to the method of Example 2, except that the heat treatment temperature was 100°C, and a platinum-carbon catalyst with a loading of 10% by mass was obtained.

[0133] Comparative Example 1

[0134] The platinum-carbon catalyst was prepared according to the method of Example 2, except that the support was Vulcan XC72, resulting in a platinum-carbon catalyst with a loading of 10% by mass.

[0135] Comparative Example 2

[0136] The platinum-carbon catalyst was prepared according to the method of Example 2, except that the support was KetjenblackECP600JD, and a platinum-carbon catalyst with a loading of 10% by mass was obtained.

[0137] Comparative Example 3

[0138] The platinum-carbon catalyst was a commercially available catalyst, brand name HISPEC4000 (platinum mass fraction 40.2%).

[0139] Test Example 1

[0140] The XRD patterns of the platinum-carbon catalysts in Examples 2, 4-5 and Comparative Examples 1-3 were determined, as follows: Figure 1 As shown. From Figure 1 The characteristic peaks of Pt(111) and Pt(200) were calculated from the XRD spectra. NI / (FWHM*m) Pt The results are shown in Table 1.

[0141] Table 1

[0142]

[0143] As shown in Table 1, the NI / (FWHM*m) characteristic peak of the platinum-carbon catalyst of the present invention is 111. Pt ) NI / (FWHM*m not greater than 1.0 and with characteristic peak of Pt(200) Pt The value of NI / (FWHM*m) for the characteristic peak of Pt(111) is not greater than 0.8. Furthermore, when the platinum content in the platinum-carbon catalyst is less than 6% by mass, the value of NI / (FWHM*m) for the characteristic peak of Pt(111) is not greater than 0.8. Pt ) NI / (FWHM*m not greater than 0.5 and with the characteristic peak of Pt(200) Pt (Not greater than 0.4)

[0144] The XRD spectra of Examples 1, 3, and 6-7 were measured using the same method described above, and the results were similar to those of Example 2. The NI / (FWHM*m) of the Pt(111) and Pt(200) characteristic peaks was calculated. Pt All of them satisfy the above relationship.

[0145] Test Example 2

[0146] Determination of N in the platinum-carbon catalyst of Example 2 1s XPS spectra, such as Figure 2 As shown. From Figure 2 It can be seen that nitrogen in the platinum-carbon catalyst of the present invention exists only in the form of pyrrole nitrogen.

[0147] N was measured in Examples 1 and 3-7 using the same method described above. 1s The XPS spectra of all samples showed similar patterns, indicating that nitrogen existed only in the form of pyrrole nitrogen.

[0148] Test Example 3

[0149] The XPS spectra of Example 5 and Comparative Examples 2-3 were measured, as follows: Figure 3 As shown. From Figure 3 It can be seen that the characteristic peak of Pt 4f 7 / 2 in Example 5 is located at 71.9 eV, which is about 0.5 eV shifted to the high electron volt direction relative to Comparative Example 2 and about 0.9 eV shifted to the high electron volt direction relative to Comparative Example 3.

[0150] The XPS spectra of Examples 1-4 and 6-7 were measured using the same method described above, and the characteristic peak of Pt 4f 7 / 2 was above 71.8 eV.

[0151] Test Example 4

[0152] The performance of the platinum-carbon catalysts prepared in the above examples and comparative examples was measured, and the results are shown in Table 2. Figure 4 The polarization curves of the platinum-carbon catalysts of Example 2 and Comparative Examples 1 and 3 are shown.

[0153] Table 2

[0154]

[0155] As can be seen from the results in Table 2, Examples 1-7 using the platinum-carbon catalyst of the present invention have lower overpotential and higher mass-to-carbon activity than the commercial catalyst of Comparative Example 3.

[0156] By comparing Example 2 with Comparative Examples 1-2, it can be seen that the platinum-carbon catalyst of the present invention can significantly reduce the overpotential and improve the mass-specific activity by using the nitrogen-modified carbon support of the present invention.

[0157] A comparison of Examples 2 and 6-7 shows that a heat treatment temperature of 100-140℃ can further reduce the overpotential while improving the specific activity.

[0158] Test Example 5

[0159] The platinum-carbon catalyst of Example 5 was observed using STEM to obtain... Figure 4 STEM photos. Through analysis of... Figure 4 Statistical analysis of the STEM images revealed that approximately 90% of the platinum particles in the platinum-carbon catalyst exhibited irregular lattice striations.

[0160] The platinum-carbon catalysts of Examples 1-4 and 6-7 were observed using the same method, and all met the requirement of at least 60% of the platinum particles having irregular lattice fringes.

[0161] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A platinum-carbon catalyst, characterized in that, This platinum-carbon catalyst comprises a nitrogen-modified carbon support and metallic platinum supported thereon. The nitrogen-modified carbon support is nitrogen-modified conductive carbon black, in which nitrogen exists only in the form of pyrrole nitrogen. In the XRD pattern of the platinum-carbon catalyst, the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (FWHM) of the Pt(111) characteristic peak is not greater than 1.0, and the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (FWHM) of the Pt(200) characteristic peak is not greater than 0.

8. In the XPS pattern, the characteristic peak of Pt 4f 7 / 2 is located above 71.8 eV.

2. The platinum-carbon catalyst according to claim 1, wherein, Based on the total mass of the platinum-carbon catalyst, the platinum content in the platinum-carbon catalyst is 1-20% by mass.

3. The platinum-carbon catalyst according to claim 1, wherein, Based on the total mass of the platinum-carbon catalyst, the platinum content in the platinum-carbon catalyst is 5-15% by mass.

4. The platinum-carbon catalyst according to claim 1, wherein, When the platinum content of the platinum-carbon catalyst is less than 6% by mass, the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (WHM) of the characteristic peak of Pt(111) is not greater than 0.5, and the ratio of the normalized peak intensity per unit mass of platinum to the full width at half maximum (WHM) of the characteristic peak of Pt(200) is not greater than 0.

4.

5. The platinum-carbon catalyst according to any one of claims 1-4, wherein, The platinum-carbon catalyst, as analyzed by XPS, showed N... 1s Apart from the characteristic peaks between 399 and 400.5 eV, there are no other characteristic peaks between 395 and 405 eV.

6. The platinum-carbon catalyst according to claim 1, wherein, The nitrogen-modified carbon support includes conductive carbon black and nitrogen and oxygen elements incorporated therein.

7. The platinum-carbon catalyst according to any one of claims 1-4 and 6, wherein, The conductive carbon black is one or more of EC-300J, EC-600JD, ECP600JD, VXC72, VXC72R, Black Pearls 2000, PRINTEX XE2-B, PRINTEX L6, and HIBLAXK 40B2.

8. The platinum-carbon catalyst according to any one of claims 1-4 and 6, wherein, The oxygen content in the conductive carbon black, as determined by XPS analysis, is greater than 4% by mass.

9. The platinum-carbon catalyst according to any one of claims 1-4 and 6, wherein, The resistivity of the conductive carbon black is less than 10 Ω·m.

10. The platinum-carbon catalyst according to any one of claims 1-4 and 6, wherein, The specific surface area of ​​the conductive carbon black is 200-2000 m². 2 / g.

11. A method for preparing the platinum-carbon catalyst according to any one of claims 1-10, characterized in that, It consists of the following steps: (1) After contacting conductive carbon black with a nitrogen source in an aqueous solution, the water is removed, and the resulting product is subjected to high-temperature treatment under an inert atmosphere to obtain nitrogen-modified conductive carbon black, wherein the nitrogen source is ammonia and / or urea. (2) Remove the solvent from the homogeneous mixture containing nitrogen-modified conductive carbon black, platinum source and solvent to obtain the precursor material; (3) In a reducing atmosphere, the precursor material obtained in step (2) is heat-treated to obtain a platinum-carbon catalyst; In step (1), the high temperature treatment is 1000-1500℃ and the constant temperature time is 0.5-10h; In step (3), the heat treatment temperature is 80-200℃ and the time is 1-4h.

12. The preparation method according to claim 11, wherein, In step (1), the conductive carbon black is one or more of EC-300J, EC-600JD, ECP600JD, VXC72, VXC72R, Black Pearls 2000, PRINTEX XE2-B, PRINTEX L6 and HIBLAXK 40B2.

13. The preparation method according to claim 11 or 12, wherein, The oxygen content in the conductive carbon black, as determined by XPS analysis, is greater than 4% by mass.

14. The preparation method according to claim 11 or 12, wherein, The resistivity of the conductive carbon black is less than 10 Ω·m.

15. The preparation method according to claim 11 or 12, wherein, The specific surface area of ​​the conductive carbon black is 200-2000 m². 2 / g.

16. The preparation method according to claim 11 or 12, wherein, In step (1), the mass ratio of the conductive carbon black to the nitrogen source (based on the mass of nitrogen element) is 30:1 to 1:

2.

17. The preparation method according to any one of claim 11 or 12, wherein, In step (1), the mass ratio of the conductive carbon black to the nitrogen source (based on the mass of nitrogen element) is 25:1 to 1:1.

5.

18. The preparation method according to claim 11, wherein, In step (2), the platinum source is one or more of chloroplatinic acid, chloroplatinate, tetraammineplatinum acetate, and platinum acetylacetonate.

19. The preparation method according to claim 11 or 18, wherein, In step (2), the solvent is one or more of water, alcohol solvents or ketone solvents.

20. The preparation method according to claim 11 or 18, wherein, In step (2), the solvent is water and / or ethanol.

21. The preparation method according to claim 11 or 18, wherein, In step (2), the solvent is a mixture of water and ethanol.

22. The preparation method according to claim 11 or 18, wherein, In step (2), the amount of platinum source used is 0.01-0.25g relative to 1g of nitrogen-modified conductive carbon black, calculated as platinum element.

23. The preparation method according to claim 11 or 18, wherein, In step (2), the uniform mixture is allowed to stand for more than 10 hours before the solvent is removed.

24. The preparation method according to claim 23, wherein, In step (2), the settling time is 15-24 hours.

25. The preparation method according to claim 23, wherein, In step (2), the drying temperature during solvent removal is below 100°C.

26. The preparation method according to claim 11, wherein, In step (3), the heat treatment temperature is 100-180℃ and the time is 2-3h.

27. The preparation method according to claim 11 or 26, wherein, In step (3), the reducing atmosphere includes hydrogen.

28. The preparation method according to claim 11 or 26, wherein, In step (3), the reducing atmosphere is a mixture of hydrogen and inert gas.

29. The preparation method according to claim 11 or 26, wherein, In step (3), the reducing atmosphere is a mixture of hydrogen and nitrogen.

30. The preparation method according to claim 29, wherein, In step (3), hydrogen accounts for 5-30% of the total gas volume.

31. A platinum-carbon catalyst, characterized in that, The catalyst is prepared by the preparation method described in any one of claims 11-30.

32. The use of the platinum-carbon catalyst according to any one of claims 1-10 and 31 in fuel cells or water electrolysis.

33. A PEM electrolytic cell, characterized in that, The cathode of the PEM electrolyzer uses a platinum-carbon catalyst according to any one of claims 1-10 and 31.

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