A porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst and its preparation method

Abstract

The present invention discloses a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst and a preparation method thereof. The preparation method comprises mixing an organic sol with a titanium dioxide sol and drying them to obtain a precursor; calcining the precursor in an ammonia atmosphere to obtain titanium nitride-doped porous carbon; stirring and mixing the titanium nitride-doped porous carbon, a solvent, and a platinum precursor, removing the solvent to obtain an intermediate; and calcining the intermediate under a protective gas atmosphere to obtain a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst. The catalyst prepared by the present invention has a highly open porous structure and a high specific surface area, which reduces the mass transfer resistance of oxygen, facilitates oxygen diffusion in the electrocatalytic reaction, and has very high catalytic activity. In addition, the redox properties of the prepared catalyst remain essentially unchanged after 300,000 cycles of accelerated aging.

Description

Technical Field

[0001] The present invention relates to the technical field, and in particular to a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst and a preparation method thereof. Background Art

[0002] Hydrogen fuel cells, methanol fuel cells, and metal-air fuel cells are new energy conversion and storage devices with the potential to alleviate the energy crisis. The oxygen reduction reaction (ORR) is a battery half-reaction in these energy storage and conversion devices, such as hydrogen fuel cells, methanol fuel cells, and metal-air batteries. Occurring at the battery's cathode, the oxygen molecule acquires electrons, combines with protons or hydroxide ions, and is reduced to water. While the ORR proceeds spontaneously, its rate, determined by chemical kinetics, is very slow, necessitating the use of catalysts to accelerate the reaction.

[0003] Carbon-supported platinum catalyst materials, including carbon-supported platinum nanoparticles and carbon-supported platinum alloy nanoparticles, are mature commercial materials that efficiently and rapidly catalyze the oxygen reduction reaction (ORR). They have been used in proton exchange membrane fuel cells, alcohol fuel cells, and metal-air batteries. However, the actual operating environment of these batteries is very harsh, typically containing oxygen and water, temperature and electric fields, and acidic or alkaline electrolytes. Platinum or alloy nanoparticles supported on carbon have high surface energy. During operation, various factors can cause deactivation through migration, agglomeration, sintering, growth, and dissolution, leading to a decrease in catalyst activity. Furthermore, the ORR is accompanied by a side reaction called the Fenton reaction, which produces highly oxidizing intermediates. These can oxidize the Pt particles and the carbon support, further deactivating the catalyst. Developing highly stable carbon-supported Pt catalyst materials by simultaneously suppressing the deactivation of the Pt particles and the oxidation of the Pt in the catalyst and the carbon support is a key challenge in the fuel cell field.

[0004] At present, there are three main types of deactivation of carbon-supported platinum catalysts: (1) migration and growth of platinum particles, (2) dissolution and re-deposition of platinum particles, and (3) shedding of platinum particles caused by corrosion of carbon supports. All of the above three situations will cause a decrease in the activity of platinum catalysts. There are currently two main strategies to alleviate platinum deactivation. One is to enhance the interaction between platinum particles and supports to prevent the dissolution of platinum particles, and the other is to use non-carbon materials such as transition metal nitrides, transition metal carbides and oxides and other corrosion-resistant materials. However, the actual situation is that the specific surface area and conductivity of these transition metal nitrides, carbides and oxides cannot be compared with carbon supports. Carbon-based and metal oxide-based coatings still have the disadvantages of not being resistant to oxidation and not resistant to electrochemical corrosion under acidic, aerobic, high humidity and high voltage conditions, while polymer-based coatings have low conductivity, which will reduce catalyst activity.

[0005] Therefore, simultaneously solving the problems of platinum particle deactivation and catalyst intolerance to oxidative corrosion remains a difficult problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention loads a highly corrosion-resistant titanium nitride material on a carbon carrier, and then loads platinum particles. At the same time, titanium nitride can not only enhance the carrier metal interaction between it and the platinum particles to prevent the migration and agglomeration of platinum particles, but also inhibit the dissolution and redeposition of platinum particles. In addition, titanium nitride can also enhance the durability of the carbon carrier.

[0007] In order to achieve the above object, the present invention provides a method for preparing a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst.

[0008] The organic sol and the titanium dioxide sol are mixed and dried to obtain a precursor;

[0009] The precursor is placed in an ammonia atmosphere and calcined to obtain titanium nitride-doped porous carbon;

[0010] Titanium nitride-doped porous carbon, a solvent and a platinum precursor are stirred and mixed, and then the solvent is removed to obtain an intermediate. The intermediate is calcined under a protective gas atmosphere to obtain a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst.

[0011] Furthermore, the organic sol is obtained by reacting an organic substance that is soluble in water and capable of forming a sol in water or an organic substance that can react in an aqueous environment to form a sol in water; wherein the organic substance that forms the sol is a polyhydroxybenzene compound or melamine and an aldehyde compound;

[0012] The titanium dioxide sol is obtained by dispersing titanium-containing substances in water or alcohol.

[0013] In the present invention, the type of organic matter capable of solubilizing in water is not strictly limited. For example, it can be at least one of polyethylene glycol, methyl cellulose, ethyl cellulose, chitosan, gelatin, polyaniline, and polyimide. The polyhydroxybenzene compound includes any one of resorcinol, phenol, phloroglucinol, and catechol. The aldehyde compound includes at least one of formaldehyde and furfural.

[0014] In the present invention, the water in the organic sol and the water or alcohol in the titanium dioxide sol must be completely dried after mixing. Therefore, their volumes are not strictly limited and can be selected as needed. The organic sol and titanium dioxide sol can be dried after mixing by any of the following drying methods: supercritical drying, freeze drying, and atmospheric pressure drying.

[0015] Furthermore, the mass ratio of the organic matter capable of being dissolved in water and forming a sol to the titanium-containing matter is 5-15:1-2;

[0016] The mass ratio of the polyhydroxybenzene compound, the aldehyde compound and the titanium-containing substance is 3-8:5-10:1-2.

[0017] Furthermore, the titanium-containing material includes at least one of titanium dioxide, titanate, titanyl sulfate, and titanyl chloride.

[0018] Furthermore, the ammonia atmosphere calcination is specifically as follows:

[0019] Under an ammonia flow rate of 1-800 mL / min, the temperature is increased to 600-1200°C at a heating rate of 2-10°C / min and kept at this temperature for 1-10 hours.

[0020] Furthermore, the mass ratio of the titanium nitride-doped porous carbon, the solvent, and the platinum precursor is 0.3-1:20-50:0.1-0.3.

[0021] Furthermore, the solvent includes water or alcohol.

[0022] Preferably, the alcohol for dispersing the titanium-containing substance and the alcohol for dispersing the titanium nitride-doped porous and platinum precursor are small molecule alcohols, which may be at least one of ethanol, n-propanol and isopropanol.

[0023] Furthermore, the calcination under a protective gas atmosphere is specifically:

[0024] In a protective gas atmosphere, heat to 600-1200°C at a heating rate of 1-10°C / min and keep warm for 0.5-4h.

[0025] The protective gas atmosphere can be one of argon atmosphere, nitrogen atmosphere, helium atmosphere, hydrogen atmosphere and ammonia atmosphere, preferably hydrogen atmosphere.

[0026] In the present invention, the platinum precursor is a compound containing the element platinum. Its type is not strictly limited and can, for example, be at least one of chloroplatinic acid, platinum acetylacetonate, and platinum chloride. Preferably, the amount of platinum precursor added is controlled so that the mass fraction of platinum in the porous carbon-supported platinum alloy catalyst is between 1% and 60%. A low platinum content results in low oxygen reduction activity in the final material; a high platinum content will form large platinum nanoparticles during high-temperature heat treatment.

[0027] The present invention also provides a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst, which is obtained by adopting the above-mentioned preparation method of the porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst.

[0028] The present invention also provides the use of the porous carbon-supported titanium nitride in conjunction with the platinum-titanium alloy catalyst in a fuel cell.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention's porous carbon-supported titanium nitride-platinum-titanium alloy catalyst is relatively simple to prepare. Titanium nitride eliminates strong oxidizing free radicals generated by the Fenton reaction, protecting the platinum alloy and carbon support from oxidation. Furthermore, the titanium atoms in the titanium nitride on the surfaces of the platinum and carbon support form a platinum-titanium alloy, while the titanium nitride anchors the platinum alloy to prevent agglomeration and migration. The prepared catalyst exhibited essentially unchanged redox properties after 300,000 cycles of accelerated aging.

[0031] The catalyst prepared by the present invention has a highly open porous structure and a high specific surface area. The specific surface area of ​​the prepared catalyst is high, and the pore size is mainly mesopores. However, the pore size distribution range is relatively wide, which can significantly reduce the mass transfer resistance of oxygen, is beneficial to the diffusion of oxygen in the electrocatalytic reaction, and has very high catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 A flow chart showing the preparation method of the porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst of the present invention is shown;

[0034] Figures 2(a), 2(b), and 2(c) show transmission electron micrographs of the catalysts prepared in Example 1, Example 2, and Comparative Example 1, respectively. Figure 2(d) shows a high-resolution transmission electron micrograph of the catalyst of Example 1.

[0035] Figure 3 Shown are the XRD patterns of the catalysts prepared in Example 1, Example 2, and Comparative Example 1;

[0036] Figure 4 shows the nitrogen adsorption and desorption curve of the catalyst prepared in Example 1;

[0037] Figure 5 shows a pore size distribution curve of the catalyst prepared in Example 1;

[0038] FIG6( a ) shows the linear sweep voltammetry curves of the catalysts prepared in Example 1, Example 2, Comparative Example 1, and commercial Pt / C, and FIG6( b ) shows the results of the accelerated durability test of Example 1. DETAILED DESCRIPTION

[0039] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the specific embodiments of the present invention and the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] Example 1

[0042] like Figure 1 As shown, a method for preparing a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst comprises the following steps:

[0043] The first step is to prepare organosol A. 10 g of polyethylene glycol is weighed and dissolved in 30 mL of deionized water and stirred until completely dissolved to form a uniform polyethylene glycol sol.

[0044] Step 2: Prepare titanium oxide sol B by dispersing 1 g of titanium dioxide powder with a particle size of 3-5 nm in 10 mL of deionized water.

[0045] Step 3: Prepare a titanium oxide-doped organic sol by mixing the organic sol A prepared in step 1 and the titanium oxide sol B prepared in step 2, stirring them uniformly to obtain a mixture. Place the mixture in a heating device at 50°C and let it stand until the mixture forms a uniform sol.

[0046] Step 4: freeze-dry the organic sol obtained in step 3 at a drying temperature of -80°C and a vacuum degree of 3Pa.

[0047] The fifth step is to prepare titanium nitride-doped porous carbon material. The organic sol prepared in the fourth step is placed in a cracking furnace. Under the protection of an ammonia atmosphere, ammonia gas is introduced at a flow rate of 400 mL / min, and the temperature is increased to 900°C at a heating rate of 2°C / min. The temperature is kept for 2 hours and the titanium nitride-doped porous carbon material is obtained by cooling the furnace.

[0048] Step 6: Prepare porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst. Grind the titanium nitride-doped porous carbon material described in the fifth step into 200 mesh powder, then take 0.500 g of powder and disperse it in 30 mL of water, add 0.150 g of chloroplatinic acid nonahydrate, ultrasonicate for 15 min, stir for 18 h, and freeze-dry to obtain an aerosol-supported Pt precursor. Under a pure H2 protective atmosphere, heat to 1000 ° C at a rate of 2 ° C / min and keep warm for 0.5 h, and cool naturally to obtain a porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst.

[0049] Example 2

[0050] A method for preparing a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst comprises the following steps:

[0051] The first step is to prepare organosol A. 5 g of resorcinol is weighed and dissolved in 30 mL of deionized water and stirred until completely dissolved. Then, 8 g of formaldehyde solution is added to form a uniform resorcinol-formaldehyde sol.

[0052] Step 2: Prepare titanium oxide sol B by dispersing 1 g of titanium dioxide powder with a particle size of 3-5 nm in 10 mL of deionized water.

[0053] Step 3: Prepare a titanium oxide-doped organic sol by mixing the A prepared in the first step and the B prepared in the second step, stirring them evenly to obtain a mixture. Place the mixture in a heating device at 50°C and let it stand until the mixture forms a uniform sol.

[0054] Step 4: freeze-dry the organic sol obtained in step 3 at a drying temperature of -80°C and a vacuum degree of 3Pa.

[0055] The fifth step is to prepare titanium nitride-doped porous carbon material. The organic sol prepared in the fourth step is placed in a cracking furnace. Under the protection of an ammonia atmosphere, ammonia gas is introduced at a flow rate of 400 mL / min, and the temperature is increased to 900°C at a heating rate of 2°C / min. The temperature is kept for 2 hours and the titanium nitride-doped porous carbon material is obtained by cooling the furnace.

[0056] Step 6: Prepare porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst. Grind the titanium nitride-doped porous carbon material described in the fifth step into 200 mesh powder. Disperse 0.500 g of the powder in 30 mL of water. Add 0.150 g of chloroplatinic acid nonahydrate, ultrasonicate for 15 min, stir for 18 h, and freeze-dry to obtain an aerosol-supported Pt precursor. Heat to 1000 ° C at a rate of 2 ° C / min under a pure H2 protective atmosphere and keep warm for 30 min. Cool naturally to obtain a porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst.

[0057] Comparative Example 1

[0058] A method for preparing porous carbon supported titanium nitride and platinum-titanium alloy catalyst, wherein the porous carbon is prepared using commercial carbon carriers instead of organic sols, and comprises the following steps:

[0059] The first step is to select 9g of commercial carbon support EC-300J and grind it into powder;

[0060] The second step is to prepare titanium oxide sol by dispersing 1 g of titanium dioxide powder with a particle size of 3-5 nm in 10 mL of deionized water.

[0061] Step 3: Mix the ground EC-300J from Step 1 and the titanium oxide sol from Step 2, stir them evenly to obtain a mixture, and place the mixture in a heating device at 80°C, stirring to evaporate the water.

[0062] Step 4: freeze-dry the titanium oxide-doped EC-300J obtained in the third step at a drying temperature of -80°C and a vacuum degree of 3Pa.

[0063] The fifth step is to prepare titanium nitride-doped porous carbon material. The titanium oxide-doped EC-300J prepared in the fourth step is placed in a cracking furnace. Under the protection of an ammonia atmosphere, ammonia gas is introduced at a flow rate of 400 mL / min, and the temperature is increased to 900°C at a heating rate of 2°C / min. The temperature is kept for 2 hours and the titanium nitride-doped porous carbon material is obtained by cooling the furnace.

[0064] Step 6: Prepare porous carbon-supported titanium nitride synergistic platinum alloy catalyst. Grind the titanium nitride-doped EC-300J described in the fifth step into 200 mesh powder, disperse 0.500 g of the powder in 30 mL of water, add 0.150 g of chloroplatinic acid nonahydrate, ultrasonicate for 15 min, stir for 18 h, and freeze-dry to obtain an aerosol-supported Pt precursor. Heat to 1000 ° C at a rate of 2 ° C / min under a pure H2 protective atmosphere and keep warm for 30 min. Cool naturally to obtain a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst.

[0065] Test Case

[0066] Transmission electron microscopy was used to observe the micromorphology of the catalysts prepared in Example 1, Example 2, and Comparative Example 1. The results are shown in Figures 2(a), 2(b), and 2(c), respectively. In these figures, the relatively small black particles are platinum-titanium alloy particles, all with an average particle size of less than 5 nm. The lighter-colored areas represent the prepared porous carbon. The particles with a size of approximately 50 nm on the surface of the porous carbon are titanium nitride particles. These figures show that the distribution of platinum-titanium alloy particles in the catalyst prepared in Example 1 is the most uniform, which contributes to the catalyst's high activity. Furthermore, the titanium nitride particles on the surface of the porous carbon anchor the platinum alloy, preventing it from agglomerating and migrating. Figure 2 (d) also shows a high-resolution transmission electron micrograph of the catalyst of Example 1. The lattice fringes on its surface were found to correspond to the (111) plane of the ordered Pt3Ti alloy and the (200) crystal plane of titanium nitride, respectively, and the Pt3Ti alloy and titanium nitride were in contact, which is more conducive to electron transfer during the oxygen reduction reaction (ORR), thereby improving the activity and stability of the catalyst.

[0067] The crystal structures of the catalysts prepared in Example 1, Example 2 and Comparative Example 1 were also observed using an X-ray diffractometer. Figure 3 shown. Figure 3 The diffraction peaks at 36.6°, 42.6°, 61.8°, 74° and 77.9° correspond to the (111), (200), (220), (311) and (222) crystal planes of titanium nitride, respectively, while the diffraction peaks at 22.9°, 32.6°, 40.1°, 46.6°, 52.4°, 57.9°, 67.9°, 72.6°, 77.1°, 81.7° and 86.2° correspond to the (100), (110), (111), (200), (210), (211), (220), (300), (310), (311) and (222) crystal planes of ordered Pt3Ti alloy, respectively, further illustrating the formation of titanium nitride and titanium-platinum alloy.

[0068] The surface area and pore size distribution of the catalyst of Example 1 were tested by nitrogen adsorption and desorption. The results were as follows: Figure 4 and Figure 5 The results show that the specific surface area of ​​the catalyst prepared in Example 1 is as high as 411m 2 / g, and the pore size is mainly mesopores. At the same time, the pore size distribution range is relatively wide, which can significantly reduce the mass transfer resistance of oxygen and is beneficial to the oxygen diffusion of the electrocatalytic reaction.

[0069] To test the ORR activity of the catalysts of the Examples and Comparative Examples, linear sweep voltammetry was performed in a 0.10 mol / L perchloric acid aqueous solution. The results are shown in Figure 6(a). It can be seen that the half-wave potentials of the catalysts of the Examples and Comparative Examples of the present invention are both higher than those of commercial Pt / C. In particular, the half-wave potential of the catalyst of Example 1 is as high as 0.9 V, and its mass activity reaches 0.35 mA / mgPt. The catalyst of Example 1 was also subjected to an accelerated durability test at a voltage between 0.6 V and 1.0 V in an oxygen atmosphere. As shown in Figure 6(b), after 300,000 cycles, its half-wave potential dropped by only 2 mV, demonstrating excellent durability, which is higher than the levels reported in most existing literature. This confirms that the porous carbon-supported titanium nitride-platinum-titanium alloy catalyst proposed in the present invention has strong catalytic activity and durability.

[0070] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst, characterized in that: include, The organic sol and the titanium dioxide sol are mixed and dried to obtain a precursor; The precursor is placed in an ammonia atmosphere and calcined to obtain titanium nitride-doped porous carbon; The titanium nitride-doped porous carbon, a solvent, and a platinum precursor are stirred and mixed, and then the solvent is removed to obtain an intermediate, and the intermediate is calcined under a protective gas atmosphere to obtain a porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst; the calcination under the protective gas atmosphere is specifically, in the protective gas atmosphere, heating the temperature to 600-1200° C. at a heating rate of 1-10° C. / min and keeping the temperature for 0.5-4 hours, and the protective gas atmosphere includes one of argon atmosphere, nitrogen atmosphere, helium atmosphere, hydrogen atmosphere and ammonia atmosphere; The organic sol is obtained by dissolving an organic substance capable of forming a sol in water or reacting an organic substance capable of forming a sol in an aqueous environment in water; wherein the organic substance capable of forming a sol is a polyhydroxybenzene compound or melamine and an aldehyde compound; The titanium dioxide sol is obtained by dispersing titanium-containing substances in water or alcohol.

2. The method for preparing porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst according to claim 1, characterized in that: The mass ratio of the organic matter that can be dissolved in water and can be sol-formed to the titanium-containing matter is 5-15:1-2; The mass ratio of the polyhydroxybenzene compound or melamine, the aldehyde compound and the titanium-containing substance is 3-8:5-10:1-2.

3. The method for preparing porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst according to claim 1, characterized in that: The titanium-containing material includes at least one of titanium dioxide, titanate, titanyl sulfate, and titanyl chloride.

4. The method for preparing porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst according to claim 1, characterized in that: The ammonia atmosphere calcination is specifically as follows: Under an ammonia flow rate of 1-800 mL / min, the temperature is increased to 600-1200°C at a heating rate of 2-10°C / min and kept at this temperature for 1-10 hours.

5. The method for preparing porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst according to claim 1, characterized in that: The mass ratio of the titanium nitride-doped porous carbon, the solvent, and the platinum precursor is 0.3-1:20-50:0.1-0.

3.

6. The method for preparing porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst according to claim 1, characterized in that: The solvent includes water or alcohol.

7. A porous carbon-supported titanium nitride synergistic platinum-titanium alloy catalyst, characterized in that: The catalyst is obtained by using the preparation method of porous carbon-supported titanium nitride synergistic with platinum-titanium alloy catalyst according to any one of claims 1 to 6.

8. Use of the porous carbon-supported titanium nitride and platinum-titanium alloy catalyst as claimed in claim 7 in a fuel cell.

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