Catalyst for oxygen reduction and preparation method thereof

Abstract

The present invention discloses a catalyst for oxygen reduction and a preparation method thereof. The catalyst includes a carbon support and a metal component Pt loaded on the carbon support, wherein the carbon support is a carbon support prepared from castor bean shells as a raw material. The method for preparing the carbon support includes: subjecting castor bean shells to pyrolysis, graphitization, phosphorus doping, and nitrogen doping to obtain the carbon support. The oxygen reduction catalyst of the present invention, which includes a carbon support and a metal component Pt loaded on the carbon support, and the carbon support is prepared from castor bean shells as a raw material, has significantly high mass specific activity, electrochemical active area, and durability of 30k cycles in electrochemical performance tests. When the Pt content is 40%, the catalytic effect of a commercial Pt content of 60% can be achieved, and the electrocatalytic activity performance is significantly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and in particular relates to a catalyst for oxygen reduction and a preparation method thereof. Background Art

[0002] Hydrogen fuel cells require platinum-on-carbon catalysts at both the cathode and anode. The HOR (hydrogen oxidation reaction) kinetics at the anode are very fast, resulting in minimal voltage loss even at very low catalyst loadings. However, the cathode requires a high catalyst loading to catalyze the slower and rate-limiting ORR (oxygen reduction reaction). Consequently, the vast majority of current research efforts focus on oxygen reduction catalysts. Commercial fuel cells commonly use 50-70% Pt / C as their oxygen reduction catalysts, but the high platinum content and high cost of platinum metal limit large-scale fuel cell adoption. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide an oxygen reduction catalyst and a preparation method thereof. The oxygen reduction catalyst of the present invention, comprising a carbon support and a metal component Pt supported on the carbon support, wherein the carbon support is prepared from castor seed shells, exhibits significantly high mass specific activity, electrochemically active area, and durability of 30k cycles in electrochemical performance tests. At a Pt content of 40%, it can achieve the catalytic effect of a commercial Pt content of 60%, demonstrating significantly improved electrocatalytic activity.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: an oxygen reduction catalyst, characterized in that it includes a carbon support and a metal component Pt supported on the carbon support, and the carbon support is a carbon support prepared using castor seed shell as raw material.

[0005] The above oxygen reduction catalyst is characterized in that the method for preparing the carbon support comprises: subjecting castor seed shells to pyrolysis, graphitization, phosphorus doping and nitrogen doping to obtain the carbon support.

[0006] The above oxygen reduction catalyst is characterized in that the pyrolysis treatment comprises: subjecting the castor seed shell to pyrolysis treatment at a temperature of 600° C. to 1000° C. for 1 hour to 8 hours under vacuum conditions.

[0007] The above oxygen reduction catalyst is characterized in that the graphitization treatment includes: graphitizing the material after pyrolysis treatment at a temperature of 1000° C. to 2000° C. for 5 hours to 36 hours under vacuum conditions.

[0008] The above-mentioned oxygen reduction catalyst is characterized in that the phosphorus doping treatment includes: placing the graphitized material in a phosphorus-containing compound solution and stirring at 80°C to 100°C for 8h to 24h; the concentration of the phosphorus-containing compound in the phosphorus-containing compound solution is 20wt.% to 60wt.%; and the phosphorus-containing compound is phosphoric acid, sodium dihydrogen phosphate or aminotri(methylene)phosphonic acid.

[0009] The above-mentioned oxygen reduction catalyst is characterized in that the nitrogen doping treatment includes: placing the material after phosphorus doping treatment in a nitrogen-containing compound solution, stirring at 80°C to 200°C for 4h to 12h in a nitrogen atmosphere of 1MPa to 5MPa; the concentration of the nitrogen-containing compound in the nitrogen-containing compound solution is 20wt.% to 60wt.%; the nitrogen-containing compound is ammonia water, ammonium chloride or melamine.

[0010] In addition, the present invention also provides a method for preparing the above-mentioned oxygen reduction catalyst, comprising: dissolving the carbon support, chloroplatinic acid and polyvinyl pyrrolidone in an ethanol-isopropanol mixed solution, refluxing, cooling, filtering, washing until no chloride ions are present, and drying to obtain the oxygen reduction catalyst.

[0011] The above method is characterized in that the mass of the chloroplatinic acid is 1.78 times the mass of the carbon support, and the mass of the polyvinyl pyrrolidone is 1 / 3 times the mass of the carbon support.

[0012] The above method is characterized in that the reflux temperature is 110°C.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. The present invention provides an oxygen reduction catalyst comprising a carbon support and a metal component Pt supported on the carbon support, wherein the carbon support is prepared from castor seed shells. In electrochemical performance tests, the oxygen reduction catalyst has significantly high mass specific activity, electrochemical active area, and durability of 30k cycles. At a Pt content of 40%, the catalytic effect of a commercial Pt content of 60% can be achieved, thereby significantly improving electrocatalytic activity performance.

[0015] 2. The method for preparing the oxygen reduction catalyst of the present invention is simple and is conducive to popularization and application. The use of castor bean shells as raw materials can effectively avoid the waste of resources and environmental pollution caused by the traditional incineration of castor bean shells.

[0016] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0017] Figures in the specification

[0018] Figure 1This is the XPS spectrum of the tetranitrogen phosphorus co-doped carbon support in step 5 and the graphitized carbon material in step 2.

[0019] Figure 2 This is a transmission electron microscope image of the catalyst of Example 5.

[0020] Figure 3 This is a transmission electron microscope image of the catalyst of Comparative Example 1.

[0021] Figure 4 This is a transmission electron microscope image of the catalyst of Comparative Example 2. DETAILED DESCRIPTION

[0022] The present invention provides an oxygen reduction catalyst. Castor seed shells are carbonized, graphitized, and doped with phosphorus and nitrogen to obtain a carbon support, which is then loaded with a metal component, Pt, to obtain the oxygen reduction catalyst. The carbon material skeleton is doped with phosphorus and nitrogen, which disrupts the electrical neutrality of adjacent carbon atoms, increases defect sites, and enhances the ability to adsorb oxygen molecules. A Pt content of 40% can achieve the same catalytic effect as a commercial Pt content of 60%, resulting in significantly improved electrocatalytic activity and effectively promoting the oxygen reduction reaction.

[0023] The reagents and materials used in the following examples are all commercially available, and the experimental methods in the following examples without specific conditions specified are all carried out according to conventional methods and conditions.

[0024] Example 1

[0025] This embodiment provides an oxygen reduction catalyst, comprising a carbon support and a metal component Pt supported on the carbon support. The mass percentage of the metal component Pt in the catalyst is 40%. The carbon support is prepared from castor bean shells.

[0026] This embodiment also provides a method for preparing the above-mentioned oxygen reduction catalyst, comprising:

[0027] Step 1: Under vacuum conditions, 100 g of washed and dried castor bean shells were pyrolyzed in a 600°C high-temperature furnace for 1 h to obtain 73.6 g of carbonized material;

[0028] Step 2: Graphitize 20 g of the carbonized material described in step 1 in a high-temperature furnace at 1000° C. for 5 h under vacuum conditions to obtain 15 g of graphitized carbon material;

[0029] Step 3: 10 g of the graphitized carbon material prepared in step 2 was placed in 100 ml of a 20 wt.% phosphoric acid aqueous solution, stirred at 80° C. for 8 h, filtered to obtain a retentate, and dried at 100° C. for 12 h to obtain 10.2 g of a phosphorus-doped carbon support; the stirring rate was 600 rpm;

[0030] Step 4: 10 g of the phosphorus-doped carbon support prepared in step 3 was placed in a 250 ml reactor, 100 ml of a 20 wt.% melamine solution was added, and nitrogen was introduced into the reactor to 1 MPa to replace the air. After three times of replacement, the nitrogen was introduced to 1 MPa and maintained. The reactor was heated to 80° C. and stirred for 4 h. The mixture was filtered to obtain a retentate, which was then dried at 100° C. for 12 h to obtain 11 g of a nitrogen-phosphorus co-doped carbon support. The reactor may be a magnetic stainless steel reactor. The stirring rate was 600 rpm.

[0031] Step 5. Dissolve 3 g of the nitrogen and phosphorus co-doped carbon support described in step 4, 5.333 g of chloroplatinic acid and 1 g of polyvinyl pyrrolidone in 100 g of ethanol-isopropanol mixed solution, stir for 6 hours, then heat to 110 ° C. and reflux for 5 hours, cool, filter, wash until there is no chloride ion, and dry in a vacuum oven at 60 ° C. for 12 hours to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contains 43.4 g of ethanol and 56.6 g of isopropanol; the stirring rate is 600 rpm; the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30 with a molecular weight of 44,000 to 54,000.

[0032] Example 2

[0033] This embodiment provides an oxygen reduction catalyst, comprising a carbon support and a metal component Pt supported on the carbon support. The mass percentage of the metal component Pt in the catalyst is 40%. The carbon support is prepared from castor bean shells.

[0034] This embodiment also provides a method for preparing the above-mentioned oxygen reduction catalyst, comprising:

[0035] Step 1: Under vacuum conditions, 100 g of washed and dried castor bean shells were pyrolyzed in a high-temperature furnace at 1000°C for 8 h to obtain 43.6 g of carbonized material;

[0036] Step 2: Graphitize 20 g of the carbonized material described in step 1 in a high-temperature furnace at 2000° C. for 36 h under vacuum conditions to obtain 10.1 g of graphitized carbon material;

[0037] Step 3: 9 g of the graphitized carbon material prepared in step 2 was placed in 100 ml of a 60 wt.% phosphoric acid aqueous solution, stirred at 100° C. for 24 h, filtered to obtain a retentate, and dried at 100° C. for 12 h to obtain 12.5 g of a phosphorus-doped carbon support; the stirring rate was 600 rpm;

[0038] Step 4: 10 g of the phosphorus-doped carbon support prepared in step 3 was placed in a 250 ml reactor, 100 ml of a 60 wt.% melamine solution was added, nitrogen was introduced into the reactor to 1 MPa to displace the air, and the replacement was repeated three times. The nitrogen was then introduced to 5 MPa and maintained, the reactor was heated to 200° C. and stirred for 12 h, filtered to obtain a retentate, and the retentate was dried at 100° C. for 12 h to obtain 11.9 g of a nitrogen-phosphorus co-doped carbon support. The reactor may be a magnetic stainless steel reactor; the stirring rate is 600 rpm.

[0039] Step 5. Dissolve 3 g of the nitrogen and phosphorus co-doped carbon support described in step 4, 5.333 g of chloroplatinic acid and 1 g of polyvinyl pyrrolidone in 100 g of an ethanol-isopropanol mixed solution, stir for 6 hours, then heat to 110 ° C. and reflux for 5 hours, cool, filter, wash until there is no chloride ion, and dry in a vacuum oven at 60 ° C. for 12 hours to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contains 43.4 g of ethanol and 56.6 g of isopropanol; the stirring rate is 600 rpm, and the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30 with a molecular weight of 44,000 to 54,000.

[0040] Example 3

[0041] This embodiment provides an oxygen reduction catalyst, comprising a carbon support and a metal component Pt supported on the carbon support. The mass percentage of the metal component Pt in the catalyst is 40%. The carbon support is prepared from castor bean shells.

[0042] This embodiment also provides a method for preparing the above-mentioned oxygen reduction catalyst, comprising:

[0043] Step 1: Under vacuum conditions, 100 g of washed and dried castor bean shells were pyrolyzed in a 600°C high-temperature furnace for 8 h to obtain 62 g of carbonized material;

[0044] Step 2: Graphitize 20 g of the carbonized material described in step 1 in a high-temperature furnace at 1000° C. for 12 h under vacuum conditions to obtain 12.9 g of graphitized carbon material;

[0045] Step 3: 10 g of the graphitized carbon material prepared in step 2 was placed in 100 ml of a 20 wt.% phosphoric acid aqueous solution, stirred at 80° C. for 24 h, filtered to obtain a retentate, and dried at 100° C. for 12 h to obtain 10.8 g of a phosphorus-doped carbon support; the stirring rate was 600 rpm;

[0046] Step 4: 10 g of the phosphorus-doped carbon support prepared in step 3 was placed in a 250 ml reactor, 100 ml of a 20 wt.% melamine solution was added, nitrogen was introduced into the reactor to 1 MPa to displace the air, and the replacement was repeated three times. The nitrogen was then introduced to 5 MPa and maintained, the reactor was heated to 80° C. and stirred for 12 h, filtered to obtain a retentate, and the retentate was dried at 100° C. for 12 h to obtain 12.4 g of a nitrogen-phosphorus co-doped carbon support. The reactor may be a magnetic stainless steel reactor, and the stirring rate is 600 rpm.

[0047] Step 5. Dissolve 3 g of the nitrogen and phosphorus co-doped carbon support described in step 4, 5.333 g of chloroplatinic acid and 1 g of polyvinyl pyrrolidone in 100 g of an ethanol-isopropanol mixed solution, stir for 6 hours, then heat to 110 ° C. and reflux for 5 hours, cool, filter, wash until there is no chloride ion, and dry in a vacuum oven at 60 ° C. for 12 hours to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contains 43.4 g of ethanol and 56.6 g of isopropanol; the stirring rate is 600 rpm, and the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30 with a molecular weight of 44,000 to 54,000.

[0048] Example 4

[0049] This embodiment provides an oxygen reduction catalyst, comprising a carbon support and a metal component Pt supported on the carbon support. The mass percentage of the metal component Pt in the catalyst is 40%. The carbon support is prepared from castor bean shells.

[0050] This embodiment also provides a method for preparing the above-mentioned oxygen reduction catalyst, comprising:

[0051] Step 1: Under vacuum conditions, 100 g of washed and dried castor seed shells were pyrolyzed in a high-temperature furnace at 1000°C for 1 hour to obtain 57.3 g of carbonized material;

[0052] Step 2: Graphitize 20 g of the carbonized material described in step 1 in a high-temperature furnace at 2000° C. for 5 h under vacuum conditions to obtain 13.2 g of graphitized carbon material;

[0053] Step 3: 10 g of the graphitized carbon material prepared in step 2 was placed in 100 ml of a 60 wt.% phosphoric acid aqueous solution, stirred at 100° C. for 8 h, filtered to obtain a retentate, and dried at 100° C. for 12 h to obtain 10.8 g of a phosphorus-doped carbon support; the stirring rate was 600 rpm;

[0054] Step 4: 10 g of the phosphorus-doped carbon support prepared in step 3 was placed in a 250 ml reactor, 100 ml of a 60 wt.% melamine solution was added, and nitrogen was introduced into the reactor to 1 MPa to replace the air. After three repetitions of replacement, the nitrogen was introduced to 5 MPa and maintained. The reactor was heated to 200° C. and stirred for 4 h. The mixture was filtered to obtain a retentate, which was then dried at 100° C. for 12 h to obtain 13.1 g of a nitrogen-phosphorus co-doped carbon support. The reactor may be a magnetic stainless steel reactor. The stirring rate is 600 rpm.

[0055] Step 5. Dissolve 3 g of the nitrogen and phosphorus co-doped carbon support described in step 4, 5.333 g of chloroplatinic acid and 1 g of polyvinyl pyrrolidone in 100 g of an ethanol-isopropanol mixed solution, stir for 6 hours, then heat to 110 ° C. and reflux for 5 hours, cool, filter, wash until there is no chloride ion, and dry in a vacuum oven at 60 ° C. for 12 hours to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contains 43.4 g of ethanol and 56.6 g of isopropanol; the stirring rate is 600 rpm, and the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30 with a molecular weight of 44,000 to 54,000.

[0056] Example 5

[0057] This embodiment provides an oxygen reduction catalyst, comprising a carbon support and a metal component Pt supported on the carbon support. The mass percentage of the metal component Pt in the catalyst is 40%. The carbon support is prepared from castor bean shells.

[0058] This embodiment also provides a method for preparing the above-mentioned oxygen reduction catalyst, comprising:

[0059] Step 1: Under vacuum conditions, 100 g of washed and dried castor bean shells were pyrolyzed in a high-temperature furnace at 800°C for 4 hours to obtain 65 g of carbonized material;

[0060] Step 2: Graphitize 20 g of the carbonized material described in step 1 in a high-temperature furnace at 1500° C. for 8 h under vacuum conditions to obtain 11.7 g of graphitized carbon material;

[0061] Step 3: 10 g of the graphitized carbon material prepared in step 2 was placed in 100 ml of a 50 wt.% phosphoric acid aqueous solution, stirred at 90° C. for 16 h, filtered to obtain a retentate, and dried at 100° C. for 12 h to obtain 11.4 g of a phosphorus-doped carbon support; the stirring rate was 600 rpm;

[0062] Step 4: 10 g of the phosphorus-doped carbon support prepared in step 3 was placed in a 250 ml reactor, 100 ml of a 50 wt.% melamine solution was added, and nitrogen was introduced into the reactor to 1 MPa to replace the air. After three repetitions of replacement, the nitrogen was introduced to 3 MPa and maintained. The reactor was heated to 120° C. and stirred for 12 h. The mixture was filtered to obtain a retentate, which was then dried at 100° C. for 12 h to obtain 11.8 g of a nitrogen-phosphorus co-doped carbon support. The reactor may be a magnetic stainless steel reactor. The stirring rate is 600 rpm.

[0063] Step 5. Dissolve 3 g of the nitrogen and phosphorus co-doped carbon support described in step 4, 5.333 g of chloroplatinic acid and 1 g of polyvinyl pyrrolidone in 100 g of an ethanol-isopropanol mixed solution, stir for 6 hours, then heat to 110 ° C. and reflux for 5 hours, cool, filter, wash until there is no chloride ion, and dry in a vacuum oven at 60 ° C. for 12 hours to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contains 43.4 g of ethanol and 56.6 g of isopropanol; the stirring rate is 600 rpm, and the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30 with a molecular weight of 44,000 to 54,000.

[0064] Comparative Example 1

[0065] In this comparative example, a commercial carrier XC-72 was used to prepare a 60% platinum-carbon catalyst, comprising the following steps: dissolving 2 g of a commercial XC-72 carbon black carrier (Vulcan), 8.0 g of chloroplatinic acid, and 1.5 g of polyvinyl pyrrolidone in 100 g of an ethanol-isopropanol mixed solution, stirring for 6 h, heating to 110° C., reflux for 5 h, cooling, filtering, washing until free of chloride ions, and drying in a vacuum oven at 60° C. for 12 h to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contained 43.4 g of ethanol and 56.6 g of isopropanol; and the stirring rate was 600 rpm.

[0066] Comparative Example 2

[0067] This comparative example provides a method for preparing an oxygen reduction catalyst. The preparation method is the same as that of Example 5, except that step three and step four are omitted.

[0068] Step five is to dissolve 3g of the graphitized carbon material described in step two, 5.333g of chloroplatinic acid and 1g of polyvinyl pyrrolidone in 100g of ethanol-isopropanol mixed solution, stir for 6h, then heat to 110°C and reflux for 5h, cool, filter, wash until there is no chloride ion, and dry in a vacuum oven at 60°C for 12h to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contains 43.4g of ethanol and 56.6g of isopropanol; the stirring rate is 600rpm.

[0069] Comparative Example 3

[0070] This comparative example is the same as Example 5, except that step 3 is not performed.

[0071] Comparative Example 4

[0072] This comparative example is the same as Example 5, except that step 4 is not performed.

[0073] Performance evaluation:

[0074] The XPS spectra of the tetranitrogen phosphorus co-doped carbon support in step 5 and the graphitized carbon material in step 2 of comparative example 2 are shown in FIG. Figure 1 .according to Figure 1 It can be seen that characteristic peaks attributed to P and N appear at the binding energies of 134 eV and 399 eV, respectively, on the nitrogen-phosphorus co-doped carbon support, indicating that nitrogen and phosphorus elements can be successfully doped into the skeleton of the carbon material by doping the graphitized carbon material using the method of the present invention.

[0075] The transmission electron microscopy image of the catalyst of Example 5 is as follows: Figure 2 As shown, the transmission electron microscopy of the catalyst of Comparative Example 1 is as follows Figure 3 As shown, the transmission electron microscopy of the catalyst of Comparative Example 2 is as follows Figure 4 As shown. Figures 2 to 4 visible, Figure 2 The metal particles are evenly distributed on the carrier and the particle size distribution is narrow. Figure 4 The metal particles are unevenly distributed on the surface of the carrier and there is significant agglomeration. Figure 3 The platinum metal particles in the catalyst are severely agglomerated, and the loading of platinum particles is almost unobservable on many commercial carbon black carriers. This indicates that the catalyst prepared by the method of the present invention can effectively improve the uniformity of platinum metal dispersion on the carrier surface, which helps to improve the electrochemical performance.

[0076] Example 6

[0077] This embodiment provides an oxygen reduction catalyst, comprising a carbon support and a metal component Pt supported on the carbon support. The mass percentage of the metal component Pt in the catalyst is 40%. The carbon support is prepared from castor bean shells.

[0078] This embodiment also provides a method for preparing the above-mentioned oxygen reduction catalyst, comprising:

[0079] Step 1: Under vacuum conditions, 100 g of washed and dried castor bean shells were pyrolyzed in a high-temperature furnace at 800°C for 4 hours to obtain 65 g of carbonized material;

[0080] Step 2: Graphitize 20 g of the carbonized material described in step 1 in a high-temperature furnace at 1500° C. for 8 h under vacuum conditions to obtain 11.7 g of graphitized carbon material;

[0081] Step 3: 10 g of the graphitized carbon material prepared in step 2 was placed in 100 ml of a 50 wt.% aqueous sodium dihydrogen phosphonate solution, stirred at 90° C. for 16 h, filtered to obtain a retentate, and dried at 100° C. for 12 h to obtain 10.9 g of a phosphorus-doped carbon support; the stirring rate was 600 rpm;

[0082] Step 4: 10 g of the phosphorus-doped carbon support prepared in step 3 was placed in a 250 ml reactor, 100 ml of a 50 wt.% ammonia solution was added, nitrogen was introduced into the reactor to 1 MPa to replace the air, and the replacement was repeated three times. The nitrogen was then introduced to 3 MPa and maintained, the reactor was heated to 120 ° C. and stirred for 12 hours, filtered to obtain a retentate, and the retentate was dried at 100 ° C. for 12 hours to obtain 10.5 g of a nitrogen-phosphorus co-doped carbon support; the reactor may be a magnetic stainless steel reactor; and the stirring rate is 600 rpm;

[0083] Step 5. Dissolve 3g of the nitrogen and phosphorus co-doped carbon support described in step 4, 5.333g of chloroplatinic acid and 1g of polyvinyl pyrrolidone in 100g of ethanol-isopropanol mixed solution, stir for 6h, then heat to 110°C and reflux for 5h, cool, filter, wash until there is no chloride ion, and dry in a vacuum oven at 60°C for 12h to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contains 43.4g of ethanol and 56.6g of isopropanol; the stirring rate is 600rpm, and the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30 with a molecular weight of 44,000 to 54,000.

[0084] Example 7

[0085] This embodiment provides an oxygen reduction catalyst, comprising a carbon support and a metal component Pt supported on the carbon support. The mass percentage of the metal component Pt in the catalyst is 40%. The carbon support is prepared from castor bean shells.

[0086] This embodiment also provides a method for preparing the above-mentioned oxygen reduction catalyst, comprising:

[0087] Step 1: Under vacuum conditions, 100 g of washed and dried castor bean shells were pyrolyzed in a high-temperature furnace at 800°C for 4 hours to obtain 65 g of carbonized material;

[0088] Step 2: Graphitize 20 g of the carbonized material described in step 1 in a high-temperature furnace at 1500° C. for 8 h under vacuum conditions to obtain 11.7 g of graphitized carbon material;

[0089] Step 3: 10 g of the graphitized carbon material prepared in step 2 was placed in 100 ml of a 50 wt.% aqueous solution of aminotri(methylenephosphonic acid), stirred at 90° C. for 16 h, filtered to obtain a retentate, and dried at 100° C. for 12 h to obtain 11.9 g of a phosphorus-doped carbon support; the stirring rate was 600 rpm;

[0090] Step 4: 10 g of the phosphorus-doped carbon support prepared in step 3 was placed in a 250 ml reactor, 100 ml of a 50 wt.% ammonium chloride solution was added, and nitrogen was introduced into the reactor to 1 MPa to replace the air. After three times of replacement, the nitrogen was introduced to 3 MPa and maintained. The reactor was heated to 120 ° C. and stirred for 12 hours. The mixture was filtered to obtain a retentate, which was dried at 100 ° C. for 12 hours to obtain 10.7 g of a nitrogen-phosphorus co-doped carbon support. The reactor may be a magnetic stainless steel reactor. The stirring rate is 600 rpm.

[0091] Step 5. Dissolve 3 g of the nitrogen and phosphorus co-doped carbon support described in step 4, 5.333 g of chloroplatinic acid and 1 g of polyvinyl pyrrolidone in 100 g of an ethanol-isopropanol mixed solution, stir for 6 hours, then heat to 110 ° C. and reflux for 5 hours, cool, filter, wash until there is no chloride ion, and dry in a vacuum oven at 60 ° C. for 12 hours to obtain an oxygen reduction catalyst; the ethanol-isopropanol mixed solution contains 43.4 g of ethanol and 56.6 g of isopropanol; the stirring rate is 600 rpm, and the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30 with a molecular weight of 44,000 to 54,000.

[0092] Performance Testing

[0093] The electrochemical performance of the oxygen reduction catalysts of Examples 1 to 7 and Comparative Examples 1 to 4 was tested using an electrochemical workstation and a rotating disk electrode. The test method includes: taking 3 mg of the catalysts of Examples 1 to 7 and Comparative Examples 1 to 4, respectively, dissolving them in a mixed solution consisting of 0.4 ml of isopropanol and 0.2 ml of deionized water, ultrasonicating for 10 minutes, measuring 30 μL of 5 wt% Nafion solution with a pipette, adding it to the ultrasonic mixed solution, continuing ultrasonic dispersion in an ice bath for 30 minutes, taking 6 μL of the dispersed system and coating it on a glassy carbon electrode with a diameter of 5 mm, drying it naturally to make a working electrode, using a standard hydrogen electrode as a reference electrode and a platinum wire as a counter electrode to form a three-electrode electrochemical system, and conducting electrochemical performance tests in a 0.1 M perchloric acid solution under nitrogen and oxygen conditions, respectively, wherein the voltage scan range under nitrogen conditions is 0 to 0.5 V and the scan rate is 20 mV / s, and the voltage scan range under oxygen conditions is 0 to 0.5 V and the scan rate is 10 mV / s. The test results are shown in Table 1.

[0094] Table 1 Electrochemical performance test results of Examples 1 to 7 and Comparative Examples 1 to 4

[0095]

[0096] In Table 1, the calculation method of mass specific activity MA is: MA = I k / [L Pt *Ag]

[0097] Among them: I k =I lim *i(I lim -i);

[0098] MA: mass specific activity, unit: mA / mg Pt ;

[0099] I k : kinetic current, unit is mA;

[0100] L pt : The amount of platinum loaded on the glassy carbon electrode, in mg Pt / cm 2 , where mg Pt is the mass of Pt;

[0101] Ag: area of glassy carbon electrode, in cm 2 ;

[0102] I lim : limiting current density, in mA;

[0103] i: LSV measures the current at a given voltage, in mA, and the given voltage is 0.9V.

[0104] The calculation method of electrochemical active area ECSA is: ECSA = Q H *10 5 / [210*L Pt *Ag]

[0105] Where: ECSA: electrochemically active area, unit is m 2 / g Pt ;

[0106] Q H : adsorption charge of hydrogen, unit is C;

[0107] L Pt : The amount of platinum loaded on the glassy carbon electrode, in mg Pt / cm 2 , where mg Pt is the mass of Pt;

[0108] 210 is the specific charge, in μC / cm2 ;

[0109] Ag: area of glassy carbon electrode, in cm 2 ;

[0110] As shown in Table 1, the catalyst mass specific activity and electrochemical active area of Example 5 are both higher than those of Comparative Example 1, indicating that the carbon support prepared using castor bean shells as raw materials can be successfully used as a fuel cell catalyst support and has obvious advantages over commercial carbon black.

[0111] The catalyst mass specific activity, electrochemical active area and durability at 30k cycles of Example 5 are all higher than those of Comparative Examples 2, 3 and 4, indicating that by using castor seed shells as a carrier and co-doping nitrogen and phosphorus elements, nitrogen and phosphorus elements can be successfully incorporated into the skeleton structure of the carbon material, creating active sites, effectively enhancing the interaction between metal platinum and the carbon carrier, and significantly improving its electrocatalytic activity and durability.

[0112] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A catalyst for oxygen reduction, characterized in that It comprises a carbon support and a metal component Pt supported on the carbon support, wherein the carbon support is a carbon support prepared from castor bean shell as a raw material; The method for preparing the carbon support comprises: subjecting castor bean shell to pyrolysis treatment, graphitization treatment, phosphorus doping treatment and nitrogen doping treatment to obtain the carbon support; the pyrolysis treatment comprises: subjecting the castor bean shell to pyrolysis treatment at a temperature of 600°C to 1000°C under vacuum conditions for 1 hour to 8 hours; the graphitization treatment comprises: subjecting the pyrolysis-treated material to graphitization treatment at a temperature of 1000°C to 2000°C under vacuum conditions for 5 hours to 36 hours; the phosphorus doping treatment comprises: subjecting the graphitized material to a phosphorus-containing compound solution at 80°C to 1000°C for 1 hour to 8 hours; ℃ and stirring for 8h to 24h; the concentration of the phosphorus-containing compound in the phosphorus-containing compound solution is 20wt.% to 60wt.%, and the phosphorus-containing compound is phosphoric acid, sodium dihydrogen phosphate or aminotri(methylenephosphonic acid); the nitrogen doping treatment comprises: placing the material after the phosphorus doping treatment in a nitrogen-containing compound solution, and stirring at 80℃ to 200℃ for 4h to 12h in a nitrogen atmosphere of 1MPa to 5MPa; the concentration of the nitrogen-containing compound in the nitrogen-containing compound solution is 20wt.% to 60wt.%, and the nitrogen-containing compound is ammonia water, ammonium chloride or melamine.

2. A method for preparing the oxygen reduction catalyst according to claim 1, comprising: The carbon support, chloroplatinic acid and polyvinyl pyrrolidone are dissolved in an ethanol-isopropanol mixed solution, refluxed, cooled, filtered, washed until no chloride ions are present, and dried to obtain an oxygen reduction catalyst.

3. The method according to claim 2, characterized in that The mass of the chloroplatinic acid is 1.78 times the mass of the carbon support, and the mass of the polyvinyl pyrrolidone is 1 / 3 times the mass of the carbon support.

4. The method according to claim 2, characterized in that The reflux temperature was 110°C.

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