Preparation method of methyl cellulose-based oxygen reduction electrocatalyst

Abstract

The invention discloses a preparation method of a methylcellulose-based oxygen reduction electrocatalyst, and belongs to the technical field of catalysts. The invention aims to solve the problems that the characteristic that existing cellulose is easy to agglomerate is not beneficial to uniform dispersion of metal and formation of a porous structure, and the development of the cellulose in the field of catalysis is limited. The method comprises the following steps: 1, adding a metal precursor, a coordination precursor, a salt template and methyl cellulose into hot water, stirring and dispersing, stirring in an ice-water bath until the solution becomes thick, freezing into a solid, and finally freeze-drying; 2, high-temperature calcination; and 3, grinding, centrifugally washing and drying. The method is used for preparing the methyl cellulose-based oxygen reduction electrocatalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts. Background Art

[0002] With the growing energy demand and the shortage of fossil fuel resources worldwide, efficient renewable energy technologies have received widespread attention. Electrocatalytic processes involving oxygen, especially the oxygen reduction reaction (ORR), are crucial in various contemporary energy storage and conversion systems, including rechargeable metal-air batteries. However, the commercialization of these electrocatalytic energy technologies is still hindered by the sluggish ORR kinetics at the cathode, and high-performance electrocatalysts such as platinum group metal materials are required to accelerate the ORR kinetics. The scarcity and high cost of platinum group metal materials limit the large-scale practical application of the above-mentioned electrocatalytic energy technologies, so the development of low-cost and highly active catalysts is crucial to accelerate the application of these clean energy sources.

[0003] In recent years, transition metal and carbon composite catalysts have been widely studied due to their low cost and high activity. Many studies have used metal organic frameworks, biomass materials, organic polymers, etc. as carbon sources, combined with heteroatom doping, template method and other strategies to construct catalysts with high ORR activity. Cellulose, as a common biomass material, has large natural reserves and is renewable. However, its easy agglomeration is not conducive to the uniform dispersion of metals and the formation of porous structures, limiting its further development in the field of catalysis. Summary of the invention

[0004] The present invention aims to solve the problem that the existing cellulose is easy to agglomerate, which is not conducive to the uniform dispersion of metals and the formation of a porous structure, thus limiting its development in the field of catalysis, and further provides a method for preparing a methylcellulose-based oxygen reduction electrocatalyst.

[0005] A method for preparing a methylcellulose-based oxygen reduction electrocatalyst is carried out according to the following steps:

[0006] 1. Add the metal precursor, coordination precursor, salt template and methyl cellulose into hot water, stir and disperse, then stir in an ice water bath until the solution becomes viscous, then freeze into a solid, and finally freeze-dry to obtain a freeze-dried solid;

[0007] 2. Under protective gas, the freeze-dried solid is heated to 700°C to 1200°C at a heating rate of 3°C / min to 40°C / min, and then calcined at high temperature for 1h to 4h under the conditions of protective gas and temperature of 700°C to 1200°C, and finally cooled to room temperature to obtain a high-temperature calcined solid;

[0008] 3. The solid after high-temperature calcination is ground, then centrifuged and washed to remove the salt template, and finally dried to obtain a methylcellulose-based oxygen reduction electrocatalyst.

[0009] The beneficial effects of the present invention are:

[0010] 1. In the preparation method of the present invention, the methyl cellulose presents different states in aqueous solutions at different temperatures, can be evenly dispersed with other raw materials in hot water, and gradually becomes viscous as the temperature of the aqueous solution decreases. Therefore, no sedimentation and agglomeration will occur during the freezing process, thereby maintaining a porous structure and uniform dispersion of loaded particles. The methyl cellulose production process is mature, which is conducive to large-scale production.

[0011] 2. In the preparation method of the present invention, the methyl cellulose contains a large amount of methoxyl groups, which can achieve a large amount of uniform oxygen doping during high-temperature calcination. In addition, it is also conducive to the formation of carbon defects and enhances the ORR electrocatalytic activity.

[0012] 3. The methyl cellulose used in the present invention has the property of swelling by absorbing water. When combined with the salt template method, it can form a large number of hierarchical porous structures, which is beneficial to the loading of active sites and the transfer of substances during the reaction process.

[0013] 4. The oxygen reduction half-wave potentials of the Co / N@C-NaCl, Fe / NS@C-NaCl and N@C electrocatalysts of the present invention are 0.90 V, 0.96 V and 0.96 V respectively; the energy density of the assembled zinc-air battery is 813 mAh g -1 , 813mAh g -1 and 814mAhg -1 The ultimate power density of the assembled zinc-air battery is 113.4 mW cm -2 、114.1mW cm -2 and 198.2 mW cm -2 ; has excellent ORR activity. In addition, the zinc-air battery assembled based on the above three electrocatalysts also has good cycle stability.

[0014] 5. The method of the present invention is simple, highly practical, and easy to realize industrial production.

[0015] Instruction Manual

[0016] Figure 1 The viscous solution after stirring in an ice-water bath in step 1 of Examples 1 and 2 is left standing for 12 hours under refrigeration conditions (5° C.), a is Example 1, and b is Example 2;

[0017] Figure 2X-ray diffraction patterns of Co / N@C-NaCl, Fe / NS@C-NaCl and N@C;

[0018] Figure 3 This is the scanning electron microscope image of Co / N@C-NaCl;

[0019] Figure 4 is the scanning electron microscope image of Fe / NS@C-NaCl;

[0020] Figure 5 is the scanning electron microscope image of N@C;

[0021] Figure 6 Transmission electron microscope image of Co / N@C-NaCl;

[0022] Figure 7 TEM image of Fe / NS@C-NaCl;

[0023] Figure 8 TEM image of N@C;

[0024] Fig. 9 The pore size distribution diagram of Fe / NS@C-NaCl and N@C;

[0025] Fig.10 X-ray photoelectron spectra of Co / N@C-NaCl, Fe / NS@C-NaCl and N@C;

[0026] Fig.11 It is the S spectrum in the X-ray photoelectron spectrum of Fe / NS@C-NaCl;

[0027] Fig.12 LSV curves were tested for oxygen reduction catalytic activity of Co / N@C-NaCl, Fe / NS@C-NaCl, N@C and commercially purchased 20% Pt / C;

[0028] Fig.13 A comparison chart of the energy density test results of Co / N@C-NaCl, Fe / NS@C-NaCl, N@C and commercially purchased 20% Pt / C in zinc-air battery tests;

[0029] Fig.14 The discharge polarization curves and power density curves of Co / N@C-NaCl, Fe / NS@C-NaCl, N@C and commercially purchased 20% Pt / C in zinc-air battery tests;

[0030] Fig.15 The Zn-air battery assembled with Co / N@C-NaCl, commercially purchased 20% Pt / C and RuO2 at 5 mA cm -2 The charge and discharge cycle life test diagram under current density;

[0031] Fig.16 The Zn-air battery assembled for Fe / NS@C-NaCl at 5 mA cm -2 Stability test diagram of continuous discharge under current density;

[0032] Fig.17 The Zn-air battery assembled by mixing N@C and RuO2 has a high current density of 5 mA cm -2 Charge and discharge cycle life test diagram under current density. DETAILED DESCRIPTION

[0033] Specific embodiment 1: This embodiment is a method for preparing a methylcellulose-based oxygen reduction electrocatalyst, which is carried out according to the following steps:

[0034] 1. Add the metal precursor, coordination precursor, salt template and methyl cellulose into hot water, stir and disperse, then stir in an ice water bath until the solution becomes viscous, then freeze into a solid, and finally freeze-dry to obtain a freeze-dried solid;

[0035] 2. Under protective gas, the freeze-dried solid is heated to 700°C to 1200°C at a heating rate of 3°C / min to 40°C / min, and then calcined at high temperature for 1h to 4h under the conditions of protective gas and temperature of 700°C to 1200°C, and finally cooled to room temperature to obtain a high-temperature calcined solid;

[0036] 3. The solid after high-temperature calcination is ground, then centrifuged and washed to remove the salt template, and finally dried to obtain a methylcellulose-based oxygen reduction electrocatalyst.

[0037] The beneficial effects of this embodiment are:

[0038] 1. In the preparation method of this embodiment, the methyl cellulose presents different states in aqueous solutions at different temperatures. It can be evenly dispersed with other raw materials in hot water, and gradually becomes viscous as the temperature of the aqueous solution decreases. Therefore, no sedimentation and agglomeration will occur during the freezing process, thereby maintaining a porous structure and uniform dispersion of loaded particles. The methyl cellulose production process is mature, which is conducive to large-scale production.

[0039] 2. In the preparation method of this embodiment, the methyl cellulose contains a large amount of methoxyl groups, which can achieve a large amount of uniform oxygen doping during high-temperature calcination. In addition, it is also conducive to the formation of carbon defects and enhances the ORR electrocatalytic activity.

[0040] 3. The methyl cellulose used in this embodiment has the property of swelling by absorbing water. When combined with the salt template method, it can form a large number of hierarchical porous structures, which is beneficial to the loading of active sites and the transfer of substances during the reaction process.

[0041] 4. The oxygen reduction half-wave potentials of Co / N@C-NaCl, Fe / NS@C-NaCl and N@C electrocatalysts in this embodiment are 0.90 V, 0.96 V and 0.96 V respectively; the energy density of the assembled zinc-air battery is 813 mAh g -1 , 813mAh g -1 and 814mAh g -1 The ultimate power density of the assembled zinc-air battery is 113.4 mW cm -2 、114.1mW cm -2 and 198.2mWcm -2 ; has excellent ORR activity. In addition, the zinc-air battery assembled based on the above three electrocatalysts also has good cycle stability.

[0042] 5. The method of the present invention is simple, highly practical, and easy to realize industrial production.

[0043] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the metal precursor in step 1 is one or a combination of ferric nitrate, ferric chloride, cobalt nitrate and cobalt chloride. Other aspects are the same as those in specific embodiment 1.

[0044] Specific embodiment 3: This embodiment is different from specific embodiment 1 or 2 in that the coordination precursor described in step 1 is one or a combination of thiourea, sodium hypophosphite, urea and ammonium chloride. Others are the same as specific embodiment 1 or 2.

[0045] Specific embodiment 4: This embodiment differs from one of specific embodiments 1 to 3 in that the salt template in step 1 is one or two of sodium chloride and potassium chloride. The rest is the same as specific embodiments 1 to 3.

[0046] Specific embodiment 5: This embodiment is different from specific embodiments 1 to 4 in that: the mass ratio of the metal precursor to methyl cellulose in step 1 is (0-1):1; the mass ratio of the coordination precursor to methyl cellulose in step 1 is (1-4):1; the mass ratio of the salt template to methyl cellulose in step 1 is (0-1):1; the mass ratio of the hot water to methyl cellulose in step 1 is (10-40):1; the temperature of the hot water in step 1 is 50°C to 90°C. Others are the same as specific embodiments 1 to 4.

[0047] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that: the ice water bath described in step 1 is stirred until the solution becomes viscous, specifically, under the conditions of a temperature of 0°C to 10°C and a stirring speed of 20r / min to 100r / min, stirring for 10min to 40min until the solution becomes viscous. Other aspects are the same as specific embodiments 1 to 5.

[0048] Specific embodiment 7: This embodiment is different from Specific embodiments 1 to 6 in that the freezing into solid in step 1 is specifically performed at a temperature of -18°C to -30°C for 6h to 24h. The rest is the same as Specific embodiments 1 to 6.

[0049] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the freeze drying in step 1 is carried out at a temperature of -30°C to -50°C for 12h to 48h. The rest is the same as specific embodiments 1 to 7.

[0050] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the protective gas in step 2 is one or a combination of nitrogen, helium, neon, argon, krypton and xenon. The rest is the same as specific embodiments 1 to 8.

[0051] Specific embodiment 10: This embodiment differs from Specific embodiments 1 to 9 in that: in step 3, the salt template is removed by centrifugal washing with water as a detergent at a rotation speed of 7000 r / min to 9000 r / min, and finally dried for 12 h to 24 h at a temperature of 50° C. to 80° C. The rest is the same as Specific embodiments 1 to 9.

[0052] The following examples are used to verify the beneficial effects of the present invention:

[0053] Embodiment 1:

[0054] A method for preparing a methylcellulose-based oxygen reduction electrocatalyst is carried out according to the following steps:

[0055] 1. Add the metal precursor, coordination precursor, salt template and methyl cellulose into hot water, stir and disperse, then stir in an ice water bath until the solution becomes viscous, then freeze into a solid, and finally freeze-dry to obtain a freeze-dried solid;

[0056] 2. Under protective gas, the freeze-dried solid was heated to 900°C at a heating rate of 5°C / min, and then calcined at high temperature for 2h under the conditions of protective gas and temperature of 900°C, and finally cooled to room temperature to obtain a high-temperature calcined solid;

[0057] 3. The solid after high-temperature calcination is ground, then centrifuged and washed to remove the salt template, and finally dried to obtain a methylcellulose-based oxygen reduction electrocatalyst, namely Co / N@C-NaCl.

[0058] The metal precursor described in step 1 is cobalt nitrate.

[0059] The coordination precursor described in step 1 is ammonium chloride.

[0060] The salt template described in step 1 is sodium chloride.

[0061] The mass ratio of the metal precursor described in step one to methyl cellulose is 0.03:1; the mass ratio of the coordination precursor described in step one to methyl cellulose is 1:1; the mass ratio of the salt template described in step one to methyl cellulose is 1:1; the mass ratio of the hot water described in step one to methyl cellulose is 40:1; the temperature of the hot water described in step one is 80°C.

[0062] The ice water bath in step 1 is stirred until the solution becomes viscous, specifically, under the conditions of a temperature of 0° C. and a stirring speed of 50 r / min, stirring for 20 min until the solution becomes viscous.

[0063] The freezing into a solid in step 1 specifically involves freezing at a temperature of -24°C for 12 hours.

[0064] The freeze drying described in step 1 is specifically freeze drying at a temperature of -50°C for 48 hours.

[0065] The protective gas in step 2 is nitrogen.

[0066] In step 3, the solid after high-temperature calcination is ground into powder with a mortar, and then centrifuged and washed with water as a detergent at a rotation speed of 9000 r / min to remove the salt template, and finally dried at a temperature of 80° C. for 12 hours.

[0067] Example 2: This example is different from Example 1 in that: the metal precursor in step 1 is ferric nitrate; the coordination precursor in step 1 is a combination of thiourea and ammonium chloride, and the mass ratio of thiourea and ammonium chloride is 0.4:1; the mass ratio of the metal precursor to methyl cellulose in step 1 is 0.07:1; the mass ratio of the coordination precursor to methyl cellulose in step 1 is 1.4:1; the hot water temperature in step 1 is 50°C; and step 3 obtains a methyl cellulose-based oxygen reduction electrocatalyst, namely Fe / NS@C-NaCl. The rest is the same as Example 1.

[0068] Example 3: This example is different from Example 1 in that: the metal precursor and salt template are omitted in step 1; the mass ratio of the coordination precursor to methyl cellulose in step 1 is 2:1; the hot water temperature in step 1 is 50°C; the heating rate in step 2 is 20°C / min; and the methyl cellulose-based oxygen reduction electrocatalyst, namely N@C, is obtained in step 3. The rest is the same as Example 1.

[0069] Figure 1 The viscous solution after stirring in an ice-water bath in step 1 of Examples 1 and 2 is left standing under refrigeration conditions (5° C.) for 12 hours, a for Example 1 and b for Example 2. As can be seen from the figure, the solution does not show obvious stratification and the raw materials are still evenly dispersed.

[0070] Figure 2 The X-ray diffraction patterns of Co / N@C-NaCl, Fe / NS@C-NaCl and N@C are shown in Figure 1. As can be seen from the figure, Co / N@C-NaCl is a carbon material loaded with Co; Fe / NS@C-NaCl is a carbon material loaded with Fe3O4; and N@C is composed only of carbon materials. In addition, no NaCl peak was observed in the diffraction patterns of Co / N@C-NaCl and Fe / NS@C-NaCl, indicating that the salt template has been completely eluted.

[0071] Figure 3 This is the scanning electron microscope image of Co / N@C-NaCl; Figure 4 is the scanning electron microscope image of Fe / NS@C-NaCl; Figure 5 The scanning electron microscope image of N@C shows that Co / N@C-NaCl, Fe / NS@C-NaCl and N@C all have rich hierarchical pore structures. This porous structure is partly formed by the swelling of methylcellulose and partly from the washed-off salt template.

[0072] Figure 6 Transmission electron microscope image of Co / N@C-NaCl; Figure 7 TEM image of Fe / NS@C-NaCl; Figure 8 The transmission electron microscope image of N@C shows that Co / N@C-NaCl and Fe / NS@C-NaCl are porous carbons loaded with Co nanoparticles and Fe3O4 nanoparticles (the size of the nanoparticles is within 150nm), respectively, and the loaded particles are evenly dispersed. In addition, the surfaces of the three carbon material samples in the figure also have defect structures of varying degrees (as indicated by the circles in the figure), which is conducive to the improvement of ORR activity.

[0073] Fig. 9 The pore size distribution diagram of Fe / NS@C-NaCl and N@C. It can be seen from the figure that the specific surface areas of Fe / NS@C-NaCl and N@C are 1350.6m 2 / g and 985.2m 2 / g, and the sample surface also has a large number of mesopores and micropores in a hierarchical porous structure.

[0074] Fig.10 The X-ray photoelectron energy spectra of Co / N@C-NaCl, Fe / NS@C-NaCl and N@C are shown in Figure 1. As can be seen from the figure, the S element doped in Fe / NS@C-NaCl has no obvious peak in the overall spectrum due to its low content. Fig.11 The S spectrum in the X-ray photoelectron spectrum of Fe / NS@C-NaCl; as can be seen from the figure, the fine spectrum shows the doping of S element in Fe / NS@C-NaCl. In addition, the three groups of samples not only contain N doping, but also contain a large amount of O doping, which is attributed to the methoxyl group of methylcellulose.

[0075] ORR catalytic activity test ( Fig.12 ) was carried out in a 0.1 M potassium hydroxide aqueous solution at room temperature using a three-electrode system. 2 ) as the working electrode, the counter electrode is Pt, and the reference electrode is Ag / AgCl electrode. The electrocatalysts on the working electrode are Co / N@C-NaCl, Fe / NS@C-NaCl, N@C and commercially purchased 20% Pt / C, and the loading amount is 0.5 mg / cm 2 .

[0076] The zinc-air battery test uses a polished zinc plate as the anode, carbon paper coated with a catalyst as the air cathode, and a mixed solution of 6M potassium hydroxide and 0.2M zinc acetate as the electrolyte. When the energy density test ( Fig.13 ), discharge polarization curve and power density curve test ( Fig.14 ) and continuous discharge stability test ( Fig.16 ), the electrocatalysts on the carbon paper were Co / N@C-NaCl, Fe / NS@C-NaCl, N@C or commercially purchased 20% Pt / C, and the loading amount was 1 mg cm -2 ; When the charge and discharge cycle life test ( Fig.15 and Fig.17 ), the electrocatalyst on the carbon paper was a combination of Co / N@C-NaCl and RuO2 (commercially purchased), or a combination of 20% Pt / C (commercially purchased) and RuO2 (commercially purchased), or a combination of N@C and RuO2 (commercially purchased), and the loading amounts of Co / N@C-NaCl, 20% Pt / C, N@C, and RuO2 were all 1 mg cm -2 .

[0077] Fig.12LSV curves were tested for the oxygen reduction catalytic activity of Co / N@C-NaCl, Fe / NS@C-NaCl, N@C and commercially purchased 20% Pt / C; the oxygen reduction half-wave potentials of Co / N@C-NaCl, Fe / NS@C-NaCl and N@C were 0.90V, 0.96V and 0.96V, respectively, which were all better than 0.88V of commercially purchased 20% Pt / C.

[0078] Fig.13 Comparison of the energy density test results of Co / N@C-NaCl, Fe / NS@C-NaCl, N@C and commercially purchased 20% Pt / C in zinc-air battery tests; at 10 mA cm -2 At a current density of 1.3 2.0 ... -1 , 813mAh g -1 and 814mAh g -1 , which is better than the 761mAh g of commercially available 20% Pt / C. -1 .

[0079] Fig.14 The discharge polarization curves and power density curves of Co / N@C-NaCl, Fe / NS@C-NaCl, N@C and commercially purchased 20% Pt / C in the zinc-air battery test; It can be seen from the figure that the ultimate power density of the zinc-air battery assembled by Co / N@C-NaCl, Fe / NS@C-NaCl and N@C is 113.4mWcm -2 、114.1mWcm -2 and 198.2 mW cm -2 , better than Pt / C's 104.4mWcm -2 .

[0080] Fig.15 The Zn-air battery assembled with Co / N@C-NaCl, commercially purchased 20% Pt / C and RuO2 at 5 mA cm -2 The charge and discharge cycle life test diagram under current density; it can be seen from the figure that the zinc-air battery assembled by Co / N@C-NaCl did not undergo obvious diffusion after 200h of stability test, which is better than the commercially purchased 20% Pt / C.

[0081] Fig.16 The Zn-air battery assembled for Fe / NS@C-NaCl at 5 mA cm -2 Stability test diagram of continuous discharge under current density; continuous discharge was carried out by replacing the zinc sheet. After 623h of continuous discharge, the voltage did not decrease significantly, indicating that the Fe / NS@C-NaCl catalyst has good stability.

[0082] Fig.17 The Zn-air battery assembled by mixing N@C and RuO2 has a high current density of 5 mA cm -2 The charge and discharge cycle life test diagram under current density; the zinc-air battery assembled by N@C did not undergo obvious diffusion after 380h of stability test, indicating that the N@C catalyst has good stability.

Claims

1. A method for preparing a methylcellulose-based oxygen reduction electrocatalyst, characterized in that It is carried out in the following steps:

1. Add the metal precursor, coordination precursor, salt template and methyl cellulose into hot water, stir and disperse, then stir in an ice water bath until the solution becomes viscous, then freeze into a solid, and finally freeze-dry to obtain a freeze-dried solid; 2. Under protective gas, the freeze-dried solid is heated to 700°C to 1200°C at a heating rate of 3°C / min to 40°C / min, and then calcined at high temperature for 1h to 4h under the conditions of protective gas and temperature of 700°C to 1200°C, and finally cooled to room temperature to obtain a high-temperature calcined solid; 3. The solid after high-temperature calcination is ground, then centrifuged and washed to remove the salt template, and finally dried to obtain a methylcellulose-based oxygen reduction electrocatalyst.

2. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that The metal precursor in step 1 is one of ferric nitrate, ferric chloride, cobalt nitrate and cobalt chloride, or a combination of several of them.

3. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that The coordination precursor described in step 1 is one or a combination of thiourea, sodium hypophosphite, urea and ammonium chloride.

4. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that The salt template described in step 1 is one or two of sodium chloride and potassium chloride.

5. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that The mass ratio of the metal precursor described in step one to methyl cellulose is (0-1):1; the mass ratio of the coordination precursor described in step one to methyl cellulose is (1-4):1; the mass ratio of the salt template described in step one to methyl cellulose is (0-1):1; the mass ratio of the hot water described in step one to methyl cellulose is (10-40):1; the temperature of the hot water described in step one is 50°C to 90°C.

6. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that The ice water bath described in step 1 is stirred until the solution becomes viscous, specifically, at a temperature of 0°C to 10°C and a stirring speed of 20 r / min to 100 r / min, stirring for 10 min to 40 min until the solution becomes viscous.

7. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that The freezing into a solid in step 1 specifically involves freezing at a temperature of -18°C to -30°C for 6h to 24h.

8. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that The freeze drying described in step 1 is specifically freeze drying at a temperature of -30°C to -50°C for 12h to 48h.

9. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that The protective gas in step 2 is one of nitrogen, helium, neon, argon, krypton and xenon, or a combination of several of them.

10. The method for preparing a methylcellulose-based oxygen reduction electrocatalyst according to claim 1, characterized in that At In step 3, the salt template is removed by centrifugal washing at a speed of 7000 r / min to 9000 r / min using water as a detergent. Finally, dry at a temperature of 50°C to 80°C for 12h to 24h.

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