CN112563517B - A kind of preparation method of rare earth metal doped carbon-based oxygen reduction electrocatalyst - Google Patents

Abstract

A preparation method of a rare earth metal doped carbon-based oxygen reduction electrocatalyst belongs to the technical field of new energy materials and electrocatalysis, and can solve the problem of the existing oxygen reduction electrocatalystThe activity and stability of the catalyst are determined by reacting aromatic compound containing carboxyl/aldehyde group/amino/hydroxyl functional group as carbon source, nitrogen-containing organic compound as nitrogen source, rare earth metal salt and Fe/Co/Ni transition metal salt as metal precursor in proper solvent to form stable metal complex, polymerizing the material in N solvent by means of solvent-thermal method, and final polymerizing₂And roasting and carbonizing at high temperature under the protection of atmosphere, and then carrying out acid washing, washing and centrifuging to obtain the rare earth metal doped carbon-based oxygen reduction electrocatalyst. The rich 4f electrons of the rare earth elements can effectively regulate and control the electronic structure of the catalyst, and the rare earth elements and the Fe/Co/Ni main metal have synergistic effect, so that the activity and the stability of the carbon-based oxygen reduction electrocatalyst are improved.

Description

A kind of preparation method of rare earth metal doped carbon-based oxygen reduction electrocatalyst

technical field

The invention belongs to the technical field of new energy materials and electrocatalysis, and particularly relates to a preparation method of a rare earth metal-doped carbon-based oxygen reduction electrocatalyst.

Background technique

With the rapid development of society, due to the non-renewability and pollution of traditional fossil energy, people's demand for clean energy is more and more urgent. Fuel cells, metal-air batteries and other clean and efficient energy conversion devices have higher conversion efficiency than traditional energy conversion devices through combustion, so they are favored by academia and industry, and are one of the key technologies for widespread use of clean energy in the future. However, the poor activity and stability of cathode oxygen reduction electrocatalysts have always been the core factors hindering the popularization and application of such technologies, and current commercial applications still rely on Pt/C catalysts. Due to the huge scale of energy utilization, Pt/C catalysts are still unable to support the large-scale development of fuel cells and other technologies due to the disadvantages of low natural reserves of precious metal Pt, high price, poor stability, and easy CO and methanol poisoning. Therefore, people are still looking for suitable efficient and cheap alternative catalysts.

Non-precious metal catalysts (NPMCs) are ideal materials to replace Pt/C catalysts. Common NPMCs include non-metallic S, P, O, N, B and other doped pure carbon materials, carbon-based transition metal materials, and transition metal sulfides. , phosphide, oxide, nitride and other non-precious metal catalysts. Among them, carbon-based transition metal catalysts rely on metal-N-C and electron-rich or electron-deficient elements such as S, P, O, N, B and carbon structures to form active sites that can adjust the internal electronic structure of the catalyst, which can significantly reduce oxygen electrocatalysis. The activation energy of the reduction reaction enhances its catalytic performance and stability. The partially filled 4f orbital of rare earth elements can improve the electronic environment. Therefore, the introduction of rare earth metals into carbon-based catalytic materials is expected to improve their oxygen electrocatalytic reduction activity, and the valence change of rare earth elements can make it a reaction site for peroxide intermediates. point, thereby improving the stability of such catalysts.

SUMMARY OF THE INVENTION

Aiming at the problems of activity and stability of the existing oxygen reduction electrocatalyst, the present invention provides a method for preparing a rare earth metal doped carbon-based oxygen reduction electrocatalyst with high catalytic activity and good stability.

The present invention adopts following technical scheme:

A preparation method of a rare earth metal-doped carbon-based oxygen reduction electrocatalyst, comprising the following steps:

In the first step, place nitrogen source, carbon source, rare earth metal salt and Fe/Co/Ni transition metal salt in a container, add solvent, seal and heat to 40-80°C, stir for 4-12h, add formaldehyde, and continue stirring 10-16h to obtain a metal-organic complex precursor;

In the second step, the metal-organic complex precursor obtained in the first step is transferred into the reaction vessel, and the solvothermal reaction is carried out at 100-200 ° C for 20-24 h;

In the third step, the product obtained in the second step is placed in a muffle furnace, heated and oxidized in the air, the oxidation temperature is 150-300 ° C, and the duration is 2-12 h;

In the fourth step, the product obtained in the third step is placed in a tube furnace, and carbonized in a nitrogen atmosphere, the carbonization temperature is 800-1000°C, and the carbonization time is 1-3h;

In the fifth step, the carbonized product obtained in the fourth step is acid-washed with 0.5M sulfuric acid, washed with deionized water until neutral, and centrifuged and dried to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst.

In the first step, the nitrogen source is a nitrogen-containing organic substance, including at least one of melamine, urea, o-phenanthroline, dicyandiamide and bipyridine.

The carbon source described in the first step is an aromatic compound containing carboxyl/aldehyde/amino/hydroxyl functional groups, including 2,4-dihydroxybenzoic acid, 2,4-dihydroxybenzaldehyde, aminophenol, aminobenzoic acid, hydroxyl At least one of quinoline, aminoquinoline, hydroxynaphthalene, aminonaphthalene, hydroxynaphthoic acid, aminonaphthoic acid, hydroxypyridine, carboxypyridine, hydroxypyrrole, and carboxypyrrole.

The rare earth metal salt in the first step includes at least one of lanthanum, cerium, neodymium, samarium, gadolinium, erbium and yttrium hydrated chlorides.

The Fe/Co/Ni transition metal salt in the first step includes at least one of hydrated chlorides of Fe/Co/Ni.

The solvent in the first step includes at least one of water, ethanol and ethylene glycol.

In the first step, the molar ratio of Fe/Co/Ni transition metal salt, rare earth metal salt, carbon source, nitrogen source and formaldehyde is 1:(0.1~0.5):(1~2):(2~5): (1~1).

In the third step, the heating rate of the muffle furnace oxidation is 1-5°C/min.

In the fourth step, the heating rate of carbonization is 1-3°C/min.

The beneficial effects of the present invention are as follows:

Rare earth elements have abundant 4f electrons, and their excellent oxophilic properties and variable valence states can often promote the activity of main catalytic active sites in redox reactions, and are beneficial to the adsorption and migration of oxygen species. At the same time, the doping of rare earth elements can form oxygen vacancies, which is not only conducive to stabilizing the catalyst, but also can effectively control the electronic structure and electron transfer performance of the catalyst. Catalyst activity and stability.

Description of drawings

Fig. 1 ORR linear scan polarization curve of cerium-doped carbon-based Co electrocatalyst (Co(Ce)-61) in 0.1 M KOH of Example 12 of the present invention.

Figure 2 shows the ORR linear scan polarization curves of Ce single-metal doped catalysts in 0.1 M KOH.

Figure 3 shows the ORR linear scan polarization curves of only Co single-metal doped catalysts in 0.1 M KOH.

Figure 4 shows the ORR linear scan polarization curves of the cerium-doped carbon-based Co electrocatalyst (Co(Ce)-61) before and after the stability test in 0.1 M KOH.

Figure 5 is a plot of Tafel slopes for a series of cerium-doped carbon-based Co electrocatalysts.

Figure 6 shows the electron transfer numbers calculated by the K-L equation for a series of cerium-doped carbon-based Co electrocatalysts.

Figure 7 is the XRD diffraction pattern of a series of cerium-doped carbon-based Co electrocatalysts.

Detailed ways

Example 1

Place 11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol lanthanum chloride heptahydrate (LaCl ₃ 7H ₂ O) in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid, washed with deionized water until neutral, centrifuged, and dried to obtain a metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(La)-41, the loading capacity of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 5.85 mA·cm ^-2 , and the onset potential is 0.817 V vs. . RHE.

Example 2

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol gadolinium chloride hexahydrate (GdCl ₃ 6H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Gd)-41, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 4.51 mA·cm ^-2 , and the onset potential is 0.825 V vs . RHE.

Example 3

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol erbium chloride hexahydrate (ErCl ₃ 6H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Er)-41, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 4.96 mA·cm ^-2 , and the onset potential is 0.799 V vs . RHE.

Example 4

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol neodymium chloride hexahydrate (NdCl ₃ 6H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Nd)-41, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 5.18 mA·cm ^-2 , and the onset potential is 0.868 V vs . RHE.

Example 5

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 6.40 mmol samarium chloride hexahydrate (SmCl ₃ 6H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Sm)-21, the loading capacity of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 6.97 mA·cm ^-2 , and the onset potential is 0.887 V vs . RHE, electron transfer number 3.74, Tafel slope 47 mV·dec ^-1 .

Example 6

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol samarium chloride hexahydrate (SmCl ₃ 6H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. . The catalyst number is Co(Sm)-41, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 6.13 mA·cm ^-2 , and the onset potential is 0.880 V vs. . RHE, electron transfer number 3.62, Tafel slope 55 mV·dec ^-1 .

Example 7

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 6.40 mmol yttrium chloride hexahydrate (YCl ₃ 6H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth/alkaline earth-cobalt-nitrogen co-doped catalyst. The catalyst number is Co(Y)-21, the loading capacity of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025rpm is 7.08 mA·cm ^-2 , and the onset potential is 0.875 V vs . RHE, electron transfer number 3.86, Tafel slope 50 mV·dec ^-1 .

Example 8

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol yttrium chloride hexahydrate (YCl ₃ 6H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth/alkaline earth-cobalt-nitrogen co-doped catalyst. The catalyst number is Co(Y)-41, the loading capacity of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 6.80 mA·cm ^-2 , and the onset potential is 0.885 V vs . RHE, electron transfer number 3.78, Tafel slope 53 mV·dec ^-1 .

Example 9

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol yttrium chloride hexahydrate (YCl ₃ 6H ₂ O) were placed in a container Add 18 mL of deionized water and 4 mL of absolute ethanol, stir at 70 °C for 10 h, add 48.9 mmol of formaldehyde and continue to stir for 14 h; then transfer to a hydrothermal kettle and react at 120 °C for 24 h; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Y)-41-70, the loading capacity of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 6.69 mA·cm ^-2 , and the onset potential is 0.881 V vs. RHE, the electron transfer number was 3.63, and the Tafel slope was 47 mV·dec ^-1 .

Example 10

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol yttrium chloride hexahydrate (YCl ₃ 6H ₂ O) were placed in a container Add 18 mL of deionized water and 4 mL of absolute ethanol, stir at 70 °C for 10 h, add 48.9 mmol of formaldehyde and continue to stir for 14 h; then transfer to a hydrothermal kettle and react at 180 °C for 24 h; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Y)-180-41, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 6.99 mA·cm ^-2 , and the onset potential is 0.889 Vvs. RHE, the electron transfer number is 3.87, and the Tafel slope is 49 mV·dec ^-1 .

Example 11

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 6.40 mmol cerium chloride heptahydrate (CeCl ₃ 7H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Ce)-21, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 6.62 mA·cm ^-2 , and the onset potential is 0.888 V vs. . RHE, electron transfer number 4.06, Tafel slope 66 mV·dec ^-1 .

Example 12

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 3.20 mmol cerium chloride heptahydrate (CeCl ₃ 7H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Ce)-41, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 6.46 mA·cm ^-2 , and the onset potential is 0.812 V vs. . RHE, electron transfer number 4.03, Tafel slope 82 mV·dec ^-1 .

Example 13

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 2.13 mmol cerium chloride heptahydrate (CeCl ₃ 7H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol, stir at 50°C for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer to a hydrothermal kettle for 24h reaction at 120°C; Heating up to 280°C for 4 hours at a heating rate of 1°C/min; moving the oxidized product into a tube furnace under nitrogen atmosphere and heating up to 900°C for carbonization at a heating rate of 1°C/min in stages, holding for 2 hours; M dilute sulfuric acid washing, deionized water washing to neutrality, centrifugation, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Ce)-61, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density at 2025 rpm is 7.15 mA·cm ^-2 , and the onset potential is 0.923 V vs . RHE, electron transfer number 4.36, Tafel slope 67 mV·dec ^-1 .

Example 14

11.51 mmol 2,4-dihydroxybenzoic acid, 7.77 mmol melamine, 12.80 mmol cobalt chloride hexahydrate (CoCl ₂ 6H ₂ O) and 1.60 mmol cerium chloride heptahydrate (CeCl ₃ 7H ₂ O) were placed in a container Add 18mL deionized water and 4mL absolute ethanol and stir for 10h, add 48.9mmol formaldehyde and continue to stir for 14h; then transfer into a hydrothermal kettle and react at 120°C for 24h; then transfer into a muffle furnace in air at 1°C/ min heating rate stepwise heating to 280 ℃ for 4h oxidation; transfer the oxidized product into a tube furnace, stepwise heating to 900 ℃ carbonization at a heating rate of 1 ℃/min under nitrogen atmosphere, and holding for 2h; Washing, washing with deionized water until neutral, centrifuging, and drying to obtain a rare earth metal-doped carbon-based oxygen reduction electrocatalyst. The catalyst number is Co(Ce)-81, the loading of the prepared catalyst on the glassy carbon electrode is 0.2018 mg·cm ^-2 , the limiting current density is 6.59 mA·cm ^-2 at 2025 rpm, and the onset potential is 0.875 V vs . RHE, electron transfer number 3.86, Tafel slope 73 mV·dec ^-1 .

Taking the cerium-doped carbon-based Co electrocatalyst (Co(Ce)-61) prepared by the present invention as an example, the rare earth metal-doped carbon-based oxygen reduction electrocatalyst prepared by the present invention and its electrochemical performance are described.

Figure 1 shows the ORR linear scan polarization curve of cerium-doped carbon-based Co electrocatalyst (Co(Ce)-61) in 0.1 M KOH, the onset potential is 0.923 V vs. RHE, and the limiting current density is 5.07 mA ·cm ^-2 . Compared with the single-metal doped catalyst, the onset potential and limiting current density are greatly improved, and the reactivity and conductivity are significantly improved, indicating that rare earth metals and transition metal cobalt have a synergistic effect in the catalytic process.

Figure 2 and Figure 3 show the ORR linear scan polarization curves of single-metal Ce-doped and single-metal Co-doped catalysts in 0.1 M KOH, respectively, and their onset potentials are 0.775 V vs. RHE and 0.880 V vs. For RHE, the limiting current densities are 3.43 mA·cm ^-2 and 4.45 mA·cm ^-2 , respectively.

Figure 4 shows the ORR linear scan polarization curves of the cerium-doped carbon-based Co electrocatalyst (Co(Ce)-61) before and after the stability test in 0.1 M KOH. As can be seen from Figure 4, after 1500 CV cycles (20h), the half-wave potential only shifted negatively by 23mV, and the limiting current density retained 94.8% of the initial value, showing good stability.

Figure 5 shows the Tafel slope of the cerium ^- doped carbon ^- based Co electrocatalyst. kinetic process.

Figure 6 shows the electron transfer number calculated by the K-L equation of the cerium-doped carbon-based Co electrocatalyst series. It can be seen from Figure 6 that the electron transfer number catalyzed by the cerium-doped carbon-based Co electrocatalyst is about 4, indicating that the number of electron transfers catalyzed by the cerium-doped carbon-based Co electrocatalyst is about 4. The electronic path is predominant.

Fig. 7 is the XRD diffraction pattern of the cerium-doped carbon-based Co electrocatalyst series, the diffraction peak of carbon appears at 26°, and the diffraction peaks of Ce and Co are absent, indicating that the particles of metal elements in the catalyst are very small or exist in a single-atom structure .

Claims (8)

1. A preparation method of a rare earth metal doped carbon-based oxygen reduction electrocatalyst is characterized by comprising the following steps: the method comprises the following steps:

firstly, putting a nitrogen source, a carbon source, a rare earth metal salt and a Fe/Co/Ni transition metal salt into a container, adding a solvent, sealing and heating to 40-80 ℃, stirring for 4-12h, adding formaldehyde, and continuously stirring for 10-16h to obtain a metal-organic complex precursor;

the rare earth metal salt comprises at least one of hydrated chlorides of lanthanum, cerium, neodymium, samarium, gadolinium, erbium and yttrium;

the Fe/Co/Ni transition metal salt comprises at least one of hydrated chlorides of Fe/Co/Ni;

secondly, transferring the metal-organic complex precursor obtained in the first step into a reaction container, and carrying out solvothermal reaction for 20-24h at the temperature of 100-200 ℃;

thirdly, placing the product obtained in the second step in a muffle furnace, and heating and oxidizing in air at the temperature of 150-;

fourthly, placing the product obtained in the third step into a tubular furnace, and carbonizing at the temperature of 800-1000 ℃ for 1-3h under the nitrogen atmosphere;

and fifthly, washing the carbonized product obtained in the fourth step by 0.5M sulfuric acid and deionized water to be neutral, and centrifugally drying to obtain the rare earth metal doped carbon-based oxygen reduction electrocatalyst.

2. The method of claim 1, wherein the rare earth metal doped carbon-based oxygen reduction electrocatalyst is prepared by the following steps: in the first step, the nitrogen source is a nitrogen-containing organic substance, and comprises at least one of melamine, urea, phenanthroline, dicyandiamide and bipyridine.

3. The method of claim 1, wherein the rare earth metal doped carbon-based oxygen reduction electrocatalyst is prepared by the following steps: in the first step, the carbon source is an aromatic compound containing carboxyl/aldehyde/amino/hydroxyl functional groups, and comprises at least one of 2, 4-dihydroxybenzoic acid, 2, 4-dihydroxybenzaldehyde, aminophenol, aminobenzoic acid, hydroxyquinoline, aminoquinoline, hydroxynaphthalene, aminonaphthalene, hydroxynaphthoic acid, aminonaphthoic acid, hydroxypyridine, carboxypyridine, hydroxypyrrole and carboxypyrrole.

4. The method of claim 1, wherein the rare earth metal doped carbon-based oxygen reduction electrocatalyst is prepared by the following steps: the solvent in the first step comprises at least one of water, ethanol and ethylene glycol.

5. The method of claim 1, wherein the rare earth metal doped carbon-based oxygen reduction electrocatalyst is prepared by the following steps: in the first step, the molar ratio of the Fe/Co/Ni transition metal salt to the rare earth metal salt to the carbon source to the nitrogen source to formaldehyde is 1: (0.1-0.5): (1-2): (2-5): (1-1).

6. The method of claim 1, wherein the rare earth metal doped carbon-based oxygen reduction electrocatalyst is prepared by the following steps: in the third step, the oxidation heating rate of the muffle furnace is 1-5 ℃/min.

7. The method of claim 1, wherein the rare earth metal doped carbon-based oxygen reduction electrocatalyst is prepared by the following steps: the carbonization temperature rise rate in the fourth step is 1-3 ℃/min.

8. A rare earth metal doped carbon-based oxygen reduction electrocatalyst prepared according to the preparation method of any one of claims 1 to 7.

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