CN102451727B - M/N-C catalyst and preparation and application thereof - Google Patents

Abstract

The present invention relates to non-platinum catalyst, specifically relate to a kind of oxygen reduction catalyst for proton exchange membrane fuel cell and its preparation and application, it can be prepared as follows, (1) the synthesis of polypyrrole (PPy); (2) ) Preparation of M/N-C catalyst; said M/N-C catalyst can be used as cathode oxygen reduction catalyst of proton exchange membrane fuel cell.

Description

A kind of M/N-C catalyst and its preparation and application

technical field

The invention relates to a non-platinum catalyst, in particular to an oxygen reduction catalyst used in a proton exchange membrane fuel cell and its preparation and application. the

Background technique

Fuel cells have the advantages of high energy conversion efficiency, no pollution, no noise, etc., and have attracted people's attention in recent years. In addition to the general characteristics of other fuel cells, proton exchange membrane fuel cells have the advantages of high specific power density and specific energy, rapid startup at room temperature, no electrolyte loss, and long service life. etc. have broad application prospects. the

Catalyst is one of the key materials of proton exchange membrane fuel cell. At present, the widely used catalysts are supported or unsupported catalysts with the noble metal Pt as the main active component, but their limited resources and high cost limit the development of proton exchange membrane fuel cells to a large extent. the

In recent years, researchers have explored non-Pt catalysts. Transition metal macrocycles with Metal- _N structure have aroused great interest of researchers due to their good activity and selectivity for oxygen reduction reaction (ORR). As early as the 1960s, Jasinski et al. reported in Nature that transition metal macrocycles with a Metal-N ₄ structure had catalytic activity for ORR. However, it was found in subsequent studies that such transition metal macrocycles are unstable in acidic media and cannot be practically used in fuel cells. In the 1970s, researchers discovered that the ORR activity and stability of transition metal macrocyclic compounds can be significantly improved by heat treatment under an inert atmosphere. Macrocyclic compounds of transition metals (including Cr, Fe, Mn, Ni, Co, etc.), such as tetraphenylporphyrin (TPP), tetramethoxyphenylporphyrin (TMPP), phthalocyanine (Pc), etc. As electrocatalysts for low-temperature fuel cells, materials have been widely studied. The results show that the main factors affecting the catalytic activity of this type of electrocatalysts include the type of transition metal at the center atom, the type of nitrogen-containing precursor during the catalyst preparation process, and the heat treatment temperature. However, the preparation of catalysts by high temperature pyrolysis of transition metal macrocycles still faces many problems, such as the preparation process of metal macrocycles such as porphyrins or phthalocyanines is relatively complicated, and the commodity price is relatively high. In the 1980s, Gupta et al. prepared ORR catalysts for the first time using macrocyclic compounds with non-N4 structures as N precursors. The advantage of this method is that it can use common inorganic salts, carbon materials, and N-containing compounds as precursors, reducing the cost of catalysts.

Currently, commonly used N precursors are NH ₃ , acetonitrile, pyrrole, N-containing polymers and N-doped carbon supports, etc. Zelenay et al. prepared a Co-PPy composite catalyst (Co-PPy/C) loaded on XC-72R by using polypyrrole (PPy) and XC-72R as a composite carrier and sodium borohydride as a reducing agent. Hydrogen-air fuel cell testing of the cathode showed no significant reduction in electrocatalyst activity during the 100-hour lifetime test. Kunchan Lee et al. compared the catalytic activity of Co-PPy/C composite catalysts before and after heat treatment, and the results showed that the catalytic activity was significantly improved after heat treatment. Although PPy is a conductive polymer, the conductivity of undoped PPy is poor. In order to improve the conductivity of the catalyst, the author uses PPy and carbon materials as composite supports, but PPy and carbon supports are only physically mixed, and the Co supported on the carbon supports cannot interact with PPy and cannot form a Co-N active site structure, resulting in Co The low coordination efficiency with N on PPy reduces the catalytic activity per unit mass of the catalyst.

Contents of the invention

Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a novel non-platinum electrocatalyst for proton exchange membrane fuel cells and its preparation and application. the

In order to achieve the above object, the present invention adopts the following specific schemes to realize:

A kind of M/N-C catalyst, preparation method comprises the following steps,

(1) Synthesis of polypyrrole (PPy):

a. Add pyrrole monomer to the water or ethylene glycol solution of surfactant, wherein the concentration of surfactant ≥ its critical micelle concentration, the concentration of pyrrole monomer is 0.1-2mol·L ^-1 , at 0-25 Stir at ℃ for 0.5-2 hours, then add an oxidant, stir at 0-25°C for 0.5-2 hours to polymerize the pyrrole monomer to generate polypyrrole (PPy), the molar ratio of the oxidant to the pyrrole monomer is 0.5:1-10: 1;

b. Immerse the synthesized PPy into an aqueous methanol solution with a mass percentage of 50-100% to remove residual surfactants and oxidants, then filter, wash, and dry under vacuum at 75°C for 3-6 hours;

(2) Preparation of M/N-C catalyst

a. Add the transition metal salt precursor to the ethylene glycol solution with a concentration of 1-2mol·L ^-1 NaOH, the molar concentration of the transition metal salt is 0.0001-0.05mol·L ^-1 , and then stir at 25-180°C 0.5-3 hours, then add PPy, the transition metal accounts for 0.1-30% of the total mass of the transition metal and PPy, continue to stir for 0.5-3 hours, then add 10-40 times the volume of water and settle under stirring at 25-60°C 1-24 hours;

b. Filter the mixture obtained in step (2)a, wash, and dry for 3-6 hours under vacuum at 30-75°C;

c. heat-treat the sample dried in step (2)b at 500-900° C. for 1-3 hours under an inert gas atmosphere to obtain the target product M/N-C catalyst, and M is one or more of Fe, Co or Ni. the

The oxidizing agent is (NH ₄ ) ₂ S ₂ O ₈ or H ₂ O ₂ or a salt solution of Fe ³⁺ and Cu ²⁺ .

Described surfactant is octadecyltrimethylammonium bromide (OTAB), dodecyltrimethylammonium bromide (DeTAB), dodecyltrimethylammonium bromide (DTAB), hexadecane One or more of trimethylammonium bromide (CTAB), sodium polyacrylate (PAAS) or polyvinylpyrrolidone (PVP). the

The transition metal salt precursor is one or more of iron, cobalt or nickel nitrate, sulfate, acetate, oxalate or chloride. the

The M/N-C catalyst prepared by the above method can be used as a proton exchange membrane fuel cell cathode oxygen reduction catalyst. the

Compared with the prior art, the present invention directly impregnates cobalt salt and polypyrrole (PPy) without adding a carbon carrier, so that after Co and N on PPy interact to form a catalytic center, the sample is directly heat-treated at high temperature to make PPy Thermal decomposition occurs to form a carbon skeleton, which directly serves as the carbon support of the novel catalyst to enhance the conductivity of the catalyst. At the same time, Co and N are in the skeleton of the carbon support, and the stability of the catalyst will be improved. Compared with the preparation of Co-PPy/C catalysts by the traditional method, this method reduces the Co loaded on the carbon support, which improves the coordination efficiency of Co and N on PPy, thereby improving the catalytic activity per unit mass of the catalyst. In addition, the catalyst also has the advantages of simple preparation process, high catalytic activity, strong electrical conductivity, good stability and the like. the

Description of drawings

Fig. 1 compares the XRD spectrogram of the sample prepared according to embodiment 4 and comparative examples 1 and 2;

Fig. 2 is according to embodiment 1, 2, the ORR activity comparison of the sample prepared in 3 and 4 in oxygen-saturated 0.5M _HClO electrolyte solution;

Fig. 3 is according to embodiment 4 and comparative example 1, 2, 3 and 4 prepare the sample in the oxygen-saturated 0.5M _HClO Electrolyte solution ORR activity comparison;

Fig. 4 is the comparison of the ORR activity of samples prepared according to Example 4 and Comparative Examples 1, 2, 3 and 4 in oxygen-saturated 0.1M NaOH electrolyte;

Fig. 5 is according to embodiment 7, and the ORR activity comparison of the sample prepared in oxygen-saturated 0.1M NaOH electrolyte in 8 and 9;

Figure 6 is a comparison of the ORR activity of the sample prepared according to Example 4 before and after the stability test in an oxygen-saturated 0.1M NaOH electrolyte. the

Detailed ways

Below in conjunction with embodiment the present invention is described in detail. Of course, the present invention is not limited to these specific examples. the

Example 1:

First, add pyrrole monomer to the cetyltrimethylammonium bromide (CTAB) ethylene glycol solution with a concentration of 0.8mol·L ^-1 , the concentration of pyrrole monomer is 1mol·L ^-1 , and stir at 0°C After 1 hour, add the oxidant ferric chloride (FeCl ₃ ), stir at 0°C for 2 hours to polymerize the pyrrole monomer to form polypyrrole (PPy), the molar ratio of ferric chloride to pyrrole monomer is 0.5:1 ;

Immerse the synthesized PPy into 100% electro-alcohol aqueous solution to remove residual surfactants and oxidants, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add cobalt nitrate (Co(NO ₃ ) ₂ 6H ₂ O) into ethylene glycol solution B with a concentration of 2 molL ^-1 NaOH, the molar concentration of cobalt nitrate is 0.02 mol L ^-1 , stir at 180°C for 3 hours, Then add the required amount of PPy, cobalt accounts for 30% of the total mass of cobalt and PPy, continue to stir for 2 hours, and then add 40 times the volume of water to settle for 12 hours under stirring at 60°C;

The resulting mixture was filtered, washed, and dried under vacuum at 75°C for 6 hours;

The dried sample was heat-treated at 500° C. for 3 hours under a high-purity nitrogen atmosphere to obtain the target product Co/N-C catalyst. the

Example 2:

First, add pyrrole monomer into cetyltrimethylammonium bromide (CTAB) ethylene glycol solution with a concentration of 0.8mol·L ^-1 , the concentration of pyrrole monomer is 1mol·L ^-1 , and stir at 0°C After 1 hour, add the oxidant ferric chloride (FeCl ₃ ), stir at 0°C for 2 hours to polymerize the pyrrole monomer to form polypyrrole (PPy), the molar ratio of ferric chloride to pyrrole monomer is 0.5:1 ;

Immerse the synthesized PPy into 100% methanol aqueous solution to remove residual surfactant and oxidant, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add cobalt nitrate (Co(NO ₃ ) ₂ ·6H ₂ O) into the ethylene glycol solution with a concentration of 2molL ^-1 NaOH, the molar concentration of cobalt nitrate is 0.02mol·L ^-1 , and then stir at 180°C for 3 hours , then add the required amount of PPy, cobalt accounts for 30% of the total mass of cobalt and PPy, continue to stir for 2 hours, and then add 40 times the volume of water to settle at 60 ° C for 12 hours;

The resulting mixture was filtered, washed, and dried under vacuum at 50°C for 6 hours;

The dried sample was heat-treated at 700°C for 3 hours under a high-purity nitrogen atmosphere to obtain the target product Co/N-C catalyst. the

Example 3:

First, add pyrrole monomer to the cetyltrimethylammonium bromide (CTAB) ethylene glycol solution with a concentration of 0.8mol·L ^-1 , the concentration of pyrrole monomer is 1mol·L ^-1 , and stir at 0°C After 1 hour, add the oxidant ferric chloride (FeCl ₃ ), stir at 20°C for 2 hours to polymerize the pyrrole monomer to form polypyrrole (PPy), the molar ratio of ferric chloride to pyrrole monomer is 0.5:1 ;

Immerse the synthesized PPy into 100% methanol aqueous solution to remove residual surfactant and oxidant, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add cobalt nitrate (Co(NO ₃ ) ₂ ·6H ₂ O) into the ethylene glycol solution with a concentration of 2molL ^-1 NaOH, the molar concentration of cobalt nitrate is 0.02mol L ^-1 , and then stir at 180°C for 3 hours, Then add the required amount of PPy, cobalt accounts for 30% of the total mass of cobalt and PPy, continue to stir for 2 hours, and then add 40 times the volume of water to settle for 12 hours under stirring at 60°C;

The resulting mixture was filtered, washed, and dried under vacuum at 75°C for 6 hours;

The dried sample was heat-treated at 800°C for 3 hours under a high-purity nitrogen atmosphere to obtain the target product Co/N-C catalyst. the

Example 4:

First, add pyrrole monomer to the cetyltrimethylammonium bromide (CTAB) ethylene glycol solution with a concentration of 0.8 mol L ^-1 , the concentration of pyrrole monomer is 1 mol L ^-1 , and stir at 0°C for 1 hour , then add the oxidant ferric chloride (FeCl ₃ ), stir at 0°C for 2 hours to polymerize the pyrrole monomer to generate polypyrrole (PPy), the molar ratio of ferric chloride to pyrrole monomer is 0.5:1;

Immerse the synthesized PPy into 100% methanol aqueous solution to remove residual surfactant and oxidant, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add cobalt nitrate (Co(NO ₃ ) ₂ ·6H ₂ O) into the ethylene glycol solution with a concentration of 2molL ^-1 NaOH, the molar concentration of cobalt nitrate is 0.02mol·L ^-1 , and then stir at 180°C for 3 hours , then add the required amount of PPy, cobalt accounts for 30% of the total mass of cobalt and PPy, continue to stir for 2 hours, and then add 40 times the volume of water to settle at 60 ° C for 12 hours;

The resulting mixture was filtered, washed, and dried under vacuum at 30°C for 6 hours;

The dried sample was heat-treated at 900° C. for 3 hours under a high-purity nitrogen atmosphere to obtain the target product Co/N-C catalyst. the

Embodiment 5:

First, add pyrrole monomer into the sodium polyacrylate aqueous solution with a concentration of 0.2 molL ^-1 , the concentration of pyrrole monomer is 0.1 molL ^-1 , stir at 25°C for 0.5 hour, then add the oxidant (NH ₄ ) ₂ S ₂ O ₈ , Stirring at 25°C for 2 hours to polymerize pyrrole monomers to generate polypyrrole (PPy), the molar ratio of (NH ₄ ) ₂ S ₂ O ₈ to pyrrole monomers is 8:1;

Immerse the synthesized PPy into 60% methanol aqueous solution by mass percentage to remove residual surfactant and oxidant, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add cobalt acetate ((CH ₃ CO ₂ ) ₂ Co) to the ethylene glycol solution with a concentration of 1.5 molL ^-1 NaOH, the molar concentration of cobalt acetate is 0.05 mol L ^-1 , then stir at 160°C for 3 hours, then Add the required amount of PPy, cobalt accounts for 18% of the total mass of cobalt and PPy, continue to stir for 1 hour, and then add 10 times the volume of water to settle at 60°C for 24 hours;

The resulting mixture was filtered, washed, and dried under vacuum at 75°C for 5 hours;

The dried sample was heat-treated at 900° C. for 1 hour under a high-purity nitrogen atmosphere to obtain the target product Co/N-C catalyst. the

Embodiment 6:

First, add pyrrole monomer to the dodecyltrimethylammonium bromide (DTAB) ethylene glycol solution with a concentration of 1molL ^-1 , the concentration of pyrrole monomer is 2molL ^-1 , stir at 25°C for 2 hours, and then add The oxidant iron nitrate (Fe(NO ₃ ) ₃ 6H ₂ O) was stirred at 25°C for 2 hours to polymerize the pyrrole monomer to generate polypyrrole (PPy), and the molar ratio of iron nitrate to pyrrole monomer was 2:1;

Immerse the synthesized PPy into 80% methanol aqueous solution to remove residual surfactants and oxidants, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add cobalt oxalate (CoC ₂ O ₄ ·2H ₂ O) into the ethylene glycol solution with a concentration of 1molL ^-1 NaOH, the molar concentration of cobalt oxalate is 0.001mol L ^-1 , stir at 25°C for 3 hours, then add the The required amount of PPy, cobalt accounted for 5% of the total mass of cobalt and PPy, continued to stir for 3 hours, and then added 30 times the volume of water to settle for 24 hours under stirring at 60°C;

The resulting mixture was filtered, washed, and dried under vacuum at 75°C for 6 hours;

The dried sample was heat-treated at 900°C for 2 hours under a high-purity nitrogen atmosphere to obtain the target product Co/N-C catalyst. the

Embodiment 7:

First, add pyrrole monomer to the cetyltrimethylammonium bromide (CTAB) ethylene glycol solution with a concentration of 1molL ^-1 , the concentration of pyrrole monomer is 1molL ^-1 , stir at 0°C for 1 hour, and then add Oxidant ferric chloride (FeCl ₃ ), stirred at 0°C for 2 hours to polymerize the pyrrole monomer to generate polypyrrole (PPy), the molar ratio of ferric chloride to pyrrole monomer was 0.5:1;

Immerse the synthesized PPy into 100% methanol aqueous solution to remove residual surfactant and oxidant, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add cobalt nitrate (Co(NO ₃ ) ₂ ·6H ₂ O) into the ethylene glycol solution with a concentration of 1molL ^-1 NaOH, the molar concentration of cobalt nitrate is 0.005mol L ^-1 , stir at 120°C for 3 hours, then Add the required amount of PPy, cobalt accounts for 5% of the total mass of cobalt and PPy, continue to stir for 1 hour, and then add 20 times the volume of water to settle for 10 hours under stirring at 40°C;

The resulting mixture was filtered, washed, and dried under vacuum at 75°C for 5 hours;

The dried sample was heat-treated at 900° C. for 3 hours under a high-purity nitrogen atmosphere to obtain the target product Co/N-C catalyst. the

Embodiment 8:

First, add pyrrole monomer to the cetyltrimethylammonium bromide (CTAB) ethylene glycol solution with a concentration of 1molL ^-1 , the concentration of pyrrole monomer is 1molL ^-1 , stir at 0°C for 1 hour, and then add Oxidant iron trichloride (FeCl ₃ ), stirred at 0°C for 2 hours to polymerize the pyrrole monomer to generate polypyrrole (PPy), the molar ratio of ferric chloride to pyrrole monomer was 0.5:1;

Immerse the synthesized PPy into 100% methanol aqueous solution to remove residual surfactant and oxidant, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add iron acetate ((CH ₃ CO ₂ ) ₃ Fe) into the ethylene glycol solution with a concentration of 1molL ^-1 NaOH, the molar concentration of iron acetate is 0.005mol L ^-1 , stir at 140°C for 3 hours, and then add the For the required amount of PPy, iron accounts for 5% of the total mass of iron and PPy, continue to stir for 1 hour, then add 30 times the volume of water and carry out sedimentation for 24 hours under stirring at 60°C;

The resulting mixture was filtered, washed, and dried under vacuum at 75°C for 3 hours;

The dried sample was heat-treated at 900° C. for 3 hours under a high-purity nitrogen atmosphere to obtain the target Fe/N-C catalyst. the

Embodiment 9:

First, add pyrrole monomer to the cetyltrimethylammonium bromide (CTAB) ethylene glycol solution with a concentration of 1molL ^-1 , the concentration of pyrrole monomer is 1molL ^-1 , stir at 0°C for 1 hour, and then add Oxidant iron trichloride (FeCl ₃ ), stirred at 0°C for 2 hours to polymerize the pyrrole monomer to generate polypyrrole (PPy), the molar ratio of ferric chloride to pyrrole monomer was 0.5:1;

Immerse the synthesized PPy into 100% methanol aqueous solution to remove residual surfactant and oxidant, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add nickel sulfate (Ni ₂ SO ₄ ) into the ethylene glycol solution with a concentration of 1molL ^-1 NaOH, the molar concentration of nickel sulfate is 0.005mol L ^-1 , stir at 100°C for 3 hours, and then add the required amount of PPy , nickel accounts for 5% of the total mass of nickel and PPy, continue to stir for 1 hour, then add 10 times the volume of water and carry out sedimentation for 12 hours under stirring at 60 ° C;

The resulting mixture was filtered, washed, and dried under vacuum at 75°C for 5 hours;

The dried sample was heat-treated at 900° C. for 3 hours under a high-purity nitrogen atmosphere to obtain the target product Ni/N-C catalyst. the

Embodiment 10:

First, add pyrrole monomer into the polyvinylpyrrolidone aqueous solution with a concentration of 0.3molL ^-1 , the concentration of pyrrole monomer is 1molL ^-1 , stir at 25°C for 2 hours, then add oxidant hydrogen peroxide (H ₂ O ₂ ), in Stir at 25°C for 2 hours to polymerize the pyrrole monomer to generate polypyrrole (PPy), and the molar ratio of hydrogen peroxide to pyrrole monomer is 10:1;

Immerse the synthesized PPy into 50% methanol aqueous solution to remove residual surfactants and oxidants, then filter, wash, and dry under vacuum at 75°C for 3 hours;

Add cobalt chloride (CoCl ₂ ·6H ₂ O) to the ethylene glycol solution with a concentration of 1molL ^-1 NaOH, the molar concentration of cobalt chloride is 0.001mol L ^-1 , stir at 25°C for 0.5 hours, and then add the The required amount of PPy, cobalt accounted for 0.1% of the total mass of cobalt and PPy, continued to stir for 0.5 hours, and then added 10 times the volume of water to settle at 60 ° C for 24 hours;

The resulting mixture was filtered, washed, and dried under vacuum at 75°C for 3 hours;

The dried sample was heat-treated at 900° C. for 3 hours under a high-purity nitrogen atmosphere to obtain the target product Co/N-C catalyst. the

Comparative example 1:

First, add pyrrole monomer into cetyltrimethylammonium bromide (CTAB) ethylene glycol solution with a concentration of 0.8molL ^-1 , the concentration of pyrrole monomer is 1molL ^-1 , stir at 0°C for 1 hour, and then Add the oxidant ferric chloride (FeCl ₃ ), stir at 0°C for 2 hours to polymerize the pyrrole monomer to form polypyrrole (PPy), and the molar ratio of ferric chloride to pyrrole monomer is 0.5:1;

Immerse the synthesized PPy into 100% methanol aqueous solution to remove residual surfactant and oxidant, then filter, wash, and dry under vacuum at 75°C for 3 hours;

The dried sample was heat-treated at 900°C for 3 hours under a high-purity nitrogen atmosphere to obtain the target product N-C catalyst. the

Comparative example 2:

Add cobalt nitrate (Co(NO ₃ ) ₂ ·6H ₂ O) into the ethylene glycol solution with a concentration of 2molL ^-1 NaOH, the molar concentration of cobalt nitrate is 0.02mol L ^-1 , stir at 180°C for 3 hours, then Add the required amount of carbon carrier Vulcan XC-72R (marked as XC, Cabot company), cobalt accounts for 30% of the total mass of cobalt and XC, continue to stir for 1 hour, then add 40 times the volume of water and carry out under stirring at 60 ° C Settled for 12 hours;

The resulting mixture was filtered, washed, and dried under vacuum at 40°C for 6 hours;

The dried sample was heat-treated at 900° C. for 3 hours under a high-purity nitrogen atmosphere to obtain the target product Co/XC catalyst. the

Comparative example 3:

Commercial 40wt.% Pt/C catalyst (Johnson Matthey Company) was used as a comparison. the

Comparative example 4:

Commercial carbon carrier Vulcan XC-72R (marked as XC, Cabot Company) was used as a comparison. the

FIG. 1 is a comparison of XRD spectra of samples prepared according to Example 4 and Comparative Examples 1 and 2. It can be seen that the N-C catalyst prepared in Comparative Example 1 shows the structural characteristics of carbon materials, and its diffraction peak near 25° belongs to the graphite (002) diffraction peak. Both the Co/N-C catalyst prepared in Example 4 and the Co/XC catalyst prepared in Comparative Example 2 exhibited a face-centered cubic (fcc) structure of metallic Co, with average particle sizes of 18.4 and 21.1 nm, respectively. the

Figure 2 is a comparison of the ORR activity of samples prepared according to Examples 1, 2, 3 and 4 in an oxygen-saturated 0.5M _HClO electrolyte. The rotation speed of the electrode is 1600rpm, and the scan rate is 10mV/s. It can be seen from the figure that as the heat treatment temperature increases, the activity of the catalyst increases accordingly.

3 is a comparison of the ORR activity of samples prepared according to Example 4 and Comparative Examples 1, 2, 3 and 4 in an oxygen-saturated _0.5M HClO electrolyte. The rotation speed of the electrode is 1600rpm, and the scan rate is 10mV/s. It can be seen from Figure 3 that the order of ORR activity is XC<NC<Co/XC<Co/NC<Pt/C. The results show that the carbon material doped with N has ORR activity; at the same time, compared with NC, the addition of Co significantly improves the ORR activity of the Co/NC catalyst; although there is still a certain gap between the activity of the commercial Pt/C catalyst , but compared with Co/XC catalysts obtained by similar preparation methods, Co/NC catalysts have obvious advantages.

Figure 4 is a comparison of the ORR activity of samples prepared according to Example 4 and Comparative Examples 1, 2, 3 and 4 in an oxygen-saturated 0.1M NaOH electrolyte. The rotation speed of the electrode is 1600rpm, and the scan rate is 10mV/s. It can be seen from Figure 4 that the order of ORR activity is XC<Co/XC<N-C<Co/N-C<Pt/C. The results show that the ORR onset oxygen reduction potential of the Co/N-C catalyst is 100-150mV lower than that of the commercial Pt/C catalyst. Although there is still a certain gap with the activity of the commercial Pt/C catalyst, the ORR activity of the Co/N-C catalyst is significantly better than that of Co /XC, its initial oxygen reduction potential shifted about 80mV forward compared with Co/XC, and its half-wave potential shifted forward about 140mV compared with Co/XC. the

Figure 5 is a comparison of the ORR activity of samples prepared according to Examples 7, 8 and 9 in an oxygen-saturated 0.1M NaOH electrolyte. The rotation speed of the electrode is 1600rpm, and the scan rate is 10mV/s. As shown in Fig. 5, the ORR activity of the Co/N-C catalyst with Co as the metal center is greater than that of the Fe/N-C and Ni/N-C catalysts with Fe and Ni as the metal center. the

Fig. 6 is a comparison of the ORR activity of the sample prepared according to Example 4 before and after the stability test in an oxygen-saturated 0.1M NaOH electrolyte. The rotation speed of the electrode is 1600rpm, and the scan rate is 10mV/s. It can be seen that after 1000 cycles of cyclic voltammetry scanning (100mV s ^-1 , -0.8～0.3Vvs.Hg/HgO), the activity of the catalyst has almost no decay, indicating that the Co/NC catalyst has a better performance under the test conditions. stability.

Claims (10)

1. M/N-C catalyst, it is characterized in that: it can prepare as follows,

(1) polypyrrole is synthetic:

A. in the water of surfactant and/or ethylene glycol solution, add pyrrole monomer, surfactant concentrations 〉=its critical micelle concentration wherein, the concentration of pyrrole monomer is 0.1-2molL ^-1, stirred 0.5-2 hour at 0-25 ℃; Add oxidant afterwards, stir at 0-25 ℃ and made pyrrole monomer polymerization reaction take place generation polypyrrole in 0.5-2 hour, the mol ratio of oxidant and pyrrole monomer is 0.5: 1-10: 1;

B. synthetic polypyrrole is impregnated in the methanol aqueous solution that the quality percentage composition is 50-100%,, filters washing, drying afterwards to remove remaining surfactant and oxidant;

(2) M/N-C Preparation of catalysts

A. one or more salt precursor among transition-metal Fe, Co or the Ni being joined concentration is 1-2molL ^-1In the ethylene glycol solution of NaOH, the molar concentration of transition metal salt is 0.0001-0.05molL ^-1Stirred 0.5-3 hour at 25-180 ℃ afterwards, add polypyrrole afterwards, transition metal accounts for the 0.1-30% of transition metal and polypyrrole quality total amount, continue to stir 0.5-3 hour, the water that adds 10-40 times of volume afterwards carried out under 25-60 ℃ of stirring sedimentation 1-24 hour;

B. the mixture that step (2) a is obtained filters, washing, drying;

C. with the sample after step (2) the b oven dry under noble gas atmosphere 500-900 ℃ heat treatment 1-3 hour, obtain target product M/N-C catalyst, M be among Fe, Co or the Ni one or more.

2. M/N-C catalyst according to claim 1, it is characterized in that: step (1) b and step (2) b drying condition are under the 30-75 ℃ of vacuum condition, dry 3-6 hour.

3. M/N-C catalyst according to claim 1, it is characterized in that: described oxidant is (NH ₄) ₂S ₂O ₈Or H ₂O ₂Or Fe ³⁺Cu ²⁺Soluble-salt solution.

4. M/N-C catalyst according to claim 1, it is characterized in that: described surfactant is one or more in octadecyl trimethylammonium bromide (OTAB), ten alkyl trimethyl ammonium bromides (DeTAB), DTAB (DTAB), softex kw (CTAB), Sodium Polyacrylate (PAAS) or the polyvinylpyrrolidone (PVP).

5. M/N-C Preparation of catalysts method, it is characterized in that: it can prepare as follows,

(1) polypyrrole is synthetic:

A. in the water of surfactant and/or ethylene glycol solution, add pyrrole monomer, surfactant concentrations 〉=its critical micelle concentration wherein, the concentration of pyrrole monomer is 0.1-2molL ^-1, stirred 0.5-2 hour at 0-25 ℃; Add oxidant afterwards, stir at 0-25 ℃ and made pyrrole monomer polymerization reaction take place generation polypyrrole in 0.5-2 hour, the mol ratio of oxidant and pyrrole monomer is 0.5: 1-10: 1;

B. synthetic polypyrrole is impregnated in the methanol aqueous solution that the quality percentage composition is 50-100%,, filters washing, drying afterwards to remove remaining surfactant and oxidant;

(2) M/N-C Preparation of catalysts

A. one or more salt precursor among transition-metal Fe, Co or the Ni being joined concentration is 1-2molL ^-1In the ethylene glycol solution of NaOH, the molar concentration of transition metal salt is 0.0001-0.05molL ^-1Stirred 0.5-3 hour at 25-180 ℃ afterwards, add polypyrrole afterwards, transition metal accounts for the 0.1-30% of transition metal and polypyrrole quality total amount, continue to stir 0.5-3 hour, the water that adds 10-40 times of volume afterwards carried out under 25-60 ℃ of stirring sedimentation 1-24 hour;

B. the mixture that step (2) a is obtained filters, washing, drying;

C. with the sample after step (2) the b oven dry under noble gas atmosphere 500-900 ℃ heat treatment 1-3 hour, obtain target product M/N-C catalyst, M be among Fe, Co or the Ni one or more.

6. as M/N-C Preparation of catalysts method as described in the claim 5, it is characterized in that: step (1) b and step (2) b drying condition are under the 30-75 ℃ of vacuum condition, dry 3-6 hour.

7. as M/N-C Preparation of catalysts method as described in the claim 5, it is characterized in that: described oxidant is (NH ₄) ₂S ₂O ₈Or H ₂O ₂Or Fe ³⁺, Cu ²⁺Soluble-salt solution.

8. as M/N-C Preparation of catalysts method as described in the claim 5, it is characterized in that: described surfactant is one or more in octadecyl trimethylammonium bromide (OTAB), ten alkyl trimethyl ammonium bromides (DeTAB), DTAB (DTAB), softex kw (CTAB), Sodium Polyacrylate (PAAS) or the polyvinylpyrrolidone (PVP).

9. as M/N-C Preparation of catalysts method as described in the claim 5, it is characterized in that: one or more in nitrate, sulfate, acetate, oxalates or the chloride that described transition metal salt precursor is iron, cobalt or nickel.

10. the described M/N-C catalyst of claim 1 proton exchange film fuel cell cathodic oxygen reduction catalyst.

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