CN107394215B

CN107394215B - Preparation and application of heteroatom-doped functional carbon material

Info

Publication number: CN107394215B
Application number: CN201710572771.1A
Authority: CN
Inventors: 童金辉; 马文梅
Original assignee: Northwest Normal University
Current assignee: Northwest Normal University
Priority date: 2017-07-14
Filing date: 2017-07-14
Publication date: 2020-07-21
Anticipated expiration: 2037-07-14
Also published as: CN107394215A

Abstract

The invention provides a preparation method of a heteroatom-doped functional carbon material, which is characterized in that ionic liquid containing heteroatoms N, B, S, Cl and F is used as a raw material, silica sol is used as a template, physical mixing is carried out in transition metal iron, cobalt and nickel salt solution, high-temperature carbonization is carried out in nitrogen atmosphere, and the template is removed by HF to prepare the heteroatom-doped functional carbon material. The functionalized carbon material has good ORR catalytic activity under acidic and alkaline conditions, excellent methanol poisoning resistance and good stability, shows good HER catalytic activity under acidic conditions, does not contain any noble metal, has low price, is an ORR and HER bifunctional catalyst which is expected to replace commercial Pt/C, and has very good industrial application prospect.

Description

Preparation and application of heteroatom-doped functional carbon material

Technical Field

The invention relates to a heteroatom-doped functionalized carbon material, in particular to a preparation method of a heteroatom-N, B, S, Cl and F-containing functionalized carbon material, which is mainly used as a catalyst for a fuel cell cathode oxygen reduction catalytic reaction (ORR) and an electrolytic water Hydrogen Evolution Reaction (HER), and has a certain application prospect in the technical field of methanol fuel cells.

Background

Fuel cells are attracting widespread attention as energy production devices due to their potential high efficiency, low pollution output, and high specific energy density. Hydrogen is regarded as one of the energy sources promising for replacing the conventional fossil fuel, and is attracting attention as an efficient energy source. In clean energy production, electrolysis of water relies on an efficient electrocatalyst that splits water into hydrogen and oxygen, storing energy in the form of chemical fuel. Fuel cells, in turn, rely to a large extent on efficient electrocatalysts for the reduction of oxygen to water in terms of clean energy utilization. Currently, electrolytic hydro-electro-catalysis research has been focused on developing low-cost, highly active and highly stable cathode materials for replacing precious metals (e.g., Pt). The cathode oxygen reduction reaction is a key step for restricting the development of the fuel cell because of the slow reaction rate. Therefore, the development of efficient ORR and HER bifunctional catalysts is of great importance.

To date, the most efficient catalytic catalysts for ORR and HER are still platinum-based catalysts. However, the use of such catalysts is somewhat limited. On one hand, the platinum catalyst has poor methanol poisoning resistance and poor chemical stability. On the other hand, the high cost of platinum and its limited supply tend to hinder the large-scale application of fuel cells. Therefore, the search for non-noble metals and catalysts without metals ORR and HER is currently the most active and competitive challenge in this research area.

The non-platinum ORR and HER catalysts currently under much research mainly include transition metal oxides, heteroatom-doped carbon materials, etc., and these catalysts have activities very close to or even exceeding those of Pt/C catalysts, especially heteroatom-doped carbon materials such as nitrogen and phosphorus, and have been widely used as electrode materials, catalyst supporting materials, and gas separation and hydrogen storage materials, etc. due to their high electrical conductivity, excellent chemical stability and catalytic activity. Conventional methods for preparing heteroatom-doped carbon materials generally carbonize some polymer precursors with lower vapor pressure, such as Polyacrylonitrile (PAN), phenolic resins, and some natural materials, among others. Non-polymerized carbon material precursors are rare because they have difficulty in forming carbon materials because of their vapor pressure at higher temperatures which is difficult to control. However, an important disadvantage of carbon materials prepared by using polymerized precursors is that it is difficult to form carbon nanocomposites, and the carbon materials obtained therefrom are difficult to use for high-quality encapsulation, and the carbon yield is low, all of which seriously hamper the development and practical application thereof. Therefore, if a carbon material ORR and HER bifunctional catalyst can be prepared by using a carbon material with low volatility and high stability as a carbon source, the production cost of the carbon material can be greatly reduced, and the sustainable development of the carbon material can be realized.

Through proper molecular design and combination, the ionic liquid can be used for directly or indirectly preparing various carbon materials and related nano hybrid catalytic materials, and has wide application prospects.

Based on the special carrier advantages of the mesoporous silicon-based material, the functionalized ionic liquid is used as an organic component and is immobilized in the mesoporous material through a grafting method or a cohydrolysis-polycondensation method to prepare the functionalized ionic liquid hybrid mesoporous silicon-based material, so that the functionalized ionic liquid hybrid mesoporous silicon-based material has the dual advantages of the mesoporous silicon-based material and the functionalized ionic liquid, and the functionalized ionic liquid hybrid mesoporous silicon-based material is a new direction for the immobilization research of the functionalized ionic liquid. The material has the special functions of functionalized ionic liquid, has the advantages of large specific surface area of mesoporous carrier, regular pore channel structure and the like, and is expected to further improve the catalytic performance of the ionic liquid.

Disclosure of Invention

The invention aims to provide a preparation method of a functionalized carbon material containing heteroatoms N, B, S, Cl and F;

another object of the present invention is to provide the use of the above functionalized carbon material containing heteroatoms as catalysts ORR and HER catalysts.

Preparation of heteroatom-doped functionalized carbon material

The catalyst containing hetero atoms of N, B, S, Cl and F has high catalytic activity, strong methanol poisoning resistance and good cyclability, and is expected to replace non-noble metal ORR and HER bifunctional catalysts of Pt/C. Based on the consideration, the heteroatom-doped functionalized carbon material is prepared by taking the ionic liquid containing the heteroatoms N, B, S, Cl and F as a raw material and taking silica sol as a template; physically mixing in a salt solution of transition metals of iron, cobalt and nickel, carbonizing at high temperature in a nitrogen atmosphere, removing a template by using HF, centrifuging, washing, drying and grinding a product to prepare the heteroatom-doped functionalized carbon material ORR and HER bifunctional catalyst.

Wherein the ionic liquid containing heteroatom N, B, S, Cl, F is 1-butyl-3-methylimidazolium chloride ([ BMIm)]Cl), 1-butyl-3-methylimidazolium tetrafluoroborate ([ BMIm)][BF₄]) 1-butyl-3-methylimidazolium hexafluorophosphate ([ BMIm)][PF₆]) 1-butyl-3-methylimidazole trifluoroacetate ([ BMIm)][TA]) 1-butyl-3-methylimidazolium p-methylbenzenesulfonate ([ BMIm)][Tos]) 1-Butylsulfonic acid-3-methylimidazolium chloride salt ([ BMIm)]Cl), 1-butyl-3-methylimidazolium dinitrile amine salt ([ BMIm)][N(CN)₂]) 1-butyl-3-methylimidazolium thiocyanate ([ BMIm)][SCN]) One kind of (1). The mass ratio of the ionic liquid containing the heteroatoms N, B, S, Cl and F to the silica sol is 1: 10-1: 1.

The transition metal iron, cobalt and nickel salt is chloride of iron, cobalt and nickel, and the concentration of the transition metal iron, cobalt and nickel salt solution is 0.05-0.08M; the dosage of the transition metal iron, cobalt and nickel salt is 5-20% of the total mass of the ionic liquid and the template agent.

The physical mixing is to ultrasonically disperse the silica sol and the ionic liquid in a transition metal iron, cobalt and nickel salt solution and stir the mixture for 8 to 12 hours at the temperature of between 50 and 65 ℃.

The temperature of the high-temperature carbonization is 600-1000 ℃, and the carbonization time is 1-8 h.

And etching the template by using HF, wherein the mass percentage of the HF is 10-50%, the etching temperature is 30-50 ℃, and the etching time is 8-16 h.

The heteroatom-doped functional carbon material prepared by the method is marked as aBmimA-T-N-F, wherein a is the mass ratio of silica sol to ionic liquid, A is the anionic species of the ionic liquid, T is the roasting temperature, N is the transition metal species, and F is the mass percentage content of the added transition metal salt. FIGS. 1 and 2 show a carbon material [ BMIm ]][BF₄]SEM and TEM images of-700-Co-20%. As can be seen from fig. 1 and 2, the sample is an ionic liquid coated spherical carbide.

Oxygen reduction and electrolytic water hydrogen evolution performance of two-heteroatom doped functional carbon material

With [ BMIm][BF₄]For example-700-Co-20%, the oxygen reduction and the electrolytic water evolution of hydrogen were carried out in a three-electrode system, the Pt wire electrode was the counter electrode, the Ag/AgCl electrode was the reference electrode, 0.1M KOH, 0.5MH₂SO₄And 0.1MHClO₄Respectively, electrolyte, and rotating speed of the rotating disk electrode is 1600rmp, [ BMIm][BF₄]700-Co-20% alkaline conditions oxygen reduction onset peak potentials reached-0.01V, with oxygen reduction performance comparable to 20% commercial Pt/C catalysts, as shown in FIG. 3. The oxygen reduction performance under acidic conditions was also comparable to the commercial Pt/C catalyst, as shown in figure 4. 0.5MH₂SO₄The electrolyzed water hydrogen evolution overpotential (10 mA/cm) is measured²) It was 240mV, and the Tafel slope was 166mV/dec, as shown in FIG. 5. By using 3M CH₃When the mixed solution of OH and 0.1M KOH is used as the electrolyte for carrying out the catalyst poisoning performance test, the peak potential is reduced to-0.035V, as shown in FIG. 6. After 5000 catalyst circulation scansThe reduction of oxygen reduction performance was not significant as shown in FIG. 7. Therefore, the catalyst is a methanol fuel cell cathode oxygen reduction catalyst with excellent oxygen reduction performance and good anti-poisoning capability, can be used repeatedly, and has good industrial application prospect.

In conclusion, the room temperature molten salt ionic liquid with low volatility and high stability is used as a main raw material, silica sol is used as a template agent, transition metal salt is used as a metal source, the template is removed by HF after high-temperature carbonization, and the heteroatom-doped functional carbon material is prepared.

Drawings

FIG. 1 shows catalyst [ BMim ]][BF₄]SEM image of-700-Co-20%.

FIG. 2 shows catalyst [ BMim ]][BF₄]TEM image of-700-Co-20%.

FIG. 3 shows catalyst [ BMIm][BF₄]Comparison of-700-Co-20% with commercial Pt/C ORR L sv in alkaline conditions.

FIG. 4 shows catalyst [ BMIm][BF₄]700-Co-20% with commercial Pt/C under acidic conditions ((a)₂SO₄(b).0.1MHClO₄) Comparative plot of middle ORR L sv.

FIG. 5 shows catalyst [ BMim ]][BF₄]-700-Co-20% HER (a) L sv and (b) Tafel slope plot.

FIG. 6 shows catalyst [ BMIm][BF₄]L sv plot of 700-Co-20% resistance to methanol poisoning.

FIG. 7 shows catalyst [ BMIm][BF₄]L sv plot for the 700-Co-20% stability test.

FIG. 8 shows catalyst 3 [ BMIm][BF₄]ORR L sv pattern at 700-Co-11%.

FIG. 9 shows catalyst 3 [ BMIm][BF₄]HER (a) L sv at 700-Co-11% and (b) Tafel slope plot.

FIG. 10 shows catalyst [ B ]MIm][BF₄]ORR L sv pattern at 800-Co-20%.

FIG. 11 shows catalyst [ BMim ]][BF₄]-800-Co-20% HER (a) L sv and (b) Tafel slope plot.

FIG. 12 is a graph comparing catalyst [ BMIm ] Cl-700-Co-20% with commercial Pt/C ORR L sv.

FIG. 13 is a graph of the slope of catalyst [ BMIm ] Cl-700-Co-20% HER (a) L sv and (b) Tafel.

FIG. 14 is a graph comparing ORR L sv for catalyst [ BMIm ] Cl-700-Fe-20% with commercial Pt/C.

FIG. 15 is a graph comparing the slopes of catalysts [ BMIm ] Cl-700-Fe-20% HER (a) L sv and (b) Tafel.

FIG. 16 is a graph comparing the ORR L sv for catalyst [ BMIm ] A-700-Co-20% with commercial Pt/C.

FIG. 17 is a graph comparing the slopes of catalysts [ BMIm ] A-700-Co-20% HER (a) L sv and (b) Tafel.

Detailed Description

The preparation of the catalyst of the invention and the performance in the ORR and HER reactions are further illustrated by the following specific examples.

Example one

1. Catalyst [ BMIm][BF₄]Preparation of-700-Co-20%

a. Preparation of doped material: 1g of [ BMIm ]][BF₄]Ultrasonic dissolution with 1g of silica sol in 30M L0.07.07M CoCl₂Magnetically stirring the solution at 60 ℃ for 12 hours, and drying the obtained product to obtain a doped material product;

b. [BMIm][BF₄]preparation of-700-Co-20%: carbonizing the doped material at 700 deg.C for 2h in nitrogen atmosphere, removing template from the obtained carbon material with HF (the carbon material is immersed in HF with mass percentage of 20% for etching for 12 h), centrifuging, washing, drying overnight, and grinding to obtain [ BMIm ]][BF₄]-700-Co-20% carbon material.

2. Oxygen reduction test

Weigh 5mg of [ BMIm ]][BF₄]700-Co-20% adding 0.5m L absolute ethyl alcohol and 10 mu L Nafion (Dupont, 5 wt%) solution, ultrasonic processing for 30min, taking 3 mu L to coat on a glassy carbon electrode, and testing in a three-electrode system, wherein the Pt wire electrode isCounter electrode, Ag/AgCl electrode as reference electrode, glassy carbon electrode coated with catalyst as working electrode, using 0.1M KOH and 0.5MH respectively₂SO₄、0.1MHClO₄The electrolyte was tested with a rotating disk electrode. As shown in FIGS. 3 and 4, when the rotating speed of the rotating disk electrode was 1600rmp and the scanning rate was 0.01V/s, and 0.1M KOH was used as the electrolyte, the initial potential of oxygen reduction was-0.01V and 0.5MH₂SO₄When the electrolyte is used, the initial potential of oxygen reduction is 0.62V, and 0.1MHClO₄In the case of the electrolyte, the initial potential of oxygen reduction is 0.6V.

3. Electrolytic water evolution of hydrogen test

Weigh 5mg of [ BMIm ]][BF₄]700-Co-20% 0.5m L absolute ethanol and 10 μ L Nafion (Dupont, 5 wt%) solution were added, sonicated for 30min, 3 μ L was applied to a glassy carbon electrode, the test was performed in a three-electrode system with a carbon rod as the counter electrode, an Ag/AgCl electrode as the reference electrode, a glassy carbon electrode coated with catalyst as the working electrode, and 0.5MH₂SO₄The test was performed for the electrolyte. As shown in FIG. 5, at a scanning rate of 0.01V/s, the electrolyzed water is used to extract hydrogen over-potential (10 mA/cm)²) The Tafel slope was 240mV and 166 mV/dec.

Example two

1. Catalyst 3 [ BMIm][BF₄]Preparation of-700-Co-11%

a. Preparation of doped material: 1g of [ BMIm ]][BF₄]Was ultrasonically dissolved in 30m L0.07.07 MCoCl together with 3g of silica sol₂In the solution, the solution is magnetically stirred for 12 hours at the temperature of 60 ℃, and the obtained product is dried.

b. 3[BMIm][BF₄]Preparation of-700-Co-11%: the same as in example 1.

2. Oxygen reduction test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 8. As can be seen from FIG. 8, when the rotation speed of the rotating disk electrode was 1600rmp and the scanning rate was 0.01V/s, and 0.1M KOH was used as the electrolyte, the initial potential of oxygen reduction was-0.03V.

3. Electrolytic water evolution of hydrogen test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 9. As can be seen from FIG. 9, during sweepingThe drawing rate is 0.01V/s, 0.5MH₂SO₄When the electrolyte is used, the electrolyzed water is used for hydrogen evolution overpotential (10 mA/cm)²) The Tafel slope was 340mV and 139 mV/dec.

EXAMPLE III

1. Catalyst [ BMIm][BF₄]Preparation of-800-Co-20%

a. Preparation of doped material: the same as in example 1.

b. [BMIm][BF₄]Preparation of-800-Co-20%: carbonizing the material obtained in the step a at 800 ℃ for 2h in a nitrogen atmosphere, removing the template from the obtained carbon material by using HF (the carbon material is immersed in HF with the mass percentage of 20 percent and etched for 12 h), centrifuging and washing a product, drying overnight, and grinding to obtain the BMIm][BF₄]-800-Co-20% carbon material.

2. Oxygen reduction test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 10. As can be seen from FIG. 10, when the rotation speed of the rotating disk electrode was 1600rmp and the scanning rate was 0.01V/s, the oxygen reduction initiation potential was-0.012V when 0.1M KOH was used as the electrolyte.

3. Electrolytic water evolution of hydrogen test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 11. As can be seen from FIG. 11, at a scanning rate of 0.01V/s, at 0.5MH₂SO₄When the electrolyte is used, the electrolyzed water is used for hydrogen evolution overpotential (10 mA/cm)²) The slope of Tafel is 316mV and 143 mV/dec.

Example four

1. Preparation of catalyst [ BMIm ] Cl-700-Co-20%

a. Preparation of doped material: 1g of [ BMIm ]]The Cl and 1g of silica sol were ultrasonically dissolved in 30m L0.07.07 MCoCl₂Magnetically stirring in the solution at 60 deg.C for 12 hr, and oven drying

b. Preparation of [ BMIm ] Cl-700-Co-20%: the same as in example 1.

2. Oxygen reduction test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 12. As can be seen from FIG. 12, when the rotating speed of the rotating disk electrode was 1600rmp and the scanning rate was 0.01V/s, the oxygen reduction initiation potential was-0.015V when 0.1M KOH was used as the electrolyte.

3. Electrolytic water evolution of hydrogen test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 13. As can be seen from FIG. 13, at a scanning rate of 0.01V/s, at 0.5MH₂SO₄When the electrolyte is used, the electrolyzed water is used for hydrogen evolution overpotential (10 mA/cm)²) The Tafel slope is 248mV and 115 mV/dec.

EXAMPLE five

1. Catalyst [ BMIm][BF₄]Preparation of-700-Fe-20%

a. Preparation of doped material: 1g of [ BMIm ]][BF₄]Ultrasonic dissolution with 1g of silica sol in 30m L0.07.07 MFeCl₃In the solution, the solution is magnetically stirred for 12 hours at the temperature of 60 ℃, and the obtained product is dried.

b. [BMIm][BF₄]Preparation of 700-Fe-20%: the same as in example 1.

2. Oxygen reduction test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 14. As can be seen from FIG. 14, when the rotation speed of the rotating disk electrode was 1600rmp and the scanning rate was 0.01V/s, the oxygen reduction initiation potential was-0.002V when 0.1M KOH was used as the electrolyte.

3. Electrolytic water evolution of hydrogen test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 15. As can be seen from FIG. 15, at a scanning rate of 0.01V/s, at 0.5MH₂SO₄When the electrolyte is used, the electrolyzed water is used for hydrogen evolution overpotential (10 mA/cm)²) 359mV for Tafel slope 203 mV/dec.

EXAMPLE six

1. Preparation of catalyst [ BMIm ] A-700-Co-20%

a. Preparation of doped material: 1g of [ BMIm ] is added][TA]、1g [BMIm][ PF₆]Ultrasonic dissolving with 1g of silica sol in 30m L0.07.07 MCoCl₂Magnetically stirring in the solution at 60 deg.C for 12 hr, and oven drying

b. [ BMIm ] A-700-Co-20% preparation: the same as in example 1.

2. Oxygen reduction test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 16. As can be seen from FIG. 16, [ BMIm ] was measured at a rotating speed of 1600rmp of the rotating disk electrode, a scanning rate of 0.01V/s, and 0.1M KOH as the electrolyte][BF₄]the-700-Co-20% oxygen reduction onset potential is closest to commercial Pt/C.

3. Electrolytic water evolution of hydrogen test

The test conditions and methods were the same as in example 1, and the test results are shown in FIG. 17. As can be seen from FIG. 17, at a scanning rate of 0.01V/s, at 0.5MH₂SO₄In the case of an electrolyte, [ BMIm][BF₄]700-Co-20% hydrogen evolution overpotential (10 mA/cm) by electrolysis of water²) Lowest and least Tafel slope.

Claims

1. A preparation method of heteroatom-doped functionalized carbon material comprises the steps of taking ionic liquid containing heteroatoms N, B, S, Cl and F as a raw material, taking silica sol as a template agent, physically mixing in transition metal iron, cobalt and nickel salt solution, carbonizing at high temperature in nitrogen atmosphere, and removing the template by using HF to prepare the heteroatom-doped functionalized carbon material;

the ionic liquid containing the heteroatoms N, B, S, Cl and F is one of 1-butyl-3-methylimidazole chloride salt, 1-butyl-3-methylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole hexafluorophosphate, 1-butyl-3-methylimidazole trifluoroacetate, 1-butyl-3-methylimidazole p-methylbenzenesulfonate, 1-butylsulfonic acid-3-methylimidazole chloride salt, 1-butyl-3-methylimidazole dinitrile amine salt and 1-butyl-3-methylimidazole thiocyanate; the mass ratio of the ionic liquid containing the heteroatoms N, B, S, Cl and F to the silica sol is 1: 10-1: 1;

the transition metal iron, cobalt and nickel salt is chloride of iron, cobalt and nickel, and the dosage of the transition metal iron, cobalt and nickel salt is 5-20% of the total mass of the ionic liquid and the template agent;

the temperature of the high-temperature carbonization is 600-1000 ℃, and the carbonization time is 1-8 h;

2. The method for preparing a heteroatom-doped functionalized carbon material according to claim 1, wherein the heteroatom-doped functionalized carbon material comprises the following steps: the concentration of the transition metal iron, cobalt and nickel salt solution is 0.05-0.08M.

3. The method for preparing a heteroatom-doped functionalized carbon material according to claim 1, wherein the heteroatom-doped functionalized carbon material comprises the following steps: the physical mixing is to ultrasonically disperse the silica sol and the ionic liquid in a transition metal iron, cobalt and nickel salt solution and stir the mixture for 8 to 12 hours at the temperature of between 50 and 65 ℃.

4. The heteroatom-doped functionalized carbon material prepared by the method of claim 1 is used as a catalyst in a fuel cell cathode oxygen reduction catalytic reaction.

5. The heteroatom-doped functionalized carbon material prepared by the method of claim 1 is used as a catalyst in an electrolytic water hydrogen evolution reaction.