A composite nanocatalyst supported on nitrogen-doped carbon and its preparation method and application

Abstract

The present invention discloses a composite nanocatalyst loaded on nitrogen-doped carbon, a preparation method and an application thereof, and belongs to the field of synthesis technology of nanocatalysts. Using nitrogen-doped carbon as a carrier, a complex of a Pt-M intermetallic compound and PtP2 is loaded on the carrier, wherein M is a transition metal atom; the molar ratio of total platinum atoms to transition metal M atoms in the complex of the Pt-M intermetallic compound and PtP2 is 0.3 to 3, and the molar ratio of carbon in the carrier to transition metal M atoms is 1.7 to 37.5. The nanocatalyst of the composite of Pt-M and PtP2 loaded on nitrogen-doped carbon in the present application is applied to catalysts of hydrogen-oxygen fuel cells, metal-air batteries and water electrolysis batteries, and has high catalytic activity and stability. The present invention improves the catalytic activity and stability and solves the disadvantage that metal nanoparticles are easy to agglomerate, and the preparation process is simple, the operation is convenient and the cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesis of nano catalysts, and in particular relates to a composite nano catalyst supported on nitrogen-doped carbon, and a preparation method and application thereof. Background Art

[0002] The development of environmentally friendly, economical and efficient energy conversion technologies such as fuel cells and water electrolysis cells is crucial to solving problems such as the growing energy demand, the rapid consumption of fossil fuels and serious environmental pollution. At present, platinum (Pt) is still the catalyst of choice for key reactions in clean energy technologies such as oxygen reduction reaction (ORR) and hydrogen evolution / oxygen reaction (HER / HOR) due to its unique electronic structure and irreplaceable comprehensive properties. Despite this, the most active Pt catalysts still have some serious defects that hinder their large-scale commercial application. In addition to its small reserves and high price, the dissolution and aggregation of the precious metal Pt in corrosive solutions lead to poor stability and catalytic activity. This requires the use of a large amount of Pt to achieve and maintain the required power density under working conditions. These dilemmas continue to prompt researchers to develop more effective solutions to rationally design Pt-based catalysts with high Pt atom utilization, high activity and stability for various electrocatalytic reactions.

[0003] In order to reduce the Pt content in the catalyst and improve its activity and stability, Pt can be "alloyed" with 3d transition metals M (Fe, Co, Ni, Mn, Zn, Cu, etc.) or non-metals. This method can not only reduce the amount of Pt to reduce costs, but also play the electronic effect of alloying to improve catalytic activity and stability. 2 ) have attracted much attention as multifunctional electrocatalysts due to their high catalytic activity and long-term durability in ORR and HER / HOR in fuel cells and water splitting. Among them, the most commonly used method for synthesizing Pt-M intermetallic compounds is co-reduction by a reducing agent in a liquid phase system and subsequent high-temperature annealing in a hydrogen atmosphere. Generally speaking, the transition from disordered to ordered structure requires heat treatment above 600°C, which inevitably causes nanoparticle aggregation and an increase in particle size, resulting in a decrease in catalytic performance. Summary of the invention

[0004] Based on the problems existing in the prior art, the present application provides a Pt-based intermetallic compound supported on nitrogen-doped carbon and PtP 2 Composite nanocatalyst and its preparation method and application, preparation of PtP in the process of Pt-M alloy ordering 2 , and doping of carbon carriers is completed at the same time. This strategy not only inhibits the 2 The growth of nanoparticles also cleverly combines Pt-M with PtP 2The composite is used as a highly efficient electrocatalyst in electrochemical reactions.

[0005] The specific technical solution adopted by the present invention is:

[0006] The present invention provides a composite nanocatalyst supported on nitrogen-doped carbon, wherein the nitrogen-doped carbon is used as a carrier, and a cubic structure of Pt-M intermetallic compound and PtP are supported on the carrier. 2 The Pt-M intermetallic compound and the PtP 2 The molar ratio of total platinum atoms to transition metal M atoms in the complex is 0.3 to 3, and the molar ratio of carbon in the carrier to transition metal M atoms is 1.7 to 37.5.

[0007] Furthermore, M includes one of Fe, Co, Ni, Mn, Zn, Cu, Ti, In, Pd, Mo, Ir, Ru and Au.

[0008] Furthermore, the carbon material in the carrier includes one of carbon black, graphene, carbon nanotubes, graphene-carbon nanotube composites, carbon nanotube cups, annealed polypyrrole tubes, carbon aerogels, mesoporous carbon, carbon nanospheres, carbon nanocages, carbon nanocapsules and carbon nanofibers.

[0009] Furthermore, the composite has a truncated octahedral morphology, and the composite is highly uniformly dispersed on the nitrogen-doped carbon carrier.

[0010] The present invention also provides a method for preparing a composite nanocatalyst supported on nitrogen-doped carbon, comprising the following steps:

[0011] (1) grinding and mixing adenine phosphate and dried carbon-supported Pt-M alloy at a mass ratio of 0.2 to 1.0, sintering and annealing in a hydrogen-argon mixed atmosphere, the sintering temperature is 600 to 1000°C, the heating rate is 5 to 10°C / min, the annealing time is 0.5 to 3h, and the sample is taken out after the temperature naturally drops to room temperature;

[0012] (2) acid washing the sample under an inert atmosphere;

[0013] Specifically, the sample is first poured into 0.1-1.0 mol / L diluted acid and uniformly mixed under ultrasonic action, and then stirred at 50-80°C for 12-24h under the protection of inert gas;

[0014] (3) After the acid wash, the sample was cooled to room temperature, centrifuged (10,000 rpm) and washed (with ultrapure water), and then dried in a vacuum freeze dryer.

[0015] Furthermore, the synthesis of the carbon-supported Pt-M alloy is carried out under the protection of an inert atmosphere, and comprises the following steps:

[0016] (1) adding a platinum precursor and a transition metal M precursor to an alcohol solution and stirring at room temperature;

[0017] (2) adding the carbon material to the alcohol solution and subjecting it to reflux reaction;

[0018] (3) adding the solution obtained in step (1) dropwise to the solution obtained in step (2), stirring at reflux reaction temperature, adding alkali to adjust the pH to >11, and continuing stirring at reflux reaction temperature to form a slurry suspension containing a metal salt;

[0019] (4) Add NaBH to the suspension obtained in step (3) 4 The alcohol solution is stirred at reflux reaction temperature for 10 to 30 minutes, then the temperature is raised to 120 to 200°C and stirred for 0.5 to 4 hours;

[0020] (5) After the reaction is completed, cool to room temperature, add acid to adjust the pH to <2, stir; centrifuge (10000 rpm), wash (first with ethanol and then with ultrapure water), and dry (in a vacuum freeze dryer) to obtain.

[0021] Furthermore, the molar ratio of the platinum precursor to the transition metal M precursor is 0.15:0.05-0.45, and the stirring time in step (1) is 1-3 hours;

[0022] In step (2), the concentration of the carbon material in the alcohol solution is 2 to 5 mg / mL, and the reaction time is 1 to 3 hours;

[0023] In step (3), the stirring time before adding alkali to adjust the pH is 15 to 60 minutes, and the stirring time after adding alkali to adjust the pH is 1 to 3 hours; the concentration of the alkali is 0.1 to 1.0 mol / L;

[0024] The temperature of the reflux reaction in step (2), step (3) and step (4) is 60 to 100° C.;

[0025] In step (4), NaBH 4 The concentration in the solution is 2-4 mmol / mL;

[0026] In step (5), the concentration of the acid is 1 to 5 mol / L, and the stirring time is 10 to 60 min.

[0027] Further, the alcohol solution includes at least one of ethylene glycol, polyethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and glycerol;

[0028] The platinum precursor includes one of potassium chloroplatinate, chloroplatinic acid, potassium chloroplatinite, hexahydroxyplatinate and platinum acetylacetonate;

[0029] The transition metal M precursor includes one of the nitrate, chloride, sulfate, acetate, acetylacetonate, oxalate and carbonate of the transition metal M;

[0030] The alkali includes at least one of KOH, NaOH and ammonia water.

[0031] Furthermore, the inert atmosphere includes at least one of nitrogen, argon and helium.

[0032] Furthermore, the pickling solution includes at least one of perchloric acid, sulfuric acid, nitric acid and hydrochloric acid with a concentration of 0.1 to 1.0 mol / L.

[0033] The present invention also provides the use of the composite nanocatalyst or the composite nanocatalyst prepared by the above preparation method, which is applied to catalysts of hydrogen-oxygen fuel cells, metal-air batteries or water electrolysis batteries.

[0034] Beneficial effects of the present invention:

[0035] (1) Pt-M intermetallic compounds with truncated octahedral structures and PtP 2 Both composite nanoparticles and doped carbon carriers can be used as active ingredients to further enhance the catalytic reaction. The doped carbon carriers can also play the role of anchoring the composite nanocatalyst particles and enhance stability.

[0036] This application presents nitrogen-doped carbon loaded with Pt-M and PtP 2 The composite nanocatalyst is used as a catalyst for hydrogen-oxygen fuel cells, metal-air batteries and water electrolysis batteries, and has high catalytic activity and stability. The present invention improves the catalytic activity and stability and solves the disadvantage that metal nanoparticles are easy to agglomerate. The preparation process is simple, the operation is convenient and the cost is low.

[0037] (2) In order to solve the problem that the Pt-M alloy particles become larger due to heat treatment, the present invention ball-mills the Pt-M alloy and adenine phosphate and then performs high temperature treatment. After the addition of adenine phosphate, on the one hand, the PtP 2 On the other hand, the heteroatom N-doped carbon support formed not only provides a protective barrier, effectively inhibits the migration and aggregation of metal nanoparticles, improves the problem of particle growth due to heat treatment, promotes the conductivity and charge / mass transfer of materials in the electrochemical process, but also can synergistically improve the overall catalytic activity as part of the catalyst.

[0038] (3) This application uses modified isopropanol at high temperature to stabilize NaBH 4The polyol reduction method was used to prepare nitrogen-doped highly active carbon-supported Pt-M nanometallic compound catalysts. The metal precursor was reduced at high temperature because polyols can act not only as solvents but also as stabilizers and dispersants under high temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The XRD diagrams of the samples without and with adenine phosphate added after heat treatment and the commercial 20% Pt / C (JM) catalyst when the cobalt precursor content is 0.06 mmol in Example 1 are shown.

[0040] Figure 2 The sample (Pt 3 EDX mapping of Co).

[0041] Figure 3 The sample (Pt 3 Co+PtP 2 )’s EDX mapping.

[0042] Figure 4 The sample (Pt 3 Co+PtP 2 ) and the linear scan curve of commercial 20% Pt / C (JM) catalyst.

[0043] Figure 5 The sample (Pt 3 Mn+PtP 2 ) and the linear scan curve of commercial 20% Pt / C (JM) catalyst. DETAILED DESCRIPTION

[0044] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0045] Example 1

[0046] A Pt-based intermetallic compound and PtP co-supported on nitrogen-doped carbon 2 Preparation method of composite nanocatalyst:

[0047] The following steps (2) to (5) and (7) were all carried out under nitrogen protection and accompanied by magnetic stirring.

[0048] (1) Add 0.15 mmol of platinum precursor and 0.06 mmol of transition metal Co precursor into 10 mL of ethylene glycol solvent and stir magnetically at room temperature for 1 h;

[0049] (2) Add 70 mg of BP2000 carbon black to 30 mL of ethylene glycol solvent, install a reflux device, raise the temperature to 80 °C, and stir magnetically at this temperature for 1 h;

[0050] (3) The solution obtained in step (1) is added dropwise to the solution obtained in step (2), and after stirring for 20 min, 0.3 mol / L alkaline substance (NaOH is used in this embodiment) is added to adjust the pH of the mixture to pH>11, and stirring is continued at 80° C. under inert gas protection for 1 h to form a slurry-like carbon black suspension containing metal salts;

[0051] (4) Rapidly (within 30-60 s) add 2.5 mmol / mL NaBH to the suspension obtained in step (3). 4 Ethylene glycol solution, after reacting for 15 min, the temperature was heated to 180°C and reacted at this temperature for 1.5 h;

[0052] (5) After the reaction is completed, the mixture is cooled to room temperature, 3 mol / L HCl is added to adjust the pH of the reaction solution to less than 2, and stirred for 30 min. The sample is then centrifuged (10,000 rpm) and washed (first with ethanol and then with ultrapure water), and finally dried in a vacuum freeze dryer for later use;

[0053] (6) grinding adenine phosphate and the dried product in a ball mill at a mass ratio of 0.5 to uniformly mix, then placing them in a porcelain boat, and annealing them at high temperature in a quartz tube with a flowing mixture of 5% hydrogen and 95% argon. The temperature was set at 850°C, the heating rate was 5°C / min, the annealing time was fixed at 1 h, and the sample was taken out after naturally cooling to room temperature;

[0054] (7) Acid wash the sample. First, pour the annealed sample into 30 mL of 0.5 mol / L H 2 SO 4 and uniformly mixed under ultrasonication, and then stirred in an oil bath at 60°C for 18h under nitrogen protection;

[0055] (8) After acid washing, the sample was cooled to room temperature, centrifuged (10,000 rpm), washed (ultrapure water), and then dried in a vacuum freeze dryer.

[0056] Figure 1The XRD patterns of the samples without adding adenine phosphate and after heat treatment with adenine phosphate in Example 1 when the cobalt precursor is 0.06 mmol and the commercial 20% Pt / C (JM) catalyst are shown in the figure. 3 Co intermetallic compound; when adenine phosphate has been added, the product formed is PtP 2 With Pt 3 Co coexisting composite catalyst, from Figure 3 It can also be seen in.

[0057] Figure 2 and Figure 3 In Example 1, when the cobalt precursor is 0.06 mmol, no (Pt 3 Co) and added (Pt 3 Co+PtP 2 ) EDX mapping of the sample after heat treatment of adenine phosphate. It can be seen from the figure that the present invention can obtain a catalyst with good dispersion, relatively uniform size and a particle size of about 10 nm.

[0058] Figure 4 The sample (Pt 3 Co+PtP 2 ) and the commercial 20% Pt / C (JM) catalyst. It can be seen from the figure that the catalytic activity of the prepared sample is better than that of the commercial 20% Pt / C (JM) catalyst.

[0059] Example 2

[0060] A Pt-based intermetallic compound and PtP co-supported on nitrogen-doped carbon 2 Preparation method of composite nanocatalyst:

[0061] The following steps (2) to (5) and (7) were all carried out under argon protection and accompanied by magnetic stirring.

[0062] (1) Add 0.15 mmol of platinum precursor and 0.10 mmol of transition metal Mn precursor to 10 mL of propylene glycol solvent and stir magnetically at room temperature for 1 h;

[0063] (2) Add 100 mg of ECP600JD carbon black to 30 mL of propylene glycol solvent, install a reflux device, raise the temperature to 60 °C, and stir magnetically at this temperature for 1 h;

[0064] (3) adding the solution obtained in step (1) dropwise to the solution obtained in step (2), stirring for 40 min, adding 0.8 mol / L alkaline substance (KOH is used in this embodiment) to adjust the pH of the mixture to pH>11, and continuing to stir at 60° C. under inert gas protection for 1 h to form a slurry carbon black suspension containing metal salt;

[0065] (4) Rapidly add 3 mmol / mL NaBH 4 Propylene glycol solution, after reacting for 25 min, the temperature was heated to 130°C and reacted at this temperature for 1 h;

[0066] (5) After the reaction is completed, the mixture is cooled to room temperature, 3 mol / L HCl is added to adjust the pH of the reaction solution to less than 2, and stirred for 30 min. The sample is then centrifuged (10,000 rpm) and washed (first with ethanol and then with ultrapure water), and finally dried in a vacuum freeze dryer for later use;

[0067] (6) grinding adenine phosphate and the dried product in a ball mill at a mass ratio of 0.3 to uniformly mix, then placing them in a porcelain boat, and annealing them at high temperature in a quartz tube with a flowing mixture of 5% hydrogen and 95% argon. The temperature was set to 750°C, the heating rate was 5°C / min, the annealing time was fixed at 1 h, and the sample was taken out after naturally cooling to room temperature;

[0068] (7) Acid wash the sample. First, pour the annealed sample into 30 mL of 0.1 mol / L HClO 4 and uniformly mixed under ultrasonication, and then stirred in an oil bath at 60°C for 24 h under nitrogen protection;

[0069] (8) After acid washing, the sample was cooled to room temperature, centrifuged (10,000 rpm), washed (ultrapure water), and then dried in a vacuum freeze dryer.

[0070] Figure 5 The sample (Pt 3 Mn+PtP 2 ) and the commercial 20% Pt / C (JM) catalyst. It can be seen from the figure that the catalytic activity of the prepared sample is better than that of the commercial 20% Pt / C (JM) catalyst.

Claims

1. A composite nanocatalyst supported on nitrogen-doped carbon, characterized in that: Nitrogen-doped carbon is used as a carrier, and a complex of a Pt-M intermetallic compound and PtP2 is loaded on the carrier, wherein M is a transition metal atom; the molar ratio of total platinum atoms to transition metal M atoms in the complex of the Pt-M intermetallic compound and PtP2 is 0.3-3, and the molar ratio of carbon in the carrier to transition metal M atoms is 1.7-37.5; the composite nanocatalyst grinds and mixes adenine phosphate and carbon-supported Pt-M, and then sinters and anneals at high temperature.

2. The composite nanocatalyst according to claim 1, characterized in that The M includes one of Fe, Co, Ni, Mn, Zn, Cu, Ti, In, Pd, Mo, Ir, Ru and Au.

3. The composite nanocatalyst according to claim 1, characterized in that: The carbon material in the carrier includes one of carbon black, graphene, carbon nanotube, graphene-carbon nanotube composite material, carbon nanotube cup, annealed polypyrrole tube, carbon aerogel, mesoporous carbon, carbon nanosphere, carbon nanocage, carbon nanocapsule and carbon nanofiber.

4. A method for preparing a composite nanocatalyst supported on nitrogen-doped carbon, characterized in that: The steps include: (1) grinding and mixing adenine phosphate and dried carbon-supported Pt-M alloy at a mass ratio of 0.2 to 1.0, sintering and annealing in a hydrogen-argon mixed atmosphere, the sintering temperature is 600 to 1000°C, the heating rate is 5 to 10°C / min, the annealing time is 0.5 to 3h, and the sample is taken out after the temperature drops to room temperature; (2) acid washing the sample under an inert atmosphere; (3) After pickling, cool to room temperature, centrifuge, wash, and dry.

5. The preparation method according to claim 4, characterized in that: The synthesis of the carbon-supported Pt-M alloy is carried out under the protection of an inert atmosphere and comprises the following steps: (1) adding a platinum precursor and a transition metal M precursor to an alcohol solution and stirring at room temperature; (2) adding the carbon material to the alcohol solution and subjecting it to reflux reaction; (3) adding the solution obtained in step (1) dropwise to the solution obtained in step (2), stirring at reflux reaction temperature, adding alkali to adjust the pH to >11, and continuing stirring at reflux reaction temperature to form a suspension containing a metal salt; (4) adding NaBH4 alcohol solution to the suspension obtained in step (3), stirring at reflux reaction temperature for 10 to 30 minutes, raising the temperature to 120 to 200°C, and stirring for 0.5 to 4 hours; (5) After the reaction is completed, cool to room temperature, add acid to adjust the pH to <2, stir, centrifuge, wash, and dry to obtain the product.

6. The preparation method according to claim 5, characterized in that: The molar ratio of the platinum precursor to the transition metal M precursor is 0.15:0.05-0.45, and the stirring time in step (1) is 1-3 hours; In step (2), the concentration of the carbon material in the alcohol solution is 2 to 5 mg / mL, and the reaction time is 1 to 3 hours; In step (3), the stirring time before adding alkali to adjust the pH is 15 to 60 minutes, and the stirring time after adding alkali to adjust the pH is 1 to 3 hours; the concentration of the alkali is 0.1 to 1.0 mol / L; The temperature of the reflux reaction in step (2), step (3) and step (4) is 60 to 100° C.; In step (4), the concentration of NaBH4 in the solution is 2 to 4 mmol / mL; In step (5), the concentration of the acid is 1 to 5 mol / L, and the stirring time is 10 to 60 min.

7. The preparation method according to claim 5, characterized in that: The alcohol solution comprises at least one of ethylene glycol, polyethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and glycerol; The platinum precursor includes one of potassium chloroplatinate, chloroplatinic acid, potassium chloroplatinite, hexahydroxyplatinate and platinum acetylacetonate; The transition metal M precursor includes one of the nitrate, chloride, sulfate, acetate, acetylacetonate, oxalate and carbonate of the transition metal M; The alkali includes at least one of KOH, NaOH and ammonia water.

8. The preparation method according to claim 5, characterized in that: The inert atmosphere includes at least one of nitrogen, argon and helium.

9. The preparation method according to claim 4, characterized in that: The pickling solution includes at least one of perchloric acid, sulfuric acid, nitric acid and hydrochloric acid.

10. Use of the composite nanocatalyst according to any one of claims 1 to 3 or the composite nanocatalyst prepared by the preparation method according to any one of claims 4 to 9, characterized in that: Catalysts used in hydrogen-oxygen fuel cells, metal-air batteries or water electrolysis batteries.

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