CN108448126A - A kind of PtAuTi nanowire catalytic material and its preparation method and application as fuel cell catalyst - Google Patents

Abstract

The invention discloses a kind of PtAuTi nanowire catalytics material and preparation method thereof and as the application of fuel-cell catalyst；PtAuTi nanowire catalytics material is made of carbon-coating cladding metal nanometer line；The metal nanometer line is made of three kinds of platinum, gold and titanium metal mixeds.Preparation method is, platinum source, Jin Yuan and titanium source and binder is soluble in water, electrostatic spinning precursor liquid is obtained, electrostatic spinning precursor liquid passes through electrostatic spinning, obtain composite nano fiber, composite nano fiber obtains nano wire, nano wire is passed through reduction treatment by heat treatment, the PtAuTi nanowire catalytic materials good up to catalytic performance, stability is high, the catalysis material has high oxygen reduction activity, and has higher stability in acidic environment, can be used as the catalyst application of fuel cell.

Description

A kind of PtAuTi nanowire catalytic material and its preparation method and as fuel cell catalyst Chemical application

technical field

The invention relates to a fuel cell catalyst material, in particular to a PtAuTi nanowire material and a method for preparing the PtAuTi nanowire material by electrospinning, and also relates to the application of the PtAuTi nanowire material as a fuel cell catalyst; it belongs to the field of fuel cell catalysts.

Background technique

In recent years, proton exchange membrane fuel cells have attracted the attention of researchers as an ideal green energy source, which can be applied to vehicles and mobile electronic devices. At present, platinum and its alloys are often used as electrode catalysts for proton exchange membrane fuel cells, but there are two important problems in proton exchange fuel cells that have not been resolved: on the one hand, due to the poisoning of the catalyst, its catalytic oxygen reduction (ORR) On the other hand, the catalyst uses precious metals, which is expensive, which limits its industrial development. Therefore, it is imperative to improve the performance of platinum catalysts for oxygen reduction and reduce their usage.

At present, fuel cells usually use platinum and its alloys as catalysts. The current commercial fuel cell catalyst is 20% platinum nanoparticles directly loaded on Carbon XC-72, but the lack of platinum resources and high cost directly restrict the development of fuel cell technology. Promotion hinders its commercialization process. In order to reduce the production cost of fuel cells and ensure its better catalytic activity, therefore, highly stable Pt-based catalysts that can provide improved ORR activity are of the most feasible research value because it will reduce the Pt content to achieve fuel cell battery performance. In recent years, many platinum-based alloy catalysts have been reported, such as: PtPd, PtAu, PtCo, PtFe, PtNi, etc. Sa. Liu reported the Pd@PtNi core-shell nanoflower structure, which greatly reduces the economic cost. It has good activity in acidic environment, but it is easy to be corroded in acidic environment.

Contents of the invention

In view of the defects of high platinum content and poor stability in existing fuel cell catalysts, the first purpose of the present invention is to provide a PtAuTi nanowire catalyst with a one-dimensional nanowire structure, low platinum content and good stability. Material.

Another object of the present invention is to provide a simple and low-cost method for preparing the PtAuTi nanowire catalytic material.

The third object of the present invention is to provide a PtAuTi nano catalytic material for application in fuel cells, which has the characteristics of low platinum content, good catalytic performance and high stability.

In order to achieve the above technical purpose, the present invention provides a PtAuTi nanowire catalytic material, which is composed of metal nanowires coated with a carbon layer; the metal nanowires are composed of platinum, gold and titanium.

The PtAuTi nanowire catalytic material of the invention has a one-dimensional metal nanowire structure, and the surface is covered with a thin carbon layer as a protective layer, which can improve the stability of the catalytic material.

In a preferred solution, the molar ratio of platinum, gold and titanium is 1:0.1-10:0.1-10; preferably 1:1-2:1-2; most preferably 1:1.5:1.5. The PtAuTi nanowire catalytic material of the present invention has the best oxygen reduction catalytic performance when the molar ratio of platinum, gold and titanium is 1:1.5:1.5, and the platinum content is greatly reduced compared with the existing platinum metal catalysts.

The present invention also provides a preparation method of PtAuTi nanowire catalytic material, which comprises the following steps:

1) dissolving platinum source, gold source, titanium source and binder in water to obtain electrospinning precursor;

2) The electrospinning precursor fluid is electrospun to obtain composite nanofibers;

3) The composite nanofibers are heat-treated to obtain nanowires;

4) The nanowires are obtained through reduction treatment.

In a preferred solution, the total mass fraction of platinum source, gold source and titanium source in the electrospinning precursor solution is 3wt%-6wt%, and the mass fraction of the binder is 4wt%-10wt%. The total mass fraction of platinum source, gold source and titanium source is preferably 3wt%. The mass fraction of the binder is preferably 6 wt%. Common sources of platinum, gold and titanium are water-soluble compounds containing platinum, gold or titanium, such as metal salts or acid compounds. A preferred source of platinum is chloroplatinic acid. A preferred gold source is chloroauric acid. A preferred source of titanium is titanium nitride.

The binder is a polymer material that can be electrospun, including at least one of PVP, PVA, PAN, PVB, and PMMA.

Preferred scheme, described electrospinning comprises A or B scheme:

Solution A: Put the body fluid of the electrospinning precursor into the liquid spraying device. The liquid spraying device is set on the electrospinning machine and connected to the negative electrode. A constant DC voltage is applied between the nozzle of the liquid spraying device and the receiving device of the positive electrode. Composite nanofibers are obtained on the receiving device;

Plan B: Put the electrospinning precursor liquid into the solution tank, immerse the roller connected to the positive electrode into the electrospinning precursor liquid, rotate the roller, pull and solidify into filaments under the action of centrifugal force and electric field, and obtain composite nano fiber.

The more preferred scheme, in scheme A, the aperture size of the nozzle opening is 0.2mm-1.86mm, the constant voltage is 6KV-100KV, the distance between the nozzle and the positive electrode is 10cm-100cm, and the propulsion speed of the electrospinning precursor is 0.3-100cm. 3mL/h.

A more preferred scheme, in scheme B, the diameter of the drum is 10-80cm, the voltage between the positive and negative electrodes is 6KV-100KV, and the distance between the positive and negative electrodes is 30-180cm.

In a preferred scheme, the heat treatment process is as follows: the composite nanofiber is heated to 200°C to 300°C at a heating rate of 0.2°C/min to 2°C/min in an air atmosphere, kept for 0.5 to 1.5h, and then heated at a temperature of 0.5°C/min to 200°C to 300°C. Min ~ 3 ℃ / min temperature rise rate to 500 ℃ ~ 700 ℃ constant temperature sintering 2h ~ 4h.

In a preferred solution, the reduction process is as follows: placing the nanowires in an atmosphere containing hydrogen, and keeping the temperature at 150° C. to 300° C. for 2 hours to 3 hours.

The invention also provides an application of the PtAuTi nanowire catalytic material, which is used as a fuel cell catalyst.

The preparation method of the PtAuTi nanowire catalytic material of the present invention comprises the following process steps:

1. Preparation of electrospinning precursor solution:

According to the molar ratio of Pt:Au:Ti=1:0.1～10:0.1～10, the precursors of chloroplatinic acid, chloroauric acid and titanium nitride were respectively weighed and dissolved in the aqueous solution, and a certain amount of binder was added slowly In the precursor solution, stir for 12 hours to fully dissolve to obtain a transparent electrospinning precursor solution; the mass fraction of the metal precursor in the electrospinning precursor solution is 3wt% to 6wt%, and the mass fraction of the binder is 4wt% to 10wt% %; the binder is a series of polymers that can be used for electrospinning such as PVP, PVA, PAN, PVB, PMMA;

2. Electrospinning

Inject the electrospinning precursor liquid obtained in step 1 into a syringe with a stainless steel needle, place the syringe on the electrospinning machine, connect it to the negative electrode, and apply a constant DC voltage between the stainless steel needle and the receiving device of the positive electrode, Composite nanofibers are obtained by rotating the receiving device; the size of the stainless steel needle is 0.20mm-1.86mm, the constant voltage is 6KV-100KV, the distance between the stainless steel needle and the positive electrode is 10cm-100cm, and the advancing speed of the electrospinning solution is 0.3- 3mL/h; the receiving device is a metal roller covered by carbon paper, aluminum foil, highly conductive PI film or a flat receiving device covered by direct barbed wire or carbon paper and aluminum foil;

Alternatively, put the electrospinning precursor liquid into the solution tank, immerse the drum connected to the positive electrode into the electrospinning precursor liquid, rotate the drum, pull and solidify into filaments under the action of centrifugal force and electric field, and obtain composite nanofibers ; The diameter of the drum is 10-80cm, the voltage between the positive and negative electrodes is 6KV-100KV, and the distance between the positive and negative electrodes is 30-180cm;

3. Heat treatment

Collect the composite nanofibers in step 2 in a quartz boat, place it in a tube furnace, raise the temperature to 200°C to 300°C in air at a rate of 0.2°C/min to 2°C/min, and then keep it warm for 1h. Then heat up to 500°C-700°C in air at a heating rate of 0.5°C/min-3°C/min and sinter at a constant temperature for 2h-4h to remove the PVP in the composite nanofibers.

4. _H2 Reduction

Cool the nanowires obtained in step 3 to 150°C to 300°C, pass through diluted H ₂ for 2h to 3h, and then reduce them to obtain PtAuTi-NWs; dilute H ₂ to form a mixture of H ₂ and N ₂ or Ar Gas, the gas flow rate is 0.1~2L/min.

Compared with the prior art, the beneficial technical effect brought by the technical solution of the present invention:

1) The PtAuTi nanowire catalytic material of the present invention has the characteristics of good stability, especially stable existence in an acidic system, and high catalytic activity, and can be widely used as an oxygen reduction catalyst for fuel cells.

2) Compared with the platinum metal catalyst in the prior art, the PtAuTi nanowire catalytic material of the present invention has lower platinum content and higher catalytic activity, which greatly reduces the use cost of the catalytic material.

3) The PtAuTi nanowire catalytic material of the present invention can be prepared by electrospinning technology, and has the advantages of convenient preparation, simple operation and mass production.

Description of drawings

[Fig. 1] is a scanning electron micrograph of the PtAuTi nanowire fuel cell catalyst prepared in Example 1.

[Fig. 2] is the scanning electron micrograph of the PtAuTi nanowire fuel cell catalyst prepared in Example 2.

[ Fig. 3 ] is a scanning electron micrograph of the PtAuTi nanowire fuel cell catalyst prepared in Example 3.

[ Fig. 4 ] is the CV comparison chart of the PtAuTi nanowire fuel cell catalyst prepared in Example 1 and 20% Pt/C.

[ Fig. 5 ] is the CV comparison chart of the PtAuTi nanowire fuel cell catalyst prepared in Example 2 and 20% Pt/C.

[ Fig. 6 ] is the CV comparison chart of the PtAuTi nanowire fuel cell catalyst prepared in Example 3 and 20% Pt/C.

Detailed ways

The present invention will be further illustrated in detail below in conjunction with non-limiting specific examples.

The reagents used in the examples of the present invention are all commercially available.

Example 1

1. Preparation of electrospinning precursor solution

According to the molar ratio of Pt:Au:Ti=1:1:0.5, respectively weigh 159mg of chloroplatinic acid, 122mg of chloroauric acid, and 9mg of titanium nitride and dissolve them in 10mL of aqueous solution, and slowly add 0.6g of PVP into the precursor solution, After stirring for 12 hours to fully dissolve, a transparent electrospinning precursor solution was obtained; the mass percent concentration of the metal precursor in the electrospinning precursor solution was 3%, and the mass percent concentration of PVP was 6%.

2. Electrospinning

Inject the electrospinning precursor liquid obtained in step 1 into a syringe with a stainless steel needle, place the syringe on the electrospinning machine, connect it to the negative electrode, and apply a constant DC voltage between the stainless steel needle and the receiving device of the positive electrode , by rotating the receiving device (carbon paper) to obtain composite nanofibers. The size of the stainless steel needle is 0.5mm, the DC voltage is 25KV, the distance between the stainless steel needle and the receiving device is 15cm, the advancing speed of the electrospinning solution is 1mL/h, the temperature inside the device is 25°C, and the relative humidity is 30°C. %.

3. Heat treatment

Collect the composite nanofibers in step 2 in a quartz boat, place it in a tube furnace, heat up to 200°C in air at a rate of 1°C/min, then keep it warm for 1h, and then heat it up at a rate of 1°C/min. Heating rate Heating up to 500°C in air and sintering at a constant temperature for 2 hours can remove the PVP in the composite nanofibers.

4. _H2 Reduction

Cool the nanowires obtained in step 3 to 150° C., pass through diluted H ₂ for 2 hours, and reduce them to obtain PtAuTi-NWs.

5. Electrochemical detection

Take 2 mg of the prepared nanowires and disperse them in 1 ml of nafion aqueous solution (1:9). After ultrasonication for half an hour, take 15 μl of the mixed solution and drop it on a glassy carbon electrode. After natural drying, use an electrochemical workstation to measure the nanowires The electrochemical performance of the catalyst, wherein the saturated calomel electrode is used as the reference electrode, the platinum sheet is used as the counter electrode, 0.1M HCLO ₄ is used as the electrolyte, and the scan rate is 0.01V/S.

Example 2

1. Preparation of electrospinning precursor solution

According to the molar ratio of Pt:Au:Ti=1:1:1, weigh 159mg of chloroplatinic acid, 122mg of chloroauric acid, and 18mg of titanium nitride and dissolve them in 10mL of aqueous solution, and slowly add 0.5g of PVP into the precursor solution. Stir for 12 hours to fully dissolve to obtain a transparent electrospinning precursor solution; the mass concentration of the metal precursor in the electrospinning precursor solution is 3%, and the mass concentration of PVP is 5%.

2. Electrospinning

Inject the electrospinning precursor liquid obtained in step 1 into a syringe with a stainless steel needle, place the syringe on the electrospinning machine, connect it to the negative electrode, and apply a constant DC voltage between the stainless steel needle and the receiving device of the positive electrode , by rotating the receiving device (carbon paper) to obtain composite nanofibers. The size of the stainless steel needle is 0.8mm, the DC voltage is 60KV, the distance between the stainless steel needle and the receiving device is 30cm, the advancing speed of the electrospinning solution is 0.5mL/h, the temperature inside the device is 25°C, and the relative humidity 30%.

3. Heat treatment

Collect the composite nanofibers in step 2 in a quartz boat, place it in a tube furnace, raise the temperature to 250°C in air at a rate of 1°C/min, keep it warm for 1h, and then heat it up at a rate of 1°C/min. Heating rate The PVP in the composite nanofibers can be removed by raising the temperature to 600° C. in the air and sintering at a constant temperature for 2 hours.

4. _H2 Reduction

Cool the nanowires obtained in step 3 to 250°C, pass through diluted H ₂ for 2 hours, and reduce them to obtain PtAuTi-NWs.

5. Electrochemical detection

Take 2 mg of the prepared nanowires and disperse them in 1 ml of nafion aqueous solution (1:9). After ultrasonication for half an hour, take 15 μl of the mixed solution and drop it on the glassy carbon electrode. After natural drying, use an electrochemical workstation to measure the nanowires The electrochemical performance of the catalyst, wherein the saturated calomel electrode is used as the reference electrode, the platinum sheet is used as the counter electrode, 0.1M HCLO4 is used as the electrolyte, and the scan rate is 0.01V/S.

Example 3

1. Preparation of electrospinning precursor solution

According to the molar ratio of Pt:Au:Ti=1:1:2, weigh 159mg of chloroplatinic acid, 122mg of chloroauric acid, and 36mg of titanium nitride and dissolve them in 10mL of aqueous solution, and slowly add 0.6g of PVA into the precursor solution. Stir for 12 hours to fully dissolve to obtain a transparent electrospinning precursor solution; the mass concentration of the metal precursor in the electrospinning precursor solution is 3%, and the mass concentration of PVA is 6%.

2. Electrospinning

Inject the electrospinning precursor liquid obtained in step 1 into a syringe with a stainless steel needle, place the syringe on the electrospinning machine, connect it to the negative electrode, and apply a constant DC voltage between the stainless steel needle and the receiving device of the positive electrode , by rotating the receiving device (aluminum foil) to obtain composite nanofibers. The size of the stainless steel needle is 0.5mm, the DC voltage is 20KV, the distance between the stainless steel needle and the receiving device is 15cm, the advancing speed of the electrospinning solution is 1.5mL/h, the temperature in the device is 25°C, and the relative humidity is 30%.

3. Heat treatment

Collect the composite nanofibers in step 2 in a quartz boat, place it in a tube furnace, heat up to 200°C in air at a rate of 1°C/min, then keep it warm for 1h, and then heat it up at a rate of 1°C/min. Heating rate Heating up to 500°C in air and sintering at a constant temperature for 2 hours can remove the PVA in the composite nanofibers.

4. _H2 Reduction

Cool the nanowires obtained in step 3 to 150° C., pass through diluted H ₂ for 2 hours, and reduce them to obtain PtAuTi-NWs.

5. Electrochemical detection

Take 2 mg of the prepared nanowires and disperse them in 1 ml of nafion aqueous solution (1:9). After ultrasonication for half an hour, take 15 μl of the mixed solution and drop it on the glassy carbon electrode. After natural drying, use an electrochemical workstation to measure the nanowires The electrochemical performance of the catalyst, wherein the saturated calomel electrode is used as the reference electrode, the platinum sheet is used as the counter electrode, 0.1M HCLO4 is used as the electrolyte, and the scan rate is 0.01V/S.

Claims (10)

1. a kind of PtAuTi nanowire catalytics material, it is characterised in that：It is made of carbon-coating cladding metal nanometer line；The metal is received Rice noodles are made of three kinds of platinum, gold and titanium metal mixeds.

2. a kind of PtAuTi nanowire catalytics material according to claim 1, it is characterised in that：Mole of platinum, gold and titanium Than being 1:0.1~10:0.1~10.

3. a kind of preparation method of PtAuTi nanowire catalytics material as claimed in claim 1 or 2, it is characterised in that：Including with Lower step：

1) platinum source, Jin Yuan and titanium source and binder is soluble in water, obtain electrostatic spinning precursor liquid；

2) the electrostatic spinning precursor liquid obtains composite nano fiber by electrostatic spinning；

3) composite nano fiber obtains nano wire by heat treatment；

4) by nano wire by reduction treatment to get.

4. a kind of preparation method of PtAuTi nanowire catalytics material according to claim 3, it is characterised in that：It is described quiet The total mass fraction in platinum source, Jin Yuan and titanium source is 3wt%~6wt% in Electrospun precursor liquid, and the mass fraction of binder is 4wt%~10wt%；The platinum source is at least one of chloroplatinic acid and metal platinum salt；The Jin Yuan is gold chloride and metal gold salt At least one of；The titanium source is titanium nitride.

5. a kind of preparation method of PtAuTi nanowire catalytics material according to claim 4, it is characterised in that：Described Binder includes at least one of PVP, PVA, PAN, PVB, PMMA.

6. a kind of preparation method of PtAuTi nanowire catalytics material according to claim 3, it is characterised in that：It is described quiet Electrospun includes A or B schemes：

A schemes：Electrostatic spinning precursor liquid is fitted into liquid-jet device, liquid-jet device is arranged on electrostatic spinning machine, with cathode It is connected, applies constant DC voltage between the nozzle and the receiving device of anode of liquid-jet device, obtained from receiving device Composite nano fiber；

B schemes：Electrostatic spinning precursor liquid is placed in solution tank, the roller being connected with anode is immersed in electrostatic spinning forerunner In body fluid, roller rotation, pull is solidified into silk under the action of centrifugal force is with electric field, obtains composite nano fiber.

7. a kind of preparation method of PtAuTi nanowire catalytics material according to claim 6, it is characterised in that：

In A schemes, nozzle mouth pore size is 0.2mm~1.86mm, and constant voltage is 6KV~100KV, between nozzle and anode Distance be 10cm~100cm, the fltting speed of electrostatic spinning precursor liquid is 0.3~3mL/h；

In B schemes, diameter of cylinder is 10~80cm, and the voltage between positive and negative anodes is 6KV~100KV, the distance between positive and negative anodes For 30~180cm.

8. a kind of preparation method of PtAuTi nanowire catalytics material according to claim 3, it is characterised in that：The heat Processing procedure is：Composite nano fiber is warming up to 200 DEG C in air atmosphere, with the heating rate of 0.2 DEG C/mi/~2 DEG C/mi/ ~300 DEG C, 0.5~1.5h is kept the temperature, then 500 DEG C~700 DEG C constant temperature are warming up to the heating rate of 0.5 DEG C/mi/~3 DEG C/mi/ It is sintered 2h~4h.

9. a kind of preparation method of PtAuTi nanowire catalytics material according to claim 3, it is characterised in that：It is described to go back Former process is：Nano wire is placed under the atmosphere of hydrogen, 2h~3h is kept the temperature at a temperature of 150 DEG C~300 DEG C.

10. a kind of application of PtAuTi nanowire catalytics material as claimed in claim 1 or 2, which is characterized in that as hydrogen fuel Cell catalyst application.