CN117039031B - Platinum-carbon catalyst prepared by atmospheric pressure discharge technology and preparation method and application thereof - Google Patents

Abstract

The present invention discloses a platinum-carbon catalyst prepared by atmospheric pressure discharge technology and its preparation method and application. The method described herein uses a plasma generator under atmospheric pressure, uses a voltage-stabilized DC power supply to provide electric energy, uses a platinum wire electrode as an anode, and uses a platinum precursor dispersion overflowing from the end of a component composed of a graphite carbon rod and a quartz capillary as a cathode. A stable plasma glow is formed between the positive and negative electrodes, and the solution after discharge is collected and obtained by filtering, drying and grinding; the plasma generator includes a reaction liquid container, a peristaltic pump and a damper; the platinum precursor dispersion flows through the damper under the action of the peristaltic pump and finally overflows at the top of the quartz capillary. The method disclosed by the present invention is a method for preparing a platinum-carbon catalyst by atmospheric pressure discharge technology, which can synthesize a platinum-carbon nanocatalyst in one step under atmospheric pressure. The method for preparing a platinum-carbon catalyst is simple, fast, green and environmentally friendly, does not require the addition of a reducing agent, can effectively control particle agglomeration, and the catalytic activity is further improved.

Description

A platinum-carbon catalyst prepared by atmospheric pressure discharge technology and its preparation method and application

Technical Field

The present invention relates to the field of electrochemical catalysis technology, and in particular to a platinum-carbon catalyst prepared by atmospheric pressure discharge technology, and a preparation method and application thereof.

Background technique

Aprotic lithium-oxygen (Li-O ₂ ) batteries have attracted increasing attention due to their high theoretical energy density (3500Wh kg ^-1 ) far exceeding the benchmark of lithium-ion batteries. However, the insulating properties of the discharge product Li ₂ O ₂ lead to slow oxygen evolution reaction (OER) kinetics, high charge overpotential and poor cycling stability, which hinder the commercialization of Li-O ₂ batteries. There is an urgent need to improve battery performance, and the use of efficient catalysts is currently an effective solution. Platinum (Pt) is a noble metal with an adjustable d-band structure and is considered to be a suitable catalyst for Li-O ₂ batteries. According to molecular orbital theory, OER catalytic activity can be improved by increasing the adsorption energy of the intermediate (LiO ₂ ), and the adsorption energy can be controlled by adjusting the e _g orbital occupancy of the noble metal.

As a special branch of non-thermal plasma, glow discharge plasma has become an efficient means of synthesizing and processing nanomaterials. The discharge process increases the collision between reactants (electrons, ions, charged particles, excited molecules, etc.), increases the dissociation of precursors, and enhances particle nucleation. At the same time, the high specific surface area can achieve efficient mass and energy transfer and prevent heat accumulation in the system. In addition, plasma electrons can not only replace traditional chemical reducing agents to avoid by-products and secondary pollution, but also make the particles charged to produce mutual repulsion and hinder particle agglomeration. Therefore, plasma preparation of platinum-based catalysts is of great significance to the commercialization of Li- _O2 batteries.

The existing application number CN202111371024.4 patent document discloses a low-content platinum-based catalyst and its preparation method and the application of full pH effective electrolysis of water to produce hydrogen, including the following steps: using chloroplatinic acid as a platinum source precursor, dicyandiamide as a nitrogen source and a platinum source primary carrier, and reducing the platinum in chloroplatinic acid and loading it on dicyandiamide by photoreduction. Then, the hydrothermal reduction method is used to hydrothermally reduce the incorporated graphene oxide, and finally annealed in a high-temperature inert gas atmosphere, and pyrolyzed into the target catalyst Pt-N-rGO, which has a lower mass fraction of platinum (10wt%), and can effectively electrolyze water to produce hydrogen at full pH (including extreme acidic, alkaline and neutral conditions), and the stability is also better than commercial platinum carbon catalysts. However, the preparation of the platinum-based catalyst requires two reduction processes and annealing in a high-temperature inert gas atmosphere. Its preparation process is very complicated, has high requirements for experimental equipment, and is not conducive to mass production and application. Cyanamide is a toxic substance and causes irreversible pollution to the environment to a certain extent.

The existing patent document with application number CN201910001774.9 discloses a method of preparing a reaction solution with ethanol and platinum precursor as raw materials, turning on a DC power supply under an argon protective atmosphere, generating micro plasma discharge and acting on the reaction solution, and then adjusting the voltage to ensure that the plasma power is 2 to 5W, and some high-energy electrons excite and crack ethanol to generate nanocarbons. At the same time, some electrons will also reduce platinum ions to generate nano platinum directly loaded on carbon. During the reaction, the solution is constantly stirred to ensure that platinum nanoparticles are evenly loaded on carbon. The preparation process is simple, the reaction speed is fast, and no surfactant, stabilizer, or chemical reducing agent is required. The one-step method obtains carbon-loaded platinum nanoparticles, which is of great significance in the preparation of functional nanomaterials. However, the process of generating carbon-loaded nanocatalysts by plasma action is carried out in an argon protective atmosphere, and its preparation cost has increased.

The existing patent document with application number CN201810637595.X discloses a method for preparing a supported catalyst by irradiating a carrier and precursors such as palladium, platinum, gold, and ruthenium with radio frequency plasma, and its application in fuel cells. The method is simple and efficient. During the reaction, the plasma generator needs to be evacuated by vacuum equipment to control the pressure at 0.1Pa-1Pa, and the discharge power is as high as 50-500W. Radio frequency plasma irradiates the mixed dispersion, and most of the electrons generated by it will be delayed before reaching the carrier. Some negative ions ( ^O- and ^O2- ) can be combined with ions dissociated from transition metal element compounds to produce transition metal oxide precipitation and/or transition metal precipitation, which are deposited on the surface of the carrier, simplifying the preparation method of the supported catalyst; and reducing the size of the catalyst grains deposited on the surface of the carrier, improving the uniformity of the catalyst dispersion on the surface of the carrier and the electrocatalytic performance. However, the plasma generator needs to be evacuated by vacuum equipment to control the pressure at 0.1Pa-1Pa, and the discharge power is as high as 50-500W, which greatly increases the production cost.

The high cost, complex process and environmental impact of the current platinum-based catalyst preparation restrict its large-scale application in the field of electrochemical catalysis to a certain extent.

Summary of the invention

In view of the problems in the prior art that the preparation cost of platinum-based catalysts is high, the process is complicated, and they are not environmentally friendly, which to a certain extent restricts the large-scale application in the field of electrochemical catalysis, the present invention provides a platinum-carbon catalyst prepared by atmospheric pressure discharge technology, and a preparation method and application thereof. A carbon source and a platinum precursor are mixed into a reaction liquid under atmospheric pressure, and a platinum-carbon nanocatalyst is synthesized in one step under atmospheric pressure in an extremely simple manner. Compared with the prior art, this method is simple, rapid, green and environmentally friendly in preparing platinum-carbon catalysts, does not require the addition of reducing agents, can effectively control particle agglomeration, and the catalytic activity is further improved.

In order to achieve the above-mentioned purpose, the technical scheme of the present invention is: a method for preparing a platinum-carbon catalyst by atmospheric pressure discharge technology, wherein a plasma generating device is used under atmospheric pressure, a voltage-stabilized DC power supply is used to provide electric energy, a platinum wire electrode is used as an anode, and a platinum precursor dispersion liquid overflowing from the end of an element composed of a graphite carbon rod and a quartz capillary is used as a cathode, and under set voltage parameters, a stable plasma glow is formed between the positive and negative electrodes, and the turbid liquid after discharge is collected and filtered, washed, dried and ground to obtain a platinum-carbon nanoparticle catalyst; the platinum wire electrode and the element composed of the graphite carbon rod and the quartz capillary are coaxially arranged, and a ballast resistor is arranged between the platinum wire electrode and the positive electrode of the voltage-stabilized DC power supply;

There are multiple graphite carbon rods, and the multiple graphite carbon rods are arranged in a circular array with the quartz capillary as the center. The upper end surfaces of the multiple graphite carbon rods are flush, and the non-contact surfaces of the graphite carbon rods and the quartz capillary are provided with arc surfaces. The negative electrode of the voltage-stabilized DC power supply leads out a wire, and the wire fixes the multiple graphite carbon rods and the quartz capillary together;

The plasma generating device comprises a reaction liquid container, a peristaltic pump, a damper and a collector; the reaction liquid container is used to contain a platinum precursor dispersion liquid, the platinum precursor dispersion liquid flows through the damper under the action of the peristaltic pump and finally overflows at the top of the quartz capillary, and the collector is used to collect turbid liquid.

Furthermore, the diameter of the platinum wire electrode is 0.5-2mm, the diameter of the graphite carbon rod is 4-8mm, the outer diameter of the quartz capillary is 0.5-2mm, and the wall thickness does not exceed 0.5mm; there are three graphite carbon rods, the three graphite carbon rods have the same diameter and length, and the ratio of the radius of the graphite carbon rod to the radius of the quartz capillary is 2-7.

Furthermore, the length of the platinum wire electrode is 5-10 cm, the length of the graphite carbon rod is 3-10 cm, and the length of the quartz capillary is 5-12 cm; the length of the quartz capillary is greater than the length of the graphite carbon rod, and the end of the quartz capillary close to the platinum wire electrode is exposed at least 2 mm from the graphite carbon rod.

Furthermore, there are two arc surfaces, which are symmetrically arranged with the axis of the graphite carbon rod as the center, and the distance between the two arc surfaces on the same graphite carbon rod gradually increases from top to bottom, so that the upper end of a single graphite carbon rod is in a straight line, and the extension lines of multiple straight-line midlines intersect at one point, which is the center of the quartz capillary. There are three graphite carbon rods, and the angles of the straight-line upper ends of the three graphite carbon rods are 120° to each other; the arc surface is an oblique section surface, and the slope of the section surface is 5-15°.

Furthermore, the platinum precursor dispersion is prepared by the following method: a platinum precursor solution is prepared using deionized water as a solvent, mixed with a carbon source carrier and stirred evenly, and then subjected to ultrasound to obtain a platinum precursor dispersion.

Further, the platinum precursor is selected from at least one of chloroplatinic acid, tetraamine platinum nitrate and tetraamine platinum oxalate;

The carbon source carrier is selected from at least one of Ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, graphene, ethanol, glucose and sucrose.

Furthermore, the platinum concentration in the platinum precursor dispersion is 0.005-0.05M, and the volume of the platinum precursor solution corresponding to each 1g of the carbon source carrier is 50-500mL.

Furthermore, the voltage of the regulated DC power supply is adjustable in the range of 300-700 V, the flow rate of the peristaltic pump is adjustable in the range of 2-20 mL/min, and the plasma discharge duration is 5-120 min.

Furthermore, the distance between the end of the platinum wire electrode and the end of the quartz capillary is 0.5-2 mm.

A platinum-carbon catalyst is prepared by adopting the method for preparing a platinum-carbon catalyst by using an atmospheric pressure discharge technology.

The invention discloses an application of a platinum-carbon catalyst prepared by a method for preparing a platinum-carbon catalyst by an atmospheric pressure discharge technology in a lithium-oxygen battery.

The platinum-carbon catalyst generation principle of the present invention is that when the mixed dispersion is excited, high-density electrons ( ^e- ) are generated, and these electrons are pushed to the electrolyte by the strong electric field, so that the platinum ions in the electrolyte are reduced to ^Pt0 atoms, which are aggregated to form platinum nanoparticles. In this process, water molecules dissociate to form active species such as H _α , H _β and O·, which further promote the formation of ^Pt0 atoms, so that the platinum nanoparticles are evenly loaded on the carbon.

Furthermore, a method for preparing a platinum-carbon catalyst using an atmospheric pressure discharge technique comprises the following steps:

(1) Preparation of platinum precursor dispersion;

(2) Building a plasma generating device: The plasma generating device includes a reaction liquid container, a peristaltic pump, a damper, a voltage-stabilized DC power supply, three graphite carbon rods, a quartz capillary, a platinum wire electrode and a ballast resistor, and a collector;

The three graphite carbon rods have the same diameter and length, and the quartz capillary passes through the component from the middle of the area surrounded by the three graphite carbon rods;

The ballast resistor is located between the platinum wire electrode and the regulated DC power supply, the positive electrode of the regulated DC power supply is connected to the ballast resistor through a wire, and the negative electrode is connected to the element composed of a graphite carbon rod and a quartz capillary; the platinum wire electrode is vertically arranged directly above the element composed of a graphite carbon rod and a quartz capillary, and the platinum wire electrode is coaxially arranged with the element composed of a graphite carbon rod and a quartz capillary, and the upper end of the platinum wire electrode is connected to the ballast resistor through a wire; the lower end of the quartz capillary is connected to the damper outlet, the damper inlet is connected to one end of the peristaltic pump, and the other end of the peristaltic pump is connected to the reaction liquid container; the reaction liquid container, the peristaltic pump, the damper and the lower end of the quartz capillary are interconnected using silicone tubes;

(3) Preparation of catalyst: Platinum precursor dispersion is placed in a reaction liquid container, and a magnetic stirrer and a peristaltic pump are turned on. When the liquid in the reaction liquid container flows out from the upper end of the quartz capillary, a regulated DC power supply switch is turned on to generate a stable plasma glow between the positive and negative electrodes. After the discharge continues for a certain period of time, the regulated DC power supply, the peristaltic pump and the magnetic stirrer are turned off in turn; the stirring time is 5-20 minutes, and the ultrasonic time is 5-20 minutes;

(4) Post-treatment: The discharge product obtained in (3) is filtered, washed with deionized water for 2-3 times, placed in a vacuum drying oven for drying, and then taken out and ground into powder to obtain the final platinum carbon nanoparticle catalyst. The vacuum drying oven drying temperature is 40-120° C. and the drying time is 3-24 h.

In summary, the present invention has the following beneficial effects:

First, the method of the present application uses a carbon source and a platinum precursor as raw materials, and deionized water as a solvent to prepare a dispersion liquid. A plasma generator is used to act on the dispersion liquid under atmospheric pressure. A needle-shaped platinum electrode is provided in the generator as an anode, and a quartz capillary is passed through a graphite carbon rod as a cathode. A peristaltic pump brings the reaction liquid between the positive and negative electrodes through the quartz capillary. A voltage is applied, and the overflow liquid produces a glow, thereby directly generating a platinum-carbon nanoparticle catalyst and applying it to optimize the performance of lithium-oxygen batteries.

Second, atmospheric pressure discharge technology is used to prepare platinum-carbon nanocatalysts. The operation process is simple and one-step synthesis is required without any pretreatment process. Plasma acts on the reaction liquid to directly load platinum nanoparticles onto the carbon carrier to synthesize the target catalyst. The prepared platinum-carbon nanocatalyst has a grain size of about 2-6nm, and the platinum nanoparticles are evenly loaded on the surface of the carrier. It has good electrocatalytic properties, which greatly improves the performance of lithium-oxygen batteries. It is carried out under atmospheric pressure and does not require additional vacuum equipment or gas protection.

Third, by adjusting the voltage of the regulated DC power supply, the power required to achieve stable discharge is only about 5W. No chemical reducing agent or surfactant is required, and no pollutants are produced during the discharge process. It is green, environmentally friendly, low-cost, highly economical, and environmentally friendly.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

FIG1 is a schematic structural diagram of an atmospheric pressure discharge plasma generating device disclosed in Example 1 of the present invention;

FIG2 is a cross-sectional view of components in the atmospheric pressure discharge plasma generating device disclosed in Examples 1 and 3-8 of the present invention;

Figure 3 shows the plasma discharge area photos recorded by ICCD camera at different times under 400V discharge voltage.

FIG4 is a side view of a single graphite carbon rod in the atmospheric pressure discharge plasma generating device disclosed in Examples 1 and 3-8 of the present invention;

FIG5 is a TEM morphology of the platinum-carbon nanoparticle catalysts prepared in Examples 3 and 5 of the present invention at a discharge voltage of 400 V;

FIG6 is a charge and discharge curve diagram of a lithium oxygen battery of a platinum carbon nanoparticle catalyst and a commercial platinum carbon catalyst at a discharge voltage of 400 V;

In Figure 1: 1. reaction liquid container; 2. platinum precursor dispersion; 3. magnetic stirrer; 4. peristaltic pump; 5. damper; 6. element; 61. graphite carbon rod; 62. quartz capillary; 7. glow discharge area; 8. platinum wire electrode; 9. ballast resistor; 10. regulated DC power supply; 11. collector.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with Figures 1-6 of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Example 1

1 , the plasma generating device involved in the present application includes: a reaction liquid container 1, a magnetic stirrer 3, a peristaltic pump 4, a damper 5, a voltage-stabilized DC power supply 10, three graphite carbon rods 61, a quartz capillary 62, a platinum wire electrode 8, a ballast resistor 9 and a collector 11;

The three graphite carbon rods 61 and the quartz capillary 62 are all arranged vertically, and the three graphite carbon rods 61 have the same diameter and length. The quartz capillary 62 passes through the component 6 from the middle of the area surrounded by the three graphite carbon rods 61; the diameter of the graphite carbon rod 61 is 4-8 mm, and the diameter of the quartz capillary 62 is 0.5-2 mm; the ratio of the radius of the graphite carbon rod 61 to the radius of the quartz capillary 62 is 2-7; the length of the quartz capillary 62 is greater than the length of the graphite carbon rod 61, the length of the graphite carbon rod 61 is 3-10 cm, and the length of the quartz capillary 62 is 5-12 cm. The quartz capillary 62 is about 1 cm longer than the graphite carbon rod, and the upper end of the quartz capillary 62 is exposed at least 2 mm from the graphite carbon rod 61. The cathode formed by three graphite carbon rods 61 of the same size and the quartz capillary 62 forms a natural groove, which is conducive to the outflow of the reaction solution and prevents the accumulation of suspended particles on the upper platform of the graphite carbon rods 61, causing slow or stagnant reaction, thereby ensuring smooth reaction.

The upper end of the graphite carbon rod 61 is provided with two oblique section surfaces, and the inclination of the oblique section surfaces is 5 to 15 degrees. The two oblique section surfaces are arranged opposite to each other, and the distance between the two oblique section surfaces located on the same graphite carbon rod 61 gradually increases from top to bottom, so that the upper end of a single graphite carbon rod 61 is in a straight line shape, and the extension lines of the three straight line midlines intersect at one point, which is the center of the quartz capillary 62. The three straight line angles are 120 degrees to each other, which is conducive to the outflow of the reaction liquid and prevents the suspended particles from accumulating in the intervals between adjacent graphite carbon rods 61, blocking the channel for liquid circulation, and causing slow or stagnant reactions.

The platinum wire electrode 8 is needle-shaped, and the needle-shaped platinum wire electrode 8 is vertically arranged directly above the element 6 composed of three graphite carbon rods 61 and a quartz capillary 62. The platinum wire electrode 8 and the element 6 composed of the graphite carbon rods 61 and the quartz capillary 62 are coaxially arranged, and the spacing between the lower end of the platinum wire electrode 8 and the upper end of the quartz capillary 62 is 0.5-2mm. The area enclosed between the lower end of the platinum wire electrode 8 and the upper end of the element 6 composed of the graphite carbon rods 61 and the quartz capillary 62 is used as the glow discharge area 7. One end of the ballast resistor 9 is connected to the positive electrode of the voltage-stabilized DC power supply 10 through a wire, and the other end is connected to the upper end of the platinum wire electrode 8 through a wire.

The negative electrode of the regulated DC power supply 10 is connected to the element 6 composed of three graphite carbon rods 61 and a quartz capillary 62 through a wire, so that a series circuit is formed between the regulated DC power supply 10, the element 6, the platinum wire electrode 8, and the ballast resistor 9.

The lower end of the quartz capillary 62 is connected to the outlet of the damper 5, the inlet of the damper 5 is connected to one end of the peristaltic pump 4, and the other end of the peristaltic pump 4 is connected to the reaction liquid container 1. The setting of the damper 5 can slow down the discharge instability caused by the peristaltic pump 4. The pulse damper 5 is connected after the peristaltic pump 4, so that the reaction liquid overflows evenly from the tip of the quartz capillary 62, the fluid fluctuation is reduced, and a stable glow is generated between the two electrodes after the voltage is applied. On the contrary, intermittent discharge is easy to damage the electrodes.

The reaction liquid container 1, the peristaltic pump 4, the damper 5 and the lower end of the quartz capillary 62 are all connected to each other using silicone tubes. The reaction liquid container 1 is placed above the magnetic stirrer 3. The speed of the magnetic stirrer 3 can be adjusted in the range of 180-240 rpm. The reaction liquid container 1 is used to hold the configured platinum precursor dispersion 2. The magnetic stirrer 3 and the peristaltic pump 4 are turned on, and the liquid in the reaction liquid container 1 can flow out from the upper end of the quartz capillary 62 through the silicone tube. When the liquid flows out, the switch of the stabilized DC power supply 10 is turned on, and a stable plasma glow is generated in the glow discharge area 7.

The collector 11 is a container with an upper opening, which is placed directly below the element 6 composed of the graphite carbon rod 61 and the quartz capillary 62. The aperture of the opening of the collector 11 is larger than the outer diameter of the element 6 composed of the graphite carbon rod 61 and the quartz capillary 62, so that the collector 11 can collect the liquid flowing downward along the outer wall of the graphite carbon rod 61 after electrolysis.

Example 2

The platinum precursor dispersion 2 involved in the present application is prepared by the following method: using deionized water as solvent, 100 mL of 0.1 M chloroplatinic acid solution is prepared for use. 1.25 mL of the reserve solution is diluted to 25 mL to obtain a 10 mM chloroplatinic acid solution.

200 mg of Ketjen black was weighed into a beaker, mixed with the above 10 mM chloroplatinic acid solution, stirred for 5 min, and then ultrasonically treated for 5 min to obtain a platinum precursor dispersion 2 with a platinum content of 10 w%.

Example 3

The method for preparing a platinum-carbon catalyst by atmospheric pressure discharge technology involved in the present application comprises the following steps:

A plasma generating device was built with reference to Example 1. The diameter of the graphite carbon rod 61 was 5 mm, the outer diameter of the quartz capillary 62 was 1.2 mm, and the inner diameter was 1 mm. The ratio of the diameter of the graphite carbon rod 61 to the outer diameter of the quartz capillary 62 was 4.2. The inclination of the oblique cross-section of the graphite carbon rod 61 was adjusted to 10°. The distance between the tip of the platinum wire electrode 8 and the top of the quartz capillary 62 was adjusted to 1 mm. The magnetic stirrer 3 was turned on at a speed of 240 rpm. The peristaltic pump 4 was turned on at a reading of 6 mL/min. Just when the liquid in the reactor gushes out from the upper end of the quartz capillary 62, turn on the switch of the stabilized DC power supply 10, use the stabilized DC power supply 10 to provide power, use the platinum wire electrode 8 as the anode, use the platinum precursor dispersion 2 overflowing from the end of the element 6 composed of the graphite carbon rod 61 and the quartz capillary 62 as the cathode, adjust the voltage reading to 400V, start discharging, and generate a stable plasma glow in the glow discharge area 7 between the positive and negative electrodes. After the discharge lasts for 20 minutes, turn off the power supply, peristaltic pump 4 and magnetic stirrer 3 in turn. The above operations are all carried out under atmospheric pressure. In the process of discharge, the turbid liquid overflowing from the top of the quartz capillary 62 flows downward along the outer wall of the graphite carbon rod 61 after electrolysis, and flows into the liquid collector 11 through the discontinuous gap between the adjacent graphite carbon rods 61 and the outer wall of the quartz capillary 62;

The collected discharge product was filtered, and the filter cake was washed with deionized water for 2-3 times, then placed in a vacuum drying oven, dried at 60° C. for 6 h, taken out and ground into powder to obtain the final platinum-carbon nanoparticle catalyst.

Example 4

The only difference from Example 3 is that the diameter of the graphite carbon rod 61 is 5 mm, the outer diameter of the quartz capillary 62 is 0.7 mm, and the inner diameter is 0.5 mm, so that the ratio of the diameter of the graphite carbon rod 61 to the outer diameter of the quartz capillary 62 is 7.

Example 5

The only difference from Example 3 is that the diameter of the graphite carbon rod 61 is 5 mm, the outer diameter of the quartz capillary 62 is 3 mm, and the inner diameter is 2.5 mm, so that the ratio of the diameter of the graphite carbon rod 61 to the outer diameter of the quartz capillary 62 is 1.7.

Example 6

The only difference from Example 3 is that the diameter of the graphite carbon rod 61 is 5 mm, the outer diameter of the quartz capillary 62 is 0.5 mm, and the inner diameter is 0.3 mm, so that the ratio of the diameter of the graphite carbon rod 61 to the outer diameter of the quartz capillary 62 is 10.

Example 7

The only difference from Example 3 is that the inclination of the oblique cross-section of the graphite carbon rod 61 is adjusted to 5°.

Example 8

The only difference from Example 3 is that the inclination of the oblique cross-section of the graphite carbon rod 61 is adjusted to 20°.

FIG2 is a schematic diagram of the top cross-section of the element composed of the graphite carbon rod and the quartz capillary in the above-mentioned Examples 3-8; FIG3 is a photograph of the plasma discharge area recorded by an ICCD camera at different times under a discharge voltage of 400V.

As can be seen from Figure 2, the diameter of the graphite carbon rod is fixed. In Figure 2(a), the ratio of the graphite carbon rod diameter to the outer diameter of the quartz capillary is 1.7. At this time, the diameter of the quartz capillary is too large, and the gap between the quartz capillary and the graphite carbon rod is large, resulting in the dispersion gushing out from the top not being in contact with the graphite carbon rod, making the conduction discontinuous during the discharge process and easily damaging the electrode. The photos of the plasma discharge area recorded by the ICCD camera at different times under a discharge voltage of 400V are shown in Figure 3(a), showing that the stability is relatively poor; in Figure 2(b), the ratio of the graphite carbon rod diameter to the outer diameter of the quartz capillary is 4.2. At this time, the quartz capillary is The diameter matches that of the graphite carbon rod, and the discharge is stable. The photos of the plasma discharge area recorded by the ICCD camera at different times under a discharge voltage of 400V are shown in Figure 3(b); in Figure 2(c), the ratio of the graphite carbon rod diameter to the outer diameter of the quartz capillary is 7. At this time, the quartz capillary is tightly attached to the outer wall of the graphite carbon rod, and the pores formed are small. The insoluble matter in the dispersion is easy to accumulate on the outer wall of the element, which is not conducive to the reaction; in Figure 2(d), the ratio of the graphite carbon rod diameter to the outer diameter of the quartz capillary is 10. At this time, the capillary diameter is too small, which is easy to cause capillary blockage, and the gap between the capillary and the graphite carbon rod is too large, making it difficult to fix the two.

As can be seen from Figure 4, the diameter of the graphite carbon rod is fixed. The slope of the oblique section of a single graphite carbon rod in Figure 4 (a) is 5°, which has certain requirements on the length of the carbon rod, and the tip is thin and easy to break during the cutting process; the slope of the oblique section of a single graphite carbon rod in Figure 4 (b) is 10°. After bundling three graphite carbon rods of the same size as shown in Figure 2, the suspended particles gushing out of the tip of the capillary after discharge can be solved to accumulate in the gap between adjacent graphite carbon rods, preventing the channel for liquid circulation from being blocked, causing slow or stagnant reactions. The slope of the oblique section of a single graphite carbon rod in Figure 4 (c) is 20°, which is relatively gentle. As the reaction continues, it still cannot effectively alleviate the accumulation of suspended particles in the gaps and tops of adjacent graphite carbon rods.

Performance Testing

1. Morphology characterization

The platinum-carbon nanoparticle catalysts provided in Examples 3-6 were analyzed by transmission electron microscopy, and the analysis structure is shown in FIG5 .

FIG5( a) is a low magnification TEM image of the platinum-carbon nanoparticle catalyst prepared in Example 3 of the present invention at a discharge voltage of 400 V;

FIG5( b ) is a high-resolution TEM morphology image of the platinum-carbon nanoparticle catalyst prepared in Example 3 of the present invention at a discharge voltage of 400 V;

FIG5( c ) is a low magnification TEM image of the platinum-carbon nanoparticle catalyst prepared in Example 5 of the present invention at a discharge voltage of 400 V;

FIG5( d ) is a high-resolution TEM morphology image of the platinum-carbon nanoparticle catalyst prepared in Example 5 of the present invention at a discharge voltage of 400 V;

As can be seen from Figure 5, in the product prepared by the method of the present invention, platinum nanoparticles are successfully loaded on Ketjen black and are evenly dispersed. The ratio of the graphite carbon rod diameter to the outer diameter of the quartz capillary affects the particle size of the platinum nanoparticles. When the ratio is 1.7, the average particle size of the platinum nanoparticles is about 4.8 nm, and when the ratio is 4.2, the average particle size is about 2.3 nm. This further illustrates that the appropriate ratio of the graphite carbon rod diameter to the outer diameter of the quartz capillary in the method can effectively prevent the agglomeration of platinum nanoparticles, and is a good supported catalyst for lithium oxygen batteries.

2. Lithium oxygen battery test

At a current density of 250 mA g ^-1 and a fixed capacity of 500 mAh g ^-1 , the first three charge-discharge cycle performances of the platinum-carbon catalyst prepared in Example 3 were evaluated and compared with commercial Pt/C.

As shown in Figure 6, the platinum-carbon catalyst prepared in the embodiment of the present invention is applied to the Li- _O2 battery test. During the charge and discharge process, the discharge voltage is maintained above 2.6V, and the charge voltage is below 3.1V, showing a lower overpotential, and the first charge and discharge overpotential is as low as 0.24V. The results show that compared with commercial Pt/C, the target catalyst prepared by the method of the present invention has good catalytic performance for lithium-oxygen battery performance tests.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims (9)

1. A method for preparing a platinum-carbon catalyst by an atmospheric pressure discharge technology is characterized in that a plasma generating device is adopted under atmospheric pressure, a voltage-stabilizing direct current power supply (10) is used for providing electric energy, a platinum wire electrode (8) is used as an anode, a platinum precursor dispersion liquid (2) overflowed from the end part of an element (6) formed by a graphite carbon rod (61) and a quartz capillary tube (62) is used as a cathode, stable plasma glow is formed between the anode and the cathode under a set voltage parameter, and discharged turbid liquid is collected, filtered, washed, dried and ground to obtain a platinum-carbon nano particle catalyst; the element (6) consisting of the platinum wire electrode (8) and the graphite carbon rod (61) and the quartz capillary tube (62) is coaxially arranged, and a ballast resistor (9) is arranged between the platinum wire electrode (8) and the positive electrode of the voltage-stabilizing direct-current power supply (10);

The graphite carbon rods (61) are a plurality of, the graphite carbon rods (61) are in a circumferential array with a quartz capillary (62) as a center, the upper end faces of the graphite carbon rods (61) are flush, the non-contact surfaces of the graphite carbon rods (61) and the quartz capillary (62) are provided with cambered surfaces, and a lead is led out from the negative electrode of the voltage-stabilizing direct-current power supply (10) and fixes the graphite carbon rods (61) and the quartz capillary (62) together;

The two cambered surfaces are symmetrically arranged by taking the axis of the graphite carbon rod (61) as the center, and the distance between the two cambered surfaces on the same graphite carbon rod (61) is gradually increased from top to bottom, so that the upper end of a single graphite carbon rod (61) is in a shape of a straight line, the extension lines of a plurality of straight line type central lines intersect at a point which is the center of a quartz capillary tube (62), three graphite carbon rods are arranged, and the included angles of the straight line type upper ends of the three graphite carbon rods are 120 degrees; the cambered surface is an oblique section, and the inclination of the section is 10 degrees;

The plasma generating device comprises a reaction liquid container (1), a peristaltic pump (4), a damper (5) and a collector (11); the reaction liquid container (1) is used for containing platinum precursor dispersion liquid (2), the platinum precursor dispersion liquid (2) flows through the damper (5) under the action of the peristaltic pump (4) and finally overflows from the top end of the quartz capillary tube (62), and the collector (11) is used for collecting turbid liquid.

2. The method for preparing a platinum carbon catalyst according to one of the atmospheric pressure discharge techniques according to claim 1, wherein the platinum wire electrode (8) has a diameter of 0.5-2 mm, the graphite carbon rod (61) has a diameter of 4-8 mm, the quartz capillary (62) has an outer diameter of 0.5-2 mm, and the wall thickness is not more than 0.5mm; the interval between the end part of the platinum wire electrode (8) and the end part of the quartz capillary tube (62) is 0.5-2 mm; the number of the graphite carbon rods (61) is 3, the diameters of the 3 graphite carbon rods (61) are the same, the lengths of the 3 graphite carbon rods are equal, and the ratio of the radius of the graphite carbon rods (61) to the radius of the quartz capillary tube (62) is 2-7.

3. The method for preparing a platinum carbon catalyst by an atmospheric pressure discharge technique according to claim 1, wherein the platinum wire electrode (8) has a length of 5-10 cm, the graphite carbon rod (61) has a length of 3-10 cm, and the quartz capillary (62) has a length of 5-12 cm; the length of the quartz capillary tube (62) is larger than that of the graphite carbon rod (61), and at least 2mm of the graphite carbon rod (61) is exposed at one end, close to the platinum wire electrode (8), of the quartz capillary tube (62).

4. The method for preparing a platinum carbon catalyst according to claim 1, wherein the platinum precursor dispersion (2) is prepared by the following method: and (3) preparing a platinum precursor solution by taking deionized water as a solvent, mixing and stirring uniformly with a carbon source carrier, and carrying out ultrasonic treatment to obtain a platinum precursor dispersion liquid (2).

5. The method for preparing a platinum carbon catalyst according to claim 4, wherein the platinum precursor is at least one selected from the group consisting of chloroplatinic acid, tetraamineplatinum nitrate and tetraamineplatinum oxalate;

the carbon source carrier is at least one selected from ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, graphene, glucose and sucrose.

6. The method for preparing a platinum carbon catalyst according to claim 4, wherein the platinum precursor dispersion (2) has a platinum concentration of 0.005 to 0.05M and a volume of the platinum precursor solution per 1 to g of the carbon source carrier of 50 to 500 to mL.

7. The method for preparing a platinum-carbon catalyst according to claim 1, wherein the voltage of the regulated dc power supply (10) is adjustable in a range of 300-700V, the flow rate of the peristaltic pump (4) is adjustable in a range of 2-20 mL/min, and the duration of the plasma discharge is 5-120 min.

8. A platinum carbon catalyst prepared by the method of preparing a platinum carbon catalyst using an atmospheric pressure discharge technique as claimed in any one of claims 1 to 7.

9. Use of a platinum carbon catalyst prepared by a method for preparing a platinum carbon catalyst using an atmospheric pressure discharge technique as defined in any one of claims 1 to 7 in a lithium-oxygen battery.