CN113140741A - Carbon-coated PtPdIr/C oxygen reduction electrocatalyst and preparation method and application thereof - Google Patents

Carbon-coated PtPdIr/C oxygen reduction electrocatalyst and preparation method and application thereof Download PDF

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CN113140741A
CN113140741A CN202110358446.1A CN202110358446A CN113140741A CN 113140741 A CN113140741 A CN 113140741A CN 202110358446 A CN202110358446 A CN 202110358446A CN 113140741 A CN113140741 A CN 113140741A
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邓晓婷
尹绍峰
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Shaoyang University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
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    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
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Abstract

The invention discloses a carbon-coated PtPdIr/C oxygen reduction electrocatalyst, and a preparation method and application thereof, and belongs to the technical field of energy materials and electrochemistry. Firstly, mixing a platinum source solution, a palladium source solution, an iridium source solution and a nano carbon carrier dispersion liquid, performing ultrasonic treatment to uniformly disperse the mixture, then transferring an obtained reaction precursor into a microwave high-pressure reaction kettle, performing constant-temperature reaction for 90-150 min at the temperature of 150-200 ℃, cooling to room temperature, centrifuging, washing and performing vacuum freeze drying on a sample to obtain the PtPdIr/C catalyst; and then carrying out surface carbon coating on the obtained PtPdIr/C catalyst by adopting an electrochemical vapor deposition (CVD) technology to obtain the carbon-coated PtPdIr/C catalyst. The carbon-coated PtPdIr/C catalyst prepared by the method has low Pt content, and the carbon layer coated on the surface can effectively prevent Pt-based alloy nanoparticles from being dissolved or agglomerated under the working condition of a fuel cell, so that the catalyst has high activity and stability.

Description

Carbon-coated PtPdIr/C oxygen reduction electrocatalyst and preparation method and application thereof
Technical Field
The invention belongs to the technical field of energy materials and electrochemistry, and particularly relates to a carbon-coated PtPdIr/C oxygen reduction electrocatalyst, and a preparation method and application thereof.
Background
The nano carbon material is cheap and highly conductive, and the surface of the nano carbon material can provide enough loading sites for platinum-based nano particles, so the nano carbon material becomes a carrier material of the fuel cell catalyst which is most widely applied at present. However, under the cathode operating conditions of proton exchange membrane fuel cells, severe corrosion of the carbon material occurs, and the electrochemical oxidation reaction (COR) of carbon is thermodynamically favored at potentials above 0.2V. When the operating temperature is less than 100 ℃ and the cell potential is less than 1.0V, the COR kinetics are slower; however, if the potential is higher than 1.0V, the carbon oxidation reaction rate becomes considerably significant. During start-stop conditions or fuel starvation of the cell, a transient hydrogen-oxygen interface is formed on the anode side, the voltage on the cathode side reaches a very high potential value (E >1.5V vs. RHE), and COR is very severe (Castaneira L, Dubauu L, Maillard F. Accordiated Stress Tests of Pt/HSAC electrolytes: an identity-Location Transmission Electron Study on the impedance of interference characteristics [ J ]. Electrolysis.2014; 5: 125-35). Carbon corrosion causes a large amount of loss of electrochemical active surface area, shedding and agglomeration of platinum particles, reduction of electric connectivity and change of pore surface characteristics, so that the kinetic loss of oxygen reduction reaction, mass transfer resistance and performance are greatly increased and greatly reduced. In order to slow down the shedding and agglomeration of the platinum particles, the carrier material should be selected from materials with chemical and electrochemical stability, strong interaction with the platinum nanoparticles, or surface coating of the catalyst.
Disclosure of Invention
Aiming at the technical problems that the fuel cell catalyst in the prior art is easy to fall off, agglomerate and the like in a harsh operating environment of a fuel cell and the service life is influenced, the invention aims to provide a carbon-coated PtPdIr/C oxygen reduction electrocatalyst, and a preparation method and application thereof. The carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared by the invention has low platinum content, high oxygen reduction catalytic activity and stability, and the catalytic activity is superior to commercial 20% Pt/C.
In order to achieve one of the above objects of the present invention, the present invention adopts the following technical solutions:
a preparation method of a carbon-coated PtPdIr/C oxygen reduction electrocatalyst specifically comprises the following steps:
1) ultrasonically dispersing a proper amount of nano carbon carrier in deionized water to form nano carbon carrier dispersion liquid; dissolving a platinum source in deionized water to form a platinum source solution; dissolving a palladium source in deionized water to form a palladium source solution; dissolving an iridium source in deionized water to form an iridium source solution; then sequentially adding the platinum source solution, the palladium source solution and the iridium source solution into the nano carbon carrier dispersion liquid according to the proportion, and uniformly mixing to obtain a reaction precursor;
2) transferring the reaction precursor obtained in the step 1) into a microwave high-pressure reaction kettle, reacting at a constant temperature of 150-200 ℃ for 90-150 min, cooling to room temperature after the reaction is finished, centrifuging, washing and carrying out vacuum freeze drying on the obtained product to obtain the PtPdIr/C catalyst;
3) putting the PtPdIr/C catalyst obtained in the step 2) into a tubular furnace, and putting the catalyst in a reaction chamber of H2/N2Heating to 600-900 deg.C in mixed atmosphere, and using hydrocarbon organic gas as carbon source coated by Chemical Vapor Deposition (CVD) carbon, and introducing into a reaction chamber2Hydrocarbon organic gas/N2Keeping the temperature of the mixed atmosphere at 600-900 ℃ for 10-50 min, and then keeping the temperature of the mixed atmosphere at N2And cooling to room temperature in the atmosphere to finally obtain the carbon-coated PtPdIr/C catalyst.
As a preferable scheme, in step 1), the nanocarbon support is at least one of graphene oxide, carbon black, carbon nanotubes, carbon nanofibers, and carbon nanowires.
As a preferable scheme, in the step 1), the platinum source is chloroplatinic acid (H)2PtCl6) And chloroplatinate.
More preferably, the chloroplatinate is sodium chloroplatinate (Na)2PtCl4) Potassium chloroplatinate (K)2PtCl4) And the like.
As a preferable embodiment, in step 1), the palladium source is chloropalladate.
More preferably, the chloropalladate is sodium chloropalladate (Na)2PdCl4) Potassium chloropalladate (K)2PdCl6) At least one of them.
As a preferable mode, in the step 1), the iridium source is chloroiridic acid (H)2IrCl6) And chloroiridate.
More preferably, the chloroiridate salt is sodium chloroiridate (Na)2IrCl4) Potassium chloroiridate (K)2IrCl4) In at leastOne kind of the medicine.
As a preferable scheme, in the step 1), the molar ratio of the platinum source, the palladium source and the iridium source is 1: 0.5-2: 0.5 to 2.
As a preferable scheme, in the step 2), the microwave high-pressure reaction conditions are as follows: the reaction is carried out in a microwave reactor, the microwave heating power is 500-3000W, and the heating rate is 5-10 ℃/min. The microwave can directly act on reactants, the heating rate is high, the heating is uniform, and the uniform distribution of the nano particles on the carrier is facilitated.
As a preferable scheme, in the step 2), the reaction temperature is 150-180 ℃, and the reaction time is 2 h.
As a preferable scheme, in the step 2), the vacuum freeze drying is carried out in the environment of-200 to-10 ℃ and-50 to-2 kPa until the sample is completely dried.
As a preferable scheme, in the step 3), H is increased in the temperature2/N2The flow rate of the mixed atmosphere is 30-300 mL/min, H2And N2The flow ratio of (1): 3 to 6. The purpose of introducing a proper amount of hydrogen in the temperature rising process is to reduce unreduced metal ions.
As a preferable scheme, in the step 3), the carbon coating conditions are as follows: by chemical vapor deposition on H2Hydrocarbon organic gas/N2The mixed atmosphere of (a), wherein: h2Hydrocarbon organic gas/N2The flow rate of the mixed atmosphere is 30-300 mL/min, and the flow rate of the mixed atmosphere is H2Hydrocarbon organic gas, N2The flow ratio of (A) to (B) is 1-3: 1:3 to 10.
In a preferred embodiment, in step 3), the hydrocarbon organic gas is at least one of methane, ethylene, propylene, and propyne.
Specifically, in the step 3), a proper amount of hydrogen is introduced in the chemical vapor deposition carbon process to ensure the generation of graphite carbon so as to prevent the generation of carbon black and tar; introduction of N2As carrier gas, carbon source gas is diluted to make the coating of carbon layer more uniform.
The second purpose of the invention is to provide the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared by the method.
As a preferable scheme, in the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, the metal accounts for 20 to 70 percent of the total catalyst by mass.
The third purpose of the invention is to provide the application of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared by the method in a fuel cell as a catalyst.
Compared with the prior art, the invention has the following beneficial effects:
(1) compared with the traditional hydrothermal reaction, the PtPdIr/C catalyst is prepared by carrying out the hydrothermal reduction reaction by adopting the microwave high-pressure reaction, and the microwave heating directly acts on the reactant, so that the heating efficiency is obviously improved, the whole reaction system is uniformly heated, and the nano particles with uniform size can be formed and uniformly dispersed on the carrier.
(2) The carbon layer coated on the surface of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst provided by the invention can effectively prevent the shedding and agglomeration of platinum-based nanoparticles, does not obstruct the contact of active sites and reactants, shows high oxygen reduction catalytic activity and stability, and has catalytic activity superior to that of a commercial 20% Pt/C catalyst.
(3) The carbon-coated PtPdIr/C catalyst prepared by the method has low Pt content, and the carbon layer coated on the surface can effectively prevent Pt-based alloy nanoparticles from being dissolved or agglomerated under the working condition of a fuel cell, so that the catalyst has high activity and stability.
(4) The preparation method of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst is simple to operate, low in cost and beneficial to large-scale production.
Drawings
FIG. 1 is a TEM image of the PtPdIr/C catalyst without carbon coating prepared in example 1 and the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in examples 2 to 6;
FIG. 2 is a comparison graph of CV curves of the PtPdIr/C catalyst without carbon coating prepared in example 1 and the PtPdIr/C oxygen reduction electrocatalyst with carbon coating prepared in examples 2-6 before and after 5000 voltage cycles.
Detailed Description
The following is a detailed description of the embodiments of the present invention, but the present invention is not limited to these embodiments, and any modifications or substitutions in the basic spirit of the embodiments are included in the scope of the present invention as claimed in the claims.
For a better understanding of the invention, and not as a limitation on the scope thereof, all numbers expressing quantities, percentages, and other numerical values used in this application are to be understood as being modified in all instances by the term "about". At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
The test methods used in the following examples are all conventional methods unless otherwise specified; the raw materials and reagents used are, unless otherwise specified, those commercially available from ordinary commercial sources.
Example 1 (comparative example)
The preparation method of the PtPdIr/C catalyst without carbon coating in this embodiment specifically includes the following steps:
(1) ultrasonically dispersing 50mg of nano carbon black in deionized water to form nano carbon black dispersion liquid; chloroplatinic acid (H)2PtCl6) Dissolving in deionized water to form H with concentration of 0.01M2PtCl6A solution; mixing sodium chloropalladate (Na)2PdCl4) Dissolving in deionized water to form Na with concentration of 0.01M2PdCl4A solution; reacting chloroiridic acid (H)2IrCl6) Dissolved in deionized water to form H with a concentration of 0.01M2IrCl6A solution; then 3mL of the H2PtCl6Solution, 6mL of the Na2PdCl4Solution, 3mL of the H2IrCl6Sequentially adding the solution into the nano carbon black dispersion liquid, and uniformly mixing by ultrasonic to obtain a reaction precursor;
(2) transferring the reaction precursor obtained in the step (1) into a microwave high-pressure reaction kettle, heating at 1500W, wherein the heating rate is 5 ℃/min, reacting at the constant temperature of 200 ℃ for 90min, cooling to room temperature after the reaction is finished, centrifuging and washing the product, and performing vacuum freeze drying at-30 ℃ and-2 kPa to obtain PtPdIr/C catalyst powder;
(3) putting the PtPdIr/C catalyst powder obtained in the step (2) into a tube furnace, and putting the tube furnace in H of 60mL/min2/N2(said H)2And N2The flow ratio of (1: 3) to 800 ℃ in the mixed atmosphere, keeping the temperature for 30min, and then carrying out N reaction2Cooling to room temperature in the atmosphere to finally obtain the PtPdIr/C catalyst without carbon coating; wherein: in the PtPdIr/C catalyst which is not coated by carbon, the mass percent of metal is 26.4 wt%.
Electrochemical performance detection
2mg of the PtPdIr/C catalyst which is not coated by CVD carbon and is prepared in the embodiment is dispersed in 1mL of perfluorosulfonic acid (nafion) aqueous solution with the concentration of 0.05 wt%, after ultrasonic treatment is carried out for half an hour, 15 mu L of the obtained mixed solution is dropped on a glassy carbon electrode, after natural drying, an electrochemical workstation is used for measuring the electrochemical performance of the PtPdIr/C catalyst which is not coated by CVD carbon and is prepared in the embodiment, wherein a saturated calomel electrode is taken as a reference electrode, a platinum sheet is taken as a counter electrode, and 0.1M HClO (hydrogen chloride oxide) is taken as an electrolyte4As an electrolyte, the sweep rate was 0.01V/S. The stability test is carried out at 0.6-1.2V and the sweep speed of 0.05V/S is 5000 cycles.
As can be seen from fig. 1a, the nanoparticles on the PtPdIr/C catalyst without CVD carbon coating are directly supported on the surface of carbon black, and the catalyst nanoparticles reduced at 200 ℃ are larger. As shown in fig. 2a, in the electrochemical performance stability test, after 5000 voltage cycles, the position of the oxygen reduction peak is reduced from 0.821V to 0.780V by comparing the cyclic voltammetry curves of the catalyst before and after the voltage cycles, which indicates that the overpotential of ORR is increased and the catalytic activity of the catalyst is obviously weakened; in addition, the electrochemical activity specific surface area of the catalyst is also obviously reduced, which indicates that the active sites of the catalyst are reduced. In summary, the performance of the PtPdIr/C catalyst without carbon coating prepared in this embodiment is significantly attenuated, and the stability of the catalyst needs to be improved.
Example 2
The preparation method of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to the embodiment specifically includes the following steps:
(1) ultrasonically dispersing 50mg of nano carbon black in deionized water to form nano carbon black dispersion liquid; chloroplatinic acid (H)2PtCl6) Dissolving in deionized water to form H with concentration of 0.01M2PtCl6A solution; mixing sodium chloropalladate (Na)2PdCl4) Dissolving in deionized water to form Na with concentration of 0.01M2PdCl4A solution; reacting chloroiridic acid (H)2IrCl6) Dissolved in deionized water to form H with a concentration of 0.01M2IrCl6A solution; then 3mL of the H2PtCl6Solution, 3mL of the Na2PdCl4Solution, 3mL of the H2IrCl6Sequentially adding the solution into the nano carbon black dispersion liquid, and uniformly mixing by ultrasonic to obtain a reaction precursor;
(2) transferring the reaction precursor obtained in the step (1) into a microwave high-pressure reaction kettle, heating at 1500W, reacting at a constant temperature of 150 ℃ for 120min at a heating rate of 5 ℃/min, cooling to room temperature after the reaction is finished, centrifuging and washing the product, and performing vacuum freeze drying at-30 ℃ and-2 kPa to obtain PtPdIr/C catalyst powder;
(3) putting the PtPdIr/C catalyst powder obtained in the step (2) into a tube furnace, and putting the tube furnace in H of 60mL/min2/N2(said H)2And N2At a flow ratio of 1:3) to 900 ℃ to obtain propylene (C)3H6) Carbon source coated with Chemical Vapor Deposition (CVD) carbon and H at 60mL/min2/C3H6/N2(said H)2、C3H6、N2At a flow ratio of 1:1:5) for 10min, and then carrying out N reaction2And cooling to room temperature in the atmosphere to finally prepare the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, wherein: in the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, the mass percent of metal is 23.1 wt%.
Electrochemical performance detection
2mg of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the embodiment is dispersed in 1mL of perfluorosulfonic acid (nafion) aqueous solution with the concentration of 0.05 wt%, after ultrasonic treatment is carried out for half an hour, 15 mu L of the obtained mixed solution is dropped on a glassy carbon electrode, after natural drying, the electrochemical performance of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst is measured by an electrochemical workstation, wherein a saturated calomel electrode is taken as a reference electrode, a platinum sheet is taken as a counter electrode, and 0.1M HClO is taken as a hydrogen peroxide solution4As an electrolyte, the sweep rate was 0.01V/S. The stability test is carried out at 0.6-1.2V and the sweep speed of 0.05V/S is 5000 cycles.
As can be seen from FIG. 1b, the PtPdIr/C catalyst prepared after 10min CVD carbon coating has a thin carbon coating on the surface, but the carbon coating is not uniform enough. As shown in fig. 2b, in the electrochemical performance stability test, after 5000 voltage cycles, the position of the oxygen reduction peak is reduced from 0.822V to 0.786V by comparing the cyclic voltammetry curves of the catalyst before and after the voltage cycles, which indicates that the overpotential of ORR is increased and the catalytic activity of the catalyst is obviously weakened; in addition, the electrochemical activity specific surface area of the catalyst is also reduced, but the electrochemical activity specific surface area is reduced less compared with that of the example 1, which shows that the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the example has improved stability compared with the non-CVD carbon-coated PtPdIr/C electrocatalyst prepared in the example 1.
Example 3
The preparation method of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to the embodiment specifically includes the following steps:
(1) ultrasonically dispersing 50mg of nano carbon black in deionized water to form nano carbon black dispersion liquid; chloroplatinic acid (H)2PtCl6) Dissolving in deionized water to form H with concentration of 0.01M2PtCl6A solution; mixing sodium chloropalladate (Na)2PdCl4) Dissolving in deionized water to form Na with concentration of 0.01M2PdCl4A solution; reacting chloroiridic acid (H)2IrCl6) Dissolved in deionized water to form H with a concentration of 0.01M2IrCl6A solution; then 3mL of the H2PtCl6Solution, 1.5mLThe above Na2PdCl4Solution, 4mL of the H2IrCl6Sequentially adding the solution into the nano carbon black dispersion liquid, and uniformly mixing by ultrasonic to obtain a reaction precursor;
(2) transferring the reaction precursor obtained in the step (1) into a microwave high-pressure reaction kettle, heating at the power of 2000W, reacting at the constant temperature of 160 ℃ for 140min, cooling to room temperature after the reaction is finished, centrifuging and washing the product, and performing vacuum freeze drying at the temperature of-30 ℃ and under the condition of-2 kPa to obtain PtPdIr/C catalyst powder;
(3) putting the PtPdIr/C catalyst powder obtained in the step (2) into a tube furnace, and putting the tube furnace in H of 60mL/min2/N2(said H)2And N2At a flow ratio of 1:3) to 800 ℃ to obtain propylene (C)3H6) Carbon source coated with Chemical Vapor Deposition (CVD) carbon and H at 60mL/min2/C3H6/N2(said H)2、C3H6、N2At a flow ratio of 1:1:5) for 30min, and then carrying out constant temperature preservation in N2And cooling to room temperature in the atmosphere to finally prepare the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, wherein: in the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, the mass percent of metal is 20.3 wt%.
Electrochemical performance detection
2mg of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the embodiment is dispersed in 1mL of perfluorosulfonic acid (nafion) aqueous solution with the concentration of 0.05 wt%, after ultrasonic treatment is carried out for half an hour, 15 mu L of the obtained mixed solution is dropped on a glassy carbon electrode, after natural drying, an electrochemical workstation is used for measuring the electrochemical performance of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the embodiment, wherein a saturated calomel electrode is used as a reference electrode, a platinum sheet is used as a counter electrode, and 0.1M HClO is used4As an electrolyte, the sweep rate was 0.01V/S. The stability test is carried out at 0.6-1.2V and the sweep speed of 0.05V/S is 5000 cycles.
As can be seen from fig. 1C, the PtPdIr/C catalyst prepared by the CVD carbon coating for 30min has a thin carbon layer coating on the surface, and the carbon layer is uniformly coated. As shown in fig. 2c, in the electrochemical performance stability test, after 5000 voltage cycles, the position of the oxygen reduction peak and the electrochemical activity specific surface area are almost kept unchanged by comparing the cyclic voltammetry curves of the catalyst before and after voltage cycles, which indicates that the catalyst prepared by carbon coating for 30min has stable performance.
Example 4 (comparative example)
The preparation method of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to the embodiment specifically includes the following steps:
(1) ultrasonically dispersing 50mg of nano carbon black in deionized water to form nano carbon black dispersion liquid; chloroplatinic acid (H)2PtCl6) Dissolving in deionized water to form H with concentration of 0.01M2PtCl6A solution; mixing sodium chloropalladate (Na)2PdCl4) Dissolving in deionized water to form Na with concentration of 0.01M2PdCl4A solution; reacting chloroiridic acid (H)2IrCl6) Dissolved in deionized water to form H with a concentration of 0.01M2IrCl6A solution; then 3mL of the H2PtCl6Solution, 6mL of the Na2PdCl4Solution, 2mL of the H2IrCl6Sequentially adding the solution into the nano carbon black dispersion liquid, and uniformly mixing by ultrasonic to obtain a reaction precursor;
(2) transferring the reaction precursor obtained in the step (1) into a microwave high-pressure reaction kettle, heating at 3000W, reacting at a constant temperature of 180 ℃ for 100min at a heating rate of 10 ℃/min, cooling to room temperature after the reaction is finished, centrifuging and washing the product, and performing vacuum freeze drying at-30 ℃ and-2 kPa to obtain PtPdIr/C catalyst powder;
(3) putting the PtPdIr/C catalyst powder obtained in the step (2) into a tube furnace, and putting the tube furnace in H of 60mL/min2/N2(said H)2And N2At a flow ratio of 1:3) to 700 ℃ to obtain propylene (C)3H6) Carbon source coated with Chemical Vapor Deposition (CVD) carbon and H at 60mL/min2/C3H6/N2(said H)2、C3H6、N2Flow rate ratio of1:1:5) for 40min at constant temperature, and then carrying out N reaction2And cooling to room temperature in the atmosphere to finally prepare the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, wherein: in the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, the mass percent of metal is 21.4 wt%.
Electrochemical performance detection
2mg of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the embodiment is dispersed in 1mL of perfluorosulfonic acid (nafion) aqueous solution with the concentration of 0.05 wt%, after ultrasonic treatment is carried out for half an hour, 15 mu L of the obtained mixed solution is dropped on a glassy carbon electrode, after natural drying, the electrochemical performance of the PtPdIr/C electrocatalyst is measured by an electrochemical workstation, wherein a saturated calomel electrode is taken as a reference electrode, a platinum sheet is taken as a counter electrode, and 0.1M HClO is taken as an electrode4As an electrolyte, the sweep rate was 0.01V/S. The stability test is carried out at 0.6-1.2V and the sweep speed of 0.05V/S is 5000 cycles.
As can be seen from fig. 1d, the PtPdIr/C catalyst prepared by the present embodiment after 40min CVD carbon coating has a thin carbon layer coated on the surface, and the carbon layer is uniformly coated, but the coated carbon layer is thicker. As shown in fig. 2d, in the electrochemical performance stability test, after 5000 voltage cycles, the position of the oxygen reduction peak and the electrochemical activity specific surface area can be found to be almost unchanged by comparing the cyclic voltammetry curves of the catalyst before and after the voltage cycles, which indicates that the catalyst prepared by carbon coating for 40min has stable performance; however, the initial oxygen reduction potential of the catalyst was 0.767V, which is lower than the initial oxygen reduction potential of the catalysts prepared in examples 1 to 3, and the electrochemical specific surface area was smaller, indicating that the carbon layer coated on the surface of the catalyst was thicker and the catalytic activity was affected by the coating of the carbon layer.
Example 5
The preparation method of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to the embodiment specifically includes the following steps:
(1) ultrasonically dispersing 50mg of nano carbon black in deionized water to form nano carbon black dispersion liquid; chloroplatinic acid (H)2PtCl6) Dissolving in deionized water to form H with concentration of 0.01M2PtCl6A solution; mixing sodium chloropalladate (Na)2PdCl4) Dissolving in deionized water to form Na with concentration of 0.01M2PdCl4A solution; reacting chloroiridic acid (H)2IrCl6) Dissolved in deionized water to form H with a concentration of 0.01M2IrCl6A solution; then 3mL of the H2PtCl6Solution, 3mL of the Na2PdCl4Solution, 6mL of the H2IrCl6Sequentially adding the solution into the nano carbon black dispersion liquid, and uniformly mixing by ultrasonic to obtain a reaction precursor;
(2) transferring the reaction precursor obtained in the step (1) into a microwave high-pressure reaction kettle, heating at 1700W, reacting at 190 ℃ for 90min at constant temperature, cooling to room temperature after the reaction is finished, centrifuging and washing the product, and performing vacuum freeze drying at-30 ℃ and-2 kPa to obtain PtPdIr/C catalyst powder;
(3) putting the PtPdIr/C catalyst powder obtained in the step (2) into a tube furnace, and putting the tube furnace in H of 60mL/min2/N2(said H)2And N2At a flow ratio of 1:3) to 800 ℃ to obtain propylene (C)3H6) Carbon source coated with Chemical Vapor Deposition (CVD) carbon and H at 60mL/min2/C3H6/N2(said H)2、C3H6、N2At a flow ratio of 1:1:5) for 30min, and then carrying out constant temperature preservation in N2And cooling to room temperature in the atmosphere to finally prepare the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, wherein: in the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, the mass percent of metal is 25.7 wt%.
Electrochemical detection
2mg of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the embodiment is dispersed in 1mL of perfluorosulfonic acid (nafion) aqueous solution with the concentration of 0.05 wt%, after ultrasonic treatment is carried out for half an hour, 15 mu L of the obtained mixed solution is dropped on a glassy carbon electrode, after natural drying, an electrochemical workstation is used for measuring the electrochemical performance of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the embodiment, wherein a saturated calomel electrode is used as a reference electrode, a platinum sheet is used as a counter electrode, and 0.1M HClO is used4Is used as electrolyte and the sweeping speed is 0.01Vand/S. The stability test is carried out at 0.6-1.2V and the sweep speed of 0.05V/S is 5000 cycles.
As can be seen from fig. 1e, the PtPdIr/C catalyst prepared by CVD carbon coating for 30min has a thin carbon layer coating on the surface, and the carbon layer is uniformly distributed; as shown in FIG. 2e, the prepared PtPdIr/C catalyst has higher ORR stability after 5000 voltage cycles.
Example 6
The preparation method of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to the embodiment specifically includes the following steps:
(1) ultrasonically dispersing 50mg of nano carbon black in deionized water to form nano carbon black dispersion liquid; chloroplatinic acid (H)2PtCl6) Dissolving in deionized water to form H with concentration of 0.01M2PtCl6A solution; mixing sodium chloropalladate (Na)2PdCl4) Dissolving in deionized water to form Na with concentration of 0.01M2PdCl4A solution; reacting chloroiridic acid (H)2IrCl6) Dissolved in deionized water to form H with a concentration of 0.01M2IrCl6A solution; then 3mL of the H2PtCl6Solution, 1.5mL of the Na2PdCl4Solution, 1.5mL of the H2IrCl6Sequentially adding the solution into the nano carbon black dispersion liquid, and uniformly mixing by ultrasonic to obtain a reaction precursor;
(2) transferring the reaction precursor obtained in the step (1) into a microwave high-pressure reaction kettle, heating at the power of 2000W, reacting at the constant temperature of 180 ℃ for 120min at the heating rate of 10 ℃/min, cooling to room temperature after the reaction is finished, centrifuging and washing the product, and performing vacuum freeze drying at the temperature of-30 ℃ and the pressure of-2 kPa to obtain PtPdIr/C catalyst powder;
(3) putting the PtPdIr/C catalyst powder obtained in the step (2) into a tube furnace, and putting the tube furnace in H of 60mL/min2/N2(said H)2And N2At a flow ratio of 1:3) to 600 ℃ to obtain propylene (C)3H6) Carbon source coated with Chemical Vapor Deposition (CVD) carbon and H at 60mL/min2/C3H6/N2(said H)2、C3H6、N2At a flow ratio of 1:1:5) for 50min, and then carrying out constant temperature preservation in N2And cooling to room temperature in the atmosphere to finally prepare the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, wherein: in the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, the mass percent of metal is 15.7 wt%.
Electrochemical performance detection
2mg of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the embodiment is dispersed in 1mL of perfluorosulfonic acid (nafion) aqueous solution with the concentration of 0.05 wt%, after ultrasonic treatment is carried out for half an hour, 15 mu L of the obtained mixed solution is dropped on a glassy carbon electrode, after natural drying, an electrochemical workstation is used for measuring the electrochemical performance of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared in the embodiment, wherein a saturated calomel electrode is used as a reference electrode, a platinum sheet is used as a counter electrode, and 0.1M HClO is used4As an electrolyte, the sweep rate was 0.01V/S. The stability test is carried out at 0.6-1.2V and the sweep speed of 0.05V/S is 5000 cycles.
As can be seen from FIG. 1f, the surface of the PtPdIr/C catalyst prepared by CVD carbon coating at 600 ℃ for 50min is coated by a carbon layer, and the carbon layer is thicker and uniformly coated. As shown in fig. 2f, in the electrochemical performance stability test, after 5000 voltage cycles, the position of the oxygen reduction peak and the electrochemical activity were reduced and the specific surface area of the electrochemical activity was reduced by comparing the cyclic voltammetry curves of the catalyst before and after the voltage cycles, which indicates that the degree of graphitization by CVD carbon coating at 600 ℃ for 50min was lower and the corrosion resistance was reduced compared to the catalyst coated with carbon at 800 ℃.

Claims (10)

1. A preparation method of a carbon-coated PtPdIr/C oxygen reduction electrocatalyst is characterized by comprising the following steps: the method specifically comprises the following steps:
1) ultrasonically dispersing a proper amount of nano carbon carrier in deionized water to form nano carbon carrier dispersion liquid; dissolving a platinum source in deionized water to form a platinum source solution; dissolving a palladium source in deionized water to form a palladium source solution; dissolving an iridium source in deionized water to form an iridium source solution; then sequentially adding the platinum source solution, the palladium source solution and the iridium source solution into the nano carbon carrier dispersion liquid according to the proportion, and uniformly mixing to obtain a reaction precursor;
2) transferring the reaction precursor obtained in the step 1) into a microwave high-pressure reaction kettle, reacting at a constant temperature of 150-200 ℃ for 90-150 min, cooling to room temperature after the reaction is finished, centrifuging, washing and carrying out vacuum freeze drying on the obtained product to obtain the PtPdIr/C catalyst;
3) putting the PtPdIr/C catalyst obtained in the step 2) into a tubular furnace, and putting the catalyst in a reaction chamber of H2/N2Heating to 600-900 deg.C in mixed atmosphere, using hydrocarbon organic gas as carbon source coated by chemical vapor deposition, and reacting in H2Hydrocarbon organic gas/N2Keeping the temperature of the mixed atmosphere at 600-900 ℃ for 10-50 min, and then keeping the temperature of the mixed atmosphere at N2And cooling to room temperature in the atmosphere to finally obtain the carbon-coated PtPdIr/C catalyst.
2. The method of preparing a carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to claim 1, wherein: in the step 1), the nano carbon carrier is at least one of graphene oxide, nano carbon black, a carbon nano tube, a carbon nano fiber and a carbon nano wire.
3. The method of preparing a carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to claim 1, wherein: in the step 1), the platinum source is at least one of chloroplatinic acid and chloroplatinic acid salt; the palladium source is chloropalladate; the iridium source is at least one of chloroiridic acid and chloroiridate.
4. The method of preparing a carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to claim 1, wherein: in the step 1), the molar ratio of the platinum source to the palladium source to the iridium source is 1: 0.5-2: 0.5 to 2.
5. The method of preparing a carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to claim 1, wherein: in the step 2), the conditions of the microwave high-pressure reaction are as follows: the reaction is carried out in a microwave reactor, the microwave heating power is 500-3000W, and the heating rate is 5-10 ℃/min.
6. The method of preparing a carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to claim 1, wherein: in the step 3), the hydrocarbon organic gas is at least one of methane, ethylene, propylene or propyne.
7. The method of preparing a carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to claim 1, wherein: step 3) in the temperature rising process H2/N2The flow rate of the mixed atmosphere is 30-300 mL/min, H2And N2The flow ratio of (1): 3 to 6.
8. The method of preparing a carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to claim 1, wherein: in the step 3), the carbon coating conditions are as follows: by chemical vapor deposition on H2Hydrocarbon organic gas/N2The mixed atmosphere of (a), wherein: h2Hydrocarbon organic gas/N2The flow rate of the mixed atmosphere is 30-300 mL/min, and the flow rate of the mixed atmosphere is H2Hydrocarbon organic gas, N2The flow ratio of (A) to (B) is 1-3: 1:3 to 10.
9. The carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared by the preparation method of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst according to any one of claims 1 to 8; wherein: in the carbon-coated PtPdIr/C oxygen reduction electrocatalyst, the mass percent of metal in the whole catalyst is 20-70%.
10. The use of the carbon-coated PtPdIr/C oxygen reduction electrocatalyst prepared according to any one of claims 1 to 8 as a catalyst in a fuel cell.
CN202110358446.1A 2021-04-01 2021-04-01 Carbon-coated PtPdIr/C oxygen reduction electrocatalyst and preparation method and application thereof Pending CN113140741A (en)

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