Electrocatalyst and preparation method thereof

Abstract

The invention relates to the technical field of electrolyzed water and fuel cells, in particular to an electrocatalyst and a preparation method thereof. The preparation method of the electrocatalyst comprises the following steps: taking a conductive carbon material as a working electrode, fixedly placing the working electrode, a counter electrode and a reference electrode in an electrolyte, keeping the potential of the working electrode at-1 to-4 V in a constant potential mode or loading 1-5 mA current in a constant current mode for activation to obtain an activated conductive carbon material; reacting the activated conductive carbon material with a noble metal salt solution to obtain an electrocatalyst; the precious metal salt solution comprises a platinum salt solution and / or a palladium salt solution. By controlling the potential or current in the activation process, it can be guaranteed that the electrocatalyst has low precious metal loading capacity and high catalytic performance, and in addition, the method has the advantages of being simple in process, easy to operate, controllable in process and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of water electrolysis and fuel cells, and in particular to an electrocatalyst and a preparation method thereof. Background Art

[0002] As an important part of the national energy strategy, hydrogen energy has attracted widespread attention. As the main source of "green hydrogen", hydrogen production by water electrolysis has aroused great interest and active layout among various companies. Hydrogen fuel cells, as a carrier of hydrogen energy, are widely used in vehicle transportation, shipping, grid energy storage and other fields. At the same time, due to its high cost, proton exchange membrane water electrolysis (PEM) water electrolysis is still in the laboratory research stage and has not completed large-scale commercial operation. In addition, there is a constant call for cost reduction of hydrogen fuel cell systems, especially the cost reduction and efficiency improvement strategy of electrocatalyst materials, which account for about 13% of the cost of the whole vehicle. It is a hot topic of research and future development trend of electrocatalyst companies. Realizing the cost reduction and efficiency improvement of electrocatalyst materials has become a key technology to promote cost reduction and rapid popularization of battery stacks and systems. At present, the loading of precious metals in electrocatalysts is relatively high, resulting in low utilization rate of precious metals and high cost of use.

[0003] Therefore, there is an urgent need to develop an electrocatalyst with low precious metal loading suitable for hydrogen fuel cells. Summary of the Invention

[0004] The present invention aims to solve, at least to some extent, one of the technical problems in the related art. To this end, the present invention provides an electrocatalyst and a method for preparing the same. The electrocatalyst prepared by the method of the present invention has a low noble metal loading and high catalytic performance.

[0005] A first aspect of the present invention provides a method for preparing an electrocatalyst, comprising the following steps:

[0006] A conductive carbon material is used as a working electrode, and the working electrode, a counter electrode and a reference electrode are fixedly placed in an electrolyte. The potential of the working electrode is maintained at -1 to -4 V in a constant potential manner or a current of 1 to 5 mA is loaded in a constant current manner for activation to obtain an activated conductive carbon material; the activated conductive carbon material is reacted with a noble metal salt solution to obtain an electrocatalyst; the noble metal salt solution includes a platinum salt solution and / or a palladium salt solution.

[0007] The present invention provides a method for preparing an electrocatalyst, which adopts a three-electrode system to activate the working electrode to obtain an activated conductive carbon material, and then uses the activated conductive carbon material as a reducing agent to reduce the precious metal ions in the precious metal salt solution. By controlling the potential or current during the activation process, the present invention can ensure that the electrocatalyst of the present invention has a low precious metal loading and a high catalytic performance, and can effectively solve the problems of low precious metal utilization and increased cost of membrane electrode and battery stack caused by the high precious metal loading in the electrocatalyst, and the problem of significant attenuation of electrocatalyst activity and durability caused by too low precious metal loading. It can be seen that the preparation method of the present invention is of great significance for expanding the application scope of hydrogen as a new energy source; in addition, the method adopted by the present invention has the advantages of simple process, easy operation, controllable process and low cost.

[0008] In some embodiments of the present invention, the potential of the working electrode is maintained at -2 to -2.4 V in a constant potential manner. This can further improve the catalytic performance of the electrocatalyst.

[0009] In some embodiments of the present invention, the activation time is 20 seconds to 3 minutes. Activation can increase the reactivity of the electrode, increase the number of active sites on the surface of the conductive carbon material, and allow cations in the electrolyte to be loaded onto the surface of the conductive carbon material, thereby improving the electrochemical performance of the electrode. By controlling the activation time, the present invention allows the electrode to reach a stable electrochemical state, which is beneficial for subsequent reactions of the conductive carbon material.

[0010] In some embodiments of the present invention, the reaction time is ≥5 seconds. Controlling the reaction time can control the size and loading of the noble metal particles in the electrocatalyst. Furthermore, controlling the reaction time can evenly disperse the noble metal in the conductive carbon material, preventing agglomeration and thereby improving the electrocatalytic performance of the electrocatalyst.

[0011] In some embodiments of the present invention, the conductive carbon material comprises one or more of graphite, carbon nanotubes, carbon black, biochar, and activated carbon. These conductive carbon materials have good electrical conductivity, can quickly transfer charge, and improve the efficiency of the activation process. In addition, these conductive carbon materials are structurally stable, which can improve the stability of the electrocatalyst.

[0012] In some embodiments of the present invention, the electrolyte comprises an organic electrolyte salt.

[0013] In some embodiments of the present invention, the organic electrolyte salt includes an organic lithium salt and / or an organic ammonium salt.

[0014] In some embodiments of the present invention, the organic lithium salt includes one or more of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(oxalatoborate), lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, and tris(trifluoromethylsulfonyl)methyllithium. The above organic lithium salts have high ionic conductivity and can form good ion transport channels in the electrolyte, which is conducive to loading lithium ions into the above conductive carbon material.

[0015] In some embodiments of the present invention, the organic ammonium salt includes one or more of ammonium tetrafluoroborate, ammonium hexafluorophosphate, bistrifluoromethylsulfonyl imide, bisfluorosulfonyl imide, tetraethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, tetraethylammonium bistrifluoromethylsulfonyl imide, tetraethylammonium bisfluorosulfonyl imide, methylammonium tetrafluoroborate, and methylammonium hexafluorophosphate. The organic ammonium salt has high ionic conductivity and can form a good ion transport channel in the electrolyte, which is conducive to loading ammonium ions in the conductive carbon material.

[0016] In some embodiments of the present invention, the concentration of the organic electrolyte salt is 0.01 to 0.1 mol / L based on the volume of the electrolyte. An appropriate electrolyte salt concentration ensures good ionic conductivity in the electrolyte, thereby improving the rate and efficiency of the electrode reaction. Furthermore, excessive electrolyte salt concentration can lead to concentration polarization, a phenomenon in which the difference in ion concentration between the electrode surface and the solution is too large, thus affecting the uniformity of the electrode reaction. Controlling the concentration can reduce concentration polarization and ensure uniformity during the activation process.

[0017] In some embodiments of the present invention, the concentration of the noble metal salt is 1 mmol / L to 1 mol / L based on the volume of the noble metal salt solution. The concentration of the noble metal salt affects the deposition rate of metal ions. By adjusting the concentration, the present invention forms more uniform and smaller particles in the conductive carbon material, thereby improving the electrocatalytic performance of the electrocatalyst. In addition, by controlling the concentration of the noble metal salt, the bonding strength between the noble metal particles and the conductive carbon material can be optimized, reducing the shedding of the noble metal particles during use and improving the stability of the electrocatalyst.

[0018] A second aspect of the present invention provides an electrocatalyst prepared by the above-mentioned method for preparing the electrocatalyst.

[0019] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0021] Figure 1 A flow chart showing a method for preparing an electrocatalyst according to one embodiment of the present invention;

[0022] Figure 2 shows the polarization activation curves of G1, G2, and G3 of Example 1 of the present invention;

[0023] Figure 3 shows the X-ray diffraction pattern of the Pt / G electrocatalyst of Example 1 of the present invention;

[0024] Figure 4 shows an energy dispersive spectrometer analysis diagram of a Pt / G electrocatalyst obtained in Example 1 of the present invention using a scanning electron microscope;

[0025] Figure 5 An electron microscope image of the Pt / G electrocatalyst of Example 1 of the present invention is shown;

[0026] Figure 6 The hydrogen evolution reaction curves of the electrocatalysts (Pd / G, Pt / G, PtPd / G) of Example 1 of the present invention and the commercial electrocatalyst (Pt / C / G) are shown;

[0027] Figure 7 shows the hydrogen evolution reaction curve of the electrocatalyst of Example 2 of the present invention;

[0028] Figure 8 shows the hydrogen evolution reaction curve of the electrocatalyst of Example 3 of the present invention;

[0029] Figure 9 shows the hydrogen evolution reaction curve of the electrocatalyst of Example 4 of the present invention;

[0030] Figure 10 shows the hydrogen evolution reaction curves of the electrocatalysts of Examples 5 and 6 of the present invention;

[0031] Figure 11 shows the hydrogen evolution reaction curves of the electrocatalysts of Examples 7 and 8 of the present invention;

[0032] Figure 12 shows the hydrogen evolution reaction curve of the Pt / G electrocatalyst of Example 1 of the present invention;

[0033] Figure 13 The graph shows the oxygen reduction reaction curve of the Pt / G electrocatalyst of Example 1 of the present invention. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0035] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0036] Cost reduction is a growing trend in hydrogen fuel cell systems. Cost reduction and efficiency improvement strategies for electrocatalyst materials, which account for approximately 13% of the vehicle cost, are a hot topic for catalyst companies and a future development trend. Achieving cost reduction and efficiency improvement for electrocatalyst materials is a key technology driving cost reduction and rapid adoption of fuel cell stacks and systems. Currently, the high loading of precious metals in electrocatalysts results in low precious metal utilization and high operating costs.

[0037] To this end, the present invention provides a method for preparing an electrocatalyst, which uses a three-electrode system to activate the working electrode to obtain an activated conductive carbon material, and then uses the activated conductive carbon material as a reducing agent to reduce the precious metal ions in the precious metal salt solution. The method adopted by the present invention has the advantages of simple process, easy operation, controllable process, and low cost. By controlling the potential or current during the activation process, it can ensure that the electrocatalyst of the present invention has a lower precious metal loading and higher catalytic performance, and can effectively solve the problems of low precious metal utilization and increased cost of membrane electrode and battery stack due to the high precious metal loading in the electrocatalyst, and the problem of significant attenuation of electrocatalyst activity and durability due to too low precious metal loading. It can be seen that the preparation method of the present invention is of great significance for expanding the application scope of hydrogen as a new energy source.

[0038] A first aspect of the present invention provides a method for preparing an electrocatalyst, comprising the following steps:

[0039] S100, using a conductive carbon material as a working electrode, fixing the working electrode, counter electrode and reference electrode in an electrolyte, maintaining the potential of the working electrode at -1 to -4 V in a constant potential manner or loading a current of 1 to 5 mA in a constant current manner for activation, to obtain an activated conductive carbon material.

[0040] In some embodiments of the present invention, the activation time is 20s to 3min. As an example, the activation time can be 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, 2min, 2.5min, or 3min. Activation can increase the reactivity of the electrode, increase the number of active sites on the surface of the conductive carbon material, and allow cations in the electrolyte to be carried on the surface of the conductive carbon material, thereby improving the electrochemical performance of the electrode. By controlling the activation time, the present invention allows the electrode to reach a stable electrochemical state, which is beneficial for the conductive carbon material to undergo subsequent reactions.

[0041] In some preferred embodiments of the present invention, the activation time is 20s to 30s.

[0042] The present invention has no special requirements for the conductive carbon material, as long as it does not react with the electrolyte. In some embodiments of the present invention, the conductive carbon material includes one or more of graphite, carbon nanotubes, carbon black, biochar, and activated carbon. These conductive carbon materials have good electrical conductivity, can quickly transfer charge, and improve the efficiency of the activation process. In addition, the conductive carbon material has a stable structure, which can improve the stability of the electrocatalyst.

[0043] In some embodiments of the present invention, the counter electrode comprises an inert material, specifically one or more of platinum and a carbon electrode.

[0044] In some embodiments of the present invention, the present invention has no special requirements for the reference electrode, and any commercially available reference electrode can be used, such as saturated mercurous sulfate / mercury, saturated calomel electrode or Ag / AgCl.

[0045] In some embodiments of the present invention, the electrolyte includes an organic electrolyte salt; the organic electrolyte salt includes an organic lithium salt and / or an organic ammonium salt.

[0046] In some embodiments of the present invention, the organic lithium salt includes one or more of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(oxalatoborate), lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, and tris(trifluoromethylsulfonyl)methyllithium. The above organic lithium salts have high ionic conductivity and can form good ion transport channels in the electrolyte, which is conducive to loading lithium ions into the above conductive carbon material.

[0047] In some embodiments of the present invention, the organic ammonium salt includes one or more of ammonium tetrafluoroborate, ammonium hexafluorophosphate, bistrifluoromethylsulfonyl imide, bisfluorosulfonyl imide, tetraethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, tetraethylammonium bistrifluoromethylsulfonyl imide, tetraethylammonium bisfluorosulfonyl imide, methylammonium tetrafluoroborate, and methylammonium hexafluorophosphate. The organic ammonium salt has high ionic conductivity and can form a good ion transport channel in the electrolyte, which is conducive to loading ammonium ions in the conductive carbon material.

[0048] In some embodiments of the present invention, the organic electrolyte salt further includes a solvent.

[0049] In some embodiments of the present invention, the solvent includes one or more of acetonitrile, propionitrile, N,N-dimethylformamide, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, sulfolane, dimethyl sulfone, trimethyl phosphate, and triethyl phosphate.

[0050] In some embodiments of the present invention, the concentration of the organic electrolyte salt is 0.01 to 0.1 mol / L based on the volume of the electrolyte. As an example, the concentration of the organic electrolyte salt can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1 mol / L based on the volume of the electrolyte. An appropriate electrolyte salt concentration can ensure that the electrolyte has good ion conductivity, thereby improving the rate and efficiency of the electrode reaction; in addition, an excessively high electrolyte salt concentration can lead to concentration polarization, i.e., the difference in ion concentration between the electrode surface and the solution is too large, thereby affecting the uniformity of the electrode reaction. By controlling the concentration, concentration polarization can be reduced to ensure the uniformity of the activation process.

[0051] In some embodiments of the present invention, as an example, the potential of the working electrode can be maintained at -1, -1.5, -2, -2.4, -2.5, -3, -3.5, or -4 V in a constant potential manner.

[0052] In some embodiments of the present invention, the potential of the working electrode is maintained at -2 to -2.4 V in a constant potential manner. This can further improve the catalytic performance of the electrocatalyst.

[0053] In some embodiments of the present invention, as examples, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mA current is loaded in a constant current manner.

[0054] In some embodiments of the present invention, the conductive carbon material is cleaned before being used as a working electrode. Furthermore, the conductive carbon material is ultrasonically cleaned. Furthermore, the ultrasonic cleaning frequency is 40-60 kHz and the duration is 15-30 minutes. Furthermore, the cleaned conductive carbon material is dried. Cleaning can effectively remove impurities, dust, oil, and other contaminants on the surface of the conductive carbon material, reducing the negative impact on subsequent activation.

[0055] In some embodiments of the present invention, after obtaining the activated conductive carbon material, the activated conductive carbon material is allowed to stand before carrying out the reaction; further, the conductive carbon material after standing is washed; water or an organic solvent can be used for washing.

[0056] S200: Reacting the activated conductive carbon material with a noble metal salt solution to obtain an electrocatalyst; the noble metal salt solution includes a platinum salt solution and / or a palladium salt solution. Platinum and palladium have excellent catalytic activity and can significantly increase the rate and efficiency of electrochemical reactions. Using the noble metal salt solution as a precursor can form highly dispersed noble metal ion particles, which react with the activated conductive carbon material.

[0057] In some embodiments of the present invention, reacting the activated conductive carbon material with a noble metal salt solution specifically includes: placing the activated conductive carbon material in a noble metal salt solution, reacting, and removing the reacted conductive carbon material from the system.

[0058] In some embodiments of the present invention, the solvent of the noble metal salt solution is a liquid that can dissolve the noble metal salt, and may include one or more of water, inorganic acid, inorganic base, and alcohol compounds.

[0059] In some embodiments of the present invention, the platinum salt of the platinum salt solution includes one or more of PtCl2, PtCl4, Pt(NO3)2, Pt(NO3)4, PtSO4, Pt(SO4)2, Pt(CH3COO)2, Pt(CN)2, Pt(CN)4, Pt(C2O4)2, PtCO3, and K2PtCl6. These platinum salts have high catalytic activity and stability and are suitable for a variety of electrocatalytic reactions.

[0060] In some embodiments of the present invention, the palladium salt of the palladium salt solution includes one or more of PdCl2, PdBr2, Pd(NO3)2, Pd(CH3COO)2, (NH4)2PdCl6, Na2PdCl4, PdI2, Pd(NH3)2Cl2, and Na2Pd(NO3)4. The above palladium salts have high catalytic activity and stability and are suitable for a variety of electrocatalytic reactions.

[0061] In some embodiments of the present invention, the concentration of the precious metal salt is 1mmol / L-1mol / L based on the volume of the precious metal salt solution. As an example, the concentration of the precious metal salt can be 1mmol / L, 10mmol / L, 50mmol / L, 100mmol / L, 200mmol / L, 300mmol / L, 400mmol / L, 500mmol / L, 600mmol / L, 700mmol / L, 800mmol / L, 900mmol / L, or 1mol / L based on the volume of the precious metal salt solution. The concentration of the precious metal salt will affect the deposition rate of the metal ions. The present invention forms more uniform and smaller particles in the conductive carbon material by adjusting the concentration, thereby improving the electrocatalytic performance of the electrocatalyst. In addition, by controlling the concentration of the precious metal salt, the bonding strength between the precious metal particles and the conductive carbon material can be optimized, reducing the shedding of the precious metal particles during use, and improving the stability of the electrocatalyst.

[0062] In some embodiments of the present invention, the concentration of the platinum salt is 1mmol / L-1mol / L based on the volume of the platinum salt solution. As an example, the concentration of the platinum salt can be 1mmol / L, 10mmol / L, 50mmol / L, 100mmol / L, 200mmol / L, 300mmol / L, 400mmol / L, 500mmol / L, 600mmol / L, 700mmol / L, 800mmol / L, 900mmol / L, or 1mol / L based on the volume of the platinum salt solution. The concentration of the platinum salt will affect the deposition rate of the metal ions. The present invention forms more uniform and smaller particles in the conductive carbon material by adjusting the concentration, thereby improving the electrocatalytic performance of the electrocatalyst. In addition, by controlling the concentration of the platinum salt, the bonding strength between the platinum particles and the conductive carbon material can be optimized, reducing the shedding of the platinum particles during use, and improving the stability of the electrocatalyst.

[0063] In some embodiments of the present invention, the concentration of the palladium salt is 1mmol / L-1mol / L based on the volume of the palladium salt solution. As an example, the concentration of the palladium salt can be 1mmol / L, 10mmol / L, 50mmol / L, 100mmol / L, 200mmol / L, 300mmol / L, 400mmol / L, 500mmol / L, 600mmol / L, 700mmol / L, 800mmol / L, 900mmol / L, or 1mol / L based on the volume of the palladium salt solution. The concentration of the palladium salt will affect the deposition rate of the metal ions. The present invention forms more uniform and smaller particles in the conductive carbon material by adjusting the concentration, thereby improving the electrocatalytic performance of the electrocatalyst. In addition, by controlling the concentration of the palladium salt, the bonding strength between the palladium particles and the conductive carbon material can be optimized, reducing the shedding of the palladium particles during use, and improving the stability of the electrocatalyst.

[0064] In some embodiments of the present invention, the reaction time is ≥5s, and further, the reaction time is 5s to 5min. As an example, the reaction time can be 5s, 6s, 7s, 8s, 9s, 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, 2min, 3min, 4min, 5min. By controlling the reaction time, the size and loading of the precious metal particles in the electrocatalyst can be controlled. In addition, controlling the reaction time can also make the precious metal uniformly dispersed in the conductive carbon material, avoid agglomeration, and thus improve the electrocatalytic performance of the electrocatalyst.

[0065] In some preferred embodiments of the present invention, the reaction time is 30 s to 1 min.

[0066] In some embodiments of the present invention, the preparation method of the electrocatalyst, such as Figure 1 As shown, the process comprises the following steps, wherein steps 3) to 4) are support activation steps, and steps 5) to 7) are metal reduction steps:

[0067] 1) Using a conductive carbon material as a carrier material, clean it, prepare an electrolyte, platinum salt solution, and palladium salt solution. Ultrasonic cleaning is performed on the grinding rod, which can effectively remove impurities, dust, oil, and other contaminants on the surface of the graphite rod;

[0068] 2) using the support material as the working electrode, and immersing the working electrode, counter electrode, and reference electrode in the electrolyte;

[0069] 3) applying activation drive, maintaining the working electrode potential at -1 to -4 V in a constant potential mode or applying a 1 to 5 mA current in a constant current mode (chronoamperometry) (cyclic voltammetry);

[0070] 4) After activation for 20 seconds to 3 minutes, rinse the activated carrier material;

[0071] 5) immersing the activated support in a noble metal salt solution to react;

[0072] 6) Immerse the activated support in a noble metal salt solution and allow the support material to stand for more than 5 seconds;

[0073] 7) After the reaction is completed, the support material carrying the platinum and / or palladium metal is removed from the electrolyte and rinsed;

[0074] 8) obtaining an electrocatalyst;

[0075] 9) Conducting relevant tests on the prepared electrocatalyst, including electrochemical performance tests.

[0076] A second aspect of the present invention provides an electrocatalyst prepared by the above-mentioned method for preparing the electrocatalyst.

[0077] The electrocatalyst of the present invention has good structural stability and high catalytic activity. When this material with stable structure and good catalytic performance is used for electrocatalytic hydrogen evolution, the electrocatalytic reaction can trigger the hydrogen evolution reaction at a lower driving current, thereby reducing the energy consumption of hydrogen evolution, obtaining higher hydrogen evolution efficiency and higher hydrogen production, and significantly improving the hydrogen evolution effect.

[0078] In some embodiments of the present invention, the mass content of platinum and / or palladium is less than 1% based on the mass of the electrocatalyst.

[0079] In some embodiments of the present invention, the mass content of platinum and / or palladium is 0.1%-1% based on the mass of the electrocatalyst. As an example, the mass content of platinum and / or palladium can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% based on the mass of the electrocatalyst.

[0080] The scheme of the present disclosure will be explained below with reference to the examples. Those skilled in the art will understand that the following examples are only used to illustrate the present disclosure and should not be regarded as limiting the scope of the present disclosure. If the specific technology or conditions are not specified in the examples, they shall be carried out in accordance with the technology or conditions described in the literature in this field or in accordance with the product instructions. The reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained commercially. The commercial Pt / C used in the examples and comparative examples of the present invention was purchased from Alfa Aesar (China) Chemical Co., Ltd., product number 047381; the source of the graphite rod carrier: purchased from Alfa Aesar (China) Chemical Co., Ltd., product number 040765.

[0081] Example 1

[0082] The preparation method of the electrocatalyst of this embodiment includes the following steps:

[0083] 1) Graphite Rod Preparation: Place the graphite rod in an ultrasonic cleaning device filled with ethanol. Turn on the device and set the ultrasonic power to 300 W for 15 minutes to perform ultrasonic cleaning on the rod. Ultrasonic cleaning can effectively remove impurities, dust, oil, and other contaminants on the surface of the graphite rod. After ultrasonic cleaning, dry the rod at 80°C for 0.5 hours to ensure that the ethanol on the surface of the graphite rod is completely evaporated without any residual liquid. After drying, store the graphite rod in a clean, dry container for use as a carrier in subsequent experiments.

[0084] 2) Solvent preparation: Polarization activation electrolyte: 0.1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in acetonitrile; Pt metal salt reduction solution A: 0.1 M potassium chloroplatinate (K2PtCl6) aqueous solution; Pd metal salt reduction solution B: 0.1 M palladium nitrate (Pd(NO3)2) aqueous solution; Pt+Pd metal salt reduction solution C: 0.05 M potassium chloroplatinate aqueous solution + 0.05 M palladium nitrate aqueous solution.

[0085] 3) Carrier activation: Graphite rods were used as working and counter electrodes, and Ag / AgCl was used as reference electrodes. In a 0.1 M solution of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the working electrode, counter electrode, and reference electrode were connected to an electrochemical workstation. Using the electrochemical cathode activation technique, -2.4 V was applied to the graphite rods to activate the working electrode for 30 seconds. Three activated graphite rod electrodes were obtained, namely G1, G2, and G3. The polarization activation curves are shown in Figure 2. Figure 2 As shown by Figure 2 It can be seen that the polarization curves have the same trend, that is, with the increase of time, the current gradually increases and then tends to be horizontal, indicating that the polarization results of the three graphite rods are almost the same.

[0086] 4) Metal reduction: After activation, the three graphite rods were quickly rinsed with anhydrous ethanol and then placed in reducing solution A, reducing solution B, and reducing solution C, respectively, for a reduction time of 30 seconds. After reduction, the rods were taken out, quickly rinsed with water, and then dried to obtain electrocatalysts with ultra-low Pt and / or Pd loadings, namely Pd / G electrocatalyst, Pt / G electrocatalyst, and PtPd / G electrocatalyst.

[0087] Example 2

[0088] The electrocatalyst of this embodiment differs from that of Example 1 in that, in step 2), the steps of preparing reducing solution B and reducing solution C are omitted, and in step 3), the electrocatalyst is prepared by applying -3 V to activate the graphite rod of the working electrode for 30 seconds.

[0089] The remaining steps are carried out with reference to Example 1.

[0090] Example 3

[0091] The electrocatalyst of this embodiment differs from that of Example 1 in that, in step 2), the steps of preparing reducing solution B and reducing solution C are omitted, and in step 3), the electrocatalyst is prepared by applying -3.2 V to the graphite rod of the working electrode for 30 seconds to activate the working electrode.

[0092] The remaining steps are carried out with reference to Example 1.

[0093] Example 4

[0094] The electrocatalyst of this embodiment differs from that of Example 1 in that, in step 2), the steps of preparing reducing solution B and reducing solution C are omitted, and in step 3), the electrocatalyst is prepared by applying -1.5 V to the graphite rod of the working electrode for 30 seconds to activate the working electrode.

[0095] The remaining steps are carried out with reference to Example 1.

[0096] Example 5

[0097] The electrocatalyst of this embodiment differs from that of Example 1 in that, in step 2), the steps of preparing reducing solution B and reducing solution C are omitted, and in step 3), the electrocatalyst is prepared by applying -2.4 V to the graphite rod of the working electrode for 1 minute to activate the working electrode.

[0098] The remaining steps are carried out with reference to Example 1.

[0099] Example 6

[0100] The electrocatalyst of this embodiment is different from that of Example 1 in that, in step 2), the steps of preparing reducing solution B and reducing solution C are omitted, and in step 3), the electrocatalyst is prepared by applying -2.4 V to the graphite rod of the working electrode for 3 minutes to activate the working electrode.

[0101] The remaining steps are carried out with reference to Example 1.

[0102] Example 7

[0103] The electrocatalyst of this embodiment differs from that of Example 1 in that, in step 2), the steps of preparing reducing solution B and reducing solution C are omitted, and in step 4), the reduction time is 5 s to obtain the electrocatalyst.

[0104] The remaining steps are carried out with reference to Example 1.

[0105] Example 8

[0106] The electrocatalyst of this embodiment differs from that of Example 1 in that, in step 2), the steps of preparing reducing solution B and reducing solution C are omitted, and in step 4), the reduction time is 5 minutes to obtain the electrocatalyst.

[0107] The remaining steps are carried out with reference to Example 1.

[0108] Comparative Example 1

[0109] The electrocatalyst of this comparative example is different from that of Example 1 in that, in step 2), the steps of preparing reducing solution B and reducing solution C are omitted, and in step 3), -2.4 V is applied to activate the graphite rod of the working electrode for 18 seconds to prepare the electrocatalyst.

[0110] The remaining steps are carried out with reference to Example 1.

[0111] Test Case

[0112] 1. X-ray diffraction (XRD) test

[0113] The Pt / G electrocatalyst of Example 1 was subjected to X-ray diffraction testing using the PANALYTICAL X'PERT PRO equipment. The test parameters used were Cu / Kα radiation. The potential is 40kV and the current is 15mA. The experimental results are as follows Figure 3 As shown, Figure 3 There is no diffraction peak of Pt metal, indicating that the mass content of Pt is less than the detection limit (1wt%). The sample mass is 0.1 mg, so the Pt loading is ≤1μg.

[0114] 2. Scanning electron microscope (SEM, Zeiss SUPRA 40) combined with energy dispersive spectrometer (EDS)

[0115] The Pt / G electrocatalyst of Example 1 was analyzed using a scanning electron microscope combined with an energy spectrometer. The accelerating potential of the scanning electron microscope was 20 kV, and the energy spectrometer used a silicon drift detector. Three sites (site 1, site 2, and site 3) were selected on the Pt / G electrocatalyst for calculation. The experimental results are shown in FIG. Figure 4 As shown in Table 1, the average value of the data obtained from the three sites in Table 1 shows that the mass fraction of Pt metal is about 0.5%. That is, in the case of 0.1 mg of sample, according to the formula m Pt =0.1*1000*0.5%, so the Pt content is 0.5 μg.

[0116] Table 1

[0117] Site 1 Site 2 Site 3 Carbon mass fraction (%) 99.56 99.46 99.51 Platinum mass fraction (%) 0.44 0.54 0.49 total 100 100 100

[0118] The Pt / G electrocatalyst of Example 1 was analyzed using a scanning electron microscope combined with an energy dispersive spectrometer. A portion of the Pt / G sample was cut out and the surface morphology was observed using a scanning electron microscope to obtain an electron microscope image. It was observed that Pt particles of about 10 nm (bright areas) were uniformly supported on the graphite support. Figure 5 shown.

[0119] 3. Analysis of catalytic hydrogen evolution performance

[0120] 1) Prepare electrolyte

[0121] Hydrogen evolution reaction electrolyte: 0.5M H2SO4 aqueous solution; oxygen reduction reaction electrolyte: 0.1M KOH aqueous solution;

[0122] 2) Preparation of electrocatalyst

[0123] 1000 μg of commercial Pt / C (purchased from Alfa Aesar (China) Chemical Co., Ltd., product number 047381) was ultrasonically homogenized in 400 μL of solution to obtain a mixed solution. 20 μL of the mixed solution was dropped onto a graphite rod (1 cm 2 ), that is, 1000 / 400*(20 / 1)=50μg / cm 2 , a commercial electrocatalyst (Pt / C / G) was obtained, and the commercial electrocatalyst, the electrocatalyst obtained in Examples 1-8 and Comparative Example 1 were subjected to subsequent tests.

[0124] 3) Use electrocatalysts to produce hydrogen (hydrogen evolution reaction) and reduce oxygen (oxygen reduction reaction).

[0125] 3.1 Hydrogen evolution reaction: In a three-electrode system, hydrogen was first bubbled into a 0.5 M H2SO4 aqueous solution for 30 min. Then, a working potential of 0.1 to -0.3 V (relative to the reversible hydrogen electrode) was applied to the working electrode using linear sweep voltammetry at a scan rate of 5 mV / s, and the linear sweep voltammetry (LSV) polarization curve was recorded.

[0126] The electrocatalysts of Pd / G, Pt / G, PtPd / G of Example 1, Examples 2-8 and Comparative Example 1 were subjected to hydrogen evolution reaction in 0.5MH2SO4 aqueous solution to obtain linear sweep voltammetry (LSV) curves. Figure 6 It can be seen that at 10mA / cm 2 At a current density of , the lower the hydrogen evolution overpotential, the better the hydrogen evolution performance, that is, the electrocatalysts of Example 1 all exhibit relatively excellent performance, and are better than the commercial electrocatalyst (Pt / C / G). Figure 7 It can be seen that the electrocatalyst of Example 2 has a 2 At a current density of , the hydrogen evolution overpotential is 85mV; Figure 8 It can be seen that the electrocatalyst of Example 3 has a 2 At a current density of , the hydrogen evolution overpotential is 93mV; Figure 9 It can be seen that the electrocatalyst of Example 4 has a 2 At a current density of , the hydrogen evolution overpotential is 85mV; Figure 10 It can be seen that the electrocatalyst of Example 5 has a 2 At a current density of 10 mA / cm, the hydrogen evolution overpotential is 64 mV. The electrocatalyst of Example 6 has a 2 At a current density of , the hydrogen evolution overpotential is 57mV; Figure 11 It can be seen that the electrocatalyst of Example 7 has a 2 At a current density of 10mA / cm, the hydrogen evolution overpotential is 60mV; the electrocatalyst of Example 8 is 2 At a current density of 10mA / cm, the hydrogen evolution overpotential is 57mV; the electrocatalyst of Comparative Example 1 is 2 At a current density of 1.5 wt %, the hydrogen evolution overpotential is 137 mV.

[0127] 3.2 Hydrogen evolution reaction: In a three-electrode system, hydrogen was first bubbled into a 0.5 M H2SO4 aqueous solution for 30 min. Then, a working potential of 0.05–1.2 V (relative to the reversible hydrogen electrode) was applied to the working electrode using cyclic voltammetry at a scan rate of 50 mV / s, and the cyclic voltammetry (CV) polarization curves were recorded.

[0128] The Pt / G sample of Example 1 was subjected to a cyclic voltammetry test in a 0.5M H2SO4 aqueous solution to obtain a cyclic voltammetry (CV) curve. The CV curve was used to determine whether the catalyst had an oxidation peak, and the catalytic activity of the catalyst was evaluated by the area of the oxidation peak. The results are shown in FIG. Figure 12 As shown in Figure 3, the CV curves confirmed the presence of Pt, that is, Pt was reduced to the graphite rod and exhibited high catalytic activity.

[0129] 3.3 Oxygen reduction reaction: In a three-electrode system, oxygen was first bubbled into a 0.1 M KOH aqueous solution for 30 min. Then, linear sweep voltammetry (LSV) was used to apply a working potential of 1.17–0.17 V (relative to the reversible hydrogen electrode) to the working electrode at a scan rate of 5 mV / s, and the LSV polarization curve was recorded.

[0130] The Pt / G sample of Example 1 was tested for oxygen reduction performance in 0.1M KOH aqueous solution to obtain an LSV curve, as shown in FIG. Figure 13 As shown, the oxygen reduction reaction begins at 0.9 V, and as the potential decreases (the more negative), the current density increases, indicating that the electrocatalyst has oxygen reduction performance.

[0131] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", "some implementation plans" or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0132] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing an electrocatalyst, characterized in that: The following steps are involved: A conductive carbon material is used as a working electrode, and the working electrode, a counter electrode, and a reference electrode are fixedly placed in an electrolyte. The working electrode is activated by maintaining a potential of -1 to -4 V in a constant potential manner or loading a current of 1 to 5 mA in a constant current manner to obtain an activated conductive carbon material; and the activated conductive carbon material is reacted with a noble metal salt solution to obtain an electrocatalyst. The noble metal salt solution includes a platinum salt solution and / or a palladium salt solution.

2. The method for preparing an electrocatalyst according to claim 1, wherein: The potential of the working electrode was maintained at -2 to -2.4 V in a constant potential manner.

3. The method for preparing an electrocatalyst according to claim 1, wherein: The activation time is 20s to 3min.

4. The method for preparing an electrocatalyst according to claim 1, wherein: The reaction time is ≥5s.

5. The method for preparing an electrocatalyst according to claim 1, wherein: The conductive carbon material includes one or more of graphite, carbon nanotubes, carbon black, biomass carbon, and activated carbon.

6. The method for preparing an electrocatalyst according to claim 1, wherein: The electrolyte includes an organic electrolyte salt; Furthermore, the organic electrolyte salt includes an organic lithium salt and / or an organic ammonium salt.

7. The method for preparing an electrocatalyst according to claim 6, wherein: The organic lithium salt includes one or more of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(oxalatoborate), lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, and lithium tris(trifluoromethylsulfonyl)methyl; And / or, the organic ammonium salt includes one or more of ammonium tetrafluoroborate, ammonium hexafluorophosphate, bistrifluoromethylsulfonyl imide, bisfluorosulfonyl imide, tetraethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, tetraethylammonium bistrifluoromethylsulfonyl imide, tetraethylammonium bisfluorosulfonyl imide, methylammonium tetrafluoroborate, and methylammonium hexafluorophosphate.

8. The method for preparing an electrocatalyst according to claim 6, wherein: The concentration of the organic electrolyte salt is 0.01 to 0.1 mol / L based on the volume of the electrolyte.

9. The method for preparing an electrocatalyst according to claim 1, wherein: Based on the volume of the noble metal salt solution, the concentration of the noble metal salt is 1 mmol / L-1 mol / L.

10. The electrocatalyst prepared by the method for preparing the electrocatalyst according to any one of claims 1 to 9.

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