CN114985754A - Preparation method and application of platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components - Google Patents

Preparation method and application of platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components Download PDF

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CN114985754A
CN114985754A CN202210690346.3A CN202210690346A CN114985754A CN 114985754 A CN114985754 A CN 114985754A CN 202210690346 A CN202210690346 A CN 202210690346A CN 114985754 A CN114985754 A CN 114985754A
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hea
electrode
precursor
surface components
entropy alloy
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CN114985754B (en
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杨春成
李健
文子
赵明
蒋青
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Jilin University
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    • B22F9/00—Making metallic powder or suspensions thereof
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    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
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    • C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

The invention relates to a preparation method and application of a platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components. The high-entropy alloy (HEA) with the gradient surface components can be prepared by taking transition metal chloride as a raw material and adopting a solvothermal method and annealing, and further adopting electrochemical activation. The composite material is prepared by the following steps: a. preparing a HEA precursor by a solvothermal method; b. preparing HEA by annealing the precursor; c. preparing the HEA-5000 with the gradient surface components by an electrochemical cyclic voltammetry method. HEA-5000 exhibits excellent Hydrogen Evolution Reaction (HER) catalytic performance at-10 mA cm ‑2 The overpotential at the current density was 10.8mV and the Tafel slope was 28.1mV dec ‑1 The performance of the catalyst exceeds that of commercial Pt/C, and the catalyst has wide application prospect. The invention can also be expanded to the design of other catalysts, and provides a new idea for developing high-efficiency electrocatalysts.

Description

Preparation method and application of platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components
The technical field is as follows:
the invention relates to a preparation method of a platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components and application of the alloy as a catalyst in hydrogen evolution reaction.
Background art:
hydrogen energy has the advantages of high energy density and environmental friendliness, and is considered as the most promising clean energy source. The electrochemical hydrogen evolution reaction is widely concerned as a high-efficiency hydrogen production method. The high-entropy alloy has the characteristics of adjustable components, rich surface components and the like, and is a catalyst material with prospect. However, there are some problems with high entropy alloys as catalysts for hydrogen evolution reactions, mainly in that: (1) the complex surface structure makes the catalytic mechanism difficult to judge; (2) redundant surface components may limit catalytic activity.
In order to improve the catalytic performance of the high-entropy alloy, scientific researchers carry out a large amount of research and obtain certain achievements. According to literature reports, the electronic structure of the high-entropy alloy can be adjusted by regulating and controlling alloy components, reasonably designing the structure, introducing methods such as a proper substrate and the like, and further, the catalytic activity is improved. The above methods are effective, but their understanding of the catalytic mechanism is not deep enough, and improvement of catalytic performance is still to be improved. After the Pt-Fe-Co-Ni-Cu high-entropy alloy designed and prepared by the invention is subjected to cyclic voltammetry activation, the Pt content on the surface layer presents a concentration gradient from high to low, so that Pt on the surface of the alloy is promoted to form an electronic concentration gradient, and the catalytic activity of the high-entropy alloy is further improved.
The invention content is as follows:
the invention aims to provide a preparation method and application of a platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components. The alloy is prepared by combining a solvothermal method, a hydrothermal method and an electrochemical cyclic voltammetry. The alloy presents uniformly distributed nano-particles, fully exposes active sites and is beneficial to material transmission. After the alloy is subjected to cyclic voltammetry activation, the Pt content of the alloy surface layer presents a concentration gradient from high to low, Pt on the alloy surface is promoted to form an electronic concentration gradient, and then the catalytic performance is improved. The alloy has good application prospect as a hydrogen evolution reaction catalyst. The invention can also be expanded to the design of other catalysts, and provides a new idea for developing high-efficiency electrocatalysts.
The above purpose of the invention is realized by the following technical scheme:
a preparation method of a platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components comprises the following steps:
a. preparing a HEA precursor by a solvothermal method, and adding 70-90 mg of FeCl 3 ，110～130mg CoCl 2 ·6H 2 O，110～130mg NiCl 2 ·6H 2 O，80～100mg CuCl 2 ·2H 2 O and 250 to 270mg H 2 PtCl 6 ·6H 2 Dissolving O in 30-50 mL of ultrapure water, and uniformly stirring by using a magnetic stirrer. And then placing the solution in an oil bath kettle at the temperature of 70-100 ℃ and continuously stirring for 20-40 h to obtain yellow powder, namely the HEA precursor.
b. Preparing the Pt-Fe-Co-Ni-Cu high-entropy alloy by annealing, placing 100-300 mg of HEA precursor in a tube furnace, and performing annealing on the alloy in 1-10% Ar/H 2 And (3) preserving the heat for 1-5 hours at 300-500 ℃ in the atmosphere to obtain the HEA.
c. And scanning the prepared HEA in a three-electrode test system for 0-20000 circles within a potential scanning range of 0-1V relative to the reversible hydrogen electrode by an electrochemical cyclic voltammetry method to obtain the HEA with the gradient surface components.
In the step a, the reactant is stirred and dried in an oil bath pan, so that the components of the precursor are uniformly distributed.
In the step b, the reactants are subjected to Ar/H 2 And annealing treatment is carried out under the atmosphere, so that the precursor is converted into HEA.
And in the step c, performing electrochemical cyclic voltammetry treatment on the HEA to enable the components on the surface layer of the HEA to be graded.
The platinum-iron-cobalt-nickel-copper high-entropy alloy prepared by the method is used as a catalyst for electrochemical activation and testing, and comprises the following steps:
a. firstly dispersing 2-3 mg of HEA catalyst in 0.4-0.6 mL of water/isopropanol/naphthol solution, carrying out ultrasonic treatment for 20-40 min to obtain a catalyst ink solution, taking out 10-20 mu L of the catalyst ink solution, dripping the catalyst ink solution on a glassy carbon electrode, and drying at room temperature to form a uniform catalyst film;
b. the electrochemical test is carried out in a standard three-electrode test system, wherein the electrode prepared in the step a is used as a working electrode, a carbon rod electrode is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, and H with the concentration of 0.4-0.6M is used as 2 SO 4 The solution is used as electrolyte;
c. the HEA is used as a working electrode to carry out cyclic voltammetry activation on an Ivium-n-Stat electrochemical workstation, the potential scanning range of the HEA relative to a reversible hydrogen electrode is 0.1-0.53V, and the scanning speed is 400mV s -1 And scanning 5000 circles to obtain the HEA-5000 with the gradient surface components.
d. The HEA-5000 is used as a working electrode to test on an Ivium-n-Stat electrochemical workstation, a polarization curve test is carried out on a rotating disc electrode with the rotating speed of 2025rpm, the potential scanning range of the reversible hydrogen electrode is 0 to-0.767V, and the scanning speed is 5mV s -1 (ii) a When the double electric layer capacitance is tested, the potential scanning range relative to the reversible hydrogen electrode is 0.1-0.2V, and the scanning speed is 20,40,60,80 and 100mV s -1 (ii) a The time potential test is carried out at a current density of-10 mA cm -2 Is carried out under the condition of (1), and the duration is 80 h;
e. the surface layer component gradient HEA-5000 is used as catalyst for hydrogen evolution reaction at current density of-10 mA cm -2 The overpotential is only 10.8mV, and the Tafel slope is 28.1mV dec -1 Has obvious advantages compared with commercial Pt/C.
The invention has the technical effects that:
after the HEA prepared by the invention is subjected to cyclic voltammetry activation, the Pt content of the alloy surface layer presents a concentration gradient from high to low, so that Pt on the alloy surface is promoted to form an electronic concentration gradient, and the alloy shows HER catalytic activity exceeding that of commercial Pt/C.
Description of the drawings:
FIG. 1 polarization curves of HEA-5000 prepared in inventive example 1 versus commercial Pt/C.
FIG. 2 XRD patterns of HEA and commercial Pt/C prepared in inventive example 1.
FIG. 3 XPS survey of HEA prepared in inventive example 1.
FIG. 4 shows high resolution XPS spectra of the Pt 4f region of HEA prepared in inventive example 1 and commercial Pt/C.
Fig. 5, TEM photograph of HEA prepared in example 1 of the present invention.
FIG. 6, HRTEM photograph of HEA prepared in inventive example 1.
FIG. 7 is an HRTEM photograph of commercial Pt/C in example 1 of the present invention.
FIG. 8, SAED profile of HEA prepared in example 1 of the present invention.
FIG. 9, HRTEM photograph of HEA-5000 prepared in inventive example 1.
FIG. 10 is a photograph of HAADF-STEM of HEA-5000 prepared in example 1 of the present invention.
FIG. 11 is a graph showing the trend of interplanar spacings in a HEA-5000 magnified HRTEM photograph prepared in example 1 of the present invention.
FIG. 12 is a HAADF-STEM photograph of HEA-5000 prepared in example 1 of the present invention at atomic resolution.
FIG. 13 is a Pt 4f region high resolution XPS spectra of HEA and HEA-5000 prepared in example 1 of the present invention.
Figure 14 polarization curves of HEA prepared in example 1 of the present invention after various cycles of activation.
Fig. 15 is a plot of current density versus scan rate for HEA prepared in inventive example 1 after various cycles of activation.
FIG. 16 is a graph comparing the Tafel curves of HEA-5000 prepared in inventive example 1 and commercial Pt/C.
FIG. 17, current density versus scan rate curves for HEA-5000 and commercial Pt/C prepared in inventive example 1.
FIG. 18, chronopotentiometric plot of HEA-5000 prepared in inventive example 1.
FIG. 19, TEM photograph of HEA-5000 chronopotentiometric test prepared in inventive example 1.
Fig. 20, TEM photograph of HEA prepared in example 2 of the present invention.
Fig. 21, TEM photograph of HEA prepared in example 3 of the present invention.
The specific implementation mode is as follows:
the specific contents and embodiments of the present invention will be further described with reference to examples, which are provided for illustration only and should not be construed as limitations on the technical solutions of the present invention. Examples 2 and 3 of the present invention are similar to those of example 1, and example 1 will be described in detail.
Example 1
The preparation process and steps in this example are as follows:
(1) preparation of HEA precursor by Solvothermal method, 81mg FeCl 3 ，119mg CoCl 2 ·6H 2 O，119mg NiCl 2 ·6H 2 O，86mg CuCl 2 ·2H 2 O and 259mg H 2 PtCl 6 ·6H 2 O was dissolved in 40mL of ultrapure water and stirred with a magnetic stirrer. The solution was then placed in an oil bath at 80 ℃ with constant stirring for 24 h. The obtained yellow powder is the HEA precursor.
(2) Preparing platinum-iron-cobalt-nickel-copper high-entropy alloy by annealing, placing 200mg of HEA precursor in a tube furnace at 5% Ar/H 2 Keeping the temperature for 2h at 400 ℃ under the atmosphere to obtain the HEA.
(3) Dispersing 3mg of HEA catalyst in 0.5mL of water/isopropanol/naphthol solution, performing ultrasonic treatment for 30min to obtain a catalyst ink solution, taking out 15 mu L of the catalyst ink solution, dripping the catalyst ink solution on a glassy carbon electrode, and drying at room temperature to form a uniform catalyst film;
(4) the HEA is used as a working electrode to carry out cyclic voltammetry activation on an Ivium-n-Stat electrochemical workstation, the potential scanning range of the HEA relative to a reversible hydrogen electrode is 0.1-0.53V, and the scanning speed is 400mV s -1 Scanning for 5000 circles to obtain the HEA-5000 with gradient surface components.
(5) Using said HEA-5000 as a working electrode is tested on an Ivium-n-Stat electrochemical workstation, a polarization curve test is carried out on a rotating disc electrode with the rotating speed of 2025rpm, the potential scanning range of the reversible hydrogen electrode is 0 to-0.767V, and the scanning speed is 5mV s -1 (ii) a During double-layer capacitance measurement, the potential scanning range relative to the reversible hydrogen electrode is 0.1-0.2V, and the scanning speeds are respectively 20,40,60,80 and 100mV s -1 (ii) a The chronopotentiometry was carried out at a current density of-10 mA cm -2 Is carried out under the condition of (1), and the duration is 80 h;
morphology and structure characterization of HEA and HEA-5000:
FIG. 2 is an XRD diffraction pattern of HEA and commercial Pt/C, wherein characteristic peaks at 42.1 °,48.9 ° and 72.0 ° correspond to the (111), (200) and (220) crystal planes of HEA, respectively. The characteristic (111) peak of HEA is shifted by 2.2 ° toward high angles, which indicates that Fe, Co, Ni, Cu and Pt are alloyed, as compared to the characteristic (111) peak of Pt in commercial Pt/C, and the shift at high angles also indicates that the alloy undergoes lattice shrinkage. FIG. 3 is an XPS survey of HEA in which characteristic peaks of Fe, Co, Ni, Cu, Pt were detected corresponding to the components of HEA. The appearance of the characteristic O peak is probably due to slight oxidation of the sample surface. FIG. 4 is a Pt 4f high resolution XPS spectra of HEA and commercial Pt/C, with Pt being separable into Pt in both samples 0 With Pt 2+ Characteristic peak. Wherein Pt 0 The characteristic peaks are dominant, indicating that in HEA and Pt/C, Pt element exists mainly in a metal form. Pt of HEA compared to Pt/C 0 4f 7/2 With Pt 0 4f 5/2 The characteristic peaks are shifted to the low binding energy direction by 0.6 and 0.5eV, respectively. This indicates that the Pt element gets electrons from other elements after the high entropy alloy is formed. FIG. 5 is a Transmission Electron Microscopy (TEM) photograph of HEA. The prepared HEA is in the form of uniformly dispersed nano particles, and the particle size is distributed in the range of 30-50 nm. FIG. 6 is a High Resolution TEM (HRTEM) photograph of HEA with an interplanar spacing of 0.210nm corresponding to the (111) facets of HEA. The HEA undergoes lattice contraction, consistent with XRD results, compared to 0.226nm for the (111) interplanar spacing of Pt in the commercial Pt/C of FIG. 7. The contracted lattice indicates a shorter Pt-Pt bond in the alloy, which is beneficial for reducing its adsorption of hydrogen and improving HER performance. FIG. 8 is a Selected Area Electron Diffraction (SAED) diagram of HEAThe diffraction rings in (a) correspond to the (111), (200), (220) and (311) crystal planes of HEA, respectively, wherein the average spacing of the (111) crystal plane is 0.210nm, which is consistent with the HRTEM characterization result. To optimize the surface structure of HEA, we activated it electrochemically. FIG. 9 is a TEM photograph of HEA-5000 after 5000 cycles of Cyclic Voltammetry (CV) activation, showing a small amount of (111) crystal planes of Pt on the surface. This is because during activation, some of the Fe, Co, Ni, Cu components in the HEA are acid etched, exposing Pt to the surface. FIG. 10 is a high angle annular dark field scanning transmission electron microscope (HAADF-STEM) photograph of HEA-5000. The (111) interplanar spacing of the surface layer HEA-5000 was 0.226nm, which is consistent with the (111) interplanar spacing of Pt, indicating that the Pt element is dominant in the surface layer of HEA-5000. And in the core part, the (111) interplanar spacing of HEA-5000 was 0.210nm, which was consistent with the (111) interplanar spacing of HEA before activation, indicating that the core part was homogeneous HEA. This also shows that the etching effect caused by activation only occurs in the outermost 15-20 layers of HEA. In the transition layer, the (111) interplanar spacing of the selected HEA-5000 is 0.217nm, and the size of the selected HEA-5000 is between the (111) interplanar spacing of Pt and the (111) interplanar spacing of HEA. This indicates that there is a partial etching phenomenon of Fe, Co, Ni, Cu, etc. in the transition layer. The (111) interplanar spacing change trend of HEA-5000 is shown in FIG. 11, and the gradual decrease of the interplanar spacing from the surface to the core represents a concentration gradient from high to low in the Pt content of the surface layer of HEA-5000, so that the Pt on the surface of the alloy is promoted to form an electron concentration gradient, and the electron concentration gradient is used as a catalytic active site to greatly improve the catalytic activity of the alloy. FIG. 12 is a HAADF-STEM photograph of HEA-5000 at atomic resolution, showing that HEA-5000 gradually decreases in (111) interplanar spacing from the surface to the core, further confirming the concentration gradient of Pt on the surface layer. FIG. 13 is a high resolution XPS spectrum of the Pt 4f region of HEA before and after activation. Pt of HEA-5000 after activation compared to HEA 0 4f 7/2 With Pt 0 4f 5/2 The characteristic peaks are shifted to the high binding energy direction by 0.4 and 0.3eV respectively, because part of Fe, Co, Ni, Cu is etched during the activation process, resulting in the reduction of electrons obtained by Pt from other elements.
Characterization of the catalytic properties of HEA at room temperature:
electrochemical experiments were performed using a standard three-electrode test system. As shown in FIG. 14, HEA is at Current DensityIs-100 mA cm -2 Is 96.8 mV. HER performance of HEA-100 is significantly improved after 100 CV activation cycles, 100mA cm -2 The lower overpotential was raised to 37.8 mV. This is because during the activation process, the Fe, Co, Ni, Cu components on the surface of the HEA are partially etched, exposing more Pt on the surface. HEA-2000 and HEA-5000 at-100 mA cm with activation -2 The overpotential of (2) is 35.4 mV and 30.7mV, respectively, and the catalytic activity is continuously improved. The activation process enables the Pt content on the surface layer of the HEA to present a concentration gradient from high to low, promotes Pt on the surface of the alloy to form an electron concentration gradient, and further improves the catalytic activity. More CV cycles showed HEA activity to decay, HEA-10000 at-100 mA cm -2 To 36.6 mV. This is due to excessive CV cycling causing the HEA surface to become almost Pt/Cu alloy, the Pt concentration gradient no longer exists and HER activity is consequently degraded. Fig. 15 is a graph of the current density of HEA at different scan rates, with the slope of the curve reflecting the magnitude of the electric double layer capacitance. As shown in the figure, the trend of the change of the electric double layer capacitance of the HEA along with the number of CV cycles is consistent with the activity, and the electric double layer capacitance started by the HEA is 12.5mF cm at the minimum -2 . As activation proceeded, the electric double layer capacitance of HEA-100, HEA-2000, HEA-5000 gradually increased to 64.7,76.1 and 111.7mF cm, respectively -2 . This indicates that the double layer capacitance of HEA gradually increases as the Pt concentration gradient on the HEA surface layer develops. A larger electric double layer capacitance means a larger electrochemically active area and therefore leads to a better catalytic activity. The electric double layer capacitance of HEA-10000 was reduced to 95.0mF cm compared with HEA-5000 -2 . This is due to the decrease in electrochemically active area of HEA due to the disappearance of the Pt concentration gradient on its surface layer. In summary, HEA-5000 has the best Pt concentration gradient and thus the largest electrochemically active area, leading to the best HER activity. We compared the hydrogen evolution catalytic performance of HEA-5000 with commercial Pt/C. FIG. 1 is a polarization curve with HEA-5000 at-10 mA cm -2 The overpotential under the condition is only 10.8mV, which is better than that of commercial Pt/C. FIG. 16 is a corresponding Tafel plot, with the Tafel slopes of 28.1 and 32.3mV dec for HEA-5000 and commercial Pt/C, respectively -1 . The tafel slope of HEA-5000 was smaller, indicating it has faster HER kinetics. In addition, HEA-5000 has a larger cross-sectionCurrent change density 8.99mA cm -2 Indicating that the catalyst has better intrinsic catalytic activity. FIG. 17 shows the electric double layer capacitance of HEA-5000 compared to commercial Pt/C. The electric double layer capacitance of HEA-5000 was 111.7mF cm -2 Much larger than commercial Pt/C, indicating a larger electrochemically active area. FIG. 18 is a chronopotentiometric curve of HEA-5000, which reaches-10 mA cm after 80h of continuous testing -2 The required potential was increased by only 23mV, indicating good electrochemical stability. FIG. 19 is a TEM photograph of HEA-5000 after 80h chronopotentiometric test, and the HEA-5000 after test still maintains uniformly distributed nano-particles, which confirms the good stability.
Example 2
The preparation process and steps in this example are as follows:
(1) preparing HEA precursor by solvothermal method, and adding 70mg FeCl 3 ，110mg CoCl 2 ·6H 2 O，110mg NiCl 2 ·6H 2 O，75mg CuCl 2 ·2H 2 O and 240mg H 2 PtCl 6 ·6H 2 O was dissolved in 40mL of ultrapure water and stirred with a magnetic stirrer. And then placing the solution in an oil bath kettle at the temperature of 80 ℃ to continuously stir for 24 hours to obtain yellow powder, namely the HEA precursor.
(2) Preparing platinum-iron-cobalt-nickel-copper high-entropy alloy by annealing, placing 200mg of HEA precursor in a tube furnace at 5% Ar/H 2 Keeping the temperature for 2h at 400 ℃ under the atmosphere to obtain the HEA.
(3) Dispersing 3mg of HEA catalyst in 0.5mL of water/isopropanol/naphthol solution, performing ultrasonic treatment for 30min to obtain a catalyst ink solution, taking out 15 mu L of catalyst ink solution, dripping the catalyst ink solution on a glassy carbon electrode, and drying at room temperature to form a uniform catalyst film;
(4) the HEA is used as a working electrode to carry out cyclic voltammetry activation on an Ivium-n-Stat electrochemical workstation, the potential scanning range of the HEA relative to a reversible hydrogen electrode is 0.1-0.53V, and the scanning speed is 400mV s -1 Scanning for 5000 circles to obtain the HEA-5000 with gradient surface components.
(5) The HEA-5000 is used as a working electrode to perform testing and polarization on an Ivium-n-Stat electrochemical workstationThe curve test is carried out on a rotating disk electrode with the rotating speed of 2025rpm, the potential scanning range of the reversible hydrogen electrode is 0 to-0.767V, and the scanning speed is 5mV s -1 (ii) a During double-layer capacitance measurement, the potential scanning range relative to the reversible hydrogen electrode is 0.1-0.2V, and the scanning speeds are respectively 20,40,60,80 and 100mV s -1 (ii) a The time potential test is carried out at a current density of-10 mA cm -2 Is carried out under the condition of (1), and the duration is 80 h;
a TEM photograph of HEA prepared in this example is shown in fig. 20. It can be seen that the high-entropy alloy prepared by the present example has a morphology similar to that of the material prepared by example 1, and shows uniformly dispersed nanoparticles.
Example 3
The preparation process and steps in this example are as follows:
(1) preparation of HEA precursor by Solvothermal method, 88mg FeCl 3 ，125mg CoCl 2 ·6H 2 O，125mg NiCl 2 ·6H 2 O，100mg CuCl 2 ·2H 2 O and 270mg H 2 PtCl 6 ·6H 2 O was dissolved in 40mL of ultrapure water and stirred with a magnetic stirrer. And then placing the solution in an oil bath kettle at the temperature of 80 ℃ to continuously stir for 24 hours to obtain yellow powder, namely the HEA precursor.
(2) Preparing platinum-iron-cobalt-nickel-copper high-entropy alloy by annealing, placing 200mg of HEA precursor in a tube furnace at 5% Ar/H 2 Keeping the temperature for 2h at 400 ℃ under the atmosphere to obtain the HEA.
(3) Dispersing 3mg of HEA catalyst in 0.5mL of water/isopropanol/naphthol solution, performing ultrasonic treatment for 30min to obtain a catalyst ink solution, taking out 15 mu L of the catalyst ink solution, dripping the catalyst ink solution on a glassy carbon electrode, and drying at room temperature to form a uniform catalyst film;
(4) the HEA is used as a working electrode to carry out cyclic voltammetry activation on an Ivium-n-Stat electrochemical workstation, the potential scanning range relative to a reversible hydrogen electrode is 0.1-0.53V, and the scanning speed is 400mV s -1 And scanning 5000 circles to obtain the HEA-5000 with the gradient surface components.
(5) Electrochemical engineering at Ivium-n-Stat using the HEA-5000 as a working electrodeThe test is carried out on a station, the polarization curve test is carried out on a rotating disc electrode with the rotating speed of 2025rpm, the potential scanning range of the reversible hydrogen electrode is 0 to-0.767V, and the scanning speed is 5mV s -1 (ii) a During double-layer capacitance measurement, the potential scanning range relative to the reversible hydrogen electrode is 0.1-0.2V, and the scanning speeds are respectively 20,40,60,80 and 100mV s -1 (ii) a The time potential test is carried out at a current density of-10 mA cm -2 Is carried out under the condition of (1), and the duration is 80 h;
a TEM photograph of HEA obtained in this example is shown in fig. 21. It can be seen that the composite material prepared in this example has similar morphology to the materials prepared in examples 1 and 2, and shows uniformly dispersed nanoparticles.
The above examples are only a few embodiments of the present invention, not all of them, and should not be construed as limiting the scope of the present invention, and all equivalent changes and modifications made according to the spirit of the present invention should be covered by the present invention.

Claims (4)

1. A preparation method of a platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components comprises the following steps:
a. preparing a HEA precursor by a solvothermal method, and adding 70-90 mg of FeCl 3 、110～130mg CoCl 2 ·6H 2 O、110～130mg NiCl 2 ·6H 2 O、80～100mg CuCl 2 ·2H 2 O and 240-270 mg H 2 PtCl 6 ·6H 2 Dissolving O in 30-50 mL of ultrapure water, and uniformly stirring by using a magnetic stirrer; then placing the solution in an oil bath kettle at the temperature of 70-100 ℃ and continuously stirring for 20-40 h to obtain yellow powder, namely a HEA precursor;
b. preparing the Pt-Fe-Co-Ni-Cu high-entropy alloy by annealing, placing 100-300 mg of HEA precursor in a tube furnace, and performing annealing on the alloy in 1-10% Ar/H 2 Preserving the heat for 1-5 h at 300-500 ℃ in the atmosphere to convert into HEA;
c. and scanning the prepared HEA in a three-electrode test system for 0-20000 circles within a potential scanning range of 0-1V relative to the reversible hydrogen electrode by an electrochemical cyclic voltammetry method to obtain the HEA with the gradient surface components.
2. A preparation method of a platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components comprises the following steps:
a. preparing a HEA precursor by a solvothermal method, and adding 70-81 mg of FeCl 3 ，110～119mg CoCl 2 ·6H 2 O，110～119mg NiCl 2 ·6H 2 O，75～86mg CuCl 2 ·2H 2 O and 240 to 259mg H 2 PtCl 6 ·6H 2 Dissolving O in 40mL of ultrapure water, uniformly stirring by using a magnetic stirrer, and then placing the solution in an oil bath kettle at the temperature of 80 ℃ for continuously stirring for 24 hours to obtain yellow powder, namely a HEA precursor;
b. preparing the Pt-Fe-Co-Ni-Cu high-entropy alloy by annealing, placing 100-300 mg of HEA precursor in a tube furnace, and performing annealing on the alloy in 1-10% Ar/H 2 Preserving the heat for 1-5 h at 300-500 ℃ in the atmosphere to convert into HEA;
c. and scanning the prepared HEA in a three-electrode test system for 0-20000 circles within a potential scanning range of 0-1V relative to the reversible hydrogen electrode by an electrochemical cyclic voltammetry method to obtain the HEA with the gradient surface components.
3. A preparation method of a platinum-iron-cobalt-nickel-copper high-entropy alloy with gradient surface components comprises the following steps:
a. preparing a HEA precursor by a solvothermal method, and adding 81-88 mg of FeCl 3 ，110～125mg CoCl 2 ·6H 2 O，110～125mg NiCl 2 ·6H 2 O，86～100mg CuCl 2 ·2H 2 O and 259 to 270mg H 2 PtCl 6 ·6H 2 Dissolving O in 40mL of ultrapure water, uniformly stirring by using a magnetic stirrer, and then placing the solution in an oil bath kettle at the temperature of 80 ℃ for continuously stirring for 24 hours to obtain yellow powder, namely a HEA precursor;
b. preparing the Pt-Fe-Co-Ni-Cu high-entropy alloy by annealing, placing 100-300 mg of HEA precursor in a tube furnace, and performing annealing on the alloy in 1-10% Ar/H 2 Preserving the heat for 1-5 h at 300-500 ℃ in the atmosphere to convert into HEA;
c. and scanning the prepared HEA in a three-electrode test system for 0-20000 circles within a potential scanning range of 0-1V relative to the reversible hydrogen electrode by an electrochemical cyclic voltammetry method to obtain the HEA with the gradient surface components.
4. The Pt-Fe-Co-Ni-Cu high entropy alloy prepared according to any one of claims 1 to 3, which is used as a catalyst for electrochemical activation and testing, comprises the following steps:
a. firstly dispersing 2-3 mg of HEA catalyst in 0.4-0.6 mL of water/isopropanol/naphthol solution, carrying out ultrasonic treatment for 20-40 min to obtain a catalyst ink solution, taking out 10-20 mu L of the catalyst ink solution, dripping the catalyst ink solution on a glassy carbon electrode, and drying at room temperature to form a uniform catalyst film;
b. the electrochemical test is carried out in a standard three-electrode test system, wherein the electrode prepared in the step a is used as a working electrode, a carbon rod electrode is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, and H with the concentration of 0.4-0.6M is used as 2 SO 4 The solution is used as electrolyte;
c. the HEA is used as a working electrode to carry out cyclic voltammetry activation on an Ivium-n-Stat electrochemical workstation, the potential scanning range relative to a reversible hydrogen electrode is 0.1-0.53V, and the scanning speed is 400mV s -1 Scanning 5000 circles to obtain HEA-5000 with gradient surface components;
d. the HEA-5000 as a working electrode is used for testing on an Ivium-n-Stat electrochemical workstation, a polarization curve test is carried out on a rotating disk electrode with the rotating speed of 2025rpm, the potential scanning range relative to a reversible hydrogen electrode is 0 to-0.767V, and the scanning speed is 5mV s -1 (ii) a When the double electric layer capacitance is tested, the potential scanning range relative to the reversible hydrogen electrode is 0.1-0.2V, and the scanning speed is 20,40,60,80 and 100mV s -1 (ii) a The time potential test is carried out at a current density of-10 mA cm -2 For a duration of 80 h.
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