High-entropy alloy electrocatalyst with core-shell structure as well as preparation method and application of high-entropy alloy electrocatalyst

Abstract

The invention discloses a high-entropy alloy electrocatalyst with a core-shell structure and a preparation method and application of the high-entropy alloy electrocatalyst with the core-shell structure, the catalyst is synthesized through a two-step method, and the stable and efficient core-shell structure is formed after reconstruction. The invention further discloses cloud application of the high-entropy alloy with the core-shell structure in an oxygen evolution reaction and an anode catalyst layer of an anion exchange membrane water electrolyser. The core-shell structure catalyst constructed by the invention has the characteristics of ultra-stability and high activity, and the performance of the core-shell structure catalyst is superior to that of commercial noble metal RuO2 and other quaternary high-entropy alloy, ternary medium-entropy alloy and binary alloy contrast sample materials.

Description

Technical Field

[0001] The present invention belongs to the technical fields of the preparation of core-shell structure catalysts and electrolytic water, and particularly relates to a core-shell structured high-entropy alloy electrocatalyst, a preparation method thereof, and an application thereof. Background Art

[0002] At present, Ir-based and Ru-based noble metal catalysts are two types of OER catalysts with the best catalytic performance for the oxygen evolution reaction. However, the high cost and scarcity of noble metals limit their large-scale application. Conventional binary or ternary alloys have poor OER catalyst activity and corrosion resistance due to fewer active sites, which hinders their further application. High-entropy alloy (HEA) materials have natural advantages in constructing multi-component catalysts due to their flexible composition and stable structure. There is a trade-off relationship between the activity and stability of non-noble metals. Most non-noble metal HEA electrocatalysts are active under laboratory conditions (such as 10 mA cm -2 ), but their stability is relatively poor; moreover, at high current densities (such as 100 mA cm -2 ), the catalyst activity and long-term stability further deteriorate. Therefore, there is an urgent need to develop non-noble metal HEA oxygen evolution catalysts with high activity and stability at high current densities. Summary of the Invention

[0003] The purpose of the present invention is to provide a core-shell structured high-entropy alloy electrocatalyst.

[0004] The purpose of the present invention is also to provide a preparation method of a core-shell structured high-entropy alloy electrocatalyst.

[0005] The purpose of the present invention is also to provide an application of a core-shell structured high-entropy alloy electrocatalyst.

[0006] A high-entropy alloy electrocatalyst, the microstructure of the high-entropy alloy electrocatalyst after a reconstruction process is a core-shell structure.

[0007] The high-entropy alloy electrocatalyst according to claim 1, characterized in that the high-entropy alloy electrocatalyst comprises five elements of iron, cobalt, nickel, molybdenum, and tungsten.

[0008] The high-entropy alloy electrocatalyst according to claim 1, characterized in that the particle size of the high-entropy alloy electrocatalyst is 10-20 nm.

[0009] A preparation method of a high-entropy alloy electrocatalyst, characterized by comprising the following steps:

[0010] S11. Synthesize a high-entropy alloy electrocatalyst;

[0011] S12. Disperse the obtained high-entropy alloy electrocatalyst in a mixed solution, and then perform ultrasonic treatment to prepare an ink solution;

[0012] S13. Drop the ink solution onto carbon paper and dry it to obtain the FeCoNiMoW high-entropy alloy oxide electrocatalyst;

[0013] S14. Perform in-situ self-reconstruction on the product of step 13 by cyclic voltammetry to obtain the core-shell structure FeCoNiMoW@FeCoNiOOH.

[0014] Preferably, the synthesis method of the high-entropy alloy electrocatalyst described in step S11 is the carbothermal shock method or the electrodeposition method.

[0015] Preferably, the ink solution described in step S12 is composed of 400 - 800 μl of ethanol, 100 - 500 μl of ultrapure water, 50 - 150 μl of Nafion, and the high-entropy alloy electrocatalyst.

[0016] Preferably, the method for dropping the ink solution in step S13 is: select a 200 μl pipette gun to take an appropriate amount of the ink solution and drop it on 1×1.5 cm carbon paper each time, and a total of one-third of the ink solution is dropped.

[0017] Preferably, the in-situ self-reconstruction described in step S14 uses the electrocatalyst as the working electrode, Hg / HgO as the reference electrode, and a platinum mesh as the counter electrode, and scans at a rate of 20 - 80 mV s-1 for 100 - 300 cycles within the potential range of 1.124 - 1.724 V vs RHE.

[0018] Application of a high-entropy alloy electrocatalyst in the oxygen evolution reaction and an anion exchange membrane water electrolyzer.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) The present invention first successfully prepares a high-entropy alloy pre-catalyst by the rapid carbothermal shock method or the electrodeposition method.

[0021] (2) The present invention performs in-situ self-reconstruction on the high-entropy alloy to prepare a core-shell structure FeCoNiMoW@FeCoNiOOH high-entropy alloy electrocatalyst. During the reconstruction process, the surface Mo and W species are etched as sacrificial agents, thereby introducing a large number of oxygen defects and accelerating the generation of active species, forming a middle-entropy alloy shell layer rich in FeCoNiOOH. Furthermore, it promotes the adsorption of OH and improves the catalytic activity.

[0022] (3) The FeCoNiMoW high-entropy alloy electrocatalyst with a core-shell structure prepared by the present invention maintains a quinary high-entropy alloy in the core, where Mo and W, as electron donors, continuously provide electrons to the active sites, thereby enabling the catalyst to maintain persistent and stable electrolysis at a high current density.

[0023] (4) When the high-entropy alloy electrocatalyst prepared by the present invention is applied to the oxygen evolution reaction of water electrolysis, using the high-entropy alloy electrocatalyst of the present invention as the working electrode, a platinum mesh as the counter electrode, and a Hg / HgO electrode as the reference electrode, the oxygen evolution reaction is carried out in a 1 M KOH electrolyte at 30 °C. The catalyst obtained by carbon thermal shock-in-situ self-reconstruction shows an overpotential of only 246.3 mV at a current density of 10 mA cm -2 ; and after continuous operation at a high current density of 100 mA cm -2 for 1000 h, the activity decay is negligible, and its stability far exceeds that of traditional transition metal oxide catalysts. The catalyst obtained by electrodeposition-in-situ self-reconstruction shows an overpotential of only 190.0 mV at a current density of 10 mA cm -2 and can operate stably for 200 h.

[0024] When the high-entropy alloy electrocatalyst prepared by the present invention through carbon thermal shock-in-situ self-reconstruction is applied to industrial-grade anion exchange membrane water electrolysis, at ultra-high current densities of 1 A cm -2 and 4 A cm -2 , the cell voltages are only 1.74 V and 2.18 V respectively, and after continuous operation under these conditions for 430 h, the cell voltage only increases by 0.01 V, and the decay rate is as low as 0.023 mV h -1 , showing excellent catalytic activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 are the scanning electron microscope images of the FeCoNiMoW@FeCoNiOOH and FeCoNiMoW catalysts prepared in Example 1 and Example 2 respectively;

[0027] Figure 2 are the transmission electron microscope images of the FeCoNiMoW@FeCoNiOOH and FeCoNiMoW catalysts prepared in Example 1 and Example 2 respectively;

[0028] Figure 3 is the dark field image of the transmission electron microscope of the FeCoNiMoW@FeCoNiOOH catalyst prepared in Example 1;

[0029] Figure 4 It is the dark field image of the transmission electron microscope of the core-shell structure catalyst prepared in Example 2;

[0030] Figure 5 It is the line scan image of the FeCoNiMoW@FeCoNiOOH catalyst prepared in Example 1;

[0031] Figure 6 They are the X-ray diffraction patterns of the FeCoNiMoW@FeCoNiOOH and FeCoNiMoW catalysts prepared in Example 1 and Example 2 respectively;

[0032] Figure 7 They are the in-situ Raman spectra of the FeCoNiMoW and FeCoNi catalysts prepared in Example 2 and Example 5 respectively;

[0033] Figure 8 It is the oxygen evolution performance of the electrode materials prepared in Example 1 and Comparative Examples 2, 3, 4, 5, 6, 7: (a) polarization curve, (b) electrochemical impedance spectroscopy and (c) Tafel curve;

[0034] Figure 9 It is the oxygen evolution stability test curve of the electrode materials prepared in Example 1 and Examples 3, 4, 5, 7;

[0035] Figure 10 It is a schematic diagram of an anion exchange membrane water electrolyzer using the core-shell structure FeCoNiMoW@FeCoNiOOH high-entropy alloy catalyst prepared in Example 1;

[0036] Figure 11 It is the performance of the anion exchange membrane water electrolyzer with the core-shell structure FeCoNiMoW@FeCoNiOOH high-entropy alloy catalyst prepared in Example 1 as the anode catalytic layer: (a) polarization curve, (b) electrochemical impedance spectroscopy;

[0037] Figure 12 It is the stability test curve of the core-shell structure FeCoNiMoW@FeCoNiOOH high-entropy alloy catalyst prepared in Example 1 in the anion exchange membrane water electrolyzer. Detailed implementation manners

[0038] The following specific descriptions are all exemplary and are intended to provide further explanations of the present invention. Those skilled in the art should understand that without departing from the spirit and scope of the present invention, the details and forms of the technical solutions of the present invention can be modified or replaced, but these modifications and replacements all fall within the protection scope of the present invention.

[0039] The test methods used in the following experimental examples are all conventional methods unless otherwise specified.

[0040] Example 1: Synthesis of FeCoNiMoW@FeCoNiOOH Core-Shell Structure High-Entropy Alloy Electrocatalyst

[0041] First, the high-entropy alloy FeCoNiMoW was obtained by the carbothermal shock method. 10 mg of the high-entropy alloy was dispersed in a mixed solution composed of 600 μl of ethanol, 300 μl of ultrapure water, and 100 μl of Nafion, and then ultrasonic treatment was carried out for 1.5 h to prepare an ink solution. Then, one-third of the ink solution was drop-coated on carbon paper and dried at 60 °C for 12 h to obtain the electrocatalyst.

[0042] The reconstruction process was as follows: The electrocatalyst was used as the working electrode, Hg / HgO was used as the reference electrode, and a platinum mesh was used as the counter electrode. In the potential range of 1.124 - 1.724 V vs RHE, it was scanned at a rate of 50 mV s -1 for 300 cycles for reconstruction. After the reconstruction was completed, the FeCoNiMoW@FeCoNiOOH high-entropy alloy electrocatalyst was obtained.

[0043] Immediately afterwards, the oxygen evolution performance was evaluated. The three-electrode system for the oxygen evolution performance evaluation used the Hg / HgO electrode and the platinum mesh as the reference electrode and the counter electrode respectively. Then, the obtained FeCoNiMoW@FeCoNiOOH high-entropy alloy electrocatalyst was characterized by XRD (X-ray diffractometer) to determine its low-crystallinity structure; characterized by SEM (field emission scanning electron microscope) to determine its structure with a coating layer on the outer layer; characterized by TEM (scanning transmission electron microscope) to determine its microscopic core-shell structure with a thick center and a thin edge; and characterized by in-situ Raman to determine the formation of M-OOH species on its surface.

[0044] Comparative Example 1. Synthesis of FeCoNiMoW Electrocatalyst

[0045] The specific implementation conditions synthesized the catalyst by the carbothermal shock method or the electrodeposition method, but no reconstruction was carried out. The FeCoNiMoW electrocatalyst was obtained. Through XRD analysis, its low-crystallinity structure was determined; characterized by SEM to determine its microscopic morphology as a spherical particle structure of 10 - 20 nm; characterized by ICP-OES to determine the element ratios of iron, cobalt, nickel, molybdenum, and tungsten to be 2:1:1:3:3.

[0046] Comparative Example 2. Synthesis of FeCoNiMo@EA High-Entropy Alloy Electrocatalyst

[0047] The specific implementation conditions were similar to those in Example 1, but tungsten was not added, and the FeCoNiMo@EA high-entropy alloy electrocatalyst was obtained.

[0048] Comparative Example 3. Synthesis of FeCoNiW@EA High-Entropy Alloy Electrocatalyst

[0049] The specific implementation conditions were similar to those of Example 1, but molybdenum was not added, and the FeCoNiW@EA high-entropy alloy electrocatalyst was obtained.

[0050] Comparative Example 4. Synthesis of FeCoNi@EA Medium-Entropy Alloy Electrocatalyst

[0051] The specific implementation conditions were similar to those of Example 1, but tungsten and molybdenum were not added, and the FeCoNi@EA medium-entropy alloy electrocatalyst was obtained.

[0052] Comparative Example 5. Synthesis of MoW@EA Alloy Electrocatalyst

[0053] The specific implementation conditions were similar to those of Example 1, but iron, cobalt, and nickel were not added, and the MoW@EA alloy electrocatalyst was obtained.

[0054] Comparative Example 6. Synthesis of RuO2@EA High-Entropy Alloy Electrocatalyst

[0055] Disperse 5 mg of commercial RuO2 in 1 ml of a mixed solution (600 μl of ethanol, 300 μl of ultrapure water, and 100 μl of Nafion). Ultrasonically treat the obtained mixture for 2 h to form a uniform ink. Finally, take 100 μl of the ink solution and coat it on the pretreated CFP and dry it. The coating area is 1×1 cm 2 , and the catalyst loading is 0.5 mg cm -2 . After drying in an oven at 60 °C for 6 h, the commercial RuO2 electrocatalyst is obtained, and then the reconstruction process is carried out.

[0056] Example 2: First, the high-entropy alloy FeCoNiMoW was obtained by electrodeposition. Then, the reconstruction was carried out, and the specific implementation conditions of the reconstruction process were similar to those of Example 1.

[0057] Appendix Figure 1 Scanning electron micrographs of the FeCoNiMoW@FeCoNiOOH core-shell structured high-entropy alloy prepared in Example 1 and the FeCoNiMoW catalyst in Comparative Example 1 are shown. It can be seen that FeCoNiMoW@FeCoNiOOH has a coating layer, and the FeCoNiMoW catalyst is spherical particles with a size of 10 - 20 nm.

[0058] Appendix Figure 2 Transmission electron micrographs of the FeCoNiMoW@FeCoNiOOH core-shell structured high-entropy alloy prepared in Example 1 and the FeCoNiMoW catalyst in Comparative Example 1 are shown Figure 2 (a) It can be seen that the inside of the FeCoNiMoW@FeCoNiOOH catalyst is thicker and the outside is thinner. From Figure 2Lattice fringes with a lattice spacing of 0.375 nm were found in (b), which belong to the (Co,Ni)O(OH) species; Figure 2 (c) It can be seen that FeCoNiMoW presents particles of 10 - 20 nm. From Figure 2 (d) Lattice fringes with lattice spacings of 0.218 nm and 0.252 nm were found, which belong to the (020) plane of FeWO4 and the (311) plane of NiFe2O4 respectively.

[0059] Appendix Figure 3 Figure 9 is the dark field transmission electron microscopy image of the FeCoNiMoW@FeCoNiOOH core - shell structured high - entropy alloy prepared in Example 1. It can be seen that the catalyst presents a core - shell structure with a thick middle and thin edges.

[0060] Appendix Figure 4 Figure 14 is the dark field transmission electron microscopy image of the core - shell structured high - entropy alloy prepared in Example 2. It can be seen that the catalyst also presents a core - shell structure with a thick middle and thin edges.

[0061] Figure 5 Figure 18 is the line scan image of the FeCoNiMoW@FeCoNiOOH catalyst prepared in Example 1. It can be seen that the outside of the FeCoNiMoW@FeCoNiOOH catalyst contains three elements of Fe, Co, and Ni, and the inside contains five elements of Fe, Co, Ni, Mo, and W.

[0062] Appendix Figure 6 Figure 23 are the X - ray diffraction patterns of the FeCoNiMoW@FeCoNiOOH and FeCoNiMoW catalysts prepared in Example 1 and Comparative Example 1 respectively, showing very weak diffraction peaks, indicating that these catalysts are mainly in the amorphous phase.

[0063] Appendix Figure 7 Figure 28 are the in - situ Raman spectra of the FeCoNiMoW and FeCoNi catalysts prepared in Comparative Example 2 and Comparative Example 4 respectively. The results further prove that M - OOH species are formed on the surface of the reconstructed catalyst, but the FeCoNiMoW catalyst shows an M - OOH peak at a lower voltage.

[0064] Appendix Figure 8 Figure 33 shows the oxygen evolution performance of the electrode materials prepared in Example 1 and Comparative Examples 1, 2, 3, 4, 5, and 6 of the present invention: (a) polarization curve, (b) electrochemical impedance spectroscopy diagram, and (c) Tafel curve.

[0065] Appendix Figure 9 Figure 38 shows the oxygen evolution stability test curves of the electrode materials prepared in Example 1 and Comparative Examples 2, 3, 4, and 6 of the present invention;

[0066] Appendix Figure 10Schematic diagram of an anion exchange membrane water electrolyzer using the FeCoNiMoW@FeCoNiOOH catalyst prepared in Example 1 of the present invention.

[0067] Appendix Figure 11 Performance of an anion exchange membrane water electrolyzer with the core-shell structured FeCoNiMoW@FeCoNiOOH high-entropy alloy catalyst prepared in Example 1 of the present invention as the anode catalytic layer: (a) polarization curve, (b) electrochemical impedance spectroscopy diagram.

[0068] Appendix Figure 12 Stability test curve of the core-shell structured FeCoNiMoW@FeCoNiOOH high-entropy alloy catalyst prepared in Example 1 of the present invention in an anion exchange membrane water electrolyzer. The durability of this AEM electrolyzer was tested at a current density of 1 A cm -2 The cell voltage increased by only 0.01 V within 430 h, and the cell decay rate was only 0.023 mV·h -1 , confirming its ultra-durable stability at a large working current. It shows that the FeCoNiMoW@FeCoNiOOH high-entropy alloy electrocatalyst is an efficient and durable industrial AEM water electrolysis anode material.

[0069] The above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, or substitutions made by those skilled in the art within the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A high-entropy alloy electrocatalyst, characterized in that, The microstructure of the high-entropy alloy electrocatalyst after the reconstruction process is a core-shell structure.

2. The high-entropy alloy electrocatalyst according to claim 1, characterized in that, The high-entropy alloy electrocatalyst includes five elements: iron, cobalt, nickel, molybdenum, and tungsten.

3. The high-entropy alloy electrocatalyst according to claim 1, wherein The particle size of the high-entropy alloy electrocatalyst is 10-20 nm.

4. The preparation method of the high-entropy alloy electrocatalyst according to claim 1, characterized in that, It includes the following steps: S11. Synthesize the high-entropy alloy electrocatalyst; S12. Disperse the obtained high-entropy alloy electrocatalyst in a mixed solution, and then perform ultrasonic treatment to prepare an ink solution; S13. Drop the ink solution onto carbon paper and dry to obtain the FeCoNiMoW high-entropy alloy oxide electrocatalyst; S14. Use cyclic voltammetry to in-situ self-reconstruct the product of step 13 to obtain the core-shell structure FeCoNiMoW@FeCoNiOOH.

5. The preparation method of the high-entropy alloy electrocatalyst according to claim 4, characterized in that, The synthesis method of the high-entropy alloy electrocatalyst described in step S11 is the carbothermal shock method or the electrodeposition method.

6. The preparation method of the high-entropy alloy electrocatalyst according to claim 4, wherein The ink solution described in step S12 is composed of 400-800 μl of ethanol, 100-500 μl of ultrapure water, 50-150 μl of Nafion, and the high-entropy alloy electrocatalyst.

7. The preparation method of the high-entropy alloy electrocatalyst according to claim 4, characterized in that, The method for dropping the ink solution described in step S13 is as follows: Select a 200-μl pipette to take an appropriate amount of the ink solution and drop it onto 1×1.5 cm carbon paper each time, and a total of one-third of the ink solution is dropped.

8. The preparation method of the high-entropy alloy electrocatalyst according to claim 4, wherein, The in-situ self-reconfiguration described in step S14 uses the electrocatalyst as the working electrode, Hg / HgO as the reference electrode, and a platinum mesh as the counter electrode. In the potential range of 1.124 - 1.724 V vs RHE, it is scanned at a rate of 20 - 80 mV s -1 for 100 - 300 cycles.

9. Application of the high-entropy alloy electrocatalyst as described in claim 1 in the oxygen evolution reaction and the anion exchange membrane water electrolyzer.

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