A catalyst for the oxygen evolution reaction, its preparation method and application

Abstract

This invention discloses a catalyst for the oxygen evolution reaction (OER), its preparation method, and its application, relating to the field of electrocatalysis technology. By precisely controlling the magnetron sputtering deposition process parameters, particularly maintaining the substrate temperature at 100°C, this invention successfully prepared a FeCrNi medium-entropy alloy film with a special amorphous / nanocrystalline structure on the substrate or the surface of a Cr film interlayer. This structure provides more active sites and lowers the reaction energy barrier, thereby significantly improving OER catalytic performance. The FeCrNi medium-entropy alloy film prepared by this invention exhibits excellent oxygen evolution activity and stability under alkaline conditions when used as an OER catalyst for water electrolysis. Specifically, it achieves this at an industrial-grade current density of 1 A / cm². 2 The overpotential is as low as 363mV and can be maintained at 200mA / cm. 2 It operates stably for over 1000 hours at current densities. This invention provides a low-cost, high-performance, and novel OER catalyst preparation method, which has broad application prospects in the field of water electrolysis to produce oxygen and / or hydrogen.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, and in particular to a catalyst for the oxygen evolution reaction, its preparation method, and its application. Background Technology

[0002] In the technology of producing hydrogen and oxygen through water electrolysis, the oxygen evolution reaction (OER) at the anode is the barrier restricting the overall reaction, and achieving high activity and stability are the two central goals of the OER reaction. Although existing IrO2 and RuO2 catalysts have excellent OER catalytic activity, their high application cost limits large-scale industrial application. Therefore, developing inexpensive metal catalysts with high catalytic performance is of great significance for promoting the practical application of water electrolysis technology for producing hydrogen and oxygen. Summary of the Invention

[0003] The purpose of this invention is to provide a catalyst for the oxygen evolution reaction (OER), its preparation method, and its application, thereby addressing the problems existing in the prior art. The catalyst for the OER of this invention can reduce the overpotential and Tafel slope of the OER under alkaline conditions, exhibits excellent oxygen production performance in water electrolysis, and can indirectly improve hydrogen production performance in water electrolysis, thus possessing excellent application value in the field of water electrolysis.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] One of the technical solutions of the present invention is a catalyst for the oxygen evolution reaction, comprising a substrate and a FeCrNi medium-entropy alloy thin film surface layer (the atomic ratio of Fe, Cr and Ni in the FeCrNi medium-entropy alloy thin film surface layer is 1:1:1); the FeCrNi medium-entropy alloy thin film surface layer is an amorphous / nanocrystalline structure (i.e., it contains both amorphous and nanocrystalline phases).

[0006] The FeCrNi medium-entropy alloy not only possesses high stability but also exhibits enhanced electrocatalytic performance through the synergistic effect between Fe, Cr, and Ni metal atoms. Specifically, Fe and Ni atoms serve as the main metal active sites for the OER reaction, forming FCC nanocrystals; Cr demonstrates a stronger affinity for O, forming an amorphous shell. Compared to crystalline materials, amorphous / nanocrystalline materials possess numerous grain boundaries and phase boundaries, resulting in lower adsorption energy barriers, which facilitates the adsorption of OER reaction intermediates and leads to superior OER catalytic performance.

[0007] Furthermore, the substrate is a graphite sheet.

[0008] Preferably, the substrate is a high-purity graphite sheet.

[0009] Furthermore, the thickness of the FeCrNi medium-entropy alloy thin film surface layer is 1~2μm.

[0010] Furthermore, a Cr thin film intermediate layer is provided between the substrate and the FeCrNi medium-entropy alloy thin film surface layer (i.e., the catalyst for the oxygen evolution reaction includes the substrate, the Cr thin film intermediate layer and the FeCrNi medium-entropy alloy thin film surface layer arranged sequentially), and the thickness of the Cr thin film intermediate layer is 10~20nm.

[0011] The Cr thin film interlayer can improve the bonding force between the FeCrNi medium-entropy alloy film surface and the substrate, further enhancing the stability of the catalyst.

[0012] The second technical solution of the present invention: a method for preparing the above-mentioned catalyst (Cr-free thin film intermediate layer) for oxygen evolution reaction, comprising the following steps: depositing a FeCrNi medium-entropy alloy thin film surface layer on the substrate surface by magnetron sputtering to obtain the catalyst for oxygen evolution reaction.

[0013] The third technical solution of the present invention: a method for preparing the above-mentioned catalyst (with a Cr thin film interlayer) for the oxygen evolution reaction, comprising the following steps:

[0014] First, a Cr thin film intermediate layer is deposited on the substrate surface by magnetron sputtering. Then, a FeCrNi medium-entropy alloy thin film surface layer is deposited on the surface of the obtained Cr thin film intermediate layer by magnetron sputtering to obtain the catalyst used for the oxygen evolution reaction.

[0015] Magnetron sputtering can control the structure of medium-entropy alloys by adjusting deposition parameters (to obtain amorphous / nanocrystalline medium-entropy alloys), thereby regulating the catalytic active sites of medium-entropy alloys.

[0016] Furthermore, the parameters for depositing the intermediate layer of the Cr thin film on the substrate surface by magnetron sputtering include: substrate temperature of 100℃, deposition power of 100W, deposition voltage of 284V, deposition time of 10~20s, and deposition is carried out under an argon protective atmosphere.

[0017] Furthermore, the parameters for depositing a FeCrNi medium-entropy alloy thin film surface layer on the obtained Cr thin film intermediate layer surface by magnetron sputtering (or directly depositing a FeCrNi medium-entropy alloy thin film surface layer on the substrate surface by magnetron sputtering) include: substrate temperature of 100℃, deposition power of 100W, deposition voltage of 284V, deposition time of 3600~7200s, and deposition is carried out under an argon protective atmosphere.

[0018] During the deposition process, the crystallization rate of the FeCrNi film is controlled by controlling the substrate temperature, thereby obtaining an amorphous / nanocrystalline FeCrNi medium-entropy alloy film.

[0019] Furthermore, before depositing the intermediate Cr thin film layer on the substrate surface by magnetron sputtering or directly depositing the FeCrNi medium-entropy alloy thin film surface layer on the substrate surface by magnetron sputtering, the process also includes grinding and polishing the substrate and ultrasonic cleaning.

[0020] Furthermore, the preparation method of the catalyst (with a Cr thin film interlayer) for the oxygen evolution reaction includes the following more specific steps:

[0021] S1. Substrate pretreatment: The high-purity graphite sheet is polished with 6000-grit sandpaper and polished with a polishing cloth, and then ultrasonically cleaned with alcohol for 15 minutes.

[0022] S2. Mounting of substrate and target: Mount the pretreated substrate, Cr target and FeCrNi target in the magnetron sputtering chamber.

[0023] S3. Air washing: Evacuate the air in the chamber to ≤1×10⁻⁶. -4 Pa, and argon gas is introduced to 1×10 -2 Pa of gas was purged, and then the vacuum was evacuated again to ≤1×10⁻⁶. -4 Pa; Repeat the process of purging with argon gas and then evacuating the vacuum again three times;

[0024] S4. Magnetron sputtering deposition of Cr thin film intermediate layer: Set the substrate temperature, deposition power, deposition voltage, substrate rotation speed, and argon gas flow rate. When the substrate reaches the set temperature, start sputtering deposition of Cr thin film intermediate layer.

[0025] S5. Magnetron sputtering deposition of FeCrNi medium-entropy alloy thin film surface layer: After the Cr thin film intermediate layer is deposited, rotate the target baffle to switch to FeCrNi target and start depositing FeCrNi medium-entropy alloy thin film surface layer.

[0026] This invention uses high-purity graphite as a thin film support substrate, which is placed in a magnetron sputtering chamber filled with inert gas (argon). The argon gas is ionized under the action of a strong electric field, and under the action of the strong electric field, it moves at high speed and bombards Cr and FeCrNi targets to obtain metal atoms with a certain initial moving speed, which are then deposited on the high-purity graphite substrate under high-speed motion.

[0027] The fourth technical solution of the present invention: the application of the above-mentioned catalyst for the oxygen evolution reaction in the electrolysis of water to produce oxygen and / or hydrogen.

[0028] The present invention discloses the following technical effects:

[0029] This invention provides an OER catalyst with an amorphous / nanocrystalline FeCrNi medium-entropy alloy thin film deposited on a substrate surface, which has good OER catalytic activity and stability and has good prospects for industrial application.

[0030] This invention successfully prepared FeCrNi medium-entropy alloy films with a special amorphous / nanocrystalline structure on the substrate or the surface of the Cr film interlayer by precisely controlling the magnetron sputtering deposition process parameters, especially by controlling the substrate temperature at 100℃. This structure provides more active sites and lowers the reaction energy barrier, thereby significantly improving the OER catalytic performance. The FeCrNi medium-entropy alloy film prepared by this invention exhibits excellent water electrolysis oxygen evolution activity and stability as an OER catalyst under alkaline conditions. Specifically, it achieves an industrial-grade current density of 1 A / cm². 2 The overpotential is as low as 363mV and can be maintained at 200mA / cm. 2 It operates stably for over 1000 hours at current densities.

[0031] The catalyst of the present invention for the oxygen evolution reaction has a simple composition, inexpensive and readily available raw materials, and a simple preparation process, thus having the advantage of low cost.

[0032] This invention provides a low-cost, high-performance, and novel OER catalyst preparation method, which has broad application prospects in the field of water electrolysis to produce oxygen and / or hydrogen. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 The above are grazing X-ray diffraction (GIXRD) patterns of the catalysts for the oxygen evolution reaction prepared at different temperatures for Example 1 and Comparative Examples 1-3.

[0035] Figure 2 Scanning electron microscope (SEM) image of the catalyst prepared in Example 1 for the oxygen evolution reaction.

[0036] Figure 3 The images shown are high-angle annular dark-field scanning transmission electron microscope (HAADF STEM) images of the catalyst prepared for the oxygen evolution reaction in Example 1, where a is a HAADF STEM image at low magnification and b is a HAADF STEM image at high magnification.

[0037] Figure 4 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the catalyst prepared in Example 1 for the oxygen evolution reaction.

[0038] Figure 5The Raman spectrum of the catalyst prepared in Example 1 for the oxygen evolution reaction is shown.

[0039] Figure 6 Linear voltammetry (LSV) curve of the catalyst prepared in Example 1 for the oxygen evolution reaction.

[0040] Figure 7 Linear voltammetric scan (LSV) curves of the catalysts for the oxygen evolution reaction prepared at different temperatures for Example 1 and Comparative Examples 1-3.

[0041] Figure 8 The catalyst prepared for the oxygen evolution reaction in Example 1 operates at 200 mA / cm². 2 At a current density of 10 mA / cm², the catalyst prepared in Comparative Example 1 for the oxygen evolution reaction was also tested. 2 Figure showing the stability test results under current density.

[0042] Figure 9 The Cr-free amorphous / nanocrystalline FeCrNi catalyst prepared in Example 2 for the oxygen evolution reaction was tested at 10 mA / cm². 2 Figure showing the stability test results under current density. Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0049] As a first aspect of the present invention, the present invention provides a catalyst for the oxygen evolution reaction, comprising a substrate and a FeCrNi medium-entropy alloy thin film surface layer; the FeCrNi medium-entropy alloy thin film surface layer is an amorphous / nanocrystalline structure.

[0050] In a preferred embodiment of the present invention, the substrate is a high-purity graphite sheet.

[0051] In a preferred embodiment of the present invention, the thickness of the FeCrNi medium-entropy alloy thin film surface layer is 1~2μm.

[0052] In a preferred embodiment of the present invention, a Cr thin film intermediate layer is further provided between the substrate and the surface layer of the FeCrNi medium-entropy alloy thin film, and the thickness of the Cr thin film intermediate layer is 10~20nm.

[0053] As a second aspect of the present invention, the present invention provides a method for preparing the above-mentioned catalyst (Cr-free thin film intermediate layer) for oxygen evolution reaction, comprising the following steps: depositing a FeCrNi medium-entropy alloy thin film surface layer on the substrate surface by magnetron sputtering to obtain the catalyst for oxygen evolution reaction.

[0054] As a third aspect of the present invention, the present invention provides a method for preparing the above-mentioned catalyst (with a Cr thin film interlayer) for the oxygen evolution reaction, comprising the following steps:

[0055] First, a Cr thin film intermediate layer is deposited on the substrate surface by magnetron sputtering. Then, a FeCrNi medium-entropy alloy thin film surface layer is deposited on the surface of the obtained Cr thin film intermediate layer by magnetron sputtering to obtain the catalyst used for the oxygen evolution reaction.

[0056] As a preferred embodiment of the present invention, the preparation method of the catalyst (with a Cr thin film interlayer) for the oxygen evolution reaction more specifically includes the following steps:

[0057] S1. Substrate pretreatment: The high-purity graphite sheet is polished with 6000-grit sandpaper and polished with a polishing cloth, and then ultrasonically cleaned with alcohol for 15 minutes.

[0058] S2. Mounting of substrate and target: Mount the pretreated substrate, Cr target and FeCrNi target in the magnetron sputtering chamber.

[0059] S3. Air washing: Evacuate the air in the chamber to ≤1×10⁻⁶. -4 Pa, and argon gas is introduced to 1×10 -2 Pa of gas was purged, and then the vacuum was evacuated again to ≤1×10⁻⁶. -4 Pa; Repeat the process of purging with argon gas and then evacuating the vacuum again three times;

[0060] S4. Magnetron sputtering deposition of Cr thin film intermediate layer: Set the substrate temperature (100℃), deposition power (100W), deposition voltage (284V), substrate rotation speed (50%), and argon flow rate (80sccm). When the substrate reaches the set temperature, start sputtering deposition of Cr thin film intermediate layer.

[0061] S5. Magnetron sputtering deposition of FeCrNi medium-entropy alloy thin film surface layer: After the Cr thin film intermediate layer is deposited, rotate the target baffle to switch to FeCrNi target and start depositing FeCrNi medium-entropy alloy thin film surface layer.

[0062] This invention provides a method for preparing FeCrNi medium-entropy alloy thin film OER catalyst by magnetron sputtering. The method uses polished high-purity graphite as a supported substrate and Cr metal and FeCrNi alloy as sputtering targets. The substrate and target are placed in an argon chamber and magnetron sputtering is performed by applying an external DC current. FeCrNi amorphous / nanocrystalline thin films of a specific thickness are obtained under specific substrate temperature, specific power, and specific time, which have good OER catalytic activity and stability.

[0063] As a fourth aspect of the present invention, the present invention provides the application of the above-described catalyst for the oxygen evolution reaction in the electrolysis of water to produce oxygen and / or hydrogen.

[0064] In the following embodiments of the present invention, room temperature refers specifically to 20-30°C.

[0065] All raw materials used in the following embodiments of the present invention are commercially available products.

[0066] Example 1

[0067] A catalyst (amorphous / nanocrystalline FeCrNi catalyst) for the oxygen evolution reaction is prepared as follows:

[0068] S1. Substrate pretreatment: A high-purity graphite sheet (carbon content > 99.99wt%) with a size of 1cm×1cm×1mm is sanded with 6000-grit sandpaper and polished with a polishing cloth, and then ultrasonically cleaned with alcohol for 15 minutes.

[0069] S2. Substrate and Target Installation: The pretreated substrate, pure Cr target, and FeCrNi target (with an atomic ratio of Fe, Cr, and Ni of 1:1:1) are installed within the magnetron sputtering chamber. The targets are pre-polished, and the chamber is pre-cleaned to ensure the absence of other metallic impurities, guaranteeing that no impurity atoms are sputtered onto the surface of the high-purity graphite substrate.

[0070] S3, Gas washing: Evacuate the air in the chamber to a vacuum of 1×10⁻⁶. -4 Pa, and argon gas is introduced to 1×10 -2 Pa of gas was washed, and then the vacuum was evacuated again to 1×10⁻⁶. -4 Pa; repeat the process of purging with argon gas and then evacuating the vacuum again three times.

[0071] S4. Magnetron sputtering deposition of the intermediate Cr thin film: Set the substrate heating temperature to 100℃, continuously introduce argon gas at a flow rate of 80 sccm, set the DC power of magnetron sputtering deposition to 100W and the voltage to 284V, set the substrate basic rotation speed to 50%, maintain the argon gas flow rate of 80 sccm continuously until 3Pa is reached, start glow sputtering, and after triggering glow discharge, adjust the argon gas to 1×10⁻⁶. -1 Pa, while maintaining the above parameters, sputter to deposit a pure Cr thin film intermediate layer for 10 s to obtain a Cr thin film intermediate layer with a thickness of 10 nm.

[0072] S5. Magnetron sputtering deposition of FeCrNi medium-entropy alloy thin film surface: Rotate the target baffle, switch the FeCrNi target, and maintain the above parameters in step S4 for sputtering for 3600s to obtain an amorphous / nanocrystalline FeCrNi medium-entropy alloy thin film surface with an average thickness of 1μm.

[0073] Example 2

[0074] A catalyst for the oxygen evolution reaction (Cr-free amorphous / nanocrystalline FeCrNi catalyst) is prepared as follows:

[0075] S1. Substrate pretreatment: A high-purity graphite sheet (carbon content > 99.99wt%) with a size of 1cm×1cm×1mm is sanded with 6000-grit sandpaper and polished with a polishing cloth, and then ultrasonically cleaned with alcohol for 15 minutes.

[0076] S2. Substrate and Target Installation: Install the pretreated substrate and FeCrNi target (with an atomic ratio of Fe, Cr, and Ni of 1:1:1) in the magnetron sputtering chamber. The target is pre-polished and the chamber is pre-cleaned to ensure that there are no other metal impurities in the chamber, ensuring that no impurity atoms are sputtered onto the surface of the high-purity graphite substrate.

[0077] S3, Gas washing: Evacuate the air in the chamber to a vacuum of 1×10⁻⁶. -4 Pa, and argon gas is introduced to 1×10 -2 Pa of gas was washed, and then the vacuum was evacuated again to 1×10⁻⁶. -4 Pa; repeat the process of purging with argon gas and then evacuating the vacuum again three times.

[0078] S4. Magnetron sputtering deposition of FeCrNi medium-entropy alloy thin film surface: The substrate heating temperature is set to 100℃, argon gas is continuously introduced at a flow rate of 80 sccm, the DC power of magnetron sputtering deposition is set to 100W and the voltage to 284V, the basic substrate rotation speed is set to 50%, and argon gas is continuously introduced at a flow rate of 80 sccm until 3Pa is reached to start glow sputtering. After triggering glow discharge, the argon gas flow rate is adjusted to 1×10 -1 Pa, maintaining the above parameters, sputtered and deposited FeCrNi medium-entropy alloy thin film surface layer for 3600s, to obtain an amorphous / nanocrystalline FeCrNi medium-entropy alloy thin film surface layer with an average thickness of 1μm.

[0079] Comparative Example 1

[0080] A catalyst (amorphous FeCrNi catalyst) for the oxygen evolution reaction is prepared as follows:

[0081] S1. Substrate pretreatment: A high-purity graphite sheet (carbon content > 99.99wt%) with a size of 1cm×1cm×1mm is sanded with 6000-grit sandpaper and polished with a polishing cloth, and then ultrasonically cleaned with alcohol for 15 minutes.

[0082] S2. Substrate and Target Installation: The pretreated substrate, pure Cr target, and FeCrNi target (with an atomic ratio of Fe, Cr, and Ni of 1:1:1) are installed within the magnetron sputtering chamber. The targets are pre-polished, and the chamber is pre-cleaned to ensure the absence of other metallic impurities, guaranteeing that no impurity atoms are sputtered onto the surface of the high-purity graphite substrate.

[0083] S3, Gas washing: Evacuate the air in the chamber to a vacuum of 1×10⁻⁶. -4 Pa, and argon gas is introduced to 1×10 -2 Pa of gas was washed, and then the vacuum was evacuated again to 1×10⁻⁶. -4 Pa; repeat the process of purging with argon gas and then evacuating the vacuum again three times.

[0084] S4. Magnetron sputtering deposition of the intermediate Cr thin film: The substrate heating temperature is set to 25℃, argon gas is continuously introduced at a flow rate of 80 sccm, the DC power of magnetron sputtering deposition is set to 100W and the voltage to 284V, the basic substrate rotation speed is set to 50%, and argon gas is continuously introduced at a flow rate of 80 sccm until 3Pa is reached. Glow sputtering begins, and after triggering glow discharge, the argon gas flow rate is adjusted to 1×10⁻⁶. - 1 Pa, while maintaining the above parameters, sputter to deposit a pure Cr thin film intermediate layer until a Cr thin film intermediate layer with a thickness of 10 nm is obtained.

[0085] S5. Magnetron sputtering deposition of FeCrNi medium-entropy alloy thin film surface: Rotate the target baffle, switch the FeCrNi target, and maintain the above parameters in step S4 for sputtering until an amorphous FeCrNi medium-entropy alloy thin film surface with an average thickness of 1 μm is obtained.

[0086] Comparative Example 2

[0087] A catalyst (nanocrystalline FeCrNi catalyst) for the oxygen evolution reaction is prepared as follows:

[0088] S1. Substrate pretreatment: A high-purity graphite sheet (carbon content > 99.99wt%) with a size of 1cm×1cm×1mm is sanded with 6000-grit sandpaper and polished with a polishing cloth, and then ultrasonically cleaned with alcohol for 15 minutes.

[0089] S2. Substrate and Target Installation: The pretreated substrate, pure Cr target, and FeCrNi target (with an atomic ratio of Fe, Cr, and Ni of 1:1:1) are installed within the magnetron sputtering chamber. The targets are pre-polished, and the chamber is pre-cleaned to ensure the absence of other metallic impurities, guaranteeing that no impurity atoms are sputtered onto the surface of the high-purity graphite substrate.

[0090] S3, Gas washing: Evacuate the air in the chamber to a vacuum of 1×10⁻⁶. -4 Pa, and argon gas is introduced to 1×10 -2 Pa of gas was washed, and then the vacuum was evacuated again to 1×10⁻⁶. -4 Pa; repeat the process of purging with argon gas and then evacuating the vacuum again three times.

[0091] S4. Magnetron sputtering deposition of the intermediate Cr thin film: The substrate heating temperature is set to 150℃, argon gas is continuously introduced at a flow rate of 80 sccm, the DC power of magnetron sputtering deposition is set to 100W and the voltage to 284V, the basic rotation speed of the substrate is set to 50%, and argon gas is continuously introduced at a flow rate of 80 sccm until 3Pa is reached to start glow sputtering. After triggering glow discharge, the argon gas flow rate is adjusted to 1×10⁻⁶. -1 Pa, while maintaining the above parameters, sputter to deposit a pure Cr thin film intermediate layer until a Cr thin film intermediate layer with a thickness of 10 nm is obtained.

[0092] S5. Magnetron sputtering deposition of FeCrNi medium-entropy alloy thin film surface: Rotate the target baffle, switch the FeCrNi target, and maintain the above parameters in step S4 for sputtering until a nanocrystalline FeCrNi medium-entropy alloy thin film surface with an average thickness of 1 μm is obtained.

[0093] Comparative Example 3

[0094] A catalyst (nanocrystalline FeCrNi catalyst) for the oxygen evolution reaction is prepared as follows:

[0095] S1. Substrate pretreatment: A high-purity graphite sheet (carbon content > 99.99wt%) with a size of 1cm×1cm×1mm is sanded with 6000-grit sandpaper and polished with a polishing cloth, and then ultrasonically cleaned with alcohol for 15 minutes.

[0096] S2. Substrate and Target Installation: The pretreated substrate, pure Cr target, and FeCrNi target (with an atomic ratio of Fe, Cr, and Ni of 1:1:1) are installed within the magnetron sputtering chamber. The targets are pre-polished, and the chamber is pre-cleaned to ensure the absence of other metallic impurities, guaranteeing that no impurity atoms are sputtered onto the surface of the high-purity graphite substrate.

[0097] S3, Gas washing: Evacuate the air in the chamber to a vacuum of 1×10⁻⁶. -4 Pa, and argon gas is introduced to 1×10 -2 Pa of gas was washed, and then the vacuum was evacuated again to 1×10⁻⁶. -4 Pa; repeat the process of purging with argon gas and then evacuating the vacuum again three times.

[0098] S4. Magnetron sputtering deposition of the intermediate Cr thin film: The substrate heating temperature is set to 200℃, argon gas is continuously introduced at a flow rate of 80 sccm, the DC power of magnetron sputtering deposition is set to 100W and the voltage to 284V, the basic substrate rotation speed is set to 50%, and argon gas is continuously introduced at a flow rate of 80 sccm until 3Pa is reached. Glow sputtering begins, and after triggering glow discharge, the argon gas flow rate is adjusted to 1×10⁻⁶. -1 Pa, while maintaining the above parameters, sputter to deposit a pure Cr thin film intermediate layer until a Cr thin film intermediate layer with a thickness of 10 nm is obtained.

[0099] S5. Magnetron sputtering deposition of FeCrNi medium-entropy alloy thin film surface: Rotate the target baffle, switch the FeCrNi target, and maintain the above parameters in step S4 to sputter for 3600s until a nanocrystalline FeCrNi medium-entropy alloy thin film surface with an average thickness of 1μm is formed.

[0100] Test Example 1

[0101] Characterization data

[0102] Figure 1 The grazing X-ray diffraction (GIXRD) patterns of the catalysts for the oxygen evolution reaction prepared at different temperatures in Example 1 and Comparative Examples 1-3 show that the FeCrNi medium-entropy alloy film surface deposited at 100℃ consists of a face-centered cubic (FCC) nanocrystalline structure and an amorphous structure. The FeCrNi medium-entropy alloy film surface deposited at 25℃ consists of an amorphous structure. The FeCrNi medium-entropy alloy film surface deposited at 150℃ and 200℃ consists of a nanocrystalline structure.

[0103] Figure 2 The scanning electron microscope (SEM) image of the catalyst prepared in Example 1 for the oxygen evolution reaction shows the surface morphology of the catalyst. It can be seen that the FeCrNi medium entropy alloy film has a dense and intact surface, indicating that it is well bonded to the substrate.

[0104] Figure 3 The images shown are high-angle annular dark-field scanning transmission electron microscope (HAADF STEM) images of the catalyst prepared for the oxygen evolution reaction in Example 1. Image a is a low-magnification HAADF STEM image, with the inset in image a showing a selected electron diffraction pattern, representing a typical amorphous / nanocrystalline diffraction spot. Image b is a high-magnification HAADF STEM image, clearly showing the amorphous / nanocrystalline structure. Furthermore, the elemental composition of the amorphous and nanocrystalline phases can be distinguished by the brightness of the lattice; the crystalline phase is rich in FeNi, while the amorphous phase is rich in Cr.

[0105] Figure 4 The X-ray photoelectron spectroscopy (XPS) spectrum of the catalyst prepared for the oxygen evolution reaction in Example 1 shows the valence states of each element: Fe exhibits valence states of 0, +2, and +3; Cr exhibits valence states of +3 and +6; and Ni exhibits valence states of 0 and +2.

[0106] Figure 5 The Raman spectrum of the catalyst prepared in Example 1 for the oxygen evolution reaction is shown at 647 cm⁻¹. -1 and 813cm -1 The peak corresponds to the oxide on the surface of the alloy film before the electrochemical reaction occurs.

[0107] Test Example 2

[0108] OER performance test

[0109] Using the catalysts for the oxygen evolution reaction prepared in Examples 1-2 or Comparative Examples 1-3 as the anode, a Pt sheet as the cathode, a mercury / mercury oxide electrode as the reference electrode, and 1M KOH solution as the electrolyte, a three-electrode system was constructed. A scan rate of 0.005 V / s was set to obtain linear voltammetric scan curves. Using the above three-electrode system, a constant current of 200 mA / cm² was set. 2The stability of the catalyst prepared in Example 1 was tested by setting a constant current of 10 mA / cm. 2 The stability of the catalysts prepared in Example 2 and Comparative Example 1 was tested.

[0110] Figure 6 The linear voltammetric scan (LSV) curve of the catalyst prepared in Example 1 for the oxygen evolution reaction is shown below. Figure 6 It can be seen that the catalyst prepared in Example 1 for the oxygen evolution reaction has an overpotential as low as 363 mV at an industrial-grade current density of 1 A / cm², and an overpotential as low as 500 mA / cm². 2 The overpotential is as low as 357mV.

[0111] Figure 7 Linear voltammetric scans (LSV) of the catalysts for the oxygen evolution reaction prepared in Example 1 and Comparative Examples 1-3 at different temperatures are shown below. Figure 7 It can be seen that Example 1 has the lowest OER overpotential (at the same current density, 10 mA / cm²). 2 For example, the overpotential in Example 1 was 298 mV, while in Comparative Examples 1-3 it was 332 mV, 315 mV, and 323 mV, respectively.

[0112] Figure 8 The catalyst prepared for the oxygen evolution reaction in Example 1 operates at 200 mA / cm². 2 At a current density of 10 mA / cm², the catalyst prepared in Comparative Example 1 for the oxygen evolution reaction was also tested. 2 The stability test results under current density are shown in the figure. Figure 8 It can be seen that the catalyst prepared in Example 1 for the oxygen evolution reaction can operate stably for more than 1000 hours at a current density of 200 mA / cm², while the catalyst prepared in Comparative Example 1 can only operate stably for 60 hours at a current density of 10 mA / cm².

[0113] Figure 9 The catalyst prepared for the oxygen evolution reaction in Example 2 is at 10 mA / cm². 2 The test results under current density are from Figure 9 It can be seen that the catalyst prepared in Example 2 for the oxygen evolution reaction can only operate stably for 83 hours at a current density of 10 mA / cm².

[0114] The above test results show that the catalyst of the present invention has good OER catalytic activity and stability, and has good cost advantages and industrial application prospects compared with traditional noble metal catalysts.

[0115] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A catalyst for the oxygen evolution reaction, characterized in that, It includes a substrate and a FeCrNi medium-entropy alloy thin film surface layer; the FeCrNi medium-entropy alloy thin film surface layer has an amorphous / nanocrystalline structure, that is, it contains both amorphous and nanocrystalline phases; The FeCrNi medium-entropy alloy thin film was deposited on the substrate surface by magnetron sputtering. The parameters of the magnetron sputtering include: substrate temperature of 100℃, deposition power of 100W, deposition voltage of 284V, deposition time of 3600~7200s, and deposition is carried out in an argon protective atmosphere.

2. The catalyst for the oxygen evolution reaction as described in claim 1, characterized in that, The substrate is a graphite sheet.

3. The catalyst for the oxygen evolution reaction as described in claim 1, characterized in that, The thickness of the FeCrNi medium-entropy alloy thin film surface layer is 1~2μm.

4. The catalyst for the oxygen evolution reaction as described in claim 1, characterized in that, A Cr thin film intermediate layer is further disposed between the substrate and the surface layer of the FeCrNi medium-entropy alloy thin film, and the thickness of the Cr thin film intermediate layer is 10~20nm.

5. A method for preparing a catalyst for the oxygen evolution reaction as described in any one of claims 1-3, characterized in that, Includes the following steps: The catalyst for the oxygen evolution reaction was obtained by depositing a FeCrNi medium-entropy alloy thin film on the substrate surface by magnetron sputtering. The parameters of the magnetron sputtering include: substrate temperature of 100℃, deposition power of 100W, deposition voltage of 284V, deposition time of 3600~7200s, and deposition is carried out in an argon protective atmosphere.

6. A method for preparing a catalyst for the oxygen evolution reaction as described in claim 4, characterized in that, Includes the following steps: First, a Cr thin film intermediate layer is deposited on the substrate surface by magnetron sputtering. Then, a FeCrNi medium-entropy alloy thin film surface layer is deposited on the surface of the obtained Cr thin film intermediate layer by magnetron sputtering to obtain the catalyst used for the oxygen evolution reaction. The parameters for depositing FeCrNi medium-entropy alloy thin films on the surface of the obtained Cr thin film intermediate layer by magnetron sputtering included: substrate temperature of 100℃, deposition power of 100W, deposition voltage of 284V, deposition time of 3600~7200s, and deposition was carried out under an argon protective atmosphere.

7. The method for preparing the catalyst for the oxygen evolution reaction as described in claim 6, characterized in that, The parameters for depositing the intermediate layer of a Cr thin film on the substrate surface by magnetron sputtering include: substrate temperature of 100℃, deposition power of 100W, deposition voltage of 284V, deposition time of 10~20s, and deposition is carried out under an argon protective atmosphere.

8. The use of a catalyst for the oxygen evolution reaction as described in any one of claims 1-4 in the oxygen evolution reaction of water electrolysis.

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