An oxygen evolution reaction catalyst, a preparation method therefor, and use thereof

Abstract

The application discloses a preparation method of an oxygen evolution reaction catalyst, and the preparation method comprises the following steps: mixing weighed nickel nitrate, thiourea, graphene oxide, ferrous sulfate, sodium hypophosphite and deionized water to obtain a suspension; freeze-drying the suspension to obtain a powdery mixture; performing surface modification treatment on the powdery mixture by using plasma generated by dielectric barrier discharge, so that carbon defects are generated on the surface of the powdery mixture; and simultaneously, under the action of the plasma, phosphorus and NiFe are fixed in the carbon defects to obtain a powdery NiFe@P-rGO.The application has the beneficial effects that: the high-energy particles generated by dielectric barrier discharge are used to perform surface treatment on graphene, and then NiFe is loaded in the graphene, so that the synthesis efficiency of the oxygen evolution catalyst is effectively improved, no toxic by-products are generated, and the performance of the oxygen evolution reaction catalyst is improved.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis technology, and more specifically, to an oxygen evolution reaction catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy is a high-calorific-value, pollution-free new energy source with wide applications in many fields. Hydrogen production through water electrolysis is an effective way to alleviate the energy crisis and reduce carbon emissions. However, the oxygen evolution reaction (OER) at the anolyte in water electrolysis involves a complex four-electron transfer process with a high overpotential, limiting hydrogen production efficiency. For a long time, water electrolysis catalysts have mainly been precious metal oxides such as Ir and Ru, which are scarce, low-cost, and difficult to apply on a large scale.

[0003] Studies have shown that transition metals and their compounds are abundant, low-cost, and easily controllable, possessing the potential to replace noble metal catalysts and have attracted widespread attention from scholars in recent years. Among them, NiFe has an easily controllable morphology and structure, making it widely used in catalysis; however, its low electrical conductivity limits further improvement in its OER performance. Meanwhile, graphene has been found to possess a unique two-dimensional structure, supporting abundant active sites, and its high electrical conductivity can accelerate electron transfer efficiency during reactions. However, current techniques for loading NiFe onto graphene primarily employ chemical synthesis methods (such as hydrothermal methods). These traditional methods are not only time-consuming but also generate various toxic byproducts. Summary of the Invention

[0004] To address the problems of time-consuming traditional methods and the presence of toxic byproducts, the present invention aims to provide an oxygen evolution reaction catalyst, its preparation method, and its application.

[0005] This invention provides a method for preparing an oxygen evolution reaction catalyst, the method comprising:

[0006] A suspension is prepared by mixing weighed nickel nitrate, thiourea, graphene oxide, ferrous sulfate, sodium hypophosphite, and deionized water.

[0007] The suspension was freeze-dried to obtain a powdered mixture;

[0008] The powdered mixture is surface modified by plasma generated by dielectric barrier discharge, which creates carbon defects on the surface of the powdered mixture. At the same time, under the action of the plasma, phosphorus and NiFe are fixed in the carbon defects to obtain powdered phosphorus-doped and NiFe-loaded reduced graphene oxide, i.e. powdered NiFe@P-rGO.

[0009] As a further improvement of the present invention, the preparation method further includes:

[0010] Powdered NiFe@P-rGO was mixed with ethanol and Nafion solution, and the resulting mixture was then coated onto nickel foam to obtain the NiFe@P-rGO / NF catalyst.

[0011] As a further improvement of the present invention, the step of mixing weighed nickel nitrate, thiourea, graphene oxide, ferrous sulfate, sodium hypophosphite, and deionized water to obtain a suspension includes:

[0012] The weighed nickel nitrate, thiourea, ferrous sulfate and hypophosphite were added to deionized water to obtain suspension A, wherein the ferrous sulfate and the sodium hypophosphite were added to the deionized water under the protection of a protective gas.

[0013] The weighed graphene oxide was added to deionized water and mixed evenly to obtain suspension B;

[0014] The suspension A and the suspension B are mixed evenly at room temperature to obtain the suspension.

[0015] As a further improvement of the present invention, the molar ratio of nickel nitrate to ferrous sulfate is 1:1, and the molar ratio of sodium hypophosphite to thiourea is 1:4.

[0016] As a further improvement of the present invention, the protective gas is argon or nitrogen.

[0017] As a further improvement of the present invention, the flow rate of the protective gas is 10 to 50 sccm.

[0018] As a further improvement of the present invention, the conditions for freeze-drying the suspension include: a temperature of -50 to -80°C, a pressure of 5 to 30 Pa, and a freezing time of 12 to 30 h.

[0019] As a further improvement of the present invention, the power of the dielectric barrier discharge is 50-100W, the plasma treatment time is 15-60min, and the gas flow rate during the dielectric barrier discharge process is 25-75sccm.

[0020] The present invention also provides an oxygen evolution reaction catalyst, comprising reduced graphene oxide doped with phosphorus and supported on NiFe, obtained by the above preparation method.

[0021] The present invention also provides an application of an oxygen evolution reaction catalyst, wherein the catalyst obtained by the above preparation method is used to catalyze the anodic oxygen evolution reaction in the process of water electrolysis under alkaline conditions.

[0022] The beneficial effects of this invention are as follows: the high-energy particles generated by dielectric barrier discharge treat the surface of graphene, thereby loading NiFe into the graphene, which effectively improves the synthesis efficiency of the oxygen evolution catalyst and produces no toxic byproducts; at the same time, the high-energy particles dope phosphorus into the graphene, allowing NiFe and phosphorus-doped graphene to work synergistically, further improving the performance of the oxygen evolution catalyst. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0024] Figure 1 This is a flowchart illustrating a method for preparing an oxygen evolution reaction catalyst according to an embodiment of the present invention.

[0025] Figure 2 A scanning electron microscope image of the oxygen evolution reaction catalyst prepared in Example 1 of this invention;

[0026] Figure 3 The X-ray diffraction pattern of the oxygen evolution reaction catalyst prepared in Example 1 of this invention;

[0027] Figure 4 The P 2p XPS diagram of the oxygen evolution reaction catalyst prepared in Example 1 of this invention;

[0028] Figure 5 The above are oxygen evolution polarization curves of different oxygen evolution reaction catalysts obtained in Example 1 and Comparative Examples 1-3 of this invention.

[0029] Figure 6 The curve showing the relationship between current density and time under constant voltage conditions for the anodic oxygen evolution reaction of the oxygen evolution catalyst prepared in Example 1 of this invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0032] Furthermore, the terminology used in the description of this invention is for illustrative purposes only and is not intended to limit the scope of the invention. The terms "comprising" and / or "including" are used to specify the presence of said elements, steps, operations, and / or components, but do not exclude the presence or addition of one or more other elements, steps, operations, and / or components. The terms "first," "second," etc., may be used to describe various elements, do not represent an order, and do not limit these elements. Moreover, in the description of this invention, unless otherwise stated, "a plurality of" means two or more. These terms are used only to distinguish one element from another. These and / or other aspects become apparent in conjunction with the following drawings, and those skilled in the art will more readily understand the description of the embodiments of the invention. The drawings are used for illustrative purposes only to depict the embodiments of the invention. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods shown in the invention can be employed without departing from the principles of the invention.

[0033] like Figure 1 As shown in the embodiment of the present invention, a method for preparing an oxygen evolution reaction catalyst includes:

[0034] A suspension is obtained by mixing weighed nickel nitrate, thiourea, graphene oxide, ferrous sulfate, sodium hypophosphite, and deionized water. Preferably, at room temperature, weighed nickel nitrate, thiourea, ferrous sulfate, and hypophosphite are added to deionized water to obtain suspension A. Weighed graphene oxide is added to deionized water and mixed evenly to obtain suspension B. Suspension A and suspension B are then mixed evenly by ultrasonic treatment at room temperature to obtain the final suspension. It should be noted that ferrous sulfate and sodium hypophosphite must be added to deionized water under the protection of a protective gas to prevent oxidation of the ferrous sulfate and sodium hypophosphite. Optionally, the protective gas is argon or nitrogen. Other protective gases can also be used in the catalyst preparation process, and this application does not specifically limit them.

[0035] The obtained suspension was freeze-dried for 12 to 30 hours at a temperature of -50 to -80°C and a pressure of 5 to 30 Pa to obtain a powdered mixture.

[0036] The powdered mixture is surface modified by plasma generated by dielectric barrier discharge, which creates carbon defects on the surface of the powdered mixture. At the same time, under the action of the plasma, phosphorus and NiFe are fixed in the carbon defects to obtain powdered phosphorus-doped and NiFe-loaded reduced graphene oxide, namely powdered NiFe@P-rGO. This powdered NiFe@P-rGO is the oxygen evolution reaction catalyst to be prepared in this application.

[0037] Specifically, the powdered mixture is evenly spread in a flat-bottomed quartz boat, and the discharge gas pressure, discharge gas flow rate, and radio frequency power are adjusted to ensure that the quartz boat is completely placed within the plasma discharge region. For example, the discharge gas is argon, and the plasma contains argon ions and OH- ions. - Active groups, including OH - Active groups can promote the reduction of graphene oxide. During the discharge process, plasma activates sodium hypophosphite and thiourea, converting them into gaseous reactants and promoting the introduction of P, S, and N elements into the catalyst. The introduction of P can optimize the local coordination environment and effectively regulate the activation energy of the OER reaction intermediate. Simultaneously, P doping increases the interlayer spacing of the reduced graphene oxide, increasing the interaction between NiFe and OH groups. - The increased contact area enhances reaction efficiency. Continuous bombardment by high-energy particles leads to the reaction of O and sp elements in graphene oxide. 3 The structural domains were removed. Graphene oxide was reduced to reduced graphene oxide. Plasma treatment altered the band structure of graphene, opening its band gap and facilitating the regulation of elemental valence states. Simultaneously, the higher plasma temperature promoted the formation of amorphous NiFe, which in turn facilitated electron migration during the OER process.

[0038] In one optional embodiment, the preparation method further includes:

[0039] After plasma treatment, the obtained powdered NiFe@P-rGO was cooled to room temperature under an argon atmosphere. The cooled powdered NiFe@P-rGO was then mixed with ethanol and Nafion solution. Finally, the resulting mixture was coated onto nickel foam to obtain a catalyst that can be used for the anodic oxygen evolution reaction in water electrolysis, namely the NiFe@P-rGO / NF catalyst.

[0040] In one optional embodiment, the molar ratio of nickel nitrate to ferrous sulfate is 1:1, the molar ratio of sodium hypophosphite to thiourea is 1:4, and the molar ratio of nickel to phosphorus is 1:2.

[0041] In one optional embodiment, the flow rate of the protective gas is 10–50 sccm.

[0042] In one optional embodiment, the power of the dielectric barrier discharge is 50-100W, the plasma treatment time is 15-60min, and the gas flow rate during the dielectric barrier discharge process is 25-75sccm.

[0043] Example 1

[0044] (1) Weigh 145.4 mg of nickel nitrate hexahydrate, 139 mg of ferrous sulfate heptahydrate, 304.5 mg of thiourea, and 88 mg of sodium hypophosphite and add them to 5 mL of deionized water. Ferrous sulfate heptahydrate and sodium hypophosphite are added to the deionized water under argon protection. Sonicate at room temperature for 30 min to mix evenly to obtain suspension A;

[0045] (2) Weigh 30 mg of graphene oxide and disperse it in 30 mL of deionized water. Sonicate the solution at room temperature for 30 min to ensure uniform dispersion, obtaining suspension B.

[0046] (3) Mix suspension A and suspension B. Sonicate the mixture at room temperature for 30 minutes to obtain a uniformly dispersed black suspension;

[0047] (4) The black suspension was freeze-dried at -75℃ and 10Pa for 24h to obtain a black powder mixture;

[0048] (5) Weigh out the black powder mixture and spread it evenly in a flat-bottomed quartz boat. The discharge gas is argon, the gas environment pressure is 8 kPa, the gas flow rate is 50 sccm, the radio frequency discharge power is 50 W, the processing time is 30 min, and the plasma emits a pale purple light during discharge. Place the quartz boat completely in the plasma discharge area.

[0049] (6) After plasma treatment, the black powder mixture after treatment was cooled to room temperature under argon atmosphere and removed to obtain powdered NiFe@P-rGO.

[0050] (7) Cut the nickel foam into pieces with a size of 1cm×1cm×1mm, and sonicate them with 3mol / L hydrochloric acid solution, ethanol and deionized water for 15min respectively, and dry them at 35℃ for 12h.

[0051] (8) Weigh 10 mg of powdered NiFe@P-rGO and add it to 400 μL of ethanol and 40 μL of 5% wt Nafion solution. Sonicate for 30 min to mix it evenly.

[0052] (9) Take 100 μL of the solution from step (8) and coat it evenly onto the nickel foam treated in step (7). Dry it at 35 °C for 12 h to obtain the NiFe@P-rGO / NF catalyst.

[0053] Comparative Example 1

[0054] The only difference from Example 1 is that the argon plasma treatment in steps (5) and (6) is omitted, resulting in a NiFe@P-rGO / NF catalyst that has not undergone plasma treatment.

[0055] Comparative Example 2

[0056] (1) Cut the nickel foam into pieces with a size of 1cm×1cm×1mm, and sonicate them with 3mol / L hydrochloric acid solution, ethanol and deionized water for 15min respectively, and dry them at 35℃ for 12h.

[0057] (2) Weigh 10 mg IrO2 and add it to 400 μL ethanol and 40 μL 5% wt Nafion solution, and sonicate for 30 min to mix it evenly.

[0058] (3) Take 100uL of the solution from step (2) and coat it evenly onto the nickel foam treated in step (1), and dry it at 35℃ for 12h to obtain the IrO2 / NF catalyst.

[0059] Comparative Example 3

[0060] Nickel foam was cut into sheets with dimensions of 1cm×1cm×1mm, and ultrasonically treated with 3mol / L hydrochloric acid solution, ethanol and deionized water for 15min respectively, and then dried at 35℃ for 12h.

[0061] like Figure 2 The image shown is a scanning electron microscope (SEM) image of the NiFe@P-rGO catalyst prepared in Example 1. From... Figure 2 The results show that aggregated NiFe particles are loaded onto the reduced graphene oxide, proving that after plasma treatment, graphene oxide (GO) is reduced to reduced graphene oxide (rGO) nanosheets, and NiFe is successfully loaded onto the reduced graphene oxide. Figure 2 The rGO flakes are clearly visible in the image, exhibiting a curled shape with distinct edge wrinkles. This structure effectively reduces the system's free energy.

[0062] Figure 3 The X-ray diffraction pattern of the NiFe@P-rGO catalyst prepared in Example 1 is shown below. Figure 3 As can be seen from the data, the NiFe@P-rGO catalyst contains NiFe, while GO is reduced to rGO. The NiFe peak is relatively weak, exhibiting an amorphous state.

[0063] Figure 4 The image shows the P 2p XPS plot of the NiFe@P-rGO catalyst prepared in Example 1. Figure 4As can be seen, the peaks near 133.5 eV and 134.2 eV indicate that the bonding forms of phosphorus are mainly PC and PO, which shows that phosphorus doping was successfully achieved in reduced graphene oxide after dielectric barrier discharge plasma treatment.

[0064] Figure 5 The polarization curves for Examples 1, Comparative Examples 1, 2, and 3 are shown at a scan rate of 5 mV s⁻¹. The test environment was 1 M KOH solution, and the anodic oxygen evolution reaction (OER) catalytic performance of each catalyst was measured using a classic three-electrode system at room temperature. Example 1 was a NiFe@P-rGO / NF catalyst after plasma treatment; Comparative Example 1 was a NiFe@P-rGO / NF catalyst without plasma treatment; Comparative Example 2 was a conventional noble metal (IrO₂ / NF) catalyst; and Comparative Example 3 was uncatalyzed nickel foam. The catalytic activity of each catalyst in Examples 1, 1, and 2 was compared using Comparative Example 3 as a baseline. Figure 5 As shown, at the same current density, the catalyst in Comparative Example 1 requires a higher voltage than that in Comparative Example 2, and the catalyst in Comparative Example 2 requires a higher voltage than that in Example 1. Therefore, the catalyst in Example 1 exhibits higher catalytic activity than that in Comparative Example 2, and the catalyst in Comparative Example 2 exhibits higher activity than that in Comparative Example 1. That is, the plasma-treated NiFe@P-rGO / NF catalyst demonstrates excellent OER catalytic activity, for example, at 50 mA cm⁻¹. -2 At the current density, the overpotential of the NiFe@P-rGO / NF catalyst is about 240mV, which is significantly better than that of the IrO2 / NF catalyst.

[0065] Figure 6 The image shows the voltage-constant It curve of the NiFe@P-rGO / NF catalyst prepared in Example 1 under alkaline conditions of 1M KOH. After 24 hours of fixed potential testing, the current density did not show a significant decrease, indicating that NiFe@P-rGO / NF has long-term OER catalytic stability under alkaline conditions.

[0066] The present invention also provides an oxygen evolution reaction catalyst, comprising reduced graphene oxide doped with phosphorus and supported on NiFe, obtained by the above preparation method.

[0067] The present invention also provides an application of oxygen evolution reaction catalysis, wherein the catalyst obtained by the above preparation method is used to catalyze the anodic oxygen evolution reaction in the process of water electrolysis under alkaline conditions.

[0068] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0069] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0070] Those skilled in the art will understand that although the invention has been described with reference to exemplary embodiments, various changes may be made and its elements may be substituted with equivalents without departing from the scope of the invention. Furthermore, many modifications may be made to adapt particular situations or materials to the teachings of the invention without departing from the essential scope of the invention. Therefore, the invention is not limited to the specific embodiments disclosed, but rather the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing an oxygen evolution reaction catalyst, characterized in that, The preparation method includes: A suspension is prepared by mixing weighed nickel nitrate, thiourea, graphene oxide, ferrous sulfate, sodium hypophosphite, and deionized water. The suspension was freeze-dried to obtain a powdered mixture; The powdered mixture is surface modified by plasma generated by dielectric barrier discharge, which creates carbon defects on the surface of the powdered mixture. At the same time, under the action of the plasma, phosphorus and NiFe are fixed in the carbon defects to obtain powdered phosphorus-doped and NiFe-loaded reduced graphene oxide, i.e. powdered NiFe@P-rGO. The molar ratio of nickel nitrate to ferrous sulfate is 1:

1. The power of the dielectric barrier discharge is 50-100W, the plasma treatment time is 15-60min, and the gas flow rate during the dielectric barrier discharge process is 25-75sccm.

2. The preparation method according to claim 1, characterized in that, Also includes: Powdered NiFe@P-rGO was mixed with ethanol and Nafion solution, and the resulting mixture was then coated onto nickel foam to obtain the NiFe@P-rGO / NF catalyst.

3. The preparation method according to claim 1, characterized in that, The process of mixing weighed nickel nitrate, thiourea, graphene oxide, ferrous sulfate, sodium hypophosphite, and deionized water to obtain a suspension includes: The weighed nickel nitrate, thiourea, ferrous sulfate and sodium hypophosphite were added to deionized water to obtain suspension A, wherein the ferrous sulfate and sodium hypophosphite were added to the deionized water under the protection of a protective gas. The weighed graphene oxide was added to deionized water and mixed evenly to obtain suspension B; The suspension A and the suspension B are mixed evenly at room temperature to obtain the suspension.

4. The preparation method according to claim 1, characterized in that, The molar ratio of sodium hypophosphite to thiourea is 1:

4.

5. The preparation method according to claim 3, characterized in that, The protective gas is argon or nitrogen.

6. The preparation method according to claim 3, characterized in that, The flow rate of the protective gas is 10–50 sccm.

7. The preparation method according to claim 1, characterized in that, The conditions for freeze-drying the suspension include: a temperature of -50 to -80°C, a pressure of 5 to 30 Pa, and a freezing time of 12 to 30 hours.

8. A catalyst for the oxygen evolution reaction, characterized in that, This includes reduced graphene oxide doped with phosphorus and loaded with NiFe, obtained using the preparation methods described in claims 1-7.

9. The application of an oxygen evolution reaction catalyst, characterized in that, The catalyst obtained by the preparation method described in claims 1-7 is used to catalyze the anodic oxygen evolution reaction during water electrolysis under alkaline conditions.

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