A high-valent metal-doped Co4N catalyst, its preparation method and application
Through the Co4N catalyst doped with Mn element, the Co4N surface is activated to generate CoO2 active phase, and the lattice oxygen reaction path is regulated, which solves the problem of surface reconstruction of cobalt-based catalysts and achieves efficient and stable oxygen precipitation reaction.
Patent Information
- Application Number
- CN202410218891.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-28
- Publication Date
- 2025-07-11
- Estimated Expiration
- 2044-02-28
AI Technical Summary
The surface reconstruction of existing cobalt-based catalysts is difficult to regulate during oxygen precipitation reactions, and the traditional adsorption and dissociation evolution mechanism leads to high theoretical overpotentials, limiting their application.
Through the Co4N catalyst doped with Mn element, the inert Co2+ on the Co4N surface is activated, the deprotonation process is promoted, the surface reconstruction is induced to generate CoO2 active phase, and the lattice oxygen reaction path is regulated.
Good catalytic activity and stability in oxygen precipitation reaction were achieved, with the overpotential of 10 mA cm-2 of only 219 mV, maintaining high activity for 240 hours, opening up the application direction of surface reconstruction and lattice oxygen reaction mechanism.
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Figure CN118127559B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of electrocatalytic chemistry, and particularly relates to a high-valent metal-doped Co4N catalyst, a preparation method thereof, and an application thereof. Background Art
[0002] Hydrogen is considered to be an ideal energy carrier for sustainable and clean energy. The electrochemical water splitting technology can be driven by the electric energy converted from renewable wind energy or solar energy, and is an attractive method for large-scale preparation of high-purity hydrogen. The oxygen evolution reaction (OER) is an important part of this technical process. However, the formation of oxygen-oxygen bonds in this reaction process involves multiple steps of proton-coupled electron transfer processes, which results in slow reaction kinetics and greatly reduces the energy efficiency. Therefore, efficient electrocatalysts are required to catalyze the reaction. In recent years, noble metal catalysts, such as ruthenium oxide, have been widely used in the electrolytic water hydrogen production technology, but factors such as high price and poor stability limit their further application.
[0003] Cobalt-based catalysts have broad application prospects in the field of OER electrocatalysts due to their unique 3d electron number attributes and special atomic orbitals. Therefore, extensive research has been carried out on cobalt-based materials to replace noble metals, including cobalt oxides, cobalt hydroxides, cobalt-based double hydroxide layers, cobalt dihalides, cobalt phosphides, and cobalt nitrides. Among them, Co4N has a more special valence bond constitution, with both cobalt-nitrogen covalent bonds and cobalt-cobalt metal bonds, and exhibits excellent electrical conductivity and good catalytic activity during the OER catalytic process. Generally, the Co4N surface is thermodynamically metastable in the strong oxidation environment of OER and is prone to form a thin oxide / (oxy)hydroxide layer. Compared with pure oxides / (oxy)hydroxides, such composite catalyst materials obtained by surface self-reconstruction often have higher OER catalytic activity. However, it is still difficult to regulate the high-activity sites obtained on the reconstructed surface. In addition, understanding the reaction mechanism of OER is also crucial. The traditional adsorption dissociation evolution mechanism (AEM) involves an inherent linear proportional relationship between the adsorption energies of various intermediates (such as *OOH and *OH), resulting in a relatively high theoretical overpotential (0.37 ± 0.10 V), which greatly limits the application of the catalyst. The lattice oxygen oxidation mechanism (LOM) based on lattice oxygen anion redox chemistry can be used as an alternative mechanism to AEM because LOM can directly participate in the reaction through the oxygen atoms in the lattice to promote O-O coupling. This path can bypass the limitation of the inherent linear proportional relationship in AEM and is a necessary reaction path for exploring efficient electrocatalysts. In fact, the research on LOM mainly focuses on perovskites or metal oxides, but the regulation of the reaction path during the catalytic process on the reconstructed surface is still a challenge. Therefore, it is necessary to deeply understand the Co4N surface reconstruction mechanism and activate the LOM reaction mechanism. Summary of the Invention
[0004] In view of the problems existing in the prior art, the present invention provides a high-valent metal-doped Co4N catalyst, a preparation method thereof and an application thereof. Through metal doping, the present patent regulates the surface reconstruction of nitrides to obtain a catalyst capable of efficiently and stably evolving oxygen through an oxygen evolution reaction path.
[0005] The present invention achieves this object through the following technical solutions:
[0006] A high-valent metal-doped Co4N catalyst, wherein the surface of the Co4N nanowire carrier doped with Mn is covered with a thin layer of CoO2 phase.
[0007] Preferably, the content of Mn in the catalyst is 2.5 wt.% to 12.5 wt.%.
[0008] The present invention also provides a preparation method of the above-mentioned high-valent metal-doped Co4N catalyst, and the method includes the following steps:
[0009] Step S1: Immerse the nickel foam substrate in a 1 M dilute hydrochloric acid solution and ultrasonically treat it for 15 minutes to remove surface oil stains and inert oxide films. Then, ultrasonically clean the treated nickel foam in deionized water and ethanol for 5 minutes respectively and repeat three times;
[0010] Step S2: Mix 2 to 15 mmol of cobalt nitrate hexahydrate, 0.03 to 0.9 mmol of manganese nitrate or manganese sulfide or manganese chloride, 7 to 20 mmol of urea and 5 to 15 mmol of ammonium fluoride and add them to 100 mL of deionized water, and stir for 10 to 60 minutes to obtain a pink clear solution;
[0011] Step S3: Immerse the nickel foam obtained in Step S1 into the solution obtained in Step S2 and perform hydrothermal treatment to obtain Mn-doped cobalt nanowires uniformly grown on the nickel foam substrate;
[0012] Step S4: Anneal the Mn-doped cobalt nanowires obtained in Step S3 in ammonia gas to obtain Mn-doped Co4N nanowires grown on the nickel foam;
[0013] Step S5: Reconstruct the surface of the Mn-doped Co4N nanowires obtained in Step S4 through cyclic voltammetry technology, and prepare a Mn-doped CoO2 / Co4N composite material after the reconstruction treatment.
[0014] Preferably, the temperature of the hydrothermal treatment in Step S3 is 100 to 160 °C, the heat preservation time is 4 to 16 hours, and the heating rate is 5 to 30 °C / minute.
[0015] Preferably, in step S4, the annealing temperature in ammonia gas is 370 - 480 °C, the heat preservation time is 1 - 6 hours, the heating rate is 2 - 10 °C / minute, and the ammonia gas flow rate is 30 - 150 mL / minute.
[0016] Preferably, in the cyclic voltammetry technique of step S5, the voltage range is 0 - 0.8 V, the scanning rate is 20 - 100 mV / s, and the number of scanning cycles is 10 - 100 cycles.
[0017] Preferably, in step S2, cobalt nitrate hexahydrate, urea, and ammonium fluoride are all of analytical purity, and the manganese salt is a solution with a mass fraction of 50%.
[0018] Preferably, the manganese salt in step S2 is any one of manganese nitrate, manganese sulfide, or manganese chloride.
[0019] The present invention also provides the application of the above-mentioned high-valent metal-doped Co4N catalyst in the oxygen evolution reaction.
[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0021] By introducing the Mn element, the present invention activates the inert Co on the surface of Co4N 2+ , and promotes its deprotonation process, finally inducing the surface reconstruction of Co4N to generate a CoO2 active phase, and obtaining a CoO2 / Co4N composite catalyst doped with the metal Mn. In the OER process with Mn-CoO2 as the active phase, Mn can adjust the oxygen 2P orbital to move up and cross the Fermi level, thereby activating the lattice oxygen on the catalyst surface and enabling it to participate in the reaction, and finally inducing the lattice oxygen path. The catalyst provided by the present invention shows good catalytic activity in OER, and the overpotential is only 219 mV at 10 mA cm -2 , and has excellent stability, and can maintain high activity for up to 240 h. The present invention obtains an efficient and stable oxygen evolution catalyst by regulating the surface reconstruction of the nitride and the oxygen evolution reaction path through metal doping, opening up a new direction for the regulation and application of the surface reconstruction and lattice oxygen reaction mechanism of transition metal nitrides in the oxygen evolution reaction catalysis process. Description of the Drawings
[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained according to the provided drawings.
[0023] Figure 1 It is a picture of the Co4N electrode material;
[0024] Figure 2 Picture of the Mn-doped Co4N electrode material;
[0025] Figure 3 In-situ Raman spectra of Co4N and Mn-Co4N;
[0026] Figure 4 Mass spectra of the isotope labeling experiments of Co4N and Mn-Co4N in Control Experiment 1 and the examples of the preparation method of the present invention;
[0027] Figure 5 In-situ Raman spectra of V-Co4N, Cr-Co4N, Mo-Co4N and W-Co4N;
[0028] Figure 6 Mass spectra of the isotope labeling experiments of V-Co4N, Cr-Co4N, Mo-Co4N and W-Co4N. Detailed implementation manners
[0029] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.
[0030] The present invention provides a high-valent metal-doped Co4N catalyst. As Figure 2 shown, the Mn-doped Co4N nanowires serving as the catalyst support grow vertically on the surface of nickel foam. The diameter of the Co4N nanowires is about 150 nm, and the surface of the Co4N nanowires is covered with a thin layer of CoO2 phase. This catalyst is a composite phase of Mn-doped CoO2 and Co4N.
[0031] As a preferred solution, the content of Mn in this catalyst is 2.5 wt.% to 12.5 wt.%.
[0032] The present invention also provides a preparation method for the above-mentioned high-valent metal-doped Co4N catalyst, including the following steps:
[0033] Step S1, put the nickel foam substrate into a 1 M dilute hydrochloric acid solution and ultrasonically treat it for 15 minutes to roughen the substrate material, remove the surface oil stain and inert oxide film, and then ultrasonically clean the treated nickel foam in deionized water and ethanol for 5 minutes respectively and repeat three times.
[0034] Step S2: Mix 2 - 15 mmol of cobalt nitrate hexahydrate, 0.03 - 0.9 mmol of manganese salt, 7 - 20 mmol of urea, and 5 - 15 mmol of ammonium fluoride and add them to 100 mL of deionized water. Stir for 10 - 60 minutes to obtain a pink clear solution. Among them, cobalt nitrate hexahydrate, urea, and ammonium fluoride are all of analytical purity, and the manganese salt is a solution with a mass fraction of 50%. The manganese salt is selected from any one of manganese nitrate, manganese sulfide, or manganese chloride.
[0035] Step S3: Immerse the nickel foam obtained in Step S1 into the solution obtained in Step S2 and perform hydrothermal treatment. The temperature range is 100 - 160 °C, the holding time is 4 - 16 hours, and the heating rate is 5 - 30 °C / minute. Obtain Mn-doped Co(OH)F nanowires uniformly grown on the nickel foam substrate.
[0036] Step S4: Put the Mn-doped cobalt nanowires obtained in Step S3 into ammonia gas for annealing treatment. In the ammonia gas atmosphere, the temperature range is 370 - 480 °C, the holding time is 1 - 6 hours, the heating rate is 2 - 10 °C / minute, and the ammonia gas flow rate is 30 - 150 mL / minute. Obtain Mn-doped Co4N nanowires grown on the nickel foam.
[0037] Step S5: Reconstruct the surface of the Mn-doped Co4N nanowires prepared in Step S4 by cyclic voltammetry technology. The voltage range is 0 - 0.8 V, the scanning rate is 20 - 100 mV / s, and the number of scanning cycles is 10 - 100 circles. After the reconstruction treatment, prepare the Mn-doped CoO2 / Co4N composite material.
[0038] The following further illustrates in conjunction with the embodiments of the catalyst preparation method disclosed in the present invention: Example 1
[0039] Put the nickel foam substrate into 1 M dilute hydrochloric acid solution and ultrasonically treat it for 15 minutes to roughen the substrate material, remove surface oil stains and inert oxide films. Then ultrasonically clean the treated nickel foam in deionized water and ethanol for 5 minutes respectively and repeat three times.
[0040] Mix 3 mmol of cobalt nitrate hexahydrate, 0.3 mmol of manganese nitrate, 15 mmol of urea, and 8 mmol of ammonium fluoride and add them to 100 mL of deionized water. Stir for 60 minutes to obtain a pink clear solution. Cobalt nitrate hexahydrate, urea, and ammonium fluoride are all of analytical purity, and manganese nitrate is a solution with a mass fraction of 50%.
[0041] Then immerse the treated nickel foam into the pink clear solution and transfer them together to a reaction kettle for hydrothermal treatment. Keep the temperature at 120 °C for 6 hours, and the heating rate is 8 °C / minute.
[0042] The obtained Mn-doped cobalt nanowires were calcined in an ammonia atmosphere at 450 °C for 2 hours for nitridation treatment, with a heating rate of 5 °C / minute and an ammonia flow rate of 50 mL / minute. The Mn-doped Co4N nanowires grown on nickel foam were obtained, as Figure 1 shown.
[0043] The prepared Mn-doped Co4N nanowires were used as electrode materials, and their surface was reconstructed by cyclic voltammetry technology in a voltage range of 0 - 0.8 V, a scan rate of 50 mV / s, and 20 scan cycles. The prepared high-valent metal-doped oxide / nitride composite material was denoted as Mn-Co4N, as Figure 2 shown. The Mn-doped Co4N nanowires were uniformly and vertically grown on the surface of nickel foam, with a nanowire diameter of approximately 150 nm. During the cyclic voltammetry reaction process, Mn induced the formation of a CoO2 phase thin layer on the surface of Co4N, and finally a composite phase catalyst of Mn-doped CoO2 and Co4N was formed. Example 2
[0044] 2 mmol of cobalt nitrate hexahydrate, 0.1 mmol of manganese chloride, 7 mmol of urea, and 10 mmol of ammonium fluoride were mixed and added to 100 mL of deionized water, and stirred for 30 minutes to obtain a pink clear solution.
[0045] Then the treated nickel foam was immersed in the pink clear solution and transferred to a reaction kettle together, and hydrothermal treatment was carried out in an oven at 130 °C for 8 hours with a heating rate of 10 °C / minute to obtain Mn-doped cobalt nanowires.
[0046] The obtained Mn-doped cobalt nanowires were calcined in an ammonia atmosphere at 420 °C for 1.5 hours for nitridation treatment, with a heating rate of 7 °C / minute and an ammonia flow rate of 100 mL / minute. The Mn-doped Co4N nanowires grown on nickel foam were obtained.
[0047] The prepared Mn-doped Co4N nanowires were used as electrode materials, and their surface was reconstructed by cyclic voltammetry technology in a voltage range of 0 - 0.8 V, a scan rate of 100 mV / s, and 40 scan cycles, and finally a composite phase catalyst of Mn-doped CoO2 and Co4N was prepared. Example 3
[0048] 15 mmol of cobalt nitrate hexahydrate, 0.9 mmol of manganese nitrate, 15 mmol of urea, and 15 mmol of ammonium fluoride were mixed and added to 100 mL of deionized water, and stirred for 10 minutes to obtain a pink clear solution.
[0049] Then, the treated nickel foam was immersed in the pink clear solution and transferred together to a reaction kettle, and hydrothermal treatment was carried out in an oven at 160 °C for 4 hours with a heating rate of 10 °C / minute to obtain Mn-doped cobalt nanowires.
[0050] The obtained Mn-doped cobalt nanowires were calcined in an ammonia atmosphere at 400 °C for 2 hours for nitridation treatment with a heating rate of 10 °C / minute and an ammonia flow rate of 50 mL / minute. The Mn-doped Co4N nanowires grown on nickel foam were obtained.
[0051] The prepared Mn-doped Co4N nanowires were used as electrode materials, and their surface was reconstructed by cyclic voltammetry technology in a voltage range of 0 - 0.8 V, a scan rate of 50 mV / s, and 100 scan cycles to finally obtain the Mn-doped CoO2 and Co4N composite phase catalyst. Example 4
[0052] 10 mmol of cobalt nitrate hexahydrate, 0.6 mmol of manganese sulfide, 20 mmol of urea, and 5 mmol of ammonium fluoride were mixed and added to 100 mL of deionized water, and stirred for 20 minutes to obtain a pink clear solution.
[0053] Then, the treated nickel foam was immersed in the pink clear solution and transferred together to a reaction kettle, and hydrothermal treatment was carried out in an oven at 100 °C for 16 hours with a heating rate of 5 °C / minute to obtain Mn-doped cobalt nanowires.
[0054] The obtained Mn-doped cobalt nanowires were calcined in an ammonia atmosphere at 370 °C for 2 hours for nitridation treatment with a heating rate of 8 °C / minute and an ammonia flow rate of 50 mL / minute. The Mn-doped Co4N nanowires grown on nickel foam were obtained.
[0055] The prepared Mn-doped Co4N nanowires were used as electrode materials, and their surface was reconstructed by cyclic voltammetry technology in a voltage range of 0 - 0.8 V, a scan rate of 50 mV / s, and 30 scan cycles to finally obtain the Mn-doped CoO2 and Co4N composite phase catalyst.
[0056] The prepared final composite material was detected by in-situ Raman technology. Mn doping enabled Co4N to generate high-valent metal oxide CoO2 at low voltages, as Figure 3 shown in a. The obtained catalyst was used as an electrode for electrochemical catalytic activity testing. In 1 M KOH, the overpotential of Mn-Co4N at 10 mA cm -2 was 219 mV. As Figure 4 shown, in the isotope labeling experiment, it was found that this catalyst had obvious 34The signal of O2 appears, indicating that lattice oxygen participates in the reaction during this process, and Mn-Co4N follows the LOM reaction mechanism.
[0057] To verify that the surface reconstruction of the catalyst caused by the doping of metallic Mn can ultimately induce the lattice oxygen pathway, the present invention sets up an array of control experiments for Example 1.
[0058] Control experiment 1 adopts the same step flow as Example 1, with the difference that no manganese salt is added as a blank control group.
[0059] Finally, an oxide / nitride composite material prepared after the reconstruction treatment is denoted as Co4N. Under in-situ Raman technology detection, Co4N undergoes surface reconstruction during voltage application but Co3O4 always exists, as Figure 3 shown in b. The obtained composite material is used as an electrode for electrochemical catalytic activity testing. In electrolytes with different pH values, Co4N exhibits nearly the same catalytic activity, indicating that this catalyst follows the traditional AEM reaction mechanism. In 1 M KOH, the overpotential of Co4N at 10 mA cm -2 is 286 mV. As Figure 4 shown, in the isotope labeling experiment, it is found that there is no 34 O2 and 36 O2 signal during the catalytic process of Co4N, indicating that no lattice oxygen participates in this process.
[0060] Control experiment 2 adopts the same step flow as Example 1, with the difference that 0.3 mmol of sodium vanadate is used to replace 0.3 mmol of manganese nitrate.
[0061] The high-valent metal-doped oxide / nitride composite material prepared after the reconstruction treatment is denoted as V-Co4N. Under in-situ Raman technology detection, V-doped Co4N undergoes surface reconstruction during voltage application but the final active phases are CoOOH and Co3O4, as Figure 5 shown in a. The obtained composite material is used as an electrode for electrochemical catalytic activity testing. In electrolytes with different pH values, V-Co4N exhibits nearly the same catalytic activity, indicating that this catalyst follows the traditional AEM reaction mechanism. In 1 M KOH, the overpotential of V-Co4N at 10 mA cm -2 is 261 mV. As Figure 6 shown in a, in the isotope labeling experiment, it is found that there is no 34 O2 and 36 O2 signal during the catalytic process of V-Co4N, indicating that no lattice oxygen participates in the reaction during this process.
[0062] Control experiment 3 adopts the same step flow as Example 1, with the difference that 0.3 mmol of chromium nitrate is used to replace 0.3 mmol of manganese nitrate.
[0063] The high-valent metal-doped oxide / nitride composite prepared after the reconstruction treatment is denoted as Cr-Co4N. Under the detection of in-situ Raman technology, surface reconstruction occurs in Cr-doped Co4N during the voltage application process, but the final active phase is CoOOH, as Figure 5 shown in Fig. b. The obtained composite material is used as an electrode for electrochemical catalytic activity testing. In electrolytes with different pH values, Cr-Co4N exhibits nearly the same catalytic activity, indicating that this catalyst follows the traditional AEM reaction mechanism. In 1 M KOH, the overpotential of Cr-Co4N at 10 mA cm -2 is 278 mV. As Figure 6 shown in Fig. b, in the isotope labeling experiment, it is found that there is no 34 O2 and 36 O2 signal in the catalytic process of Cr-Co4N, indicating that no lattice oxygen participates in this process.
[0064] Control experiment 4 adopts the same procedure as in Example 1, except that 0.3 mmol of manganese nitrate is replaced with 0.3 mmol of sodium molybdate.
[0065] The high-valent metal-doped oxide / nitride composite prepared after the reconstruction treatment is denoted as Mo-Co4N. Under the detection of in-situ Raman technology, the active phase of surface reconstruction in Mo-doped Co4N during the voltage application process is CoO2, but a higher potential is required compared with Mn doping, as Figure 5 shown in Fig. c. The obtained composite material is used as an electrode for electrochemical catalytic activity testing. In electrolytes with different pH values, Mo-Co4N exhibits nearly the same catalytic activity, indicating that this catalyst follows the traditional AEM reaction mechanism. In 1 M KOH, the overpotential of Mo-Co4N at 10 mA cm -2 is 261 mV. As Figure 6 shown in Fig. c, in the isotope labeling experiment, it is found that there is no 34 O2 and 36 O2 signal in the catalytic process of Mo-Co4N, indicating that no lattice oxygen participates in the reaction.
[0066] Control experiment 5 adopts the same procedure as in Example 1, except that 0.3 mmol of manganese nitrate is replaced with 0.3 mmol of ammonium metatungstate.
[0067] The high-valent metal-doped oxide / nitride composite prepared after the reconstruction treatment is denoted as W-Co4N. Under the detection of in-situ Raman technology, surface reconstruction occurs in W-doped Co4N during the voltage application process, but the final active phases are CoOOH and Co3O4, as Figure 5As shown in d. The obtained composite material was used as an electrode for electrochemical catalytic activity testing. W-Co4N showed nearly the same catalytic activity in electrolytes with different pH values, indicating that this catalyst follows the traditional AEM reaction mechanism. As Figure 6 As shown in d, it was found in the isotope labeling experiment that no 34 O2 and 36 signal of O2 appeared during the catalysis of W-Co4N, indicating that lattice oxygen did not participate in the reaction during this process.
[0068] The results of Example 1 and the control experiment show that the present invention activates the inert Co on the surface of Co4N by introducing metal Mn 2 + , and promotes its deprotonation process, and finally induces the reconstruction of Co4N to generate the active phase CoO2, obtaining a composite catalyst of CoO2 / Co4N doped with metal Mn. Through theoretical research by density functional theory calculation, during the OER process with Mn-CoO2 as the active phase, Mn can adjust the upward shift of the oxygen 2P orbitals across the Fermi level, thereby activating the lattice oxygen on the catalyst surface and enabling it to participate in the reaction, ultimately inducing the lattice oxygen path.
[0069] The present invention also provides the application of the above-mentioned Co4N catalyst doped with high-valence metals in the oxygen evolution reaction. The content of Mn in the catalyst applied to the oxygen evolution reaction is 2.5 wt.% to 12.5 wt.%.
[0070] The OER process is the anodic reaction of various electrochemical reactions. Its slow reaction kinetics causes a relatively high overpotential. Therefore, it is necessary to use highly efficient and low-cost electrocatalysts to reduce the reaction energy consumption. The OER reaction path usually follows the traditional adsorption-dissociation evolution mechanism (AEM). Due to its limitation by the linear relationship of the adsorption energy of intermediates, the theoretical overpotential is relatively high. By reasonably designing the catalyst to bypass the limitation of the inherent linear relationship of adsorption energy in AEM, it is an effective means to reduce the overpotential of the OER reaction. The present invention activates the inert Co on the surface of Co4N by introducing the Mn element 2+ , and promotes its deprotonation process, and finally induces the reconstruction of Co4N to generate the active phase CoO2. During the OER process with Mn-CoO2 as the active phase, Mn can adjust the upward shift of the oxygen 2P orbitals across the Fermi level, thereby activating the lattice oxygen on the catalyst surface and enabling it to participate in the reaction, ultimately inducing the lattice oxygen path. The catalyst provided by the present invention shows good catalytic activity in OER, at 10 mA cm -2The overpotential is only 219 mV, and it has excellent stability and can maintain high activity for up to 240 h. The present invention obtains an efficient and stable oxygen evolution catalyst by regulating the reconstruction of the surface oxygen evolution reaction path of nitrides through metal doping, opening up a new direction for the regulation and application of surface reconstruction and LOM mechanism of transition metal nitrides in the catalytic process of oxygen evolution reaction.
[0071] The above has described the embodiments of the present invention in detail through examples. However, the content described above is only an exemplary embodiment of the embodiments of the present invention and cannot be considered as defining the scope of implementation of the embodiments of the present invention. The scope of protection of the embodiments of the present invention is defined by the claims. All those who use the technical solutions described in the embodiments of the present invention, or those skilled in the art, inspired by the technical solutions of the embodiments of the present invention, within the essence and scope of protection of the embodiments of the present invention, design similar technical solutions to achieve the above technical effects, or make equivalent changes and improvements to the scope of the application, etc., should still fall within the scope of patent coverage and protection of the embodiments of the present invention.
Claims
1. A high-valent metal-doped Co4N catalyst, characterized in that, The surface of the Mn-doped Co4N nanowire carrier of the catalyst is covered with a thin layer of CoO2 phase, and the content of Mn in the catalyst is 2.5 wt.% to 12.5 wt.%, and the Mn element activates the inert Co on the surface of Co4N. 2+ The deprotonation process was promoted, and finally the Co4N surface was reconstructed to generate the CoO2 active phase. When the catalyst was used in the oxygen evolution reaction, the 2 The overpotential was 219 mV and the catalytic activity was maintained for 240 h. In the OER process with Mn-CoO2 as the active phase, Mn regulated the oxygen 2P orbital to move up across the Fermi level, thereby activating the lattice oxygen on the catalyst surface to participate in the reaction and inducing the lattice oxygen oxidation mechanism.
2. A method for preparing a catalyst as described in claim 1, characterized in that, The method includes the following steps: Step S1: Immerse the nickel foam substrate in a 1 M dilute hydrochloric acid solution and ultrasonically treat it for 15 minutes to remove surface oil stains and inert oxide films. Then, ultrasonically clean the treated nickel foam in deionized water and ethanol for 5 minutes each and repeat three times; Step S2: Mix 3 mmol of cobalt nitrate hexahydrate, 0.03 - 0.9 mmol of manganese salt, 15 mmol of urea, and 8 mmol of ammonium fluoride and add them to 100 mL of deionized water, and stir for 1 hour to obtain a pink clear solution; Step S3: Immerse the nickel foam obtained in Step S1 into the solution obtained in Step S2 and perform hydrothermal treatment. The temperature of the heat treatment is 100 - 160 °C, the holding time is 4 - 16 hours, and the heating rate is 5 - 30 °C / minute to obtain Mn-doped cobalt nanowires uniformly grown on the nickel foam substrate; Step S4: Anneal the Mn-doped cobalt nanowires obtained in Step S3 in ammonia. The annealing temperature in ammonia is 450 - 480 °C, the holding time is 2 - 6 hours, the heating rate is 2 - 10 °C / minute, and the ammonia flow rate is 30 - 150 mL / minute to obtain Mn-doped Co4N nanowires grown on nickel foam; Step S5: Reconstruct the surface of the Mn-doped Co4N nanowires obtained in Step S4 by cyclic voltammetry. In the cyclic voltammetry technique, the voltage range is 0 - 0.8 V, the scan rate is 50 mV / s, and the number of scan cycles is 20. After the reconstruction treatment, a Mn-doped CoO2 / Co4N composite material is prepared.
3. The preparation method according to claim 2, characterized in that, The cobalt nitrate hexahydrate, urea, and ammonium fluoride in Step S2 are all of analytical grade, and the manganese salt is a solution with a mass fraction of 50%; 4. The preparation method according to claim 2, characterized in that, The manganese salt in Step S2 is any one of manganese nitrate, manganese sulfide, or manganese chloride.