Fe-induced CoMoO4 partial oxidation electrocatalyst, preparation method and application

Abstract

The application discloses an Fe-induced CoMoO4 partial oxidation electrocatalyst, a preparation method and application, and belongs to the technical field of hydrogen evolution of electrocatalytic materials. A cobalt source, a molybdenum source and an iron source are dissolved in water to form a uniform mixed solution; the mixed solution is transferred to a reaction kettle, pretreated foamed nickel is added, and hydrothermal reaction is carried out at 100-150 DEG C for 4-12 h; after the reaction is completed, the foamed nickel loaded with the catalyst is taken out, washed and dried to obtain the Fe-induced CoMoO4 partial oxidation electrocatalyst. The crystal structure and surface morphology of CoMoO4 are regulated and controlled through doping of the Fe element, the OER catalytic activity and stability of CoMoO4 are improved, the cost of water electrolysis hydrogen production is reduced, and industrial application is promoted.

Description

Technical Field

[0001] This invention relates to the field of hydrogen evolution electrocatalytic materials, specifically to an electrocatalyst for Fe-induced local oxidation of CoMoO4, its preparation method, and its application. Background Technology

[0002] With the growth of global energy demand and the transformation of the energy structure, the development and utilization of clean and renewable energy have become particularly important. Hydrogen energy, as a clean energy source with high energy density and zero carbon emissions, is considered an important component of the future energy system. Electrolysis of water is one of the important pathways to achieve large-scale hydrogen production. However, the oxygen evolution reaction (OER) at the anode in the water electrolysis process is slow due to its complex four-electron transfer process, becoming a key factor limiting the overall hydrogen production efficiency. Therefore, developing efficient and stable OER electrocatalysts is of great significance for improving the efficiency of water electrolysis for hydrogen production.

[0003] Currently, noble metal catalysts such as iridium (Ir), ruthenium (Ru), and their oxides exhibit excellent catalytic performance in electrocatalysis (OER), but their high cost and scarcity limit their large-scale application. Therefore, exploring non-noble metal-based OER electrocatalysts has become a research hotspot. Cobalt molybdate (CoMoO4), as a transition metal molybdate, shows potential application value in electrocatalysis due to its unique structure and electrochemical properties. However, the activity of CoMoO4 catalysts synthesized by conventional methods still needs improvement. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an electrocatalyst for Fe-induced local oxidation of CoMoO4, its preparation method, and its application. This invention regulates the crystal structure and surface morphology of CoMoO4 by doping with Fe, thereby improving its OER catalytic activity and stability, reducing the cost of hydrogen production through water electrolysis, and promoting its industrial application.

[0005] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing an electrocatalyst for Fe-induced local oxidation of CoMoO4, comprising the following steps: (1) Preparation of precursor solution: Cobalt source, molybdenum source and iron source are dissolved in water to form a homogeneous mixed solution; (2) Hydrothermal reaction: The mixed solution in step (1) is transferred to the reactor, pretreated nickel foam is added, and hydrothermal reaction is carried out at 100~150℃ for 4~12h; (3) Post-processing: After the reaction is completed, the nickel foam loaded with catalyst is removed, washed and dried to obtain the electrocatalyst for Fe-induced local oxidation of CoMoO4.

[0006] Furthermore, the cobalt source mentioned in step (1) is CoCl2·6H2O, and the molybdenum source is (NH4)6Mo7O. 24 The iron source is FeCl3·6H2O.

[0007] Furthermore, in step (1), the molar ratio of molybdenum in the molybdenum source, cobalt in the cobalt source, and iron in the iron source is 1:0.7~0.9:0.1~0.2.

[0008] Further, the preparation method of the pretreated nickel foam in step (2) is as follows: place the nickel foam in 3 mol / L hydrochloric acid, then dilute the hydrochloric acid to a concentration of 2 mol / L, sonicate for 5~15 min, dilute with water to 1 mol / L, seal and store, and wash with deionized water 4~5 times before use, and use after drying; the purpose of hydrochloric acid treatment is to remove the oxide layer and impurities on the surface of the nickel foam and improve its surface activity and wettability.

[0009] Furthermore, in step (2), the hydrothermal reaction temperature is 120℃ and the reaction time is 12h.

[0010] Furthermore, in step (3), the drying conditions are drying at 80°C for 3 hours.

[0011] In a second aspect, the present invention provides an electrocatalyst for Fe-induced local oxidation of CoMoO4 prepared by the above-described preparation method.

[0012] In a third aspect, the present invention provides the application of the Fe-induced CoMoO4 local oxidation electrocatalyst in the field of water electrolysis for hydrogen production.

[0013] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1) Enhanced catalytic activity: Fe doping alters the crystal structure and surface morphology of CoMoO4, increasing the number of active sites and intrinsic activity, thereby enhancing the OER catalytic activity.

[0014] 2) Enhanced stability: The localized oxidation effect induced by Fe doping enhances the structural stability of the catalyst and extends its service life.

[0015] 3) Reduced cost: The use of non-precious metal element Fe for doping reduces the dependence on precious metals and significantly reduces the cost of electrocatalysts.

[0016] 4) Simple preparation process: The one-step hydrothermal method and electrodeposition method are easy to operate and easy to scale up for production. Attached Figure Description

[0017] Figure 1The images are scanning electron microscope (SEM) images of CFMO-1 and CMO. a is a 5000x SEM image of CMO, b is a 5000x SEM image of CFMO-1, c is a 20000x SEM image of CMO, and d is a 20000x SEM image of CFMO-1. Figure 2 The mapping image of CFMO-1 prepared in Example 2; Figure 3 The mapping image is of the CMO prepared in Comparative Example 2; Figure 4 The images show the EDS spectra of CMO and CFMO-1, with a being the EDS spectrum of CMO and b being the EDS spectrum of CFMO-1. Figure 5 CV-OER curves for CFMO-1, CFMO-2, CFMO-3, and CMO; Figure 6 The figures show the OER polarization curves, histograms of initial overpotentials, and Tafel plots for CFMO-1, CFMO-2, CFMO-3, and CMO. a is the OER polarization curve, b is the histogram of initial overpotentials, and c is the OER polarization curve. Detailed Implementation

[0018] The present invention is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods not specifically described in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0020] Example 1 Pretreatment of nickel foam: Several nickel foam samples (2 cm × 1 cm × 2 mm, with nickel foam as the carrier) were placed in a 150 mL beaker. 50 mL of 3 mol / L hydrochloric acid solution was poured into the beaker, followed by 75 mL of deionized water for dilution to a mixed solution concentration of 2 mol / L. The beaker was then placed in an ultrasonic cleaner for 10 min, removed, and allowed to stand for 30 min until the solution stabilized. Deionized water was then added to the beaker until the total solution volume reached 150 mL. Finally, the beaker was sealed with plastic wrap for storage. Before use, the nickel foam was rinsed 5 times with deionized water to thoroughly remove any residual hydrochloric acid solution and avoid affecting subsequent experiments. Then, it was placed in an oven at 80 °C for 2 h to dry the surface of the nickel foam, facilitating the loading of subsequent catalysts.

[0021] Example 2 (1) Preparation of precursor solution: 0.18 mmol CoCl2·6H2O, 0.029 mmol (NH4)6Mo7O 24 ·4H2O and 0.02 mmol FeCl3·6H2O were dissolved in 36 mL of deionized water and stirred at room temperature for 30 min to form a homogeneous mixed solution; (2) Hydrothermal reaction: The mixed solution in step (1) was transferred to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor, pretreated nickel foam was added, and after sealing, it was placed in a 120℃ oven for hydrothermal reaction for 12 h. (3) After the reaction is complete, the nickel foam loaded with catalyst is removed, washed with deionized water 4 times, and dried at 80℃ for 3 h to obtain the Fe-induced local oxidation of CoMoO4 electrocatalyst (CFMO-1).

[0022] Example 3 (1) Preparation of precursor solution: 0.16 mmol CoCl2·6H2O, 0.029 mmol (NH4)6Mo7O 24 ·4H2O and 0.04 mmol FeCl3·6H2O were dissolved in 36 mL of deionized water and stirred at room temperature for 30 min to form a homogeneous mixed solution; (2) Hydrothermal reaction: The mixed solution in step (1) was transferred to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor, pretreated nickel foam was added, and after sealing, it was placed in a 120℃ oven for hydrothermal reaction for 12 h. (3) After the reaction is complete, the nickel foam loaded with catalyst is removed, washed with deionized water 4 times, and dried at 80℃ for 3 h to obtain the Fe-induced local oxidation of CoMoO4 electrocatalyst (CFMO-2).

[0023] Comparative Example 1 (1) Preparation of precursor solution: 0.14 mmol CoCl2·6H2O, 0.029 mmol (NH4)6Mo7O 24 ·4H2O and 0.06 mmol FeCl3·6H2O were dissolved in 36 mL of deionized water and stirred at room temperature for 30 min to form a homogeneous mixed solution; (2) Hydrothermal reaction: The mixed solution in step (1) was transferred to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor, pretreated nickel foam was added, and after sealing, it was placed in a 120℃ oven for hydrothermal reaction for 12 h. (3) After the reaction is complete, the nickel foam loaded with catalyst is removed, washed with deionized water 4 times, and dried at 80℃ for 3 h to obtain the Fe-induced local oxidation of CoMoO4 electrocatalyst (CFMO-3).

[0024] Comparative Example 2 (1) Preparation of precursor solution: 0.16 mmol CoCl2·6H2O and 0.029 mmol (NH4)6Mo7O 24 • Dissolve 4H2O in 36 mL of deionized water and stir at room temperature for 30 min to form a homogeneous mixed solution; (2) Hydrothermal reaction: The mixed solution in step (1) was transferred to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor, pretreated nickel foam was added, and after sealing, it was placed in a 120℃ oven for hydrothermal reaction for 12 h. (3) After the reaction is complete, the nickel foam loaded with catalyst is removed, washed with deionized water 4 times, and dried at 80°C for 3 h to obtain undoped Fe CMO catalyst (CMO).

[0025] Characterization (1) The morphology of the catalysts was characterized by scanning electron microscopy (SEM). The SEM images of the Fe-induced local oxidation of CoMoO4 electrocatalyst (CFMO-1) prepared in Example 2 and the undoped Fe CMO catalyst (CMO) prepared in Comparative Example 2 are shown below. Figure 1 As shown, a is a 5000x SEM image of CMO, b is a 5000x SEM image of CFMO-1, c is a 20000x SEM image of CMO, and d is a 20000x SEM image of CFMO-1. Figure 1It is evident that both CMO and CFMO-1 exhibit regular nanoscale morphologies. CMO possesses a porous microstructure with relatively small and uniformly distributed particles. CFMO-1, on the other hand, displays a porous structure with numerous honeycomb-like or mesh-like pores. Porous structures typically imply a larger specific surface area. A larger specific surface area provides more active sites, which facilitates sufficient contact between the electrode material and the electrolyte in electrochemical reactions, thereby improving the electrode's reactivity and the efficiency of the electrochemical reaction. Both CMO and CFMO-1 are composed of numerous ultrathin nanosheets. Fe doping increased the diameter of the 3D nanoflowers, demonstrating that Fe doping promotes nanosheet formation and accelerates their growth rate.

[0026] (2) Energy-dispersive X-ray spectroscopy (EDS) was performed on CFMO-1 prepared in Example 2 and CMO prepared in Comparative Example 2. The mapping diagrams of CFMO-1 and CMO are shown below. Figure 2 and Figure 3 As shown, the elements are uniformly distributed in the sample. The EDS spectra of CFMO-1 and CMO are shown below. Figure 4 As shown (a is the EDS spectrum of CMO, b is the EDS spectrum of CFMO-1). Figure 4 Characteristic peaks of four elements, Ni, O, Co, and Mo, can be identified in the spectrum. The atomic percentages of oxygen, cobalt, and molybdenum are 76.61%, 18.85%, and 4.54%, respectively. The presence of peaks of Co and Mo proves that CoMoO4 was successfully synthesized, indicating that the CMO catalyst was successfully loaded onto Ni foam. Figure 4 The spectrum of b CFMO-1 showed the addition of a characteristic peak for Fe, with atomic percentages of oxygen, cobalt, iron, and molybdenum of 75.34%, 15.62%, 3.10%, and 5.94%, respectively, proving that the sample contains Fe.

[0027] Electrochemical performance testing (1) Cyclic voltammetry oxygen evolution reaction Cyclic voltammetry (CV-OER) curves are an important tool for investigating the kinetics of the oxygen evolution reaction (OER) of catalysts, providing a direct visual representation of the redox behavior and OER catalytic activity of catalysts across different potential ranges. The CV-OER curves for CFMO-1, CFMO-2, CFMO-3, and CMO are shown below. Figure 5 As shown, by Figure 5It can be seen that CFMO-1 exhibits superior electrocatalytic water oxidation activity in the OER reaction, CFMO-2's performance is comparable to that of Comparative Example 2, while CFMO-3 results in inferior performance compared to Comparative Example 2. All samples exhibit typical redox peak characteristics, indicating that the electrode reaction has a certain degree of reversibility. The current densities of the oxidation and reduction peaks generally show a trend of first increasing and then decreasing, with CFMO-1 showing the highest current densities in both oxidation and reduction peaks among all samples, exhibiting the best electrocatalytic activity. Among all catalysts, CFMO-1 has the best catalytic activity; further increasing the Fe doping amount actually decreases the OER activity. As shown in the figure, the current densities of CFMO-2 and CFMO-3 decrease sequentially, while the undoped CFMO has the lowest current density. This phenomenon indicates that appropriate Fe doping can effectively improve catalyst activity, but excessive doping may have negative effects.

[0028] (2) By deeply analyzing the OER polarization curves, Tafel slopes and related electrochemical characterization results, the intrinsic relationship between Fe doping amount and catalyst activity is systematically analyzed. The polarization curves of CFMO-1, CFMO-2, CFMO-3 and CMO are as follows: Figure 6 As shown in figure a, it can be seen from the figure that at 10 mA cm -2 At the given current density, CMO and CFMO-3 exhibited the highest overpotentials. With increasing Fe doping concentration, the overpotential first decreased and then increased, with CFMO-1 showing the lowest overpotential and exhibiting the best catalytic performance among all samples. The overpotentials of CFMO-2 and CFMO-3 increased sequentially. A histogram comparing the initial overpotentials is shown below. Figure 6 As shown in b, it can be seen that at 10 mA cm -2 At the specified current density, the histogram of initial overpotentials clearly shows that CFMO-1 has the lowest overpotential, indicating its best performance. The performance of CFMO-2 and CFMO-3 gradually decreases with increasing Fe doping concentration. This result clearly demonstrates that appropriate Fe doping can significantly reduce the activation energy of the OER reaction and effectively improve the oxygen evolution reaction efficiency of the catalyst; however, excessive doping may negatively impact catalytic activity. To further investigate the OER reaction kinetics, Tafel slope curves were fitted based on the OER polarization curves, and the results are as follows: Figure 6 As shown in Figure c, it can be seen that the Tafel slope first decreases and then increases with the increase of Fe doping amount. The smaller Tafel slope indicates that the electrode has faster OER reaction kinetics, confirming that CFMO-1 has better catalytic performance.

[0029] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing an electrocatalyst for Fe-induced localized oxidation of CoMoO4, characterized in that, Includes the following steps: (1) Preparation of precursor solution: Cobalt source, molybdenum source and iron source are dissolved in water to form a homogeneous mixed solution; (2) Hydrothermal reaction: The mixed solution in step (1) is transferred to the reactor, pretreated nickel foam is added, and hydrothermal reaction is carried out at 100~150℃ for 4~12h; (3) Post-processing: After the reaction is completed, the nickel foam loaded with catalyst is removed, washed and dried to obtain the electrocatalyst for Fe-induced local oxidation of CoMoO4.

2. The method for preparing the Fe-induced local oxidation electrocatalyst for CoMoO4 according to claim 1, characterized in that, The cobalt source mentioned in step (1) is CoCl2·6H2O, and the molybdenum source is (NH4)6Mo7O. 24 The iron source is FeCl3·6H2O.

3. The method for preparing the Fe-induced localized oxidation electrocatalyst for CoMoO4 according to claim 1, characterized in that, In step (1), the molar ratio of molybdenum in the molybdenum source, cobalt in the cobalt source, and iron in the iron source is 1:0.7~0.9:0.1~0.

2.

4. The method for preparing the Fe-induced local oxidation electrocatalyst for CoMoO4 according to claim 1, characterized in that, The preparation method of the pretreated nickel foam in step (2) is as follows: place the nickel foam in 3 mol / L hydrochloric acid, then dilute the hydrochloric acid to a concentration of 2 mol / L, sonicate for 5~15 min, dilute with water to 1 mol / L, seal and store, and wash with deionized water 4~5 times before use.

5. The method for preparing the Fe-induced localized oxidation electrocatalyst for CoMoO4 according to claim 1, characterized in that, In step (2), the hydrothermal reaction temperature is 120℃ and the reaction time is 12h.

6. The method for preparing the Fe-induced local oxidation electrocatalyst for CoMoO4 according to claim 1, characterized in that, In step (3), the drying conditions are 80℃ for 3 hours.

7. An electrocatalyst for Fe-induced localized oxidation of CoMoO4 prepared by the preparation method according to any one of claims 1 to 6.

8. The application of an electrocatalyst for Fe-induced local oxidation of CoMoO4 prepared by the preparation method according to any one of claims 1 to 6, or the electrocatalyst for Fe-induced local oxidation of CoMoO4 according to claim 7, in the field of hydrogen production by water electrolysis.

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