Mo-Co-S-V2O5 / NF composite electrocatalyst and preparation method and application thereof

Abstract

The application belongs to the field of electrocatalysts, and particularly relates to a Mo-Co-S-V2O5 / NF composite electrocatalyst and a preparation method and application thereof. The Mo-Co-S-V2O5 / NF composite electrocatalyst is obtained by loading Mo-Co-S doped with different contents of V2O5 adjuvants on foam nickel through a two-step hydrothermal method. The content of the V2O5 adjuvant is optimized to obtain the electrocatalyst with excellent oxygen evolution performance, and the electrochemical active surface area is increased, so that the electrocatalyst has high activity and good stability in the electrocatalytic oxygen evolution reaction in an alkaline solution. The catalyst has the advantages of low cost, simple synthesis operation, greenness and no pollution.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalyst preparation and application, specifically relating to a Mo-Co-S-V2O5 / NF composite electrocatalyst, its preparation method, and its application. Background Technology

[0002] Due to the widespread reliance on traditional fossil fuels, environmental pollution is escalating, making the development of sustainable and environmentally friendly alternative energy sources urgently needed. Hydrogen energy, as a renewable and pollution-free energy carrier, has attracted widespread attention. Utilizing renewable energy sources such as wind and solar power to drive electrochemical water splitting provides an efficient method for obtaining green and sustainable hydrogen energy. To minimize the energy consumption of electrochemical water splitting and improve hydrogen production efficiency, researchers have been working to develop highly efficient electrocatalysts. Traditional catalysts, such as oxides based on the noble metals iridium (Ir) and ruthenium (Ru), exhibit good catalytic performance, but the scarcity and high cost of these precious metals limit their large-scale application.

[0003] To find more economical and abundant alternative catalysts, researchers have begun exploring transition metal-based compounds. Transition metal sulfides (such as Co3S4) possess high conductivity, inherent intrinsic activity, and excellent stability, exhibiting significant catalytic activity and strong resistance to poisoning. However, the catalytic performance of Co3S4 is hampered by the scarcity of active sites and its unique electronic structure. This limited number of active sites and the specialized electronic structure result in a small electrochemical active surface area, making it thermodynamically unstable under OER oxidation conditions, necessitating further improvements. The electronic structure of cobalt sulfide can be adjusted by incorporating other metal ions (such as Mo), thereby enhancing its stability and electrochemical activity. For example, Chinese patent CN109364954A describes the growth of Co9S8 and CoMoS8 on nickel foam. 3.13 By combining MoS2, a nickel-based Co-Mo-S bifunctional nanocomposite was obtained, and its catalytic performance was improved through the synergistic effect among the three phases. However, its OER catalytic performance was poor, and the preparation method was complex. Summary of the Invention

[0004] The purpose of this invention is to provide a Mo-Co-S-V2O5 / NF composite electrocatalyst and its preparation method, and to apply it to the electrolysis of water in an alkaline environment to produce oxygen. The aim is to achieve high efficiency in electrocatalytic activity and stability through a reasonable combination of elements.

[0005] The technical solution of this invention: This invention provides a Mo-Co-S-V2O5 / NF composite electrocatalyst, which is prepared by a two-step hydrothermal method on nickel foam to synthesize the Mo-Co-S-V2O5 / NF composite electrocatalyst. The specific process is as follows:

[0006] (1) Preparation of Mo-Co / NF composite electrocatalyst:

[0007] First, the nickel foam is ultrasonically cleaned with 3M hydrochloric acid solution for 10 minutes to remove oxides from the material surface. Then, it is ultrasonically cleaned with acetone solution for 10 minutes to remove grease from the material surface. Finally, it is ultrasonically cleaned with ethanol and ultrapure water for 20 minutes each to remove residual hydrochloric acid and acetone from the material surface.

[0008] Next, cobalt nitrate hexahydrate and sodium molybdate dihydrate were added to deionized water and mixed evenly. The solution and nickel foam were then transferred to a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 150°C for hydrothermal reaction for 9 hours. After the reaction was completed, the reactants were removed and washed several times with deionized water and ethanol, and then dried under vacuum. The resulting catalyst was a Mo-Co / NF electrocatalyst.

[0009] (2) Preparation of Mo-Co-S-V2O5 / NF composite electrocatalyst:

[0010] Sodium sulfide nonahydrate and vanadium pentoxide were dissolved in deionized water. After the mixture was dissolved and homogeneous, it was transferred to a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 110°C for 9 hours. After the reaction was completed, the reactants were removed, washed with deionized water and ethanol, and then dried under vacuum to obtain the Mo-Co-S-V2O5 / NF composite electrocatalyst.

[0011] Furthermore, the ratio of cobalt nitrate hexahydrate, sodium molybdate dihydrate, sodium sulfide nonahydrate, and V2O5 is 4.5 mmol: 0.5 mmol: 0.04 mol: 0.1–0.3 mmol.

[0012] Preferably, the ratio of cobalt nitrate hexahydrate to sodium molybdate dihydrate, sodium sulfide nonahydrate, and V2O5 is 4.5 mmol: 0.5 mmol: 0.04 mol: 0.2 mmol.

[0013] This invention synthesizes a Mo-Co-S-V2O5 / NF composite electrocatalyst by loading Mo-Co-S with different V2O5 doping contents onto nickel foam using a two-step hydrothermal method, and applies it to oxygen evolution in water electrolysis under alkaline conditions. The process includes the following steps:

[0014] A three-electrode system was constructed using a Mo-Co-S-V2O5 / NF composite electrocatalyst as the working electrode, and the system was placed in an alkaline electrolyte to carry out electrocatalytic oxygen evolution.

[0015] In the three-electrode system, the counter electrode is a graphite rod electrode, and the reference electrode is an Hg / HgO electrode.

[0016] The alkaline electrolyte is a 1 mol / L KOH solution.

[0017] The technical effects achieved by this invention are:

[0018] (1) This invention uses nickel foam as a substrate and supports Mo-Co-S and V2O5 to prepare a Mo-Co-S-V2O5 / NF composite electrocatalyst. First, a Mo-Co nanosheet array structure is formed on the surface of nickel foam to form a larger electrochemical active region, which is conducive to the full exposure of active sites and promotes the improvement of electrochemical performance. It can more effectively support sulfur and catalyze the conversion of sulfur substances through a relatively large surface area. Then, it is combined with nanotube-shaped vanadium pentoxide and sulfur doped to obtain the Mo-Co-S-V2O5 / NF composite electrocatalyst. The nanotube-shaped structure of vanadium pentoxide forms a more effective conductive network, which further improves the electrochemical performance of the catalyst.

[0019] (2) This invention achieves high-efficiency electrocatalytic activity and stability by rationally controlling the combination ratio of Mo-Co-S and V2O5. It can promote oxygen evolution at a low overpotential and has excellent OER performance in alkaline electrolytes at 10 mA / cm². 2 The overpotential can reach 53mV at the given current density.

[0020] (3) The present invention synthesizes Mo-Co-S-V2O5 / NF composite electrocatalyst by a two-step hydrothermal method. The synthesis method is simple and the synthesis process is green and pollution-free. Attached image description:

[0021] Figure 1 The XRD patterns are of the catalysts prepared in Examples 1-5 and Comparative Examples 1-2 of this invention.

[0022] Figure 2 The images shown are SEM images (a) and elemental mapping images (bf) of Mo-Co-S-V2O5 / NF-3 obtained in Example 1 of this invention.

[0023] Figure 3 The above are oxygen evolution polarization curves of electrodes composed of catalysts prepared in Examples 1-5 and Comparative Examples 1-2 of this invention in 1.0M KOH solution.

[0024] Figure 4 The oxygen evolution Tafel slope curves of the electrodes composed of the catalysts prepared in Examples 1-5 and Comparative Examples 1-2 of this invention in 1.0M KOH solution are shown.

[0025] Figure 5 The image shows the chronopotential graph of the electrode made of the catalyst prepared in Example 1 of this invention in 1.0 M KOH solution.

[0026] Figure 6 The graph shows the oxygen evolution polarization curves of the electrodes made of the catalysts prepared in Example 1 and Comparative Examples 3-4 of this invention in 1.0M KOH solution. Detailed Implementation

[0027] The technical features of the present invention are further illustrated by the following examples, but the scope of protection of the present invention is not limited to the following embodiments.

[0028] Example 1

[0029] 1. Catalyst Preparation

[0030] 1.1. Preparation of Nickel Foam

[0031] A piece of nickel foam (NF, 2.0cm × 2.0cm) was immersed in 3M hydrochloric acid solution and sonicated for 10 minutes. Then, the surface was sonicated with acetone solution for 10 minutes. Finally, it was sonicated with ethanol and ultrapure water for 20 minutes each.

[0032] 1.2. Preparation of Mo-Co / NF electrocatalysts

[0033] 4.5 mmol of cobalt nitrate hexahydrate and 0.5 mmol of sodium molybdate dihydrate were dissolved in deionized water. After the solution and nickel foam were mixed evenly, the solution and nickel foam were transferred to a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 150°C for hydrothermal reaction for 9 hours. After the reaction was completed, the reactants were removed and washed several times with deionized water and ethanol, and then dried under vacuum. The resulting catalyst was a Mo-Co / NF electrocatalyst.

[0034] 1.3. Preparation of Mo-Co-S-V2O5 / NF-3 composite electrocatalyst

[0035] 0.04 mol sodium sulfide nonahydrate and 0.2 mmol vanadium pentoxide (99.99% metals basis, purchased from Shanghai Aladdin Reagent Co., Ltd.) were dissolved in deionized water. After the solution and Mo-Co / NF electrocatalyst were mixed evenly, the solution and Mo-Co / NF electrocatalyst were transferred to a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 110°C for hydrothermal reaction for 9 hours. After the reaction was completed, the reactants were removed and washed several times with deionized water and ethanol, and then dried under vacuum. The resulting catalyst was a Mo-Co-S-V2O5 / NF-3 composite electrocatalyst.

[0036] 2. Application

[0037] 2.1. Activation treatment of electrocatalyst

[0038] The electrochemical oxygen evolution reaction (OER) uses a three-electrode system, with the working electrode having an area of ​​0.9 cm². 2The electrocatalyst has a graphite rod electrode as the counter electrode, a Hg / HgO electrode as the reference electrode, and a 1 mol / L KOH electrolyte.

[0039] Cyclic voltammetry (CV) activation: A Jiangsu Donghua DH7000C electrochemical workstation was used with a CV program. The OER test range was 0–0.8 V vs. RHE, the scan rate was 100 mV / s, and the cycle was 10 times until the electrode reached a stable state.

[0040] 2.2. Linear Scan Voltammetry (LSV) Test

[0041] After activation, the program was switched to linear sweep voltammetry, with the OER test range being 0–1 V vs. RHE, and a scan rate of 5 mV / s. The electrocatalyst was tested in an alkaline electrolyte at 10 mA / cm². 2 The electrocatalyst prepared in Example 1 had an overpotential of 53 mV, which was within the range of 50 mA / cm². 2 The overpotential of the electrocatalyst prepared in Example 1 was 167 mV.

[0042] from Figure 1 The XRD pattern shows that the Mo-Co-S-V2O5 / NF-3 composite electrocatalyst prepared in Example 1 has diffraction peaks for Co3S4, V2O5, and nickel foam, while there are no obvious diffraction peaks for Mo-based sulfides, indicating that the Mo-based sulfides exhibit high amorphization. Figure 2 The elemental mapping diagram shows successful Mo doping, indicating the successful preparation of the Mo-Co-S-V2O5 / NF-3 composite electrocatalyst. Meanwhile, from... Figure 2 SEM images reveal the nanosheet array structure of Mo-Co-S and the tubular structure of V2O5.

[0043] from Figure 3 and Figure 6 As can be seen from the LSV plot, the Mo-Co-S-V2O5 / NF-3 prepared in this invention exhibits better OER performance in 1M KOH solution compared to other prepared catalysts, requiring only 53mV to provide 10mA / cm. 2 The current density. Moreover, from... Figure 4 As can be seen from the Tafel slope plot, Mo-Co-S-V2O5 / NF-3 has the lowest Tafel slope (53 mV dec). -1 This indicates that it has the fastest OER kinetics.

[0044] The long-term stability of the material was assessed using a 15-hour chronopotential method. For example... Figure 5 As shown, at a current density of 10 mA cm⁻¹ -2The electrode was tested by chronopotential method at a current density of 15 h, and the potential remained basically stable after 15 h, which suggests that the prepared electrode has excellent OER stability.

[0045] Example 2

[0046] Compared with Example 1, the difference is that the amount of vanadium pentoxide added in step 1.3 is 0.10 mmol, resulting in Mo-Co-S-V2O5 / NF-1.

[0047] The application method is the same as in Example 1, and the OER performance is 10 mA / cm. 2 It exhibits an overpotential of 164 mV at a current density of 50 mA / cm². 2 It exhibits an overpotential of 262mV at a given current density.

[0048] Example 3

[0049] Compared with Example 1, the difference is that the amount of vanadium pentoxide added in step 1.3 is 0.15 mmol, resulting in Mo-Co-S-V2O5 / NF-2.

[0050] Using the same method as in Example 1, the OER performance was 10 mA / cm. 2 It exhibits an overpotential of 146 mV at a current density of 50 mA / cm². 2 It exhibits an overpotential of 298 mV at a given current density.

[0051] Example 4

[0052] Compared with Example 1, the difference is that the amount of vanadium pentoxide added in step 1.3 is 0.25 mmol, resulting in Mo-Co-S-V2O5 / NF-4.

[0053] Using the same method as in Example 1, the OER performance was 10 mA / cm. 2 It exhibits an overpotential of 101 mV at a current density of 50 mA / cm². 2 It exhibits an overpotential of 240mV at a given current density.

[0054] Example 5

[0055] Compared with Example 1, the difference is that the amount of vanadium pentoxide added in step 1.3 is 0.30 mmol, resulting in Mo-Co-S-V2O5 / NF-5.

[0056] Using the same method as in Example 1, the OER performance was 10 mA / cm. 2 It exhibits an overpotential of 107 mV at a current density of 50 mA / cm². 2 It exhibits an overpotential of 254 mV at a given current density.

[0057] Comparative Example 1

[0058] 1. Catalyst Preparation

[0059] 1.1. Preparation of Mo-Co electrocatalysts

[0060] 4.5 mmol of cobalt nitrate hexahydrate and 0.5 mmol of sodium molybdate dihydrate were dissolved in deionized water. After the mixture was homogeneous, the solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 150°C for hydrothermal reaction for 9 hours. After the reaction was completed, the reactants were removed, centrifuged, and washed several times with deionized water and ethanol. Then, they were vacuum dried to obtain the catalyst, which was a Mo-Co electrocatalyst.

[0061] 1.2. Preparation of Mo-Co-S composite electrocatalysts

[0062] 0.04 mol sodium sulfide nonahydrate was dissolved in deionized water. After the solution was dissolved and mixed evenly, it was transferred to a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 110°C for hydrothermal reaction for 9 hours. After the reaction was completed, the reactants were removed, centrifuged, and washed several times with deionized water and ethanol. Then, they were vacuum dried to obtain the catalyst, which was a Mo-Co-S composite electrocatalyst.

[0063] 2. Application: Same as Example 1, the OER performance is at 10 mA / cm 2 It exhibits an overpotential of 325 mV at a current density of 50 mA / cm². 2 It exhibits an overpotential of 576 mV at a given current density.

[0064] Comparative Example 2

[0065] 1. Catalyst Preparation

[0066] 1.1. Preparation of Nickel Foam

[0067] A piece of nickel foam (NF, 2.0cm × 2.0cm) was immersed in 3M hydrochloric acid solution and sonicated for 10 minutes. Then, the surface was sonicated with acetone solution for 10 minutes. Finally, it was sonicated with ethanol and ultrapure water for 20 minutes each.

[0068] 1.2. Preparation of Mo-Co / NF electrocatalysts

[0069] 4.5 mmol of cobalt nitrate hexahydrate and 0.5 mmol of sodium molybdate dihydrate were dissolved in deionized water. After the solution and nickel foam were mixed evenly, the solution and nickel foam were transferred to a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 150°C for hydrothermal reaction for 9 hours. After the reaction was completed, the reactants were removed and washed several times with deionized water and ethanol, and then dried under vacuum. The resulting catalyst was a Mo-Co / NF electrocatalyst.

[0070] 1.3. Preparation of Mo-Co-S / NF composite electrocatalysts

[0071] 0.04 mol sodium sulfide nonahydrate was dissolved in deionized water. After the solution and nickel foam (Mo-Co / NF) were mixed evenly, the solution and the foamed nickel (Mo-Co / NF) were transferred to a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 110°C for hydrothermal reaction for 9 hours. After the reaction was completed, the reactants were removed and washed several times with deionized water and ethanol, and then dried under vacuum. The resulting catalyst was a Mo-Co-S / NF electrocatalyst.

[0072] 2. Application: Same as Example 1, the OER performance is at 10 mA / cm 2 It exhibits an overpotential of 255 mV at a current density of 50 mA / cm². 2 It exhibits an overpotential of 528 mV at a given current density.

[0073] Comparative Example 3

[0074] 1. Catalyst Preparation

[0075] 1.1. Preparation of Nickel Foam

[0076] A piece of nickel foam (NF, 1.0cm × 1.0cm) was immersed in 3M hydrochloric acid solution and sonicated for 10 minutes. Then, the surface was sonicated with acetone solution for 10 minutes. Finally, it was sonicated with ethanol and ultrapure water for 20 minutes each.

[0077] 1.2. Preparation of V2O5 / NF electrocatalyst

[0078] 5 mg V2O5, 125 μL anhydrous ethanol, 375 μL deionized water and 20 μL Nafion solution were ultrasonically mixed for 30 min. 250 μL of the above solution was then drop-coated onto the treated nickel foam in 5 portions and then vacuum dried. The resulting electrocatalyst was a V2O5 / NF electrocatalyst.

[0079] 2. Application: Same as Example 1, the OER performance is at 10 mA / cm 2 It exhibits an overpotential of 388 mV at a current density of 50 mA / cm². 2 It exhibits an overpotential of 551 mV at a given current density.

[0080] Comparative Example 4

[0081] 1. Catalyst Preparation

[0082] 1.1. Preparation of Nickel Foam

[0083] A piece of nickel foam (NF, 1.0cm × 1.0cm) was immersed in 3M hydrochloric acid solution and sonicated for 10 minutes. Then, the surface was sonicated with acetone solution for 10 minutes. Finally, it was sonicated with ethanol and ultrapure water for 20 minutes each.

[0084] 1.2. Preparation of stirred composite Mo-Co-S-V2O5 / NF electrocatalyst

[0085] 4.5 mmol of cobalt nitrate hexahydrate, 0.5 mmol of sodium molybdate dihydrate, 0.04 mol of sodium sulfide nonahydrate and 0.2 mmol of vanadium pentoxide were dissolved in deionized water, stirred at room temperature for 24 h, and then subjected to multiple centrifugation and washing processes. Finally, the mixture was dried under vacuum to obtain pure stirred composite Mo-Co-S-V2O5.

[0086] 5 mg Mo-Co-S-V2O5, 125 μL anhydrous ethanol, 375 μL deionized water and 20 μL Nafion solution were ultrasonically mixed for 30 min. 250 μL of the above solution was then dropped onto the treated nickel foam in 5 portions and vacuum dried. The resulting electrocatalyst was a pure stirred composite Mo-Co-S-V2O5 / NF electrocatalyst.

[0087] 2. Application: Same as Example 1, the OER performance is at 10 mA / cm 2 It exhibits an overpotential of 262mV at a given current density.

[0088] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a Mo-Co-S-V2O5 / NF composite electrocatalyst, characterized in that, It comprises the following steps: (1) adding cobalt nitrate hexahydrate and sodium molybdate dihydrate into deionized water, mixing uniformly, and then transferring the mixture and pretreated nickel foam into a high-pressure kettle lined with polytetrafluoroethylene, and placing the kettle into an oven for hydrothermal reaction; after the reaction is completed, the reaction product is taken out, washed and dried to obtain a Mo-Co / NF composite electrocatalyst; (2) adding sodium sulfide nonahydrate and vanadium pentoxide into deionized water, mixing uniformly, and then transferring the mixture and the Mo-Co / NF composite electrocatalyst into a high-pressure kettle lined with polytetrafluoroethylene, and placing the kettle into an oven for reaction; after the reaction is completed, the reaction product is taken out, washed and dried to obtain a Mo-Co-S-V2O5 / NF composite electrocatalyst; The amount ratio of the cobalt nitrate hexahydrate, the sodium molybdate dihydrate, the sodium sulfide nonahydrate and the V2O5 is 4.5 mmol:0.5 mmol:0.04 mol:0.1-0.3 mmol.

2. The method for preparing the Mo-Co-S-V2O5 / NF composite electrocatalyst according to claim 1, characterized in that, In step (1), the hydrothermal reaction temperature is 150 ℃, and the reaction time is 9 h.

3. The method for preparing the Mo-Co-S-V2O5 / NF composite electrocatalyst according to claim 1, characterized in that, In step (2), the reaction temperature is 110 ℃, and the reaction time is 9 h.

4. The method for preparing the Mo-Co-S-V2O5 / NF composite electrocatalyst according to claim 1, characterized in that, In step (1), the specific pretreatment steps of the nickel foam are as follows: first, cleaning the oxide on the surface of the material by ultrasonic treatment in a 3 M hydrochloric acid solution for 10 min; then, cleaning the grease on the surface of the material by ultrasonic treatment in an acetone solution for 10 min; and then, cleaning the residual hydrochloric acid and acetone on the surface of the material by ultrasonic treatment in ethanol and ultrapure water for 20 min each.

5. A Mo-Co-S-V2O5 / NF composite electrocatalyst prepared by the method according to any one of claims 1-4.

6. Use of the Mo-Co-S-V2O5 / NF composite electrocatalyst according to claim 5 in electrocatalytic oxygen evolution.

7. Use according to claim 6, characterized in that, A three-electrode system is formed with the Mo-Co-S-V2O5 / NF composite electrocatalyst as a working electrode, and is placed in an alkaline electrolyte for electrocatalytic oxygen evolution.

8. Use according to claim 7, characterized in that, The counter electrode of the three-electrode system is a graphite rod electrode, and the reference electrode is a Hg / HgO electrode; and the alkaline electrolyte is a KOH solution.

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