Electrocatalyst of RuFe nanoparticles synergized with Ni3S2 and MXene heterojunction and application thereof

Abstract

The application discloses an electrocatalyst of RuFe nanoparticles cooperated with Ni3S2 and MXene heterojunction and application thereof, and the electrocatalyst can be expressed as RuFe / Ni3S2MX / NF. The self-supporting electrocatalyst with a composite structure is prepared by a hydrothermal method. The electrocatalyst has a multilayer structure, the NF is used as a self-supporting skeleton, the surface of the NF is a heterojunction structure composed of Ni3S2 and MXene (the two-dimensional sheet structure Mxene wraps the granular Ni3S2), and some RuFe nanoparticle active sites exist on the MXene, so that excellent OER performance is provided. The method is simple in operation, low in preparation and raw material cost, and suitable for large-scale application. In the application, the introduction of Ru and Fe and the formation of an alloy comprehensively improve the OER performance of the catalyst, and the synergistic effect of the three promotes the formation of RuFe alloy nanoparticles on the surface of the heterojunction, increases the active site and the specific surface area.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalysis, and particularly relates to an RuFe nanoparticle coordinated electrocatalyst of a Ni3S2 and MXene heterojunction and application thereof. BACKGROUND

[0002] In today's world, with the increasing demand for energy and the growing environmental problems, it is particularly important to develop efficient and sustainable energy conversion technologies. Water electrolysis as a clean and renewable hydrogen energy production method has attracted widespread research attention. Among them, the oxygen evolution reaction (OER) as a key half-reaction in the water electrolysis process, its efficiency directly affects the energy conversion efficiency of the whole water electrolysis process. However, the OER reaction has a slow kinetic process and requires a high overpotential to proceed, which greatly limits its practical application.

[0003] In recent years, self-supporting electrodes based on NF have received significant attention because of their inherent advantages such as stable spatial framework, no binder, good electrical conductivity, and cost-effectiveness. In recent years, transition metal chalcogenides such as Ni3S2 have received widespread attention, but need to overcome the disadvantages of material instability and relatively high overpotential. Existing heterojunction electrocatalysts based on NF generally require high-temperature calcination processes, which are relatively costly, and some have yet to improve their stability in long-term use. SUMMARY

[0004] To overcome the shortcomings of the prior art, the technical problem to be solved by the present application is to provide an RuFe nanoparticle coordinated electrocatalyst of a Ni3S2 and MXene heterojunction and application thereof. The electrocatalyst can be represented as RuFe / Ni3S2 MX / NF. A self-supporting electrocatalyst with a composite structure is prepared by a hydrothermal method. This catalyst has a multi-layer structure. NF serves as a self-supporting framework, and the surface is a heterojunction structure composed of Ni3S2 and MXene (two-dimensional sheet structure Mxene wrapping granular Ni3S2). Some RuFe nanoparticle active sites exist on the MXene, providing excellent OER performance.

[0005] The technical solution adopted by the application to solve the technical problem is as follows:

[0006] In a first aspect, the application provides an RuFe nanoparticle coordinated electrocatalyst of a Ni3S2 and MXene heterojunction. The electrocatalyst has a multi-layer structure. Foam nickel NF is used as a self-supporting framework. A heterojunction structure composed of Ni3S2 and two-dimensional sheet titanium carbide MXene is formed on the surface of the foam nickel NF. RuFe nanoparticles are distributed on the heterojunction structure.

[0007] Further, the RuFe nanoparticles are nanoparticles of RuFe alloy.

[0008] Further, the preparation method of the electrocatalyst is:

[0009] S1, using 1-3 mol / L sulfuric acid, water, ethanol to treat the foamed nickel in turn, removing the surface impurities and oxidation layer before reaction treatment, obtaining the cleaned NF; the thickness of the foamed nickel is less than 1 mm and greater than 0.2 mm;

[0010] S2, dispersing the suspension of two-dimensional sheet-shaped titanium carbon compound MXene in a homogeneous solution containing iron salt, ruthenium salt, thiourea and NH4F, adding CTAB after uniform dispersion, stirring uniformly at room temperature, obtaining a reaction solution; the metal molar ratio of the iron salt to the ruthenium salt is 0.8-1.2:1; the molar ratio of thiourea to NH4F is 2-3:1; the added mass of CTAB is 4-5 times the mass of MXene;

[0011] S3, immersing the cleaned NF in the reaction solution of step S2, and then performing hydrothermal reaction at 100-140℃ for 8-16 hours in an autoclave;

[0012] S4, ultrasonic treating the solid material obtained in step S3 with an alcohol-water mixture for 5-20 min, and vacuum drying to obtain the electrocatalyst.

[0013] Further, the concentration of the suspension of two-dimensional sheet-shaped titanium carbon compound MXene is 5-10 mg / mL, and MXene is at least one of Ti3C2T x , Ti3C2T x represents a certain functional group.

[0014] Further, the volume ratio of the reaction material to the volume of the autoclave in the autoclave is 1:1.5-3.

[0015] Further, the thickness of the foamed nickel is 0.3-0.7 mm, and the size is 4 cm*10 cm; preferably 0.5 mm.

[0016] Further, in step S3, the temperature of the hydrothermal reaction is 120℃, and the time is 12 hours.

[0017] In a second aspect, the application provides a use of the above-mentioned electrocatalyst in electrocatalytic oxygen evolution, the process comprising the following steps:

[0018] S100, cutting the electrocatalyst into 1cm*1cm size, ultrasonic treating for 5-15 min for standby;

[0019] S200, as a working electrode, graphite as a counter electrode, saturated calomel electrode as a reference electrode, connected to an electrochemical workstation, and an electrocatalytic oxygen evolution reaction was carried out in 1.0M potassium hydroxide solution;

[0020] S300, the three-electrode system was placed in a 40kHz ultrasonic cleaner, the temperature was kept at 27±2℃, and the ultrasonic physical field was added during the electrocatalytic oxygen evolution reaction process, and the electrocatalytic oxygen evolution reaction process was carried out in the three-dimensional ultrasonic physical field formed by the ultrasonic cleaner, which reduced the adhesion of oxygen bubbles on the surface of the catalyst and promoted the occurrence of chemical reaction, reduced the overpotential of the electrocatalyst, and the overpotential was reduced by 10mV under the current density of 10mA·cm -2

[0021] S400, the chronoamperometry method was used to carry out 20 hours long cycle under the current density of 10mA·cm -2 The relative initial value of the overpotential was controlled to be within 4mV.

[0022] Further, in step S300, the ultrasonic frequency is 40kHz, and the ultrasonic power is 40-120W.

[0023] Compared with the prior art, the beneficial effects of the present application are:

[0024] (1) The electrocatalyst for oxygen evolution of the present application has RuFe nanoparticles and Ni3S2 and MXene heterojunctions, which is synthesized by one-step hydrothermal method. The method is simple to operate, low in preparation and raw material cost, and suitable for large-scale application.

[0025] (2) The present application synthesizes a composite catalyst with the structure of RuFe nanoparticles, Ni3S2 and MXene heterojunctions and NF substrate. The nanoparticles are RuFe alloy, which has a complex structure and rich active area, larger active area and more excellent electrochemical activity, and the synergistic effect between the components further improves the material performance.

[0026] (3) In an alkaline solution, the RuFe / Ni3S2 MX / NF electrocatalyst has a lower overpotential as a working electrode, and its performance is better than most reported electrocatalysts. The electrocatalyst as a working electrode can have an overpotential of 262mV under a current density of 10mA·cm -2 , and a Tafel slope of 31mV dec -1 , and an overpotential of 252mV under ultrasonic environment. And in the chronoamperometry test, the overpotential is reduced by 10mV under the current density of 10mA·cm -2 ​The overpotential only increases within 4mV under 20 hours long cycle at current density, and the stability is better. The present application combines electrochemistry with ultrasonic wave, and the performance of RuFe / Ni3S2 MX / NF is significantly improved by using ultrasonic wave, so that the OER reaction can be carried out at a lower overpotential, and the catalyst can remain stable in the ultrasonic environment.

[0027] (4) The introduction of Ru and Fe and the formation of alloy in the present application improve the OER performance of the catalyst in all directions, wherein thiourea is used as the sulfur source of Ni3S2, the weak reducing property of NH4F can reduce Ru salt and iron salt, the positive electricity of CTAB makes the negative MXene precipitate outside the NF, and the synergistic effect of the above-mentioned factors promotes the formation of RuFe alloy nanoparticles on the heterojunction surface, increases the active site and specific surface area. BRIEF DESCRIPTION OF DRAWINGS

[0028] The advantages and implementation modes of the present application will be more obvious by specifically describing the present application by referring to the accompanying drawings and combining examples, and the contents shown in the drawings are only used for explaining and describing the present application, and do not constitute any sense of limitation to the present application, and in the drawings:

[0029] Figure 1 The SEM and TEM of RuFe / Ni3S2 MX / NF in the present application.

[0030] Figure 2 The XRD of RuFe / Ni3S2 MX / NF and the product of the comparative example in the present application.

[0031] Figure 3 The XPS of RuFe / Ni3S2 MX / NF in the present application.

[0032] Figure 4 The BET of RuFe / Ni3S2 MX / NF in the example of the present application.

[0033] Figure 5 The electrochemical performance comparison chart of different samples in the example of the present application. DETAILED DESCRIPTION

[0034] In order to make the person skilled in the art better understand the technical solutions of the present application, the present application will be further described in detail by combining the best embodiment.

[0035] The application discloses an electrocatalyst of RuFe nanoparticles cooperated with a Ni3S2 and MXene heterojunction (denoted as RuFe / MXene / NF electrocatalyst), which has a multilayer structure, takes a nickel foam (NF) as a self-supporting skeleton, forms a heterojunction structure composed of Ni3S2 and two-dimensional sheet-shaped titanium carbide compound MXene on the surface of the nickel foam, and distributes RuFe nanoparticles on the heterojunction structure.

[0036] The preparation method of the electrocatalyst is as follows:

[0037] S1, the nickel foam is sequentially treated with 1-3 mol / L sulfuric acid, water and ethanol to remove surface impurities and an oxide layer before reaction treatment, so that the cleaned NF is obtained; the thickness of the nickel foam is less than 1 mm and greater than 0.2 mm;

[0038] S2, a suspension of two-dimensional sheet-shaped titanium carbide compound MXene is dispersed in a homogeneous solution containing an iron salt, a ruthenium salt, thiourea and NH4F, CTAB is added after uniform dispersion, and the reaction solution is obtained after uniform stirring at room temperature; the metal molar ratio of the iron salt to the ruthenium salt is 0.8-1.2:1; the molar ratio of thiourea to NH4F is 2-3:1; and the added mass of CTAB is 4-5 times the mass of MXene;

[0039] S3, the cleaned NF is immersed in the reaction solution of step S2, and then a hydrothermal reaction is carried out at 100-140 DEG C in an autoclave for 8-16 hours;

[0040] S4, the solid material obtained in step S3 is ultrasonically treated with an alcohol-water mixture for 5-20 min, and then vacuum dried to obtain the electrocatalyst.

[0041] In the application, the thickness of the nickel foam is 0.2-1 mm, preferably 0.3-0.7 mm.

[0042] Further optimization, in S1, the 0.5 mm-thick nickel foam is sequentially treated with 2 mol / L sulfuric acid, water and ethanol for three times.

[0043] Further optimization, in S2, 6 mL of 10 mg / mL Ti3C2T x suspension is dispersed in 44 mL of a homogeneous solution containing 1 mmol FeCl3·6H2O, 1 mmol RuCl3·3H2O, 5 mmol thiourea and 2.5 mmol NH4F, and then 25 mg of CTAB is introduced into the solution and magnetically stirred at room temperature for 30 min.

[0044] Further optimization, in S3, the temperature of the hydrothermal reaction is 120 DEG C, and the time is 12 hours.

[0045] Further optimization, the ultrasonic time of the catalyst in S4 is 10 min, and drying in a vacuum drying box for 12 hours.

[0046] The application of the above-mentioned RuFe / MXene / NF electrocatalyst in the electrocatalytic oxygen evolution reaction, the specific steps of the application method are:

[0047] S100, the electrocatalyst is cut to 1cm*1cm size, and ultrasonic treatment is 5-15min for standby;

[0048] S200, the electrocatalyst is used as a working electrode, graphite is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, and an electrochemical workstation is connected, and an electrocatalytic oxygen evolution reaction is carried out in 1.0M potassium hydroxide solution;

[0049] S300, the three-electrode system is placed in a 40kHz ultrasonic cleaning machine, the temperature is kept at 27±2℃, the ultrasonic physical field is added during the electrocatalytic oxygen evolution reaction process, the electrocatalytic oxygen evolution reaction process is carried out in the three-dimensional ultrasonic physical field formed by the ultrasonic cleaning machine, the adhesion of oxygen bubbles on the surface of the catalyst is reduced, and the chemical reaction is promoted to occur, the overpotential of the electrocatalyst is reduced, and the overpotential is reduced by 10mV under the current density of 10mA·cm -2

[0050] S400, using chronopotentiometry in a non-ultrasonic environment, the overpotential is controlled to be increased by 4mV or less relative to the initial value under the current density of 10mA·cm -2

[0051] The application of the above-mentioned RuFe / MXene / NF electrocatalyst in the electrocatalytic oxygen evolution reaction, the specific steps of the application method are:

[0052] Example 1

[0053] The electrocatalyst of RuFe nanoparticles cooperated with Ni3S2 and MXene heterojunction in this embodiment, the preparation process is:

[0054] Firstly, 0.5mm thick foam nickel (NF) is treated with 1-3mol / L sulfuric acid, water and ethanol in sequence, so as to remove surface impurities and oxide layer before reaction treatment. The size of the foam nickel is 4cm*10cm.

[0055] 6mL of 10mg / mL Ti3C2T x ​​The suspension was dispersed in 44 mL of a homogeneous solution containing 1 mmol FeCl3·6H2O, 1 mmol RuCl3·3H2O, 5 mmol thiourea, and 2.5 mmol NH4F. Then, 0.025 g CTAB was introduced and magnetically stirred at room temperature for 30 min to obtain the reaction solution.

[0056] The cleaned NF was immersed in the obtained reaction solution and transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave for hydrothermal reaction at 120 °C for 12 hours.

[0057] The solid material obtained by hydrothermal treatment was ultrasonically treated with a 1:1 volume ratio of ethanol and water for 10 min to remove surface impurities, and then dried in a vacuum drying oven at 60℃ to obtain RuFe / Ni3S2MX / NF electrocatalyst.

[0058] The following tests were performed on the electrocatalyst using SEM, TEM, XRP, and adsorption performance:

[0059] Figure 1 Images (a) and (b) show the morphology of the RuFe / Ni3S2 MX / NF electrocatalyst under a scanning electron microscope. The NF framework surface has many protrusions wrapped with Mxene wrinkles, which is the morphology of Ni3S2 and Ti3C2T. x The resulting heterojunction. In the hydrothermal reaction system, the positively charged CTAB can act as a chelating component, promoting the formation of the negatively charged Ti3C2T. x Deposition outside the NF layer leads to the formation of Ni3S2 and Ti3C2T. x Heterogeneous junctions. Figure 1 Image (c) is a TEM image of RuFe / Ni3S2MX / NF. It can be observed that RuFe nanoparticles are dispersed on the MXene support. Measurements of the RuFe nanoparticle lattice fringes revealed an interplanar spacing of 0.224 nm, slightly smaller than that of Ru(100), indicating the formation of a RuFe alloy. Based on selected area (SAED) and HRTEM analysis (selecting a region of the solid sample and then photographing it where diffraction patterns and rings of these materials are present), it can be determined that Ti3C2T... x Ni3S2 and RuFe coexist in this region.

[0060] The surface chemical properties of RuFe / Ni3S2 MX / NF were characterized by XPS measurements. The XPS spectra revealed the coexistence of Ru, Fe, Ni, and S elements in the RuFe / Ni3S2 MX / NF electrocatalyst. The Ni 2p spectrum is shown below. Figure 3 As shown in (a), the peaks at 873.4 eV and 855.7 eV are Ni 2p 1 / 2 and Ni 2p 3 / 2 This is attributed to Ni2+ The peaks at 861.3 eV and 879.2 eV were identified as satellite peaks of Ni. Figure 3 As shown in (b), the fitting signals for the binding energies of metallic Fe at 706.8 eV, 710.1 eV, and 721.9 eV represent Fe with surface oxidation. 2+ The fitted signals of 712.9 eV and 726.1 eV represent Fe2+ with surface oxidation. 3+ The spectrum of Ru 3p is in Figure 3 As explained in (c), the peaks at 462.1 eV and 484.5 eV are related to Ru 3p, respectively. 3 / 2 and Ru 3p 1 / 2 This is related to Ru. 0 The peaks at 465.0 eV and 487.0 eV are related to Ru 3p 3 / 2 and Ru 3p 1 / 2 Related to, attributed to Ru 2+ ;exist Figure 3 In the S2p spectrum of (d), the peaks at 163.15 eV and 151.9 eV were identified as S2p ​​peaks. 1 / 2 and S2p 3 / 2 The peak at 168.5 eV is attributed to the highly oxidized state of the sulfate substance. The presence of 0 valence in Ru / Fe indicates that it exists in an alloy form, while the presence of only 2+ in Ni indicates that it exists as Ni3S2.

[0061] The N2 adsorption-desorption curves of RuFe / Ni3S2 MX / NF are as follows: Figure 4 As shown, a typical mesoporous structure is exhibited. The specific surface area of ​​RuFe / Ni3S2MX / NF is 3.792 m² / g. 2 / g, greater than the specific surface area of ​​NF (3.225m²). 2 / g), which indicates that the Ni3S2 / MXene heterojunction and RuFe nanoparticles (NPs) provide more active regions for RuFe / Ni3S2 MX / NF.

[0062] The following is an application test of the electrocatalyst for the oxygen evolution reaction in the example: A 1.0M potassium hydroxide solution was prepared as the electrolyte for electrocatalysis, argon gas was introduced to purge the air, the prepared electrocatalyst was used as the working electrode, graphite was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. The electrocatalyst was connected to an electrochemical workstation, and the hydrogen evolution reaction was carried out in the electrolyte.

[0063] Without the addition of an ultrasonic environment during the electrocatalytic hydrogen evolution reaction, this electrocatalyst operates at a current density of 10 mA·cm⁻¹. -2 The overpotential is 262mV, and the Tafel slope is 31mV dec. -1After adding a three-dimensional ultrasonic environment, the overpotential of the electrocatalyst decreased to 252 mV.

[0064] Using chronopotential method at 10 mA·cm -2 During a 20-hour long-cycle operation at current density, the increase in overpotential relative to the initial value was controlled to be within 4mV (see [reference]). Figure 5 (As shown in Figure (c)). As can be seen from the figure, the RuFe nanoparticles introduced in this invention exhibit significantly better long-term cycling stability.

[0065] The electrocatalytic activity of ultrasound on OER was evaluated using linear sweep voltammetry (LSV). Figure 5 In figure a, the dashed line represents the area with ultrasound, and the solid line represents the area without ultrasound; b is the corresponding Tafel plot; c is the chronopotential method; d is the LSV of other control samples. LSV testing was performed at an extremely low potential scan rate (2 mV s). -1 This ensures that steady-state conditions are achieved at each potential value. After ultrasonication, the performance of different catalysts was improved, with RuFe / Ni3S2MX / NF, Ru / Ni3S2MX / NF, Fe / Ni3S2MX / NF, and NF showing improvements at overpotentials (10 mA·cm⁻¹). -2 The values ​​were reduced by 10mV, 10mV, 11mV, and 9mV respectively, and the addition of ultrasound ensured that the performance of the catalyst was steadily improved throughout the entire test range.

[0066] Comparative Example 1

[0067] The difference between this comparative example and Example 1 is that only RuCl3·3H2O was added to the homogeneous solution, without adding FeCl3·6H2O.

[0068] Electrocatalytic oxygen evolution reaction application test: The electrocatalyst of this comparative example was tested at a current density of 10 mA·cm⁻¹. -2 The overpotential is 309 mV, and the Tafel slope is 41 mV dec. -1 After the addition of ultrasound, the overpotential of the electrocatalyst decreased to 299 mV.

[0069] At 10mA·cm -2 During a 20-hour long cycle at current density, the overpotential increases by 8 mV.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that only FeCl3·6H2O was added to the homogeneous solution, instead of RuCl3·3H2O.

[0072] Electrocatalytic oxygen evolution reaction application test: at a current density of 10 mA·cm -2of 317 mV and a Tafel slope of 79 mV dec -1 The lower the Tafel slope, the better the performance of the catalyst, which is only related to the intrinsic performance of the catalyst. After adding ultrasound, the overpotential of the electrocatalyst decreased to 306 mV. Chronoamperometry was used to test the long-term stability of the electrocatalyst in 20 hours of long cycling at a current density of 10 mA·cm -2 The overpotential increased by 47 mV.

[0073] Comparative Example 3 (only containing Ni3S2and Ti3C2T x heterojunction)

[0074] The difference between this comparative example and Example 1 is that FeCl3·6H2O and RuCl3·3H2O are not added in the homogeneous solution.

[0075] Electrocatalytic oxygen evolution reaction application test: The overpotential of the material at a current density of 10 mA·cm -2 was 340 mV.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Example 1 is that Ti3C2T x is not added in the homogeneous solution.

[0078] First, the 0.5 mm thick nickel foam (NF) was treated with 1-3 mol / L sulfuric acid, water, and ethanol in sequence to remove surface impurities and oxide layers before reaction treatment. 50 mL of a homogeneous solution containing 1 mmol FeCl3·6H2O, 1 mmol RuCl3·3H2O, 5 mmol thiourea, and 2.5 mmol NH4F was prepared, and then 0.025 g of CTAB was introduced into the solution and magnetically stirred at room temperature for 30 min. The cleaned NF was immersed in the reaction solution and transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, and a hydrothermal reaction was carried out at 120°C for 12 hours. The catalyst obtained by hydrothermal reaction was ultrasonically treated with a volume ratio of 1:1 of ethanol and water for 10 min to remove surface impurities, and then placed in a vacuum drying oven at 60°C to obtain the electrocatalyst.

[0079] Electrocatalytic oxygen evolution reaction application test: The overpotential of the material at a current density of 10 mA·cm -2 was 276 mV.

[0080] Comparing Example 1 and Comparative Examples 1-4, it can be found that the simultaneous presence of iron and ruthenium can significantly reduce the overpotential, and its effect is greater than that of the heterojunction. Under the same conditions, the overpotential of the commercial ruthenium oxide tested at a current density of 10 mA cm-2was 351 mV, and the overpotential of the Ni3S2and Ti3C2T xThe performance of the heterojunction itself has been superior to commercial RuO2, and the RuFe nanoparticles further improve the performance of the electrocatalyst in cooperation with it.

[0081] Comparative Example 5

[0082] The difference between this comparative example and Example 1 is that the substrate is carbon cloth, and does not contain Ni3S2 and Ti3C2T x heterojunction.

[0083] First, 0.5 mm thick carbon cloth (CC) was treated with 1-3 mol / L sulfuric acid, water, and ethanol in sequence to remove surface impurities and oxide layers before reaction treatment. 50 mL of a homogeneous solution containing 1 mmol FeCl3·6H2O, 1 mmol RuCl3·3H2O, 5 mmol thiourea, and 2.5 mmol NH4F was prepared, and then 0.025 g of CTAB was introduced into the solution under room temperature magnetic stirring for 30 min. The cleaned CC was immersed in the obtained solution and transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave for hydrothermal reaction at 120°C for 12 hours. The hydrothermally obtained catalyst was washed with a 1:1 volume ratio of ethanol and water mixture to remove surface impurities, and then placed in a vacuum drying oven at 60°C to obtain the electrocatalyst.

[0084] Electrocatalytic oxygen evolution reaction application test: the material has a current density of 10 mA·cm -2 and a overpotential of 346 mV.

[0085] Comparing Comparative Examples 5 and 4, it can be found that the nickel foam substrate also has a significant promoting effect on the reduction of overpotential.

[0086] Figure 2 The XRD test comparison results of the three samples of RuFe / Ni3S2 MX / NF, Ru / Ni3S2 MX / NF, and Fe / Ni3S2 MX / NF are shown. Due to the extremely strong diffraction peak of NF and the extremely low content of other substances, the signal from RuFe combined with Ti3C2T x MXene is not visible, and only the peaks of Ni3S2 and Ni can be observed, indicating that the content of these substances is extremely low. The extremely low content of active substances can greatly improve the performance of the catalyst, indicating that the cost of the catalyst is also low.

[0087] Example 2

[0088] The thickness of the foamed nickel in this embodiment is changed to 0.2mm, 0.4mm, 0.8mm and 1mm respectively on the basis of embodiment 1 to test the electrocatalytic oxygen evolution reaction performance. When the thickness of the foamed nickel is less than 0.2mm, the nickel skeleton will become fragile after the reaction, and will be broken and have poor performance after ultrasonic treatment. The foamed nickel with a thickness of 1mm will be peeled into two layers after ultrasonic treatment, affecting its catalytic performance.

[0089] Embodiment 3

[0090] In this embodiment, the RuFe / Ni3S2 MX / NF electrocatalyst is a composite self-supporting electrode of RuFe nanoparticles and Ni3S2 and MXene heterojunction. The thickness of the foamed nickel is 0.4mm, the reaction solution is a gray solution (mainly the color of MXene, the MXene solution is gray), the metal molar ratio of iron salt to ruthenium salt is 0.8:1 or 1.2:1, the total reaction solution volume is 60mL, and the reaction kettle volume is 100mL. In the hydrothermal synthesis process, the RuFe nanoparticles and Ni3S2 and MXene heterojunction grown in situ on the foamed nickel have higher active area and intrinsic activity, higher stability, smaller overpotential change, excellent cycle durability, and can stably exist in a three-dimensional ultrasonic environment.

[0091] In the present application, the noble metal Ru can effectively reduce the overpotential of the reaction, improve the reaction rate, and make the water splitting process more efficient. In addition, Ru can effectively promote the reaction path of OER, reduce the energy barrier of the reaction, exhibit excellent chemical stability, and also have a synergistic effect with Fe metal, which is more economical. The prepared catalyst can stably exist in an ultrasonic environment, and ultrasonic accompanies the whole reaction process in the reaction application, which can promote the formation and release of bubbles, reduce the adhesion of bubbles on the catalyst surface; it can also induce sonochemical reactions, resulting in transient phenomena of local high temperature and high pressure, promoting the occurrence of chemical reactions, and avoiding the problem that in the process of electrocatalysis, due to the generation of bubbles and the existence of bubble adhesion on the catalyst surface, a physical barrier is formed, which hinders the contact of reactants with the catalyst, and significantly adversely affects the performance of the catalyst.

[0092] The present application is composed of three major elements of RuFe nanoparticles, Ni3S2 and Ti3C2T x heterojunction, and NF matrix multilayer structure. The electrocatalyst can realize stable self-supporting effect, can maintain stability under ultrasonic conditions on the premise of ensuring the active sites on the catalyst, and can make the electrocatalytic oxygen evolution reaction process accompanied by a three-dimensional ultrasonic environment, so that the reaction is coupled with ultrasonic, which can further reduce the overpotential, and the effect is remarkable.

[0093] The application can realize lower overpotential at the lowest cost under the condition of one-step hydrothermal process without high-temperature calcination, the effect is remarkable, and it is helpful to popularization and application and improvement of economic benefits.

[0094] The above detailed the embodiments of the present application, but the content is only the preferred embodiments of the present application, and cannot be considered to limit the scope of the present application. Any equivalent changes and improvements made within the scope of the present application should still belong to the scope of the present application.

Claims

1. An electrocatalyst for RuFe nanoparticles in synergy with Ni3S2 and MXene heterojunctions, characterized in that, The electrocatalyst has a multilayer structure with nickel foam NF as a self-supporting framework. A heterojunction structure composed of Ni3S2 and two-dimensional sheet-like titanium-carbon compound MXene is formed on the surface of the nickel foam NF. RuFe nanoparticles are distributed on the heterojunction structure. The RuFe nanoparticles are RuFe alloy nanoparticles.

2. The electrocatalyst according to claim 1, characterized in that, The preparation method of the electrocatalyst is as follows: S1. Treat the nickel foam sequentially with 1-3 mol / L sulfuric acid, water, and ethanol to remove surface impurities and oxide layers before the reaction treatment, and obtain cleaned NF; the thickness of the nickel foam is less than 1 mm and greater than 0.2 mm; S2. A suspension of two-dimensional sheet-like titanium-carbon compound MXene is dispersed in a homogeneous solution containing iron salt, ruthenium salt, thiourea, and NH4F. After uniform dispersion, CTAB is added and stirred evenly at room temperature to obtain a reaction solution. The molar ratio of the iron salt to the ruthenium salt is 0.8-1.2:1; the molar ratio of thiourea to NH4F is 2-3:1; and the mass of CTAB added is 4-5 times the mass of MXene. S3. Immerse the cleaned NF in the reaction solution of step S2, and then carry out a hydrothermal reaction at 100-140°C for 8-16 hours in an autoclave. S4. The solid material obtained in step S3 is ultrasonically treated with an alcohol-water mixture for 5-20 minutes and then vacuum dried to obtain the electrocatalyst.

3. The electrocatalyst according to claim 2, characterized in that, The concentration of the suspension of the two-dimensional sheet-like titanium-carbon compound MXene is 5–10 mg / mL, and MXene is Ti3C2T. x At least one of Ti3C2, T x It represents a certain functional group.

4. The electrocatalyst according to claim 2, characterized in that, The volume ratio of the reactants in the autoclave to the autoclave volume is 1:1.5-3.

5. The electrocatalyst according to claim 2, characterized in that, The thickness of the nickel foam is 0.3-0.7 mm, and the size is 4 cm × 10 cm; 6. The electrocatalyst according to claim 5, characterized in that, The thickness of the nickel foam is 0.5 mm.

7. The electrocatalyst according to claim 2, characterized in that, In step S3, the hydrothermal reaction temperature is 120℃ and the time is 12 hours.

8. The application of the electrocatalyst according to any one of claims 1-7 in electrocatalytic oxygen evolution, characterized in that, The application process in electrocatalytic oxygen evolution includes the following steps: S100. Cut the electrocatalyst into 1cm*1cm pieces and sonicate for 5-15 minutes for later use. S200. Using an electrocatalyst as the working electrode, graphite as the counter electrode, and a saturated calomel electrode as the reference electrode, connect to an electrochemical workstation and carry out the electrocatalytic oxygen evolution reaction in a 1.0 M potassium hydroxide solution. S300. The three-electrode system is placed in a 40kHz ultrasonic cleaner, maintaining the temperature at 27±2℃. An ultrasonic physical field is continuously added during the electrocatalytic oxygen evolution reaction (OER). The OER process takes place within the three-dimensional ultrasonic physical field formed by the ultrasonic cleaner, reducing the adhesion of oxygen bubbles to the catalyst surface and promoting the chemical reaction, thus lowering the overpotential of the electrocatalyst at 10mA·cm. -2 The overpotential at current density decreases by 10mV; S400, using the chronopotential method at 10mA·cm -2 During a 20-hour long cycle at current density, the increase in overpotential relative to the initial value was controlled to be within 4mV.

9. The application according to claim 8, characterized in that: In step S300, the ultrasonic frequency is 40kHz and the ultrasonic power is 40-120W.

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