P-NiCo-MOF / Ti3C2Tx-coated NF composite electrocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of alkaline electrolyzed water catalysts, and discloses a P-NiCo-MOF / Ti < 3 > C < 2 > T < x >-N < F > composite electrocatalyst as well as a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: soaking pretreated NF in a hexadecyl trimethyl ammonium bromide aqueous solution to obtain positively charged NF; performing ultrasonic treatment on the NF and a Ti3C2Tx suspension, and performing freeze drying to obtain Ti3C2Tx (at) NF; the preparation method comprises the following steps of: soaking Ti3C2Tx-coated NF into a DMF (Dimethyl Formamide) mixed solution of 2-methylimidazole, Ni (NO3) 2 and Co (NO3) 2, and carrying out hydrothermal reaction at 150-200 DEG C to obtain NiCo-MOF / Ti3C2Tx-coated NF; and in an Ar atmosphere, placing the precursor at the downstream, placing NaHPO2.xH2O at the upstream of a tubular furnace, and carrying out phosphating treatment at 300-400 DEG C, thereby obtaining the product. The hydrogen evolution reaction (HER) activity is improved through interface engineering and phosphating treatment, and the method can be applied to the field of hydrogen production through water electrolysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials and catalysts for alkaline water electrolysis, and more specifically, relates to a P-NiCo-MOF / Ti3C2T x @NF composite electrocatalyst and its preparation method and application. Background Art

[0002] With the increasing global demand for clean energy, finding efficient, environmentally friendly, and renewable energy production methods has become a top priority. Water is an abundant resource with enormous energy potential. Electrocatalytic water splitting technology is one of the methods for directly producing clean energy, promising to reduce greenhouse gas emissions and address energy storage issues. H₂ produced by water electrolysis is a carbon-free, clean, and environmentally friendly green resource with the highest energy density. It is widely considered to have the greatest potential for clean energy. Efficiently converting water into electricity through electrolysis, water electrolysis is an ideal and environmentally friendly method for producing H₂. Its pollution-free, zero-emission nature helps address global warming. It is also highly compatible with a variety of renewable energy sources and can effectively address the intermittent and unpredictable nature of renewable energy generation. Due to its long-term stability and durability, alkaline electrolysis is the most promising and valuable electrolysis system currently available. The two half-reactions in water electrolysis are the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. High overpotentials and expensive electrodes are the main limiting factors, significantly reducing the efficiency of alkaline electrolysis and increasing the overall stack cost. Due to these various limitations, the proportion of hydrogen produced by water electrolysis is only 4%. HER, as a cathode reaction, directly determines the overall hydrogen production efficiency. Therefore, the development of inexpensive and highly active alkaline HER catalysts to reduce the overpotential required for the reaction to produce H2 on a large scale is the most critical aspect and has attracted widespread attention. To date, platinum and its compound catalysts remain excellent electrochemical hydrogen evolution catalysts, but their low reserves and high prices limit their development and application. Therefore, the development of non-precious metal catalysts with multiple advantages such as low cost, simple preparation process, and high catalytic activity to replace platinum and its compounds is of great significance to promoting the efficiency and economy of water splitting technology.

[0003] Nickel foam (NF) is widely used as an electrode substrate due to its high conductivity, porous structure and good mechanical stability. However, it is difficult for nickel foam to show good electrocatalytic hydrogen evolution activity in alkaline electrolytic cells. In order to improve the catalytic activity of nickel metal, it is usually modified to prepare nickel-based metal oxides, nickel-based alloys, nickel-based heterostructures and nickel-based composites as catalytic materials. Metal-organic framework materials (MOFs) have high specific surface areas and abundant active sites, but poor conductivity, which limits their electrochemical performance. Ti3C2T xIt has excellent electrical conductivity, rich surface functional groups and layered structure, which can improve the charge transport capacity of composite materials. x Electrode materials have problems of insufficient conductivity or poor structural stability, while MOF and Ti3C2T x Although the combination improves the electrochemical performance and stability to a certain extent, there is a x Oxidative instability of MOF and Ti3C2T x The problem of insufficient interfacial bonding strength is that a NiCo-MOF and Ti3C2T x Composite material (P-NiCo-MOF / Ti3C2T x @NF), which improves the overall performance of water decomposition and hydrogenation, and has important research value and application prospects. Summary of the Invention

[0004] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the present invention aims to provide a P-NiCo-MOF / Ti3C2T x @NF composite electrocatalyst, the composite electrocatalyst is P-NiCo-MOF / Ti3C2T x Composite materials modified with nickel foam, phosphating Ti3C2T x Loaded MOF composite structure electrocatalyst; its novel structure, excellent performance, prepared two-dimensional Ti3C2T x P-MOF-loaded composite electrocatalyst.

[0005] Another object of the present invention is to provide the above-mentioned P-NiCo-MOF / Ti3C2T x The preparation method of @NF composite electrocatalyst adopts hydrothermal method and vapor deposition method to prepare NiCo-MOF / Ti3C2T x @NF, the metal nodes in NiCo-MOF are converted into NiCoP, providing bimetallic sites with high intrinsic activity, and the dense phosphide protective layer inhibits the Ti3C2T x Direct contact with the electrolyte reduces oxidation, forms a strong covalent connection through the Ti-P-Co / Ni bond, avoids interfacial peeling, and enhances interfacial bonding. Preparation of P-NiCo-MOF / Ti3C2T with high catalytic activity x @NF three-dimensional structured electrocatalytic materials provide new ideas for meeting industrial standards and improving the performance of HER electrocatalysts.

[0006] Another object of the present invention is to provide the above-mentioned P-NiCo-MOF / Ti3C2T xThe application of @NF composite electrocatalysts can be widely used in the field of hydrogen production by water electrolysis, solving the problem of insufficient hydrogen evolution activity of nickel-based electrocatalysts.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A P-NiCo-MOF / Ti3C2T x The NF composite electrocatalyst is prepared by immersing the pretreated nickel foam (NF) in a hexadecyltrimethylammonium bromide aqueous solution to obtain a positively charged nickel foam. x The suspension was mixed with ultrasound and freeze-dried to obtain Ti3C2T x @NF; then immersed it in a DMF mixed solution of 2-methylimidazole, Ni(NO3)2·6H2O and Co(NO3)2·6H2O, and hydrothermally reacted at 150-200℃ to obtain NiCo-MOF / Ti3C2T x @NF; Finally, NaHPO2·xH2O (x=0.5~1) was placed in the upstream position of the tube furnace under Ar atmosphere, and NiCo-MOF / Ti3C2T x @NF is placed in the downstream position and heated to 300-400℃ for phosphating treatment.

[0009] Preferably, the concentration of the hexadecyltrimethylammonium bromide aqueous solution is 50-60 mmol / L, and the Ti3C2T x The concentration of the suspension is 10-20 mg / mL; the molar ratio of the 2-methylimidazole, Ni(NO3)2·6H2O and Co(NO3)2·6H2O is 0.2:(0.05-0.1):0.1; the NiCo-MOF / Ti3C2T x The mass ratio of @NF and NaHPO2·xH2O is 1:(5-20); the concentration of the mixed solution is 0.1-0.2 mol / L.

[0010] The P-NiCo-MOF / Ti3C2T x The preparation method of the @NF composite electrocatalyst includes the following specific steps:

[0011] S1. Using nickel foam (NF) as a catalyst support, the nickel foam was ultrasonically cleaned with acetone, then immersed in a hydrochloric acid solution for ultrasonic treatment, sequentially washed with anhydrous ethanol and deionized water, and dried to obtain a pretreated NF;

[0012] S2. The pretreated NF was immersed in an aqueous solution of hexadecyltrimethylammonium bromide and stirred, and then vacuum dried to obtain a positively charged NF;

[0013] S3. LiF and Ti3AlC2 were added to a hydrochloric acid solution, stirred in a water bath at 40-50°C, centrifuged for the first time until the solution became viscous, and then ultrasonicated in an ice bath. After a second centrifugation, freeze-dried, a single layer of Ti3C2T x , a single layer of Ti3C2T x Add NN-dimethylformamide (DMF) to prepare Ti3C2T x suspension;

[0014] S4. Combine positively charged NF and Ti3C2T x The suspension was mixed, ultrasonicated, and freeze-dried to obtain Ti3C2T x @NF;

[0015] S5. Add 2-methylimidazole to DMF and ultrasonicate it. Then add Ni(NO3)2·6H2O and Co(NO3)2·6H2O and stir to dissolve. x @NF was immersed in the above mixed solution in a sealed reactor and hydrothermally reacted at 150-200 °C. After cooling, washing and drying, NiCo-MOF / Ti3C2T x @NF Composites;

[0016] S6. Under Ar atmosphere, NaHPO2·xH2O was placed upstream of the tube furnace, and NiCo-MOF / Ti3C2T x The @NF composite material was placed in the downstream position and heated to 300-400℃ for phosphating to obtain P-NiCo-MOF / Ti3C2T x @NF composite electrocatalyst.

[0017] Preferably, the thickness of the nickel foam in step S1 is 1.5-2 mm, the pore size is 90-110 ppi, and the area of ​​the nickel foam is (1-1.5)×(1-3) cm 2 The concentration of the hydrochloric acid solution is 0.5-1.5 mol / L, the ultrasonic time is 10-130 min, the drying temperature is 50-70°C, and the drying time is 6-12 h.

[0018] Preferably, the vacuum drying temperature in step S2 is 50-70° C., and the vacuum drying time is 6-12 h.

[0019] Preferably, the mass ratio of LiF and Ti3AlC2 in step S3 is (1-2):1, the concentration of the hydrochloric acid solution is 6-9 mol / L, the stirring time is 24-48 h, the first centrifugal rate is 5000-8000 rpm, the centrifugal time is 1-5 min, the ice bath ultrasound is 30-60 min, the second centrifugal rate is 3000-4000 rpm, the centrifugal time is 15-30 min, the freeze-drying time is 24-48 h, Ti3C2T x The concentration of the suspension is 10-20 mg / mL.

[0020] Preferably, the ultrasonication time in step S4 is 15 to 30 minutes, and the freeze-drying time is 24 to 48 hours.

[0021] Preferably, in step S5, the stirring time is 30 to 60 minutes, the drying time is 6 to 12 hours, and the hydrothermal reaction time is 10 to 12 hours.

[0022] Preferably, the heating rate of the phosphating treatment in step S6 is 1-10° C. / min, and the time of the phosphating treatment is 1-3 hours.

[0023] The P-NiCo-MOF / Ti3C2T x Application of @ / NF composite electrocatalyst in alkaline water electrolysis.

[0024] The present invention utilizes electrostatic action to grow Ti3C2T on the surface of nickel foam x The lamellar structure is then hydrothermally processed in Ti3C2T x Spherical porous NiCo-MOF was grown on the @NF, and then phosphating was performed to obtain a unique heterostructure material P-NiCo-MOF / Ti3C2T composed of lamellar carbon material and P-MOF. x @NF not only inherits the inherent properties of the two components, but also benefits from the synergistic effect associated with the heterogeneous interface, which fully combines the respective advantages of the materials; MOF is partially converted into NiCoP and combined with Ti3C2T x The layered structure of the Ti3C2T4O4 enhances the exposure of the active sites, making the multi-layer interconnected layers provide abundant active sites. The layered and porous structure greatly facilitates the penetration of electrolytes. The material reacts normally in alkaline electrolytes and has excellent electrocatalytic hydrogen production performance. x Composite structure electrocatalyst loaded with P-MOF, composed of Ti3C2T x and the spherical MOF on its surface; among them, Ti3C2T xAs the substrate, spherical MOF grows uniformly on its surface and is phosphated to obtain uniform NiCoP, thereby achieving a catalytic effect. Through the above method, P-NiCo-MOF / Ti3C2T x The @NF composite structure electrocatalyst is used for electrocatalytic hydrogen evolution. By adjusting the interfacial water molecular structure, the interfacial microenvironment of the electrocatalytic hydrogen evolution reaction is improved, thereby enhancing the catalytic activity of the nickel-based electrocatalyst.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention uses chemical etching of the metal "Al" layer in the Ti3AlC2MAX phase to prepare two-dimensional Ti3C2T x ; Then Ti3C2T x Combined with nickel foam (NF), the treated NF is used to make it positively charged, and then the electronegative Ti3C2T x Finally, the hydrothermal method was used to prepare NiCo-MOF / Ti3C2T at a certain temperature and pressure. x @NF. It has the advantages of being easy, fast and efficient to obtain;

[0027] 2. The electrocatalyst of the present invention is a nano-scale catalyst with a multi-layer structure, which combines porous nano-spherical MOF with Ti3C2T x The exposure of active sites is enhanced on the sheet structure, so that the multi-layer interconnected sheets provide abundant active sites, and then NiCo-MOF / Ti3C2T is treated by vapor deposition phosphating. x @NF.

[0028] 3. Ti3C2T prepared by electrostatic action in the present invention x NF provides a fast electron transport channel and has high conductivity, which helps to reduce the energy barrier that needs to be overcome in the rate-determining step of the reaction. NF acts as a supporting skeleton to prevent the material from falling off and has excellent mechanical stability.

[0029] 4. The NiCo-MOF of the present invention provides abundant active sites, which can convert Ti3C2T x It combines well with MOF materials, takes advantage of the composite structure, provides a significant synergistic coupling effect, promotes electron transfer, helps reduce the energy barrier that needs to be overcome in the rate-determining step of the reaction, has a high specific surface area, exposes a large number of catalytic reaction active sites, and effectively improves its hydrogen evolution catalytic performance.

[0030] 5. NiCo-MOF / Ti3C2T after phosphating treatment x@NF, the metal nodes in NiCo-MOF are converted into NiCoP, providing bimetallic sites with high intrinsic activity, and the dense phosphide protective layer inhibits the Ti3C2T x Direct contact with the electrolyte reduces oxidation and forms a strong covalent connection through the Ti-P-Co / Ni bond, avoiding interface peeling and enhancing interface bonding strength. x The high conductivity of Ni / Co accelerates electron transport and reduces charge transfer resistance. Phosphide provides catalytic active sites. Strong electronic coupling is formed at the interface between the two, which adjusts the d-band center of Ni / Co, weakens the excessive adsorption of reaction intermediates, optimizes ΔGH* and ΔGO*, and the P and Ti3C2T x Form Ti-P bonds and enhance chemical stability.

[0031] 6. The present invention provides a method for preparing metal-organic framework (MOF) materials with strong universality. Its technical solution is applicable to the synthesis of MOFs with a variety of metal nodes and organic ligand combinations, and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The single-layer Ti3C2T after Ti3AlC2 peeling in Example 1 x SEM photos of

[0033] Figure 2 Ti3C2T obtained by electrostatic adsorption in Example 1 x SEM image of @NF;

[0034] Figure 3 NiCo-MOF / Ti3C2T prepared by hydrothermal method in Example 1 x SEM image of @NF;

[0035] Figure 4 NiCo-MOF / Ti3C2T3 after phosphating treatment in Example 1 x P-NiCo-MOF / Ti3C2T obtained by @NF x SEM image of @NF composite electrocatalyst;

[0036] Figure 5 The composite electrocatalyst P-NiCo-MOF / Ti3C2T was phosphated at 350℃. x @NF, NiCo-MOF / Ti3C2T composite electrocatalyst without phosphating treatment x @NF, no Ti3C2T added x MOF materials NiCo-MOF@NF, Ti3C2T x LSV plot of @NF and NF;

[0037] Figure 6 The composite electrocatalyst P-NiCo-MOF / Ti3C2T was phosphated at 350℃. x @NF, NiCo-MOF / Ti3C2T composite electrocatalyst without phosphating treatment x @NF, no Ti3C2T added x MOF materials NiCo-MOF@NF, Ti3C2T x @ Tafel slope plot of NF and NF;

[0038] Figure 7 The composite electrocatalyst P-NiCo-MOF / Ti3C2T was phosphated at 350℃. x @NF, NiCo-MOF / Ti3C2T composite electrocatalyst without phosphating treatment x @NF, no Ti3C2T added x MOF materials NiCo-MOF@NF, Ti3C2T x @NF and NF impedance spectra;

[0039] Figure 8 The composite electrocatalyst P-NiCo-MOF / Ti3C2T was phosphated at 350℃. x @NF, NiCo-MOF / Ti3C2T composite electrocatalyst without phosphating treatment x @NF, no Ti3C2T added x MOF materials NiCo-MOF@NF, Ti3C2T x Overpotential diagram of @NF and NF. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0041] The thickness of the nickel foam used in the embodiment of the present invention is 1.5-2 mm, the pore size is 90-110 ppi, and the area of ​​the nickel foam is (1-1.5)×(1-3) cm 2 .

[0042] Example 1

[0043] 1. Using nickel foam (NF) as a catalyst support, the nickel foam (2 cm × 3 cm) was ultrasonically cleaned with acetone to remove organic contaminants. The treated nickel foam was immersed in a 1 mol / L hydrochloric acid solution and ultrasonically treated for 15 minutes to remove surface oxides and other impurities. The nickel foam was then washed with anhydrous ethanol and deionized water, followed by drying at 60°C for 12 hours to obtain pretreated NF.

[0044] 2. Dissolve cetyltrimethylammonium bromide (CTAB) in deionized water to prepare a 20 mg / mL solution. Immerse the pretreated NFs in this solution and stir for 30 minutes until uniform. The cationic groups of CTAB adsorb on the NF surface, neutralizing and reversing its original negative charge, giving it a positive charge. The NFs are then vacuum-dried at 60°C for 12 hours to obtain positively charged NFs.

[0045] 3. 1.6 g of lithium fluoride was placed in a polytetrafluoroethylene bottle and 9 mol / L hydrochloric acid solution was added. 1 g of Ti3AlC2 was slowly added at 40 ° C and stirred in a water bath for 48 h. Then, the solution was centrifuged at a speed of 5000 rpm for 1 min. After repeated centrifugation until the solution became viscous, ice bath ultrasound was performed for 30 min. Finally, the speed of the centrifugation was changed to 3500 rpm and centrifuged for 15 min. The sample after centrifugation was freeze-dried for 48 h to obtain a single layer of Ti3C2T x ,from Figure 1 It can be seen that Ti3C2T x It is the material after Al is stripped off from Ti3AlC2, and the obtained Ti3C2T x It is a lamellar structure. x Add NN-dimethylformamide (DMF) to prepare 10 mg / mL Ti3C2T x suspension;

[0046] 4. Combine positively charged NF and Ti3C2T x The suspension was mixed with ultrasound for 30 min and freeze-dried for 24 h to obtain Ti3C2T x @NF, from Figure 2 It can be seen that Ti3C2T x Grow evenly on nickel foam;

[0047] 5. 1.614 g of 2-methylimidazole was added to 100 mL of DMF and ultrasonicated for 30 min to obtain a 0.2 mol / L 2-methylimidazole solution. Then 1.4539 g of Ni(NO3)2·6H2O and 2.91035 g of Co(NO3)2·6H20 were slowly added and stirred for 30 min until completely dissolved to obtain a 0.05 mol / L Ni(NO3)2 solution and a 0.1 mol / L Co(NO3)2 solution. The mixed solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and Ti3C2T x The @NF was immersed in the reaction solution and sealed in a reactor. The reaction was carried out at 180℃ for 12 hours. The reaction was cooled to room temperature and then taken out. The NiCo-MOF / Ti3C2T x @ / NF composite materials, from Figure 3 It can be seen that NiCo-MOF is a spherical nanostructure;

[0048] 6. Place 0.1g NaHPO2·xH2O (x=0.5~1) upstream of the tube furnace, NiCo-MOF / Ti3C2T x The @ / NF was placed in the downstream of the tube furnace and heated to 350℃ at a rate of 10℃ / min under Ar atmosphere for 2h. After the reaction was completed, it was naturally cooled and taken out. It was washed with deionized water and ethanol several times and then dried to obtain P-NiCo-MOF / Ti3C2T x @ / NF catalyst, from Figure 4 It can be seen that the NiCo-MOF nanospherical structure is not changed after phosphating treatment.

[0049] The electrocatalytic hydrogen production performance of the samples was measured using a three-electrode system to measure the P-NiCo-MOF / Ti3C2T x @ / NF electrochemical performance was characterized, and P-NiCo-MOF / Ti3C2T x @ / NF catalyst was used as the working electrode, carbon rod as the auxiliary electrode, mercury oxide electrode as the reference electrode, and 1 M KOH solution as the electrolyte. Before evaluating the HER performance, all catalysts were activated to a stable state by cyclic voltammetry (CV) scanning at a scan rate of 50 mV / s and linear sweep voltammetry (LSV) at a scan rate of 5 mV / s. All electrochemical tests were performed with IR compensation (90%). Figure 5 P-NiCo-MOF / Ti3C2T x @NF (abbreviated as NCM / MX-P350@NF), NiCo-MOF / Ti3C2T x @NF (abbreviated as NCM / MX@NF), NiCo-MOF@NF (abbreviated as NCM@NF), Ti3C2T x@NF (abbreviated as MX@NF) and NF LSV diagram; from Figure 5 It can be seen that after adding Ti3C2T x The NiCo-MOF after phosphating treatment was tested at a current density of 10 mA / cm 2 The overpotential decreases when Ti3C2T is added x The charge transfer resistance is then reduced and the interfacial charge transfer rate is increased. After phosphating, the electronic structure is adjusted and the HER performance is improved. Figure 6 The composite electrocatalyst P-NiCo-MOF / Ti3C2T was phosphated at 350℃. x @NF, NiCo-MOF / Ti3C2T composite electrocatalyst without phosphating treatment x @NF, no Ti3C2T added x MOF materials NiCo-MOF@NF, Ti3C2T x @NF and NF tafel slope graph. Figure 6 It can be seen that P-NiCo-MOF / Ti3C2T x The @NF material has the lowest Tafel slope, indicating that the smaller the reaction energy barrier on the catalyst surface, the faster the charge transfer rate and the higher the catalytic activity. Figure 7 The composite electrocatalyst P-NiCo-MOF / Ti3C2T was phosphated at 350℃. x @NF, NiCo-MOF / Ti3C2T composite electrocatalyst without phosphating treatment x @NF, no Ti3C2T added x MOF materials NiCo-MOF@NF, Ti3C2T x @NF and NF impedance spectrum. Figure 7 It can be seen that after adding Ti3C2T x The charge transfer resistance of NiCo-MOF after phosphating treatment is reduced, indicating that the activation energy required for charges to cross the double layer is reduced. Figure 8 The composite electrocatalyst P-NiCo-MOF / Ti3C2T was phosphated at 350℃. x @NF, NiCo-MOF / Ti3C2T composite electrocatalyst without phosphating treatment x @NF, no Ti3C2T added x MOF materials NiCo-MOF@NF, Ti3C2T x Overpotential diagram of @NF and NF. Figure 8 It can be seen that after adding Ti3C2T x The NiCo-MOF after phosphating treatment has the lowest overpotential at high and low current densities, which shows that the addition of Ti3C2T xThe NiCo-MOF then improved its electrocatalytic hydrogen evolution performance, and after further phosphating treatment, the electronic structure was optimized, which further enhanced the HER performance.

[0050] Example 2

[0051] 1. Using nickel foam (NF) as a catalyst support, the nickel foam (2 cm × 3 cm) was ultrasonically cleaned with acetone to remove organic contaminants. The treated nickel foam was immersed in a 1.5 mol / L hydrochloric acid solution and ultrasonically treated for 100 min to remove surface oxides and other impurities. The nickel foam was then washed with anhydrous ethanol and deionized water, followed by drying at 70°C for 8 h to obtain pretreated NF.

[0052] 2. Dissolve cetyltrimethylammonium bromide (CTAB) in deionized water to prepare a 20 mg / mL solution. Immerse the pretreated NFs in this solution and stir for 30 minutes until uniform. The cationic groups of CTAB adsorb on the NF surface, neutralizing and reversing its original negative charge, making it positively charged. The NFs are then vacuum-dried at 70°C for 8 hours to obtain positively charged NFs.

[0053] 3. 2g of lithium fluoride was placed in a polytetrafluoroethylene bottle and 6mol / L hydrochloric acid solution was added. 1g of Ti3AlC2 was slowly added at 40°C and stirred in a water bath for 24h. Then, the solution was centrifuged at 8000rpm for 5min. After repeated centrifugation until the solution became viscous, ice bath ultrasound was performed for 60min. Finally, the centrifugal speed was changed to 4000rpm and centrifuged for 30min. The sample after centrifugation was freeze-dried for 24h to obtain a single layer of Ti3C2T x , Ti3C2T x Add NN-dimethylformamide (DMF) to prepare 20 mg / mL Ti3C2T x suspension;

[0054] 4. Combine positively charged NF and Ti3C2T x The suspension was mixed with ultrasound for 20 min and freeze-dried for 48 h to obtain Ti3C2T x @NF;

[0055] 5. 1.614 g of 2-methylimidazole was added to 100 mL of DMF and ultrasonicated for 30 min to obtain a 2-methylimidazole solution with a concentration of 0.2 mol / L. Then 1.4539 g of Ni(NO3)2·6H2O and 2.91035 g of Co(NO3)2·6H2O were slowly added and stirred for 60 min until completely dissolved to obtain a Ni(NO3)2 solution with a concentration of 0.05 mol / L and a Co(NO3)2 solution with a concentration of 0.1 mol / L. The mixed solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and Ti3C2T x The NiCo-MOF / Ti3C2T@NF was immersed in the reaction solution and sealed in a reactor. The reaction was carried out at 200℃ for 10h, and then naturally cooled to room temperature. The product was taken out and washed with deionized water and ethanol for several times and then dried to obtain NiCo-MOF / Ti3C2T@NF. x @ / NF composite materials;

[0056] 6. Place 0.1g NaHPO2·xH2O (x=0.5~1) upstream of the tube furnace, NiCo-MOF / Ti3C2T x @ / NF was placed in the downstream of the tube furnace and heated to 380℃ at a rate of 5℃ / min under Ar atmosphere for 3h. After the reaction was completed, it was naturally cooled and taken out. It was washed with deionized water and ethanol several times and then dried to obtain P-NiCo-MOF / Ti3C2T x @ / NF composite catalyst.

[0057] The present invention introduces Ti3C2T x The composite structure formed with P-NiCo-MOF can effectively improve the reaction kinetics of water electrolysis of nickel-based catalysts. x The bifunctional water electrolysis performance of @ / NF is comparable to that of nickel-based catalysts recently reported in the literature, showing excellent prospects for industrial application.

[0058] The above embodiments are preferred implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any other changes, modifications, substitutions, combinations and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A P-NiCo-MOF / Ti3C2T x @NF composite electrocatalyst, characterized in that The composite electrocatalyst is abbreviated as P-NiCo-MOF / Ti3C2T x @NF is to soak the pretreated nickel foam in a hexadecyltrimethylammonium bromide aqueous solution to obtain a positively charged nickel foam, which is then mixed with Ti3C2T x The suspension was mixed with ultrasound and freeze-dried to obtain Ti3C2T x @NF; then immersed it in a DMF mixed solution of 2-methylimidazole, Ni(NO3)2·6H2O and Co(NO3)2·6H2O, and hydrothermally reacted at 150-200℃ to obtain NiCo-MOF / Ti3C2T x @NF; Finally, NaHPO2·xH2O (x=0.5~1) was placed in the upstream position of the tube furnace under Ar atmosphere, and NiCo-MOF / Ti3C2T x @NF is placed in the downstream position and heated to 300-400℃ for phosphating treatment.

2. NiCo-MOF / Ti3C2T according to claim 1 x @NF composite electrocatalyst, characterized in that The concentration of the hexadecyltrimethylammonium bromide aqueous solution is 50-60 mmol / L, and the Ti3C2T x The concentration of the suspension is 10-20 mg / mL; the molar ratio of the 2-methylimidazole, Ni(NO3)2·6H2O and Co(NO3)2·6H2O is 0.2:(0.05-0.1):0.1; the NiCo-MOF / Ti3C2T x The mass ratio of @NF and NaHPO2·xH2O is 1:(5-20); the concentration of the mixed solution is 0.1-0.2 mol / L.

3. P-NiCo-MOF / Ti3C2T according to claim 1 or 2 x The preparation method of @NF composite electrocatalyst is characterized in that: The specific steps include: S1. Using nickel foam as a catalyst support, the nickel foam was ultrasonically cleaned with acetone, then immersed in a hydrochloric acid solution for ultrasonic treatment, sequentially washed with anhydrous ethanol and deionized water and dried to obtain a pretreated nickel foam; S2. The pretreated nickel foam was immersed in an aqueous solution of hexadecyltrimethylammonium bromide and stirred, and then vacuum dried to obtain a positively charged nickel foam; S3. LiF and Ti3AlC2 were added to a hydrochloric acid solution, stirred in a water bath at 40-50°C, centrifuged for the first time until the solution became viscous, and then ultrasonicated in an ice bath. After a second centrifugation, freeze-dried, a single layer of Ti3C2T x , a single layer of Ti3C2T x Add NN-dimethylformamide to prepare Ti3C2T x suspension; S4. Combine positively charged nickel foam and Ti3C2T x The suspension was mixed, ultrasonicated, and freeze-dried to obtain Ti3C2T x @Foam nickel, abbreviated as Ti3C2T x @NF; S5. Add 2-methylimidazole to DMF and ultrasonicate it. Then add Ni(NO3)2·6H2O and Co(NO3)2·6H2O and stir to dissolve. x @NF was immersed in the above mixed solution in a sealed reactor and hydrothermally reacted at 150-200 °C. After cooling, washing and drying, NiCo-MOF / Ti3C2T x @NF Composites; S6. Under Ar atmosphere, NaHPO2·xH2O was placed upstream of the tube furnace, and NiCo-MOF / Ti3C2T x The @NF composite material was placed in the downstream position and heated to 300-400℃ for phosphating to obtain P-NiCo-MOF / Ti3C2T x @NF composite electrocatalyst.

4. NiCo-MOF / Ti3C2T according to claim 3 x The preparation method of @NF composite electrocatalyst is characterized in that: The thickness of the nickel foam in step S1 is 1.5-2 mm, the pore size is 90-110 ppi, and the area of ​​the nickel foam is (1-1.5)×(1-3) cm 2 The concentration of the hydrochloric acid solution is 0.5-1.5 mol / L, the ultrasonic time is 10-130 min, the drying temperature is 50-70°C, and the drying time is 6-12 h.

5. NiCo-MOF / Ti3C2T according to claim 3 x The preparation method of @NF composite electrocatalyst is characterized in that: The vacuum drying temperature in step S2 is 50-70° C., and the vacuum drying time is 6-12 hours.

6. NiCo-MOF / Ti3C2T according to claim 3 x The preparation method of @NF composite electrocatalyst is characterized in that: In step S3, the mass ratio of LiF and Ti3AlC2 is (1-2):1, the concentration of the hydrochloric acid solution is 6-9 mol / L, the stirring time is 24-48 h, the first centrifugation rate is 5000-8000 rpm, the centrifugation time is 1-5 min, the ice bath ultrasound is 30-60 min, the second centrifugation rate is 3000-4000 rpm, the centrifugation time is 15-30 min, the freeze-drying time is 24-48 h, Ti3C2T x The concentration of the suspension is 10-20 mg / mL.

7. NiCo-MOF / Ti3C2T according to claim 3 x The preparation method of @NF composite electrocatalyst is characterized in that: The ultrasonication time in step S4 is 15 to 30 minutes, and the freeze-drying time is 24 to 48 hours.

8. NiCo-MOF / Ti3C2T according to claim 3 x The preparation method of @NF composite electrocatalyst is characterized in that: In step S5, the stirring time is 30 to 60 minutes, the drying time is 6 to 12 hours, and the hydrothermal reaction time is 10 to 12 hours.

9. NiCo-MOF / Ti3C2T according to claim 3 x The preparation method of @NF composite electrocatalyst is characterized in that: The heating rate of the phosphating treatment in step S6 is 1-10° C. / min, and the time of the phosphating treatment is 1-3 hours.

10. P-NiCo-MOF / Ti3C2T according to claim 1 or 2 x Application of @ / NF composite electrocatalyst in alkaline water electrolysis.

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