Preparation method and application of composite hydrogen evolution catalyst for in-situ growth of MoS2 on Ti3C2Tx ultrathin nanosheet

Abstract

The invention discloses a preparation method and application of a composite hydrogen evolution catalyst for in-situ growth of MoS2 on a Ti3C2Tx ultrathin nanosheet, relates to a preparation method and application of a hydrogen evolution catalyst, and aims to solve the technical problems of low utilization rate of active sites and low catalytic efficiency of the conventional MoS2 catalyst. The method comprises the following steps: etching titanium aluminum carbide to obtain Ti < 3 > C < 2 > F < x > powder; stripping the powder or performing alkali heat treatment, vulcanization or hydro-thermal treatment after stripping to prepare an ultrathin nanosheet; the ultrathin nanosheets and a mixed solution of ammonium heptamolybdate tetrahydrate and thiourea are subjected to a hydrothermal reaction, separation, washing and drying are carried out, the composite hydrogen evolution catalyst MoS2 / Ti3C2Tx is obtained, and T is F, S, O or OH. When the composite material is used for producing hydrogen by electrolyzing water, the current density of 10mA. Cm <-2 > can be realized only by virtue of 86-97mV overpotential in alkaline electrolyte, and the composite material is used in the field of producing hydrogen by electrolyzing alkaline water.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a hydrogen evolution catalyst. Background Art

[0002] With the continuous growth of global energy demand and the increasingly serious environmental pollution problems, the development of efficient, clean and sustainable energy conversion and storage technologies has become an important direction of current scientific and technological development. Among them, hydrogen energy, as an ideal clean energy, has received extensive attention due to its high energy density, zero carbon emission and renewable nature. Hydrogen production by electrolysis of water is considered to be an important technology for large-scale hydrogen production in the future due to its green environmental protection and high efficiency and stability. However, the key to efficient hydrogen production by electrolysis of water lies in the development of a hydrogen evolution reaction (HER) catalyst with high catalytic activity, excellent stability and low cost to reduce the overpotential and improve the hydrogen production efficiency.

[0003] At present, noble metal platinum (Pt)-based catalysts are widely used in the field of electrocatalytic water splitting due to their excellent hydrogen evolution performance. However, due to the scarcity and high price of noble metals, their large-scale industrial application is severely restricted. Therefore, researchers are actively exploring low-cost and high-performance non-noble metal catalysts to replace Pt-based materials. Among them, molybdenum disulfide (MoS2) is considered to be one of the most promising non-noble metal catalysts due to its unique layered structure, abundant catalytic active sites and good chemical stability. However, MoS2 still faces some challenges in the HER reaction, such as low conductivity, limited utilization rate of catalytic active sites and weak electron transport ability, resulting in its overall catalytic performance being inferior to noble metal catalysts. Summary of the Invention

[0004] The present invention aims to solve the technical problems of low utilization rate of active sites and low catalytic efficiency of existing MoS2 catalysts, and provides a preparation method and application of a composite hydrogen evolution catalyst in which MoS2 is in-situ grown on Ti3C2T x ultrathin nanosheets, where T in Ti3C2Tx is F, S, O or OH.

[0005] The preparation method of the composite hydrogen evolution catalyst in which MoS2 is in-situ grown on Ti3C2T x ultrathin nanosheets of the present invention is carried out according to the following steps:

[0006] I. Etch aluminum carbide with a mixed solution of lithium fluoride and hydrochloric acid, and then separate to obtain Ti3C2F x powder without Al intercalation;

[0007] II. Exfoliate the Ti3C2F x powder obtained in step I to obtain Ti3C2F x nanosheets;

[0008] Alternatively, exfoliate the Ti3C2F powder obtained in Step 1 to obtain Ti3C2F nanosheets, and then perform alkali heat treatment to obtain Ti3C2O ultrathin nanosheets; x x x

[0009] Alternatively, exfoliate the Ti3C2F powder obtained in Step 1 to obtain Ti3C2F nanosheets, and then modify the surface of Ti3C2F to -S end groups by gas-phase or liquid-phase sulfidation to obtain Ti3C2S ultrathin nanosheets; x x x x

[0010] Alternatively, exfoliate the Ti3C2F powder obtained in Step 1 to obtain Ti3C2F nanosheets, and then perform hydrothermal treatment to obtain Ti3C2OH ultrathin nanosheets; x x x

[0011] III. Disperse the Ti3C2F nanosheets, Ti3C2O ultrathin nanosheets, Ti3C2S ultrathin nanosheets or Ti3C2OH ultrathin nanosheets obtained in Step 2 in deionized water, add ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24·4H2O) and thiourea (SC(NH2)2) under stirring conditions to obtain a mixed solution; then transfer the mixed solution to a high-pressure reaction kettle and carry out hydrothermal reaction at a temperature of 120 - 240 °C for 6 - 36 h; x x x x 24

[0012] IV. Filter or centrifuge the obtained product, wash the obtained solid matter with deionized water until it is clean, and then dry it to obtain a composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2T ultrathin nanosheets, denoted as MoS2 / Ti3C2T, where T = F, S, O or OH, and it is a black powder. x x

[0013] Furthermore, the preparation method of the mixed solution of lithium fluoride and hydrochloric acid in Step 1 is: adding 1 - 5 g of lithium fluoride and 35 - 55 mL of hydrochloric acid with a concentration of 6 - 11 M to 20 - 100 mL of distilled water and magnetically stirring for 20 - 30 min.

[0014] ​​​​​​​​​​​​​​​​​Further, the etching in step one is to add aluminum titanium carbide into a mixed solution of lithium fluoride and hydrochloric acid, and stir for 24 to 120 h under the conditions of a temperature of 35 to 65 °C and a stirring speed of 50 to 200 revolutions per minute.

[0015] Further, the separation in step one is centrifugal separation and / or suction filtration separation.

[0016] Further, the exfoliation in step two is to exfoliate the Ti3C2F x powder by means of ultrasonic assisted by an organic solvent, or by pretreatment with an organic intercalating agent, or by gentle exfoliation through hand shaking and ion intercalation.

[0017] Further, the method of ultrasonic assisted exfoliation by an organic solvent in step two is as follows: according to the concentration of the Ti3C2Tx powder being 10 mg / mL, add the Ti3C2T x powder into a polar solvent, where the polar solvent is IPA, ethanol, DMSO, NMP or water, and then use a probe type or water bath type ultrasonic to perform ultrasonic treatment for 30 min to 2 h under temperature control conditions, where the temperature control is to prepare the temperature in an ice bath or below 25 °C; then centrifuge at a low speed of 1000 to 3000 rpm for 5 to 10 min to remove unexfoliated large pieces, and then centrifuge the supernatant at a high speed of 8000 to 12000 rpm for 5 to 10 min, and collect the solid phase to obtain nanosheets.

[0018] Further, the method of exfoliation by pretreatment with an organic intercalating agent in step two is as follows: add the Ti3C2T x powder into DMSO and gently stir or let it stand at a speed of 60 to 80 rpm for 12 to 24 h. After intercalation, add water or ethanol and perform ultrasonic exfoliation for 30 to 60 min; then centrifuge at a low speed of 1000 to 3000 rpm for 5 to 10 min to remove unexfoliated large pieces, and then centrifuge the supernatant at a high speed of 8000 to 12000 rpm for 5 to 10 min, and collect the solid phase to obtain nanosheets.

[0019] Further, the method of gentle exfoliation by hand shaking and ion intercalation in step two is as follows: add the Ti3C2T x powder into a TMAOH or TBAOH solution with a concentration of 0.05 to 0.1 M and soak it, then let it stand at room temperature for 6 to 12 hours, shake it by hand or perform vortex oscillation for 10 to 30 minutes, then centrifuge at a low speed of 1000 to 3000 rpm for 5 to 10 min to remove unexfoliated large pieces, and then centrifuge the supernatant at a high speed of 8000 to 12000 rpm for 5 to 10 min, and collect the solid phase to obtain nanosheets.

[0020] Further, the specific method of the alkali heat treatment in Step 2 is as follows: Add Ti3C2F x nanosheets into a NaOH or KOH solution with a concentration of 1 - 5 M, and heat and reflux for 6 - 24 hours at a temperature of 70 - 100 °C; then perform centrifugal separation, wash the solid phase to neutrality, and freeze-dry or air-dry to complete the alkali heat treatment.

[0021] Further, the specific method of the gas-phase sulfidation in Step 2 is as follows: Place Ti3C2F x nanosheets into a quartz tube, introduce a gas with a volume percentage concentration of 5% H2S or a gas with a volume percentage concentration of 5% CS2, and perform heat treatment at a temperature of 300 - 600 °C for 0.5 - 2 hours. After cooling, complete the hydrogen sulfide gas-phase treatment.

[0022] Further, the specific method of the liquid-phase sulfidation in Step 2 is as follows: Disperse Ti3C2F x nanosheets in a compound solution containing a mercapto (-SH) group, where the compound with a mercapto group is thioethanol or mercaptoacetic acid, stir and react for 12 - 24 hours, then wash to remove impurities and dry to complete the liquid-phase sulfidation.

[0023] Further, the specific method of the hydrothermal treatment in Step 2 is as follows: Disperse Ti3C2F x nanosheets in 0.1 - 1 M NaOH or KOH and stir for 1 hour, then place them in a Teflon-lined autoclave and perform hydrothermal reaction at a temperature of 120 - 180 °C for 4 - 12 hours. After the reaction, wash to neutrality and dry to complete the hydrothermal treatment.

[0024] Further, the centrifugal separation in Step 4 is carried out at a rotational speed of 3500 - 8000 rpm for 3 - 5 min.

[0025] The composite hydrogen evolution catalyst with MoS2 in-situ grown on the Ti3C2T x ultrathin nanosheets prepared by the above method is to construct a catalyst layer with MoS2 in-situ grown on a series of Ti3C2T x (T = F, S, O, and OH) ultrathin nanosheets. The application of this composite hydrogen evolution catalyst is to use it for hydrogen production by electrolyzing water.

[0026] The composite material with MoS2 in-situ grown on a series of Ti3C2T x (T = F, S, O, and OH) ultrathin nanosheets prepared by the present invention exhibits significantly enhanced electrocatalytic performance for the hydrogen evolution reaction (HER). Its excellent catalytic activity is attributed to the following advantages:

[0027] (1) High-density catalytic active sites: The synergistic effect of MoS2 nanosheets and Ti3C2T x (T = F, S, O, and OH) ultrathin nanosheet substrates significantly increases the number of catalytic active sites exposed on the surface of the composite material, effectively promoting the hydrogen adsorption-desorption process, thereby enhancing the overall catalytic rate.

[0028] (2) Fast interfacial electron transport ability: The excellent intrinsic conductivity of Ti3C2T x (T = F, S, O, and OH) ultrathin nanosheets effectively promotes the rapid transfer of electrons from the electrode substrate to the catalytic sites, greatly reducing the interfacial charge transfer resistance and significantly improving the kinetic efficiency of the electrocatalytic reaction.

[0029] (3) Low-cost and easy large-scale preparation: The composite material preparation method adopted in the present invention is simple, efficient, and economical, suitable for large-scale industrial production, and has significant commercial application potential.

[0030] The in-situ grown MoS2 obtained in the present invention on a series of Ti3C2T x (T = F, S, O, and OH) ultrathin nanosheet composite catalysts exhibit excellent HER activity in an alkaline electrolyte environment, achieving a current density of 10 mA·cm -2 with a low overpotential of only 86 - 97 mV. In addition, the catalyst shows excellent stability during long-term electrolysis operation and is expected to be used as an efficient, stable, and economical non-precious metal catalyst in the field of alkaline electrolytic water hydrogen production. Description of the Drawings

[0031] Figure 1 XRD pattern of the composite hydrogen evolution catalyst with in-situ grown MoS2 on Ti3C2F x ultrathin nanosheets prepared in Example 1;

[0032] Figure 2 Scanning electron microscope image of the Ti3C2F x powder prepared in Step 1 of Example 1;

[0033] Figure 3 Scanning electron microscope image of the Ti3C2T x ultrathin nanosheets prepared in Step 2 of Example 1;

[0034] Figure 4 Scanning electron microscope image of the composite hydrogen evolution catalyst with in-situ grown MoS2 on Ti3C2F x ultrathin nanosheets prepared in Step 4 of Example 1;

[0035] Figure 5 MoS2 / Ti3C2F prepared in Example 1 xLinear voltammetry scan of the electrode;

[0036] Figure 6 The MoS2 / Ti3C2O prepared for Example 2 x Linear voltammetry scan of the electrode;

[0037] Figure 7 The MoS2 / Ti3C2S prepared for Example 3 x Linear voltammetry scan of the electrode;

[0038] Figure 8 The MoS2 / Ti3C2OH prepared for Example 4 x Linear voltammetry scan of the electrode;

[0039] Figure 9 The catalyst Ti3C2F prepared for Comparative Example 1 x Linear voltammetry scan of the electrode;

[0040] Figure 10 Linear voltammetry scan of the catalyst MoS2 electrode prepared for Comparative Example 2;

[0041] Figure 11 Electrochemical specific surface area diagrams of the catalysts of Example 1, Comparative Example 1 and Comparative Example 2;

[0042] Figure 12 Electrochemical impedance diagrams of the catalysts of Example 1, Comparative Example 1 and Comparative Example 2. Detailed implementation mode

[0043] The beneficial effects of the present invention are verified by the following examples.

[0044] Example 1: The preparation method of the composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2F x ultrathin nanosheets is carried out according to the following steps:

[0045] I. Add 100 mg of aluminum titanium carbide into the mixed solution of lithium fluoride and hydrochloric acid, stir for 48 h at a temperature of 45 °C for etching, then centrifuge, wash and dry to obtain Ti3C2F x powder without Al intercalation; the mixed solution of lithium fluoride and hydrochloric acid is obtained by adding 2 g of lithium fluoride and 35 mL of 6 M HCl into 100 mL of distilled water and stirring evenly;

[0046] II. According to the concentration of Ti3C2T x powder being 10 mg / mL, the Ti3C2F obtained in step I xThe powder was added to the polar solvent DMSO, and then probe-type ultrasound was used to ultrasonically treat it for 2 h under ice bath conditions. Then, it was centrifuged at a low speed of 3000 rpm for 5 min to remove the unpeeled large chunks. Subsequently, the supernatant was centrifuged at a high speed of 8000 rpm for 10 min, and the solid phase was collected to obtain Ti3C2F x ultrathin nanosheets;

[0047] III. 0.1 g of the Ti3C2F x ultrathin nanosheets obtained in Step II were dispersed in 35 ml of deionized water. Under stirring conditions, 0.275 g of ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O) and 0.15 g of thiourea (SC(NH2)2) were added. At room temperature, it was vigorously stirred at a speed of 200 rpm for 30 min to obtain a mixed solution. Then, the mixed solution was transferred to a high-pressure reaction kettle and hydrothermally reacted at 220 °C for 20 h;

[0048] IV. The obtained product was centrifuged at a speed of 8000 rpm for 3 min. The obtained solid phase was washed clean with deionized water and then dried in an oven at 60 °C for 12 h to obtain a composite hydrogen evolution catalyst with MoS2 in-situ grown on the Ti3C2T x ultrathin nanosheets, denoted as MoS2 / Ti3C2F x , which is a black powder.

[0049] Figure 1 XRD pattern of the composite hydrogen evolution catalyst MoS2 / Ti3C2F x prepared in Example 1; It can be seen from Figure 1 that MoS2 / Ti3C2F x was successfully prepared.

[0050] Figure 2 SEM image of the Ti3C2F x powder prepared in Example 1; It can be seen from Figure 2 that the unstratified Ti3C2F x powder exhibits an accordion structure. Compared with this structure, the stratified ultrathin nanosheets effectively increase the specific surface area, thus providing more sites for the in-situ growth of MoS2.

[0051] Figure 3 SEM image of the Ti3C2F x ultrathin nanosheets prepared in Step II of Example 1; It can be seen from Figure 3 that the stratified and peeled Ti3C2F x exhibits the morphology of ultrathin nanosheets, effectively increasing the specific surface area, thus providing more sites for the in-situ growth of MoS2.

[0052] Figure 4 The composite hydrogen evolution catalyst MoS2 / Ti3C2F prepared in Step 4 of Example 1 x SEM image; As can be seen from Figure 4 the electrode sheet surface is composed of MoS2 / Ti3C2F with a flower-like ultrathin nanosheet structure x This structure can provide a large specific surface area, which is beneficial to mass transfer.

[0053] 10 mg of the composite hydrogen evolution catalyst was added to 0.8 mL of absolute ethanol, 0.2 mL of deionized water, and 50 μL of a 5% mass concentration of naphthol solution to prepare a slurry; the nickel foam was placed in acetone and ultrasonically treated for 10 minutes, then placed in 3M hydrochloric acid and ultrasonically treated for 10 minutes, and washed and dried with deionized water to obtain clean nickel foam; the slurry was coated on the nickel foam substrate and dried to obtain an electrode.

[0054] The composite hydrogen evolution catalyst MoS2 / Ti3C2F prepared in Example 1 x electrode was directly used as the working electrode (cathode) in the electrocatalytic hydrogen evolution reaction, the Hg / HgO electrode was used as the reference electrode, and the platinum electrode was used as the counter electrode. An electrochemical workstation (Chenhua 760e) was connected, 1M KOH solution was used as the electrocatalytic electrolyte, and nitrogen was introduced at a rate of 25 mL·min -1 for 10 minutes to saturate the solution with nitrogen, and then the linear sweep voltammetry test was carried out on this electrode material at a scanning rate of 2 mV·s -1 The obtained linear sweep voltammogram is as shown in Figure 5 As can be seen from Figure 5 the overpotential of the composite hydrogen evolution catalyst MoS2 / Ti3C2F prepared in Example 1 x at a current density of 10 mA·cm 2 is 97 mV (HER).

[0055] Example 2: The preparation method of the composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2O x ultrathin nanosheets is carried out according to the following steps:

[0056] I. 100 mg of aluminum titanium carbide was added to a mixed solution of lithium fluoride and hydrochloric acid, and etched under stirring at a temperature of 45 °C for 48 h, and then centrifuged, washed, and dried to obtain Ti3C2F x powder without Al intercalation; the mixed solution of lithium fluoride and hydrochloric acid was obtained by adding 2 g of lithium fluoride and 35 mL of 6M HCl to 100 mL of distilled water and stirring evenly;

[0057] II. According to Ti3C2Tx The concentration of the powder is 10 mg / mL. Add the Ti3C2F powder obtained in Step 1 x to the polar solvent DMSO, then use a probe-type ultrasonic device and perform ultrasonic treatment for 2 h under ice bath conditions. Then, centrifuge at a low speed of 3000 rpm for 5 min to remove unpeeled large chunks, and then centrifuge the supernatant at a high speed of 8000 rpm for 10 min. Collect the solid phase to obtain the Ti3C2F x nanosheets;

[0058] Add the Ti3C2F x nanosheets to a 3 M NaOH solution, and heat and reflux react at 80 °C for 12 hours; then perform centrifugation and separation, wash the solid phase until it is neutral, and freeze-dry to obtain Ti3C2O x ultrathin nanosheets;

[0059] III. Uniformly disperse 0.1 g of Ti3C2O x ultrathin nanosheets in 35 ml of deionized water, then add 0.275 g of ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O) and 0.15 g of thiourea (SC(NH2)2), and vigorously stir at 200 rpm for 30 min at room temperature to obtain a mixed solution; then transfer the mixed solution to a high-pressure reaction kettle and perform hydrothermal reaction at 220 °C for 20 h;

[0060] IV. Centrifuge the obtained product at 8000 rpm for 3 min, wash the obtained solid phase with deionized water until it is clean, and then dry it in an oven at 60 °C for 12 hours to obtain a composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2T x ultrathin nanosheets, denoted as MoS2 / Ti3C2O x , which is a black powder.

[0061] Using the same method as in Example 1, prepare the composite hydrogen evolution catalyst MoS2 / Ti3C2O of Example 2 x into an electrode. Use the composite hydrogen evolution catalyst MoS2 / Ti3C2O electrode prepared in this Example 2 x directly as the working electrode (cathode) in the electrocatalytic hydrogen evolution reaction, use a Hg / HgO electrode as the reference electrode, use a platinum electrode as the counter electrode, connect to an electrochemical workstation (Chenhua 760e), use a 1 M KOH solution as the electrocatalytic electrolyte, and pass nitrogen at a rate of 25 mL·min -1 for 10 min to achieve nitrogen saturation of the solution, and then at 2 mV·s -1The linear sweep voltammetry curve obtained by performing linear sweep voltammetry on the electrode material at a scan rate of Figure 6 is as shown in Figure 6 . It can be seen that the composite hydrogen evolution catalyst MoS2 / Ti3C2O prepared in Example 2 x has an overpotential of 90 mV (HER) at a current density of 10 mA·cm 2 .

[0062] Example 3: The preparation method of the composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2S x ultrathin nanosheets is carried out according to the following steps:

[0063] I. Add 100 mg of aluminum titanium carbide to the mixed solution of lithium fluoride and hydrochloric acid, stir for 48 h at a temperature of 45 °C for etching, then centrifuge, wash, and dry to obtain Ti3C2F x powder without Al intercalation; the mixed solution of lithium fluoride and hydrochloric acid is obtained by adding 2 g of lithium fluoride and 35 mL of 6 M HCl to 100 mL of distilled water and stirring evenly;

[0064] II. According to the concentration of Ti3C2T x powder being 10 mg / mL, add the Ti3C2F x powder obtained in step I to the polar solvent DMSO, then use a probe-type ultrasonic wave, ultrasonically treat for 2 h under ice bath conditions, then centrifuge and separate at a low speed of 3000 rpm for 5 min to remove unpeeled large pieces, and then centrifuge and separate the supernatant at a high speed of 8000 rpm for 10 min to collect the solid phase, that is, Ti3C2F x nanosheets;

[0065] Put the Ti3C2F x nanosheets into a quartz tube, introduce dilute H2S gas with a volume percentage concentration of 5%, and perform heat treatment at a temperature of 300 °C for 2 hours. After cooling, Ti3C2S x ultrathin nanosheets are obtained;

[0066] III. Uniformly disperse 0.1 g of Ti3C2S x ultrathin nanosheets in 35 ml of deionized water, then add 0.275 g of ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O) and 0.15 g of thiourea (SC(NH2)2), and vigorously stir at a speed of 200 rpm at room temperature for 30 min to obtain a mixed solution; then transfer the mixed solution to a high-pressure reaction kettle and perform hydrothermal reaction at a temperature of 220 °C for 20 h;

[0067] IV. The obtained product was centrifuged at 8000 rpm for 3 min, and the obtained solid phase was washed thoroughly with deionized water and then dried in an oven at 60 °C for 12 h to obtain a composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2T x ultrathin nanosheets, denoted as MoS2 / Ti3C2S x , which is a black powder.

[0068] Using the same method as in Example 1, the composite hydrogen evolution catalyst MoS2 / Ti3C2S of Example 3 x was prepared into an electrode. The composite hydrogen evolution catalyst MoS2 / Ti3C2S electrode prepared in this Example 3 x was directly used as the working electrode (cathode) in the electrocatalytic hydrogen evolution reaction, the Hg / HgO electrode was used as the reference electrode, and the platinum electrode was used as the counter electrode to connect to an electrochemical workstation (Chenhua 760e). Using 1 M KOH solution as the electrocatalytic electrolyte and passing nitrogen at a rate of 25 mL·min -1 for 10 min to saturate the solution with nitrogen, and then performing linear sweep voltammetry testing on this electrode material at a scanning rate of 2 mV·s -1 . The obtained linear sweep voltammogram is as shown Figure 7 . It can be seen from Figure 7 that the MoS2 / Ti3C2S composite catalyst prepared in Example 3 x has an overpotential of 88 mV (HER) at a current density of 10 mA·cm 2 .

[0069] Example 4: The preparation method of the composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2OH x ultrathin nanosheets is carried out according to the following steps:

[0070] I. Add 100 mg of aluminum titanium carbide into the mixed solution of lithium fluoride and hydrochloric acid, stir at 45 °C for 48 h for etching, and then centrifuge, wash, and dry to obtain Ti3C2F x powder without Al intercalation; the mixed solution of lithium fluoride and hydrochloric acid is obtained by adding 2 g of lithium fluoride and 35 mL of 6 M HCl to 100 mL of distilled water and stirring evenly

[0071] II. According to the concentration of Ti3C2T x powder being 10 mg / mL, the Ti3C2F obtained in step I xThe powder was added to the polar solvent DMSO, and then probe-type ultrasound was used to ultrasonically treat it for 2 h under ice bath conditions. Then, it was centrifuged at a low speed of 3000 rpm for 5 min to remove the unpeeled large pieces. The supernatant was then centrifuged at a high speed of 8000 rpm for 10 min, and the solid phase was collected to obtain Ti3C2F x nanosheets;

[0072] Disperse the Ti3C2F x nanosheets in 0.5 M NaOH and stir for 1 hour. Then, place it in a Teflon-lined autoclave and hydrothermally react at 150 °C for 8 hours. After the reaction, wash it to neutrality and dry it to obtain Ti3C2OH x ultrathin nanosheets;

[0073] III. Disperse 0.1 g of Ti3C2OH x ultrathin nanosheets evenly in 35 ml of deionized water, and then add 0.275 g of ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O) and 0.15 g of thiourea (SC(NH2)2). Stir vigorously at 200 rpm for 30 min at room temperature to obtain a mixed solution. Then, transfer the mixed solution to a high-pressure reaction kettle and hydrothermally react at 220 °C for 20 h;

[0074] IV. Centrifuge the obtained product at 8000 rpm for 3 min. Wash the obtained solid phase with deionized water until it is clean, and then dry it in an oven at 60 °C for 12 hours to obtain a composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2T x ultrathin nanosheets, denoted as MoS2 / Ti3C2OH x which is a black powder.

[0075] Using the same method as in Example 1, prepare the composite hydrogen evolution catalyst MoS2 / Ti3C2OH of Example 4 x into an electrode. Use the composite hydrogen evolution catalyst MoS2 / Ti3C2OH prepared in this Example 4 x electrode directly as the working electrode (cathode) in the electrocatalytic hydrogen evolution reaction, use the Hg / HgO electrode as the reference electrode, use the platinum electrode as the counter electrode and connect it to an electrochemical workstation (Chenhua 760e). Use 1 M KOH solution as the electrolyte for electrocatalysis and pass nitrogen at a rate of 25 mL·min -1 for 10 min to saturate the solution with nitrogen. Then, perform linear sweep voltammetry testing on this electrode material at a scanning rate of 2 mV·s -1 . The obtained linear sweep voltammogram is as shown Figure 8 and from Figure 8It can be seen that the composite hydrogen evolution catalyst MoS2 / Ti3C2OH prepared in Example 4 x has an overpotential of 86 mV (HER) at a current density of 10 mA·cm 2 .

[0076] Comparative Example 1: In this example, the catalyst Ti3C2F was prepared x , and the specific preparation method was carried out according to the following steps:

[0077] I. Add 100 mg of aluminum titanium carbide to a mixed solution of lithium fluoride and hydrochloric acid, stir for 48 h at a temperature of 45 °C for etching, then centrifuge, wash, and dry to obtain Ti3C2F x powder without Al intercalation; the mixed solution of lithium fluoride and hydrochloric acid is obtained by adding 2 g of lithium fluoride and 35 mL of 6 M HCl to 100 mL of distilled water and stirring evenly;

[0078] II. According to the concentration of Ti3C2T x powder being 10 mg / mL, add the Ti3C2F x powder obtained in step I to the polar solvent DMSO, then use a probe-type ultrasonic wave, ultrasonically treat for 2 h under ice bath conditions, then centrifuge and separate at a low speed of 3000 rpm for 5 min to remove unpeeled large pieces, and then centrifuge and separate the supernatant at a high speed of 8000 rpm for 10 min, and collect the solid phase to obtain Ti3C2F x nanosheets, that is, the catalyst Ti3C2F x .

[0079] Using the same method as in Example 1, the catalyst Ti3C2F of Comparative Example 1 x was prepared into an electrode. The catalyst Ti3C2F x electrode prepared in this Comparative Example 1 was directly used as the working electrode (cathode) in the electrocatalytic hydrogen evolution reaction, the Hg / HgO electrode was used as the reference electrode, the platinum electrode was used as the counter electrode, and an electrochemical workstation (Chenhua 760e) was connected. 1 M KOH solution was used as the electrolyte for electrocatalysis, and nitrogen was introduced at a rate of 25 mL·min -1 for 10 min to saturate the solution with nitrogen, and then the linear sweep voltammetry test was carried out on this electrode material at a scanning rate of 2 mV·s -1 . The obtained linear sweep voltammetry curve is as Figure 9 shown. It can be seen from Figure 9 that the Ti3C2F x catalyst prepared in Comparative Example 1 has an overpotential of 157 mV (HER) at a current density of 10 mA·cm 2 .

[0080] Comparative Example 2: This example is to prepare the catalyst MoS2, and the specific preparation method is carried out according to the following steps:

[0081] I. Add 0.275 g of ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O) and 0.15 g of thiourea (SC(NH2)2) into 35 ml of deionized water. At room temperature, vigorously stir at a speed of 200 for 30 min to obtain a precursor solution; then load the precursor solution into a hydrothermal autoclave and keep it at a temperature of 220 °C for 20 h;

[0082] II. Centrifuge the obtained product at a speed of 8000 rpm for 3 min, wash the solid phase with deionized water 3 times, and then dry it in an oven at a temperature of 60 °C for 12 hours to obtain the catalyst MoS2.

[0083] Using the same method as in Example 1, prepare the catalyst MoS2 of Comparative Example 2 into an electrode. Use the catalyst MoS2 electrode prepared in this Comparative Example 2 directly as the working electrode (cathode) in the electrocatalytic hydrogen evolution reaction, use the Hg / HgO electrode as the reference electrode, and use the platinum electrode as the counter electrode to connect to an electrochemical workstation (Chenhua 760e). Use 1 M KOH solution as the electrolyte for electrocatalysis and pass nitrogen at a rate of 25 mL·min -1 for 10 min to saturate the solution with nitrogen, and then perform linear sweep voltammetry testing on this electrode material at a scanning rate of 2 mV·s -1 . The obtained linear sweep voltammogram is as Figure 10 shown. It can be seen from Figure 10 that the overpotential of the catalyst MoS2 prepared in Comparative Example 2 is 191 mV (HER) at a current density of 10 mA·cm 2 .

[0084] List the overpotentials of the electrode sheets prepared in Examples 1-4 and Comparative Examples 1-2 in Table 1.

[0085] Table 1 Overpotential data of the electrode sheets prepared in Examples 1-3 and Comparative Examples 1-3

[0086] Sample Overpotential (HER) (mV) Example 1 97 Example 2 90 Example 3 88 Example 4 86 Comparative Example 1 157 Comparative Example 2 191

[0087] Analyze and compare the data in Table 1, indicating that in-situ growth of MoS2 on the Ti3C2T x ultrathin nanosheet substrate greatly avoids the problem of the active sites of single MoS2 being covered, improves its catalytic efficiency and stability, and verifies the modification ability of different end groups for the overall catalyst. At the same time, Ti3C2F xAfter further alkali heat treatment, sulfidation treatment or hydrothermal treatment of the nanosheets, when the F end group is replaced by an O, OH or S end group, the electronegativity of the end group is weakened, thereby regulating the electron density and electron structure on the surface of Ti atoms, and promoting the formation of a more efficient charge transfer channel between MXene and MoS2. This end group replacement can optimize the electron density of the d orbitals of MXene, form a more effective interfacial coupling between the MXene substrate and MoS2, thereby accelerating the electron transfer rate during the electrocatalytic process and further improving the performance of the composite hydrogen evolution catalyst.

[0088] The electrochemical specific surface area of the composite hydrogen evolution catalyst MoS2 / Ti3C2F of Example 1 was tested by an electrochemical workstation x , the catalyst Ti3C2F of Comparative Example 1 x and the catalyst MoS2 of Comparative Example 2, as Figure 11 shown. It can be seen from Figure 11 that the composite hydrogen evolution catalyst MoS2 / Ti3C2F after compounding x has a larger electrochemical active specific surface area.

[0089] The electrochemical impedance diagrams of the composite hydrogen evolution catalyst MoS2 / Ti3C2F of Example 1 were tested by an electrochemical workstation x , the catalyst Ti3C2F of Comparative Example 1 x and the catalyst MoS2 of Comparative Example 2, as Figure 12 shown; it can be seen from Figure 12 that the composite hydrogen evolution catalyst MoS2 / Ti3C2F after compounding x has a smaller charge transfer resistance.

[0090] The Ti3C2T of the present invention x has excellent electrical conductivity, adjustable surface chemistry and abundant active sites (such as F, S, O, etc.). It can not only provide a fast electron transfer channel, but also act as a catalyst carrier to regulate the dispersion degree and electron structure of active species, thereby improving the catalytic performance. The present invention combines MoS2 with Ti3C2T x ultrathin nanosheets to construct an efficient hydrogen evolution catalytic system. The MoS2 / Ti3C2T x composite catalyst can make full use of the high electrical conductivity of Ti3C2T x , the flexible end groups that can be manipulated and the abundant catalytic active sites of MoS2 to achieve a synergistic enhancement effect, thereby significantly improving the HER performance. In addition, the stability and mechanical strength of the composite catalyst are also improved, which can meet the actual application requirements. The composite hydrogen evolution catalyst of the present invention can not only effectively reduce the energy consumption of the hydrogen evolution reaction and improve the stability of the catalyst, but also is a non-precious metal catalyst with low cost and high performance.

Claims

1. A preparation method of a composite hydrogen evolution catalyst for in-situ growth of MoS2 on Ti3C2T x ultrathin nanosheets, characterized in that, The method is carried out according to the following steps:

1. After etching aluminum titanium carbide with a mixed solution of lithium fluoride and hydrochloric acid, separate to obtain Ti3C2F powder with Al interlayers removed. x Powder; II. Exfoliate the Ti3C2F x powder obtained in Step I to obtain Ti3C2F x nanosheets; Alternatively, exfoliate the Ti3C2F powder obtained in Step 1 to obtain Ti3C2F x nanosheets, and then perform alkali heat treatment to obtain Ti3C2O x ultrathin nanosheets; x ​ Alternatively, exfoliate the Ti3C2F x powder obtained in Step 1 to obtain Ti3C2F x nanosheets, and then modify the surface of Ti3C2F x to -S end groups by gas-phase or liquid-phase sulfidation to obtain Ti3C2S x ultrathin nanosheets; Alternatively, exfoliate the Ti3C2F x powder obtained in Step 1 to obtain Ti3C2F x nanosheets, and then perform hydrothermal treatment to obtain Ti3C2OH x ultrathin nanosheets; III. Disperse the Ti3C2F x nanosheets, Ti3C2O x ultrathin nanosheets, Ti3C2S x ultrathin nanosheets or Ti3C2OH x ultrathin nanosheets in deionized water, add ammonium heptamolybdate tetrahydrate and thiourea under stirring conditions to obtain a mixed solution; then transfer the mixed solution to a high-pressure reaction kettle and carry out hydrothermal reaction at a temperature of 120-240 °C for 6-36 h; IV. Filter the obtained product by suction filtration or centrifuge separation, wash the obtained solid phase with deionized water until it is clean, and then dry it to obtain a composite hydrogen evolution catalyst with MoS2 in-situ grown on Ti3C2T x ultrathin nanosheets, denoted as MoS2 / Ti3C2T x , where T = F, S, O or OH.

2. A preparation method of a composite hydrogen evolution catalyst for in-situ growth of MoS2 on a Ti3C2T x ultrathin nanosheet, characterized in that, The preparation method of the mixed solution of lithium fluoride and hydrochloric acid described in step one is as follows: 1-5 g of lithium fluoride and 35-55 mL of hydrochloric acid with a concentration of 6-11 M are added to 20-100 mL of distilled water and magnetically stirred for 20-30 min to obtain the solution.

3. A method for preparing a composite hydrogen evolution catalyst with MoS2 in-situ grown on a Ti3C2T x ultrathin nanosheet, characterized in that, The etching described in step one is to add aluminum titanium carbide to the mixed solution of lithium fluoride and hydrochloric acid, and stir at a temperature of 35-65 °C and a stirring speed of 50-200 revolutions per minute for 24-120 h.

4. A method for preparing a composite hydrogen evolution catalyst with MoS2 in-situ grown on a Ti3C2T x ultrathin nanosheet, characterized in that The exfoliation described in Step 2 is to exfoliate Ti3C2F x powder by ultrasonic assistance with organic solvents, or by pretreatment with organic intercalants, or by gentle exfoliation through hand shaking and ion intercalation.

5. A preparation method of a composite hydrogen evolution catalyst for in-situ growth of MoS2 on a Ti3C2T x ultra-thin nanosheet, characterized in that, The exfoliation method assisted by organic solvent ultrasound described in step two is as follows: According to the concentration of Ti3C2Tx powder being 10 mg / mL, the Ti3C2Tx powder is added to a polar solvent, where the polar solvent is IPA, ethanol, DMSO, NMP or water. Subsequently, probe-type or water-bath ultrasound is used to ultrasonically treat for 30 min to 2 h under temperature control conditions, where the temperature control is to prepare the temperature in an ice bath or below 25 °C; then centrifugally separate at a low speed of 1000-3000 rpm for 5-10 min to remove unexfoliated large pieces, and then centrifugally separate the supernatant at a high speed of 8000-12000 rpm for 5-10 min, and collect the solid phase to obtain nanosheets.

6. A preparation method of a composite hydrogen evolution catalyst for in-situ growth of MoS2 on a Ti3C2T x ultra-thin nanosheet, characterized in that The specific method of the alkali heat treatment described in Step 2 is as follows: Add Ti3C2F x nanosheets into a NaOH or KOH solution with a concentration of 1 - 5 M, and heat under reflux at a temperature of 70 - 100 °C for 6 - 24 hours; then perform centrifugal separation, wash the solid phase to neutrality, and dry it by freeze-drying or air-drying at room temperature to complete the alkali heat treatment.

7. A method for preparing a composite hydrogen evolution catalyst with MoS2 in-situ grown on a Ti3C2T x ultra-thin nanosheet, characterized in that, The specific method of gas-phase sulfidation described in Step 2 is as follows: Put the Ti3C2F x nanosheets into a quartz tube, introduce H2S gas with a volume percentage concentration of 5% or CS2 gas with a volume percentage concentration of 5%, and perform heat treatment at a temperature of 300 to 600 °C for 0.5 to 2 hours. After cooling, the hydrogen sulfide gas-phase treatment is completed.

8. A preparation method of a composite hydrogen evolution catalyst for in-situ growth of MoS2 on a Ti3C2T x ultra-thin nanosheet, characterized in that, The specific method of liquid-phase sulfidation described in Step 2 is as follows: Disperse Ti3C2F x nanosheets in a compound solution containing a mercapto group, where the compound with a mercapto group is thioethanol or mercaptoacetic acid, stir and react for 12 - 24 hours, then wash to remove impurities and dry to complete liquid-phase sulfidation.

9. A method for preparing a composite hydrogen evolution catalyst with MoS2 in-situ grown on a Ti3C2T x ultrathin nanosheet, characterized in that The detailed method of the hydrothermal treatment described in Step 2 is as follows: Disperse the Ti3C2F x nanosheets in 0.1 - 1 M NaOH or KOH and stir for 1 hour, then place them in a Teflon-lined autoclave and carry out hydrothermal reaction at 120 - 180 °C for 4 - 12 hours. After the reaction, wash until neutral and dry to complete the hydrothermal treatment.

10. Application of a composite hydrogen evolution catalyst with MoS2 in-situ grown on ultrathin nanosheets prepared by the method according to claim 1, characterized in that, x This application is about using a composite hydrogen evolution catalyst with MoS2 grown in-situ on Ti3C2T x ultrathin nanosheets for hydrogen production by electrolyzing water. ​

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