Preparation and application of a superhydrophilic bifunctional electrocatalyst with built-in electric field

Abstract

The present invention discloses the preparation and application of a super-hydrophilic bifunctional electrocatalyst with a built-in electric field, which relates to the technical field of energy-saving hydrogen production electrocatalyst preparation, including: pretreatment of a conductive current collector substrate, hydrothermal synthesis of a NiMoO4 precursor, hydrothermal synthesis of NiTe2 / MoTe2, and energy-saving hydrogen production application of SOR-assisted water electrolysis. The present invention utilizes a built-in electric field strategy to effectively enhance the electron transfer path of the catalyst by in-situ self-growing active substances on a conductive current collector substrate, promotes sufficient infiltration of active sites with electrolytes, and improves the effective utilization of electrocatalytic reaction sites, thereby realizing the application of telluride in the sulfur ion oxidation reaction to assist water electrolysis for energy-saving hydrogen production. Compared with traditional full water decomposition hydrogen production technology, it saves energy consumption, not only promotes the development of green chemical technology, but also provides important support for energy transformation and clean energy production, demonstrating its great potential in meeting the policies of the times and promoting sustainable development goals.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and particularly relates to the preparation and application of a superhydrophilic bifunctional electrocatalyst with an internal electric field. Background Art

[0002] The organic combination of small molecule electrochemical oxidation reaction and electrolytic water hydrogen production technology has opened up a forward-looking and feasible path for the energy-saving development of renewable energy. Nowadays, a large amount of sulfide pollutant resources are蕴藏 in domestic sewage and industrial wastewater, with an annual discharge exceeding 60 million tons. This abundant sulfide resource provides an ideal raw material basis for large-scale hydrogen production. The electrochemical sulfide oxidation reaction (SOR) technology can not only efficiently purify these environmental pollutants, but also convert them into products with high added value, thus realizing the efficient utilization of waste resources and the simplification of the treatment process. More importantly, the sulfur ion oxidation reaction is a two-electron reaction, which has a lower oxidation-reduction potential than the oxygen evolution reaction (OER) in traditional electrolytic water hydrogen production, giving it significant advantages and great potential in the coupled technology of electrochemical desulfurization and energy-saving hydrogen production, and injecting new impetus into the sustainable development of the energy industry.

[0003] In past research, researchers have always been committed to exploring and developing efficient and stable non-noble metal catalysts in order to achieve breakthroughs in the field of catalysis. Among them, due to telluride having a lower electronegativity (Te < Se < S < O) and better band alignment, it exhibits the highest electronic conductivity (up to 1×10 at 300K) -5S / m) and stronger metallic properties, resulting in excellent electron transfer rates in electrocatalytic reactions. However, the electrocatalytic performance of single-phase TMT is unsatisfactory, and modification and optimization are needed to enhance its electrocatalytic activity. For example, Zhang et al. prepared cobalt-based tellurides with good electronic conductivity by co-doping with Ni and Fe. Electronic modification of TMT through doping enhanced its electrochemical oxidation activity, but its hydrogen evolution activity still needs to be further improved to achieve efficient hydrogen production (DOI: 10.1039 / d4ta01929f). Wu et al. designed one-dimensional NiFeCo-OH / NiTe nanorod arrays with amorphous / crystalline interfaces through defect engineering. Defect design was used to enhance electrocatalytic activity, but traditional electrochemical synthesis results in easy accumulation of catalyst particles and uneven deposition, making it difficult to maximize the exposure of active sites (DOI: 10.1039 / d4ta00772g). Kim et al. designed a MOF structure to assist in the synthesis of porous CoTe2 / MnTe2, enhancing the material's inherent electrochemical surface area and charge transfer, thereby improving electrocatalytic activity. However, this method requires the catalyst material to have excellent affinity for the electrolyte to effectively utilize the active sites (DOI: 10.1039 / d4ta01929f). Therefore, the design and synthesis of existing telluride catalysts have the following problems:

[0004] (1) There is relatively little research on tellurides. The electrocatalytic activity of individual tellurides is insufficient, and the high overpotential in sulfur oxidation and hydrogen evolution reactions makes it difficult to achieve energy-saving desulfurization and hydrogen production.

[0005] (2) In the synthesis of traditional tellurides, there are problems of catalyst particle clustering and the electrocatalytic active sites being covered, making it difficult to maximize the utilization of the electrochemically active surface area;

[0006] (3) In electrochemical reactions involving gas participation, it is difficult for the catalyst to achieve rapid contact with the electrolyte, and the gas products are difficult to diffuse quickly, resulting in low utilization of active sites on the catalyst surface. Summary of the Invention

[0007] To solve the above technical problems, the present invention uses a rough three-dimensional porous nickel foam NF as a conductive current collector substrate to effectively increase the electrocatalytic active surface area of ​​the catalyst. NiTe2 and MoTe2 are tightly coupled by a hydrothermal method, and a built-in electric field between the two phase components is constructed through the redistribution of spontaneous electron flow at the heterogeneous interface. By using the built-in electric field strategy to increase the charge density of the active sites, a super-hydrophilic NiTe2 / MoTe2 bifunctional catalyst with excellent conductivity, low reaction overpotential, and catalytic activity is finally prepared. The technical solution is as follows:

[0008] A method for preparing a super-hydrophilic bifunctional electrocatalyst with a built-in electric field comprises the following steps:

[0009] (1) Pretreatment of the conductive current collector substrate: ultrasonically etch the conductive current collector substrate in dilute hydrochloric acid, rinse with deionized water and anhydrous ethanol, and vacuum dry for later use;

[0010] (2) Hydrothermal synthesis of NiMoO4 precursor: nickel salt and molybdenum salt are uniformly dispersed in a solvent, added to a pretreated conductive current collector substrate, and subjected to a hydrothermal reaction to obtain a NiMoO4 precursor;

[0011] (3) Hydrothermal synthesis of NiTe2 / MoTe2: The reducing agent and tellurium source are uniformly dispersed in the solvent, NiMoO4 precursor is added, and a hydrothermal tellurization reaction is carried out to obtain NiTe2 / MoTe2.

[0012] As a preferred embodiment of the preparation method of the present invention, the conductive current collector substrate in step (1) is one or more of foamed nickel, foamed iron, foamed copper, and foamed molybdenum.

[0013] As a preferred embodiment of the preparation method of the present invention, the concentration of the dilute hydrochloric acid in step (1) is 2-5 M, and the etching time is 20-40 min.

[0014] In an exemplary embodiment of the present invention, the nickel foam is cut into pieces of 1.5×1.0 cm in size and ultrasonically etched in 3 M dilute hydrochloric acid for 30 minutes to remove the surface oxide layer. After the ultrasonic etching is completed, the nickel foam is washed multiple times with deionized water and anhydrous ethanol to ensure that the residual dilute hydrochloric acid is completely removed. Finally, the treated nickel foam is dried under vacuum conditions at 60°C to completely remove moisture and prevent oxidation, preparing for subsequent use.

[0015] As a preferred embodiment of the preparation method of the present invention, the nickel salt in step (2) is one or more of nickel nitrate, nickel chloride, and nickel sulfate, preferably nickel nitrate; the molybdenum salt is one or more of ammonium molybdate and sodium molybdate, preferably ammonium molybdate; and the solvent is one or more of N,N-dimethylformamide (DMF), ethanol, and deionized water, preferably a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 1:5.

[0016] As a preferred embodiment of the preparation method of the present invention, the molar ratio of the nickel salt to the molybdenum salt in step (2) is 1:0.5-2; preferably, the molar ratio of the nickel salt to the molybdenum salt is 1:1-2; more preferably, the molar ratio of the nickel salt to the molybdenum salt is 1:1.

[0017] As a preferred embodiment of the preparation method of the present invention, the hydrothermal reaction in step (2) is carried out in a 70 mL hydrothermal kettle at a hydrothermal temperature of 120-180°C for a hydrothermal time of 4-7 h. Preferably, the hydrothermal temperature is 150°C for a hydrothermal time of 6 h.

[0018] As a preferred embodiment of the preparation method of the present invention, the reducing agent in step (3) is one or more of citric acid, hydrazine hydrate, ammonia water, and NaBH4, preferably NaBH4; the tellurium source is one or more of tellurium dioxide, sodium tellurite, and tellurium powder, preferably tellurium powder.

[0019] As a preferred embodiment of the preparation method of the present invention, the molar mass ratio of the tellurium source to the reducing agent in step (3) is 0.6-0.9:28-33.

[0020] As a preferred embodiment of the preparation method of the present invention, the hydrothermal reaction in step (3) is carried out in a 70 mL hydrothermal kettle, the hydrothermal temperature is 120-180°C, and the hydrothermal time is 10-15 h; preferably, the hydrothermal reaction temperature is 160°C and the reaction time is 12 h.

[0021] Another object of the present invention is to overcome the deficiencies in the prior art and provide a super-hydrophilic bifunctional electrocatalyst with a built-in electric field prepared by the above-mentioned preparation method. The composite material has super-hydrophilic properties and a built-in electric field effect exists between the two heterogeneous components.

[0022] Another object of the present invention is to overcome the deficiencies in the prior art and provide the application of the above-mentioned super-hydrophilic bifunctional electrocatalyst with a built-in electric field in electrocatalytic sulfur ion oxidation coupled with water electrolysis to produce hydrogen.

[0023] (1) Unique built-in electric field strategy: Through electron rearrangement at the heterojunction interface, interface polarization is induced and a potential difference is generated. Electrons move until the Fermi level is aligned, forming electron-rich and electron-deficient regions, and establishing a built-in electric field. This built-in electric field can increase the charge density of active sites, improve intrinsic activity, increase the reaction concentration at the interface, and thus improve the reaction rate and overall reaction activity.

[0024] (2) Super-hydrophilic properties: NiTe2 / MoTe2 loaded on the conductive current collector substrate has super-strong hydrophilicity. On the one hand, its hydrophilicity facilitates rapid contact with the electrolyte. On the other hand, its surface affinity for liquid water inherently reduces the material's adhesion to bubbles, thereby allowing for the rapid release of gas products. The two synergistically promote mass transfer and electron transfer in the electrocatalytic reaction, thereby enhancing its electrocatalytic activity.

[0025] (3) In-situ self-growth strategy based on porous conductive current collector nickel foam: The robust anchoring and dispersion of NiTe2 / MoTe2 on nickel foam not only enhances the effective load and the number of active sites, but also circumvents polymer binders and conductive additives. In addition, the strong adhesion and high integration between NiTe2 / MoTe2 and the conductive substrate nickel foam ensure stability under sustained high current density electrocatalysis.

[0026] (4) NiTe2 / MoTe2, as a bifunctional electrocatalyst, has realized the application of telluride in the sulfur ion oxidation reaction to assist water electrolysis to produce energy-efficient hydrogen, saving nearly 63% of energy consumption compared to traditional full water splitting hydrogen production technology. This application not only promotes the development of green chemical technology, but also provides important support for energy transition and clean energy production, demonstrating its great potential in meeting contemporary policies and promoting sustainable development goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0028] Figure 1 is the XRD pattern of NiTe2 / MoTe2 in the embodiment of the present invention;

[0029] Figure 2 This is a picture of the water contact angle of NiTe2 / MoTe2 in an embodiment of the present invention;

[0030] Figure 3 The LSV curves of the electrochemical SOR and HER of the materials prepared in the embodiments of the present invention are shown in FIG. 1 , wherein (a) is the LSV curve of SOR and (b) is the LSV curve of HER;

[0031] Figure 4 The electrochemically active surface area ECSA diagram in the embodiment of the present invention;

[0032] Figure 5 Impedance diagrams of NiTe2 / MoTe2 and NiMoO4 in the embodiments of the present invention;

[0033] Figure 6 LSV curves of the SOR / / HER and OER / / HER coupled systems based on NiTe2 / MoTe2 electrodes. DETAILED DESCRIPTION

[0034] In order to more clearly demonstrate the purpose, features and advantages of the present invention, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0035] In the following description, a large number of specific details are provided to help fully understand the present invention. However, the present invention can also be implemented in other ways different from those described here. Those skilled in the art can make similar generalizations without violating the core concept of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Furthermore, the phrases "one embodiment" or "embodiment" herein refer to a specific feature, structure, or characteristic included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0037] The nickel foam in the embodiment of the present invention was purchased from Hefei Kejing Material Technology Co., Ltd., with specifications of: length 1000 mm * width 300 mm * thickness 1.6 mm, 3N surface density 350 g / m 2 ; Other raw materials are common commercial products.

[0038] The present invention uses an X-ray diffractometer and a Chenhua 660e electrochemical workstation to characterize and analyze the comparative material prepared in this example.

[0039] In the embodiment of the present invention, the SOR and HER performance tests under the three-electrode system are as follows:

[0040] (1) Electrochemical performance test of SOR: The test was carried out on a CHI 660E electrochemical workstation using a traditional three-electrode system. The synthesized catalyst was directly used as the working electrode, the platinum electrode was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode. The electrolyte was 1.00 M NaOH + 1.00 M Na2S. The electrochemical performance of SOR was tested at a rate of 5 mV·s in the range of -0.2 to -1.0 V (relative to Ag / AgCl). -1 The linear sweep voltammetry (LSV) curve was tested at a scan rate of 100 nm, and the final LSV curve was obtained by 90% impedance compensation.

[0041] (2) HER electrochemical performance test: The test was also carried out on a CHI 660E electrochemical workstation using a traditional three-electrode system. The synthesized catalyst was directly used as the working electrode, the platinum electrode was used as the counter electrode, and Ag / AgCl was used as the reference electrode. The electrolyte was 1.00 M NaOH. The HER electrochemical performance was tested at 5 mV·s in the range of 1.0 ~ 1.6 V (relative to Ag / AgCl). -1The LSV curve was tested at a scan rate of 100 nm and the final LSV curve was obtained through 90% impedance compensation.

[0042] In the embodiment of the present invention, the electrochemically active surface area (ECSA) of the catalyst is tested as follows:

[0043] The test was carried out on a CHI 660E electrochemical workstation using a traditional three-electrode system. The synthesized catalyst was directly used as the working electrode, the platinum electrode was used as the counter electrode, and Ag / AgCl was used as the reference electrode. The electrolytes were 1.00 M NaOH and 1.00 M NaOH + 1.00 M Na2S. At different scan rates (20 mV·s) in the non-Faraday region, the -1 , 40 mV·s -1 、60 mV·s -1 、80 mV·s -1 , 100 mV·s -1 ) to test the CV curve. dl ) is closely related to ECSA, which can be obtained by plotting the charge current difference ∆j = (j a -j c ) to estimate, where the linear slope fit C dl is twice the scanning rate. Therefore, C dl It can be approximately expressed by the following formula.

[0044] j=S×C dl ×ν

[0045] Where j is half of the double layer capacitance current density (mA·cm -2 ), S is the measured area of ​​the electrode (S = 1.0 × 1.0 cm 2 ), ν is the scan rate (mV·S -1 ).

[0046] In the embodiment of the present invention, the performance test of the two-electrode SOR / / HER and OER / / HER coupled systems is as follows:

[0047] (1) Assembly and testing of SOR / / HER: The test was carried out on a CHI 660E electrochemical workstation. The prepared catalyst served as both the cathode and anode working electrodes. The cathode electrolyte was 1.00 M NaOH, and the anode electrolyte was 1.00 M NaOH + 1.00 M Na2S. The SOR / / HER was tested at 5 mV·s in the range of 0 ~ 0.8 V (vs. Ag / AgCl). -1 The linear sweep voltammetry (LSV) curve was tested at a scan rate of 100 nm, and the final LSV curve was obtained by 90% impedance compensation.

[0048] (2) Assembly and testing of OER / / HER: The tests were carried out on a CHI 660E electrochemical workstation, with the prepared catalyst as the working electrode, a platinum electrode as the counter electrode, and 1.00 M NaOH as the cathode and anode electrolytes. Linear sweep voltammetry (LSV) curves were measured in the range of 1.2 to 2.0 V (relative to Ag / AgCl) at a scan rate of 5 mV·s-1, and the final LSV curve was obtained by 90% impedance compensation. Example 1

[0049] NiTe2 / MoTe2 was synthesized as follows:

[0050] (1) Pretreatment of the conductive current collector substrate: First, the nickel foam was cut into a size of 1.5 × 1.0 cm;

[0051] Then, the cut nickel foam was placed in 3 M dilute hydrochloric acid and ultrasonically etched for 30 minutes to remove the surface oxide layer;

[0052] After ultrasonic etching, the nickel foam was washed several times with deionized water and anhydrous ethanol to ensure that the residual dilute hydrochloric acid was completely removed;

[0053] Finally, the treated nickel foam is dried under vacuum conditions at 60°C to completely remove moisture and prevent oxidation, preparing it for subsequent use.

[0054] (2) Hydrothermal synthesis of NiMoO4 precursor:

[0055] Accurately weigh 0.3 mmol nickel nitrate and 0.3 mmol ammonium molybdate tetrahydrate, evenly disperse them in 15 mL deionized water, stir for 30 min, then add 3 mL anhydrous ethanol and continue stirring for 15 min to obtain a uniform mixed solution.

[0056] The conductive substrate pretreated in step (1) and the mixed solution were transferred to a reactor for hydrothermal reaction at a temperature of 150°C and a hydrothermal time of 6 h.

[0057] After the reaction was cooled naturally to room temperature, the sample was carefully taken out and repeatedly rinsed with deionized water and anhydrous ethanol, respectively. The rinsed sample was placed in a vacuum oven at 60°C for drying to obtain a NiMoO4 precursor.

[0058] (3) Hydrothermal synthesis of NiTe2 / MoTe2:

[0059] Accurately weigh 31 mmol of NaBH4 and add it to 18 mL of deionized water. Stir for 15 min until dissolved. Then accurately weigh 0.8 mmol of tellurium powder and add it to the mixed solution. Stir for 3 h to obtain a purple uniform solution.

[0060] The precursor obtained in step (2) and the mixed solution were transferred to a reactor for hydrothermal reaction at a temperature of 160°C and a reaction time of 12 h.

[0061] After the reaction was cooled naturally to room temperature, the sample was carefully taken out and repeatedly rinsed with deionized water and anhydrous ethanol, respectively. The rinsed sample was placed in a vacuum oven at 60°C for drying to obtain NiTe2 / MoTe2.

[0062] Depend on Figure 1 It can be seen that the samples NiTe2 / MoTe2, NiTe2, MoTe2 and NiMoO4 correspond well to the standard cards, indicating that the samples of the embodiment were successfully synthesized. Figure 2 The water contact angle indicates that the NiTe2 / MoTe2 synthesized in the example has superhydrophilic properties. Based on the energy balance principle of the solid-liquid-gas three-phase interface, the surface affinity for liquid water will inherently reduce the material's adhesion to bubbles. Therefore, the superhydrophilic NiTe2 / MoTe2 catalyst not only facilitates rapid contact with the electrolyte in the electrochemical reaction, but also facilitates the rapid release of gas products, which is crucial for catalytic reactions involving gas generation. Example 2

[0063] NiTe2 was synthesized as follows:

[0064] (1) Pretreatment of the conductive current collector substrate: same as in Example 1.

[0065] (2) Hydrothermal synthesis of NiO precursor:

[0066] Accurately weigh 0.3 mmol of nickel nitrate and evenly disperse it in 15 mL of deionized water. After stirring for 30 min, add 3 mL of anhydrous ethanol and continue stirring for 15 min to obtain a uniform mixed solution.

[0067] The conductive substrate pretreated in step (1) and the mixed solution were transferred to a reactor for hydrothermal reaction at a temperature of 150°C and a hydrothermal time of 6 h.

[0068] After the reaction was cooled naturally to room temperature, the sample was carefully taken out and repeatedly rinsed with deionized water and anhydrous ethanol, respectively. The rinsed sample was placed in a vacuum oven at 60° C. and dried to obtain a NiO precursor.

[0069] (3) Hydrothermal synthesis of NiTe2:

[0070] Accurately weigh 31 mmol of NaBH4 and add it to 18 mL of deionized water. Stir for 15 min until dissolved. Then accurately weigh 0.8 mmol of tellurium powder and add it to the mixed solution. Stir for 3 h to obtain a purple uniform solution.

[0071] The precursor obtained in step (2) and the mixed solution were transferred to a reactor for hydrothermal reaction at a temperature of 160°C and a reaction time of 12 h.

[0072] After the reaction was cooled naturally to room temperature, the sample was carefully taken out and repeatedly rinsed with deionized water and anhydrous ethanol, respectively. The rinsed sample was placed in a vacuum oven at 60°C for drying to obtain NiTe2. Example 3

[0073] MoTe2 was synthesized as follows:

[0074] (1) Pretreatment of the conductive current collector substrate: same as in Example 1.

[0075] (2) Hydrothermal synthesis of MoO3 precursor:

[0076] Accurately weigh 0.3 mmol of ammonium molybdate tetrahydrate and evenly disperse it in 15 mL of deionized water. After stirring for 30 min, add 3 mL of anhydrous ethanol and continue stirring for 15 min to obtain a uniform mixed solution.

[0077] The conductive substrate pretreated in step (1) and the mixed solution were transferred to a reactor for hydrothermal reaction at a temperature of 150°C and a hydrothermal time of 6 h.

[0078] After the reaction was cooled naturally to room temperature, the sample was carefully taken out and repeatedly rinsed with deionized water and anhydrous ethanol, respectively. The rinsed sample was placed in a vacuum oven at 60°C for drying to obtain a MoO3 precursor.

[0079] (3) Hydrothermal synthesis of MoTe2:

[0080] Accurately weigh 31 mmol of NaBH4 and add it to 18 mL of deionized water. Stir for 15 min until dissolved. Then accurately weigh 0.8 mmol of tellurium powder and add it to the mixed solution. Stir for 3 h to obtain a purple uniform solution.

[0081] The precursor obtained in step (2) and the mixed solution were transferred to a reactor for hydrothermal reaction at a temperature of 160°C and a reaction time of 12 h.

[0082] After the reaction was cooled naturally to room temperature, the sample was carefully taken out and repeatedly rinsed with deionized water and anhydrous ethanol, respectively. The rinsed sample was placed in a vacuum oven at 60°C for drying to obtain MoTe2. Example 4

[0083] Synthesize NiMoO4 according to the following steps:

[0084] (1) Pretreatment of the conductive current collector substrate: same as in Example 1.

[0085] (2) Hydrothermal synthesis of NiMoO4:

[0086] Accurately weigh 0.3 mmol nickel nitrate and 0.3 mmol ammonium molybdate tetrahydrate, evenly disperse them in 15 mL deionized water, stir for 30 min, then add 3 mL anhydrous ethanol and continue stirring for 15 min to obtain a uniform mixed solution.

[0087] The conductive substrate pretreated in step (1) and the mixed solution were transferred to a reactor for hydrothermal reaction at a temperature of 150°C and a hydrothermal time of 6 h.

[0088] After the reaction was cooled naturally to room temperature, the sample was carefully taken out and repeatedly rinsed with deionized water and anhydrous ethanol, respectively. The rinsed sample was placed in a vacuum oven at 60°C for drying to obtain a NiMoO4 precursor. Example 5

[0089] The following steps were used to synthesize NiTe2 / MoTe2-2 / 3 with a Ni:Mo ratio of 2:3:

[0090] (1) Pretreatment of the conductive current collector substrate: same as in Example 1.

[0091] (2) Hydrothermal synthesis of NiMoO4-2 / 3 precursor: The difference from Example 1 is that the amount of ammonium molybdate tetrahydrate used is 0.45 mmol, and the preparation method is the same as Example 1.

[0092] (3) Hydrothermal synthesis of NiTe2 / MoTe2-2 / 3: Referring to the preparation method of Example 1, NiTe2 / MoTe2-2 / 3 was obtained. Example 6

[0093] The following steps were used to synthesize NiTe2 / MoTe2-1 / 2 with a Ni:Mo ratio of 1:2:

[0094] (1) Pretreatment of the conductive current collector substrate: same as in Example 1.

[0095] (2) Hydrothermal synthesis of NiMoO4-1 / 2 precursor: The difference from Example 1 is that the amount of ammonium molybdate tetrahydrate used is 0.6 mmol, and the preparation method is the same as Example 1.

[0096] (3) Hydrothermal synthesis of NiTe2 / MoTe2-1 / 2: Referring to the preparation method of Example 1, NiTe2 / MoTe2-1 / 2 was obtained. Example 7

[0097] The following steps were used to synthesize NiTe2 / MoTe2-2 / 1 with a Ni:Mo ratio of 2:1:

[0098] (1) Pretreatment of the conductive current collector substrate: same as in Example 1.

[0099] (2) Hydrothermal synthesis of NiMoO4-2 / 1 precursor: The difference from Example 1 is that the amount of ammonium molybdate tetrahydrate used is 0.15 mmol, and the preparation method is the same as Example 1.

[0100] (3) Hydrothermal synthesis of NiTe2 / MoTe2-2 / 1: Referring to the preparation method of Example 1, NiTe2 / MoTe2-2 / 1 was obtained.

[0101] Evaluation of electrocatalytic performance of three-electrode system:

[0102] The LSV curves of the electrochemical SOR and HER of NiTe2 / MoTe2 and the examples are shown in Figure 3 .Depend on Figure 3 It can be seen that the electrocatalytic activity of NiTe2 / MoTe2 is significantly better than that of NiTe2 and MoTe2, and only an overpotential of 0.32 V and 0.15 V are required to reach 100 mA cm in SOR and HER, respectively. -2 This is attributed to the built-in electric field strategy inducing electron localization around the heterogeneous interface, adjusting the electronic structure of the active center, and significantly reducing the reaction energy barrier of the key steps of the electrochemical reaction, thereby effectively improving the electrocatalytic activity of NiTe2 / MoTe2.

[0103] The electrocatalytic SOR and HER performance of the examples were evaluated using a 100 mA·cm -2 The overpotential at a current density of 100 nm was used as a measure of catalytic activity. The specific results are shown in Table 1.

[0104] Table 1

[0105]

[0106] As shown in Table 1, the HER and SOR performance of samples with different Ni:Mo ratios is unsatisfactory. This is because different Ni:Mo ratios have different effects on the construction of the built-in electric field, which in turn has different effects on electron rearrangement at the heterojunction interface, resulting in poor electron transfer rate and electrochemical activity during the electrocatalytic reaction. As shown in Table 1, rationally controlling the ratio of transition metal sources can optimize the electrostatic field and electron transfer at the heterojunction interface of the sample, thereby further improving its responsiveness to the electrochemical reaction and optimizing its electrocatalytic performance.

[0107] Exploration of electrochemical intrinsic dynamics:

[0108] Since the electrochemical double layer capacitance (Cdl) is closely related to ECSA, the electrochemical active surface area is calculated by testing CV at different scan rates. Figure 4 It can be seen that NiTe2 / MoTe2 has the largest electrochemical active surface area (154.5 mF·cm -2 and 567.44 mF·cm -2 This is attributed to two factors. First, the three-dimensional porous conductive current collector substrate has more electron transfer pathways and a rougher surface, which effectively exposes active sites. Second, the construction of a built-in electric field effectively exposes the electrochemically active surface area through electron rearrangement and electron transfer.

[0109] like Figure 5 The impedance diagram of the equivalent circuit fitting shows that NiTe2 / MoTe2 has a smaller interfacial resistance, indicating that it has the best electrocatalytic kinetics. In summary, the good electrocatalytic activity of NiTe2 / MoTe2 is attributed to its good electrochemical intrinsic kinetics.

[0110] Evaluation of electrocatalytic performance of two-electrode system:

[0111] Depend on Figure 6 It can be seen that the SOR\\HER system is at 100 mA·cm -2 The overpotential at this current density is only 0.61 V, while that of the OER\\HER system is 1.67 V. The SOR\\HER system saves about 63% of energy consumption. It can be seen that the bifunctional NiTe2 / MoTe2 can be used as both the cathode and anode catalysts of the SOR\\HER system, indicating that the integrated overall reaction has great prospects in energy-saving H2 generation and environmentally friendly sulfur recovery with improved electron utilization efficiency.

[0112] In summary, in view of the long-standing problems of insufficient electrocatalytic activity of tellurides and easy clustering of catalyst particles, the present invention effectively improves the electrocatalytic activity of catalysts from the following two aspects: (1) Using three-dimensional porous nickel foam as a conductive substrate, on the one hand, it improves the mechanical strength of the independent electrode, and on the other hand, it significantly increases the specific surface area of ​​the catalyst. This enhancement in turn increases the availability of active sites, promotes charge transfer, and provides diffusion channels, thereby improving the catalytic activity of the resulting material; (2) Using a built-in electric field strategy, through the construction of heterogeneous structures, it promotes the rearrangement of electrons at the interface between different components, which is conducive to regulating the strip structure and limiting the intermediate activation barrier during the catalytic reaction; (3) By in-situ growing a catalytic material with super-hydrophilic material properties, it achieves rapid contact between the electrocatalytic active sites and the electrolyte, thereby promoting rapid mass transfer and electron transfer of the catalyst in the electrochemical reaction.

[0113] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for preparing a super-hydrophilic bifunctional electrocatalyst with a built-in electric field, characterized by: The structural unit of the super-hydrophilic bifunctional electrocatalyst with a built-in electric field includes a conductive current collector substrate, nickel telluride and molybdenum telluride in situ grown on the substrate layer; the preparation method includes the following steps: (1) Pretreatment of the conductive current collector substrate: ultrasonically etch the conductive current collector substrate in dilute hydrochloric acid, rinse with deionized water and anhydrous ethanol, and vacuum dry for later use; the conductive current collector substrate is one or more of foamed nickel, foamed iron, foamed copper, and foamed molybdenum; (2) Hydrothermal synthesis of NiMoO4 precursor: nickel salt and molybdenum salt are uniformly dispersed in a solvent, added to a pretreated conductive current collector substrate, and subjected to a hydrothermal reaction to obtain a NiMoO4 precursor; the nickel salt is one or more of nickel nitrate, nickel chloride, and nickel sulfate; the molybdenum salt is one or more of ammonium molybdate and sodium molybdate; the molar ratio of nickel salt to molybdenum salt is 1:0.5-2; the hydrothermal temperature of the hydrothermal reaction is 120-180°C, and the hydrothermal time is 4-7 h; (3) Hydrothermal synthesis of NiTe2 / MoTe2: The reducing agent and the tellurium source are uniformly dispersed in a solvent, and a NiMoO4 precursor is added to carry out a hydrothermal tellurization reaction to obtain NiTe2 / MoTe2; the tellurium source is one or more of tellurium dioxide, sodium tellurite, and tellurium powder; the temperature of the hydrothermal tellurization reaction is 120~180℃, and the time is 10~15 h.

2. The method for preparing the super-hydrophilic bifunctional electrocatalyst with a built-in electric field according to claim 1, wherein: In step (1), the concentration of dilute hydrochloric acid is 2-5 mol / L, and the etching time is 20-40 min.

3. The method for preparing the super-hydrophilic bifunctional electrocatalyst with a built-in electric field according to claim 1, wherein: In step (2), the solvent is one or more of DMF, ethanol, and deionized water.

4. The method for preparing a super-hydrophilic bifunctional electrocatalyst with a built-in electric field according to claim 1, wherein: In step (3), the reducing agent is one or more of citric acid, hydrazine hydrate, ammonia water, and NaBH4; wherein the molar mass ratio of the tellurium source to the reducing agent is 0.6-0.9:28-33 mmol.

5. A super-hydrophilic bifunctional electrocatalyst with a built-in electric field obtained by the method according to any one of claims 1 to 4.

6. Use of the super-hydrophilic bifunctional electrocatalyst with a built-in electric field as claimed in claim 5 in hydrogen production by water electrolysis.

7. The use according to claim 6, characterized in that: The application of the super-hydrophilic bifunctional electrocatalyst with a built-in electric field in electrocatalytic sulfur ion oxidation coupled with water electrolysis to produce hydrogen.

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