Selenide heterojunction catalyst for coupling hydrogen evolution, method and application of selenide heterojunction catalyst in electro-catalysis of 5-hydroxymethylfurfural

Abstract

The invention belongs to the technical field of functional material preparation and catalysis and transition metal review materials, and discloses a coupling hydrogen evolution selenide heterojunction catalyst, a method and application. During preparation, a cobalt source and a mixed solution of urea, foamed nickel and ammonium fluoride are subjected to hydrothermal synthesis in a reaction and cooled to the room temperature; the preparation method comprises the following steps: preparing a precursor Co (OH) 2 / NF, washing with ethanol and water, drying to obtain a precursor Co (OH) 2 / NF, adding selenium powder and strong base into a reaction kettle, heating and selenizing to obtain the high-density heterojunction catalyst NiSe-coated CoSe2 / NF, the obtained heterojunction material can be used for electro-catalysis of 5-hydroxymethylfurfural, the potential is 1.29 V when the current density is 10mAcm <-2 >, and the optimal conversion rate exceeds 98%. And the catalyst has excellent catalytic activity of electro-catalysis of oxidation of 5-hydroxymethylfurfural.

Description

Technical Field

[0001] The invention belongs to the technical fields of functional material preparation and catalysis, and transition metal complex material, and in particular to a selenide heterojunction catalyst coupled with hydrogen evolution, a method and an application in electrocatalysis of 5-hydroxymethylfurfural. Background Art

[0002] Nuclear wastewater treatment is one of the major environmental challenges in the world today. Traditional nuclear wastewater treatment methods include chemical precipitation, adsorption, ion exchange, etc. Although these methods can remove some radioactive isotopes and heavy metals, their treatment efficiency is limited and there is a risk of secondary pollution. In recent years, electrolysis of water technology has attracted much attention in the treatment of nuclear wastewater due to its high efficiency and environmental protection. Electrolysis of water technology uses the redox reaction on the electrode when an electric current passes through an electrolyte solution (such as water), thereby achieving the decomposition and transformation of substances in the solution. At present, the liquid phase enrichment technology of hydrogen (H) isotopes is mainly based on electrolysis and water distillation. Among them, the electrolysis method is a method of achieving isotope enrichment in an electrolytic cell by electrolyzing a liquid phase solution containing deuterium (D) (tritium). The first method for producing heavy water in industry is electrolysis. Its main principle is that the three isotopes of H, D, and T have differences in mobility and overvoltage in the solution. During the electrolysis process, the smaller hydrogen isotopes preferentially form gas and are released from the solution, while the larger hydrogen isotopes remain in the solution and are enriched. For example, Pan Jingshun of the China Institute of Atomic Energy designed a tritium electrolysis enrichment device with nickel as the anode and stainless steel as the cathode, and the tritium recovery rate reached about 65%. Xia Xiulong and others from the China Academy of Engineering Physics simulated the hydrogen-deuterium system and found that the molar fraction of semi-heavy water in the electrolytic cell increased from 2.88×10 -4 Increased to 8.35×10 -4 , achieving significant enrichment. In the electrolysis process, due to the large separation coefficient between the three isotopes, it has a good separation effect. However, since the electrolysis method consumes a lot of electricity, it is of great significance to develop an efficient electrode material to facilitate the application of this technology.

[0003] Platinum is a highly efficient electrocatalyst that can catalyze the evolution reactions of hydrogen (H2) and deuterium (D2). However, since deuterium has a slightly larger mass than hydrogen and its chemical reactivity is slightly lower than that of hydrogen, and hydrogen has a smaller mass than deuterium and diffuses faster, their reduction potentials are different. Normally, the evolution potential of hydrogen is more negative than that of deuterium, meaning that under the same conditions, hydrogen is generated preferentially. The generation of hydrogen is easier during electrolysis, which is related to the isotope effect. However, the current electrolysis method has high equipment requirements, complex equipment, high energy consumption, and high cost. High energy consumption has prevented the further commercialization of hydrogen production by electrolysis of heavy water. The key to reducing the energy consumption of the system for hydrogen production by electrolysis of water is to reduce the high overpotential of the anode oxygen evolution reaction (OER), because the four-electron reaction step at the anode requires a higher theoretical potential (1.23V) than the hydrogen evolution reaction at the cathode. Therefore, lowering the reaction energy barrier of the anode will effectively reduce the energy consumption of the entire water electrolysis and hydrogen evolution system. Currently, most research is still focused on the preparation and modification of reaction catalysts. Commercial catalysts iridium oxide and ruthenium oxide can barely meet the requirements of industrial water electrolysis, but their high prices further increase the cost of the electrolysis system.

[0004] Replacing the OER reaction by electro-oxidation of small organic molecules (urea, glycerol, 5-hydroxymethylfurfural (HMF), etc.) is becoming a research hotspot in academia. This method can not only reduce the high potential of the anode reaction but also produce additional products with economic value, which will help reduce the cost of the electrolysis system. The reaction conditions of electrocatalysis are mild and environmentally friendly; it has strong manipulability, can regulate the reaction rate, start and terminate the reaction at any time, and can achieve high selectivity; it does not require oxygen or external oxidants through electron transfer, which is in line with the development concept of green synthesis and "dual carbon". The HMF electro-oxidation product 2,5-furandicarboxylic acid (FDCA) has great commercial value. According to statistics, the global FDCA market size was approximately US$150 million in 2018, and it is expected that by 2025, the global FDCA market size will reach US$300 million, with a compound annual growth rate of 15.7% from 2019 to 2025. FDCA has a "rigid" planar structure and the versatility of dicarboxylic acid side chains. FDCA-derived amine compounds can be used as bactericides. FDCA can not only be used in the fields of medicine, pesticides and metal organic frameworks, but also is a building block for many polyesters and polyamides. What has attracted much attention is the biomass-based polymer - polyethylene furandicarboxylate (PEF). Studies have shown that PEF synthesized from FDCA as a monomer is superior to polyethylene terephthalate in many properties. PEF is not only non-reproductive toxic, but also has good oxygen, carbon dioxide, water barrier properties, as well as better thermal stability and mechanical properties. Therefore, the preparation of an electrocatalytic HMF catalyst with high catalytic activity coupled to the cathode hydrogen evolution reaction will not only reduce the cost of the entire electrolysis system, but also produce raw materials with added value products, which will have ideal application prospects. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a selenide heterojunction catalyst coupled with hydrogen evolution, a method and an application in the electrocatalysis of 5-hydroxymethylfurfural.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for preparing a selenide heterojunction catalyst coupled with hydrogen evolution comprises the following steps:

[0008] (1) adding a cobalt precursor, ammonium fluoride and urea into water and mixing them uniformly to obtain a clear mixed solution;

[0009] (2) transferring the mixed solution obtained in step (1) into a reaction kettle, adding pre-cleaned nickel foam, performing hydrothermal synthesis, cooling, washing, and vacuum drying to obtain Co(OH)2 / NF;

[0010] (3) After adding selenium powder, alkali and clean water and ultrasonically homogenizing, the Co(OH)2 / NF obtained in step (2) is placed in the above solution and placed in a hydrothermal kettle for selenization to obtain NiSe@CoSe2 / NF, which is a selenide heterojunction catalyst for coupled hydrogen evolution.

[0011] Furthermore, the ratio of cobalt precursor in step (1): ammonium fluoride: urea: water: nickel foam prefabricated and cleaned in step (2) is 0.5-5: 1-15: 2-18: 50-100: 0.4 in mmol: mmol: mmol: mL: g;

[0012] Alternatively, the temperature of the hydrothermal synthesis in step (2) is 100° C. to 150° C., and the time is 2 to 8 hours;

[0013] Alternatively, the temperature of selenization in step (3) is 100° C. to 200° C., and the time of selenization is 2 to 10 hours;

[0014] Alternatively, in step (3), the ratio of selenium powder: alkali: clean water is 5-10: 100-200: 50-100 in mmol: mmol: mL, and the molar ratio of cobalt precursor: selenium powder is 0.5-5: 5-10.

[0015] Furthermore, the cobalt precursor is an organic or inorganic compound containing cobalt, and the organic or inorganic compound containing cobalt includes cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt oxalate, and cobalt acetylacetonate;

[0016] Alternatively, the selenization temperature in step (3) is 180°C.

[0017] Furthermore, the specific steps are as follows:

[0018] (1) adding a cobalt precursor, ammonium fluoride and urea into water and mixing them uniformly to obtain a clear mixed solution;

[0019] (2) adding pre-cleaned nickel foam to the mixed solution obtained in step (1) to obtain an aqueous solution containing nickel foam;

[0020] The preparation method of the pre-cleaned nickel foam is as follows: first, the nickel foam is ultrasonically cleaned with 3 mol / L hydrochloric acid for 30 minutes, then ultrasonically cleaned with ethanol for 30 minutes, and then vacuum dried to obtain the nickel foam;

[0021] (3) The aqueous solution containing nickel foam obtained in step (2) was transferred to a stainless steel heating kettle lined with polytetrafluoroethylene, and hydrothermally synthesized at 120° C. for 2-8 h, and then washed with ethanol and deionized water, and vacuum dried to obtain the precursor Co(OH)2 / NF:

[0022] (4) After adding selenium powder, alkali and clean water and ultrasonically homogenizing, the Co(OH)2 / NF obtained in step (2) is placed in the above solution and placed in a hydrothermal kettle for selenization to obtain NiSe@CoSe2 / NF, which is a selenide heterojunction catalyst for coupled hydrogen evolution.

[0023] The nickel-cobalt-selenide heterojunction catalyst is prepared by the preparation method described above.

[0024] The application of the selenide heterojunction catalyst as described above in the electrocatalytic HMF coupled hydrogen evolution.

[0025] The heterojunction catalyst as described above is used in the electrocatalytic production of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural.

[0026] The method for electrocatalyzing 5-hydroxymethylfurfural to produce 2,5-furandicarboxylic acid using the nickel-cobalt-selenide heterojunction catalyst as described above comprises the following steps:

[0027] 1) Cut the prepared nickel-cobalt-selenide heterojunction catalyst into a size of 1 cm*1.5 cm, fix it with a platinum electrode clip, and use it as a working electrode;

[0028] 2) Tested under a three-electrode system, using a platinum sheet as the counter electrode, Hg / HgO as the reference electrode, an H-type cell as the electrolytic cell, 1Mol / L KOH as the electrolyte, and a proton exchange membrane between the two cells;

[0029] 3) Activating the working electrode by cyclic voltammetry until it is stable;

[0030] 4) HMF was added to perform a linear scan test and a test with different coulomb electron numbers, and the Faradaic efficiency of 2,5-furandicarboxylic acid was calculated.

[0031] Furthermore, the reaction conditions in step 2) are: the reactor temperature is room temperature, i.e., 25° C., the pressure is normal pressure, and the reaction time is 2-10 h.

[0032] Furthermore, the scanning range of the linear scanning voltammetry in step 4) is 1.0V-1.6V (relative to the reversible hydrogen electrode), the scanning speed is 10mV / s, and the potential constant range of different coulombs applied in step 4) is 1.4V-1.6V (relative to the reversible hydrogen electrode).

[0033] The advantages and positive effects achieved by the present invention are:

[0034] 1. The method of the present invention utilizes a one-step hydrothermal and one-step selenization method to obtain a selenide heterojunction catalyst with high density, and the selenide heterojunction catalyst is used to electrocatalyze 5-hydroxymethylfurfural to produce 2,5-furandicarboxylic acid. The present invention regulates the electronic structure of the active site by transferring electrons at the interface of the heterojunction, and improves the efficiency of the catalytic conversion by increasing the adsorption capacity of HMF. The HMF conversion rate exceeds 98%, and the Faradaic efficiency of 2,5-furandicarboxylic acid is as high as 97%.

[0035] 2. The present invention reduces the overall voltage of the water electrolysis system by coupling the hydrogen evolution reaction, and the anode potential reaches 10 and 50 mA cm -2 The potential required for the current density is only ≈1.29 and 1.36 V, respectively, which is significantly lower than other commercial catalysts. -2 The potential difference between it and OER reaches 270 mV.

[0036] 3. The present invention provides a simple and convenient method for preparing a selenide heterojunction catalyst. The method has a simple process, is easy to operate, and takes a short time. The method has high reactivity in electrocatalyzing HMF to produce 2,5-furandicarboxylic acid.

[0037] 4. Compared with traditional epitaxial heterojunction catalysts, the selenide heterojunction catalyst prepared by the present invention has more active sites, and the highly dispersed heterojunction catalyst increases the specific surface area of ​​the catalyst and reduces the particle size, which enables the catalyst to expose more active sites, thereby improving the conversion rate and selectivity of the reaction.

[0038] 5. The present invention is to hydrothermally synthesize a cobalt source and a mixed solution of urea, nickel foam and ammonium fluoride in a reaction, cool it to room temperature, wash it with ethanol and water, and dry it to obtain a precursor Co(OH)2 / NF. Then, selenium powder and a strong base are added to the reactor to heat and selenize to obtain a high-density heterojunction catalyst NiSe@CoSe2 / NF. The obtained heterojunction material can be used for electrocatalysis of 5-hydroxymethylfurfural at a current density of 10 mA cm -2The potential is 1.29 V, and the optimal conversion rate exceeds 98%, which has excellent catalytic activity for electrocatalytic 5-hydroxymethylfurfural oxidation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is the XRD pattern of the NiSe@CoSe2 / NF catalyst in Example 1 of the present invention;

[0040] Figure 2 This is a SEM image of the NiSe@CoSe2 / NF catalyst in Example 1 of the present invention;

[0041] Figure 3 TEM image of the NiSe@CoSe2 / NF catalyst in Example 1 of the present invention;

[0042] Figure 4 is the XRD pattern of the NiSe@CoSe2 / NF catalyst in Example 2 of the present invention;

[0043] Figure 5 This is a SEM image of the NiSe@CoSe2 / NF catalyst in Example 2 of the present invention;

[0044] Figure 6 TEM image of the NiSe@CoSe2 / NF catalyst in Example 2 of the present invention;

[0045] Figure 7 This is the XRD pattern of the NiSe@CoSe2 / NF catalyst in Example 3 of the present invention;

[0046] Figure 8 This is a SEM image of the NiSe@CoSe2 / NF catalyst in Example 3 of the present invention;

[0047] Fig. 9 This is the TEM image of the NiSe@CoSe2 / NF catalyst in Example 3 of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with the embodiments. The following embodiments are descriptive rather than restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0049] The various experimental operations involved in the specific embodiments are all routine techniques in the art. For parts not specially annotated in this document, ordinary technicians in the art can implement them by referring to various commonly used reference books, scientific and technological literature or related instructions, manuals, etc. before the filing date of this invention.

[0050] A method for preparing a heterojunction of selenide, the method comprising the following steps: (1) stirring a cobalt source, urea and ammonium fluoride to obtain a clear aqueous solution, and adding clean foamed nickel washed with hydrochloric acid and anhydrous ethanol.

[0051] (2) transferring the system obtained in step (1) into a reaction kettle, performing hydrothermal synthesis, cooling, washing, centrifuging, and drying to obtain a precursor Co(OH)2 of cobalt hydroxide supported on nickel foam;

[0052] (3) transferring the precursor Co(OH)2 obtained in step (3) into a polytetrafluoroethylene liner, adding sodium hydroxide and selenium powder, and heating and keeping warm in an oven to form a high-density heterojunction catalyst;

[0053] Preferably, the specific steps are as follows:

[0054] First, using a typical hydrothermal method, cobalt ligand, ammonium fluoride, and urea were weighed and added into a beaker containing 60 mL of ultrapure water and stirred for 15 minutes.

[0055] The mixed solution of step (2) and nickel foam (3 x 4 cm) were transferred to an autoclave containing 100 mL of polytetrafluoroethylene lining, heated at 120°C to 180°C in an oven for 6 h, then cooled to room temperature and dried in a vacuum oven (60°C) overnight to obtain a cobalt hydroxide precursor supported on nickel foam.

[0056] 5 mmol of selenium powder and 130 mmol of NaOH were added to a polytetrafluoroethylene liner containing 60 mL of aqueous solution in sequence, and the mixture was ultrasonicated for 5 minutes. Then, the Co(OH)2 / NF in step (2) was added. The polytetrafluoroethylene liner was then placed in an autoclave and kept at 180°C in an oven for 4 hours. The polytetrafluoroethylene liner was then cooled to room temperature and washed several times with deionized water and anhydrous ethanol. The catalyst was dried in a vacuum oven to obtain a selenide heterojunction catalyst.

[0057] Preferably, the molar ratio of the cobalt ligand to the urea is 1:3 to 3:5. The stirring speed is 600-1000 revolutions per minute.

[0058] Preferably, the nickel foam needs to be treated with hydrochloric acid to remove oxides on the surface, and with ethanol ultrasound to remove organic matter on the surface before use.

[0059] Preferably, the selenization time is 2-10 hours.

[0060] Preferably, the cobalt source is a cobalt-containing compound, including one of cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt acetylacetonate, and cobalt acetate.

[0061] The preparation method described above obtains a highly dense selenide heterojunction catalyst.

[0062] The application of the selenide heterojunction catalyst as described above in the electrocatalytic HMF coupled hydrogen evolution.

[0063] The method of using the selenide heterojunction catalyst as described above in electrocatalytic HMF coupled hydrogen evolution comprises the following steps:

[0064] A suitable amount of the selenide heterojunction catalyst loaded on nickel foam is cut and prepared and used as a working electrode, a saturated mercury electrode is used as a reference electrode, and a platinum sheet is used as a counter electrode.

[0065] The three-electrode system test was adopted, the electrolytic cells were separated by proton exchange membranes, an appropriate amount of alkaline electrolyte was weighed, and the standard three-electrode system test was adopted.

[0066] Preferably, the concentration of the alkali solution is 0.8 mol / L to 1 mol / L.

[0067] Weigh an appropriate amount of HMF and add it to the electrolyte, and stir with a porcelain stirrer to increase mass transfer.

[0068] Preferably, the test temperature is 20-35°C and the test pressure is normal pressure.

[0069] The conversion rate and Faraday efficiency of HMF were tested by applying different potentials, and the relationship between the HMF conversion rate and the Coulomb number was tested by applying different electron coulomb numbers. The test time was within 2-10 hours.

[0070] Specifically, the relevant preparation and detection are as follows:

[0071] Preferably, the nickel foam described below needs to be cleaned with diluted hydrochloric acid to remove surface oxides, and ultrasonically cleaned with ethanol to remove surface organic matter before use. Specifically, the preparation method of the pre-cleaned nickel foam is: first ultrasonically clean the nickel foam with 3 mol / L hydrochloric acid for 30 minutes, then ultrasonically clean it with ethanol for 30 minutes, and vacuum dry it.

[0072] Example 1

[0073] (I) Preparation method

[0074] A method for preparing a selenide heterojunction catalyst coupled with hydrogen evolution, the specific steps are as follows:

[0075] (1) Using a typical hydrothermal method, Co(NO3)29H2O (1 mmol), NH4F (3 mmol), and CH4N2O (6 mmol) were added into a beaker containing 60 mL of ultrapure water and stirred for 15 minutes.

[0076] (2) The mixed solution of step (1) and nickel foam (3 x 4 cm, thickness 1.5 mm, mass 0.4 g) were transferred to an autoclave containing 100 mL of polytetrafluoroethylene lining, heated to 120° C. in an oven for 6 h, then cooled to room temperature, washed with ethanol and deionized water, and dried in a vacuum oven (60° C.) overnight to obtain a cobalt hydroxide precursor supported on nickel foam, namely Co(OH)2 / NF.

[0077] (3) 5 mmol of selenium powder and 130 mmol of NaOH were added to a polytetrafluoroethylene liner containing 60 mL of aqueous solution in sequence, and then ultrasonicated for 5 minutes. Then, the Co(OH)2 / NF in step (2) was added. The polytetrafluoroethylene liner was then placed in an autoclave and selenized in an oven at 180°C for 4 hours. The polytetrafluoroethylene liner was then cooled to room temperature, washed several times with deionized water and anhydrous ethanol, and dried in a vacuum oven to obtain a selenide heterojunction catalyst for coupled hydrogen evolution. The obtained catalyst was denoted as O-1.

[0078] (II) Related tests are as follows

[0079] Through the X-ray diffraction (XRD) pattern ( Figure 1 ) confirmed the coexistence of CoSe2 and NiSe phases. Specifically, the diffraction peaks at 29.06°, 34.06°, 36.04°, 38.69°, 48.04°, 50.03°, 55.11° correspond to the (101), (021), (220), (211), (410), (401), (330) crystal planes of the hexagonal structure of NiSe (JCPDS No: 18-0887), proving the existence of NiSe crystalline phase, and 30.48°, 34.19°, 37.57°, 43.65°, 51.69°, 56.58°, 58.93°, 63.45°, 76.13° correspond to the cubic structure of CoSe2 (JCPDS No:88-1712) (200), (210), (211), (220), (311), (023), (321), (400), (332) of the crystal planes are highly consistent, and no impurity peaks are observed, proving that no impurities are generated. The morphology of the NiSe@CoSe2 / NF heterostructure was characterized by scanning electron microscopy and transmission electron microscopy. Figure 2 The composite material is uniform rod-shaped nanorods with a diameter of about 400 nm. In addition, high-resolution transmission electron microscopy ( Figure 3 ) shows the staggered arrangement of lattice fringes with different crystal plane spacings, proving the formation of a heterojunction structure.

[0080] (III) The relevant comparative experiments are as follows:

[0081] The same molar amount of cobalt oxalate, cobalt acetylacetonate and cobalt chloride were selected as cobalt precursors, and other conditions were the same as a comparative experiment, and the reaction results were shown in Table 1. Comparative Example 1 uses cobalt oxalate as an iron precursor, Comparative Example 2 uses cobalt acetylacetonate as a cobalt precursor, and Comparative Example 3 uses cobalt chloride as a cobalt precursor.

[0082] Specifically, in Comparative Example 1, the catalyst prepared using cobalt oxalate as a cobalt precursor was electrocatalyzed to catalyze HMF, and the other conditions were the same as in Example 1. The prepared catalyst was named C-1. The preparation steps of the nickel selenium compound were the same as steps (1) to (3) in Example 1.

[0083] Comparative Example 2 is to use cobalt acetylacetonate as the cobalt precursor to electrocatalyze HMF. The other conditions are the same as those in Example 1. The prepared catalyst is named Y-1. The preparation steps of the nickel selenium compound are the same as steps (1) to (3) in Example 1.

[0084] Comparative Example 3 uses cobalt chloride as a cobalt precursor to electrocatalyze HMF, and the other conditions are the same as those in Example 1. The prepared catalyst is named L-1. The preparation steps of the nickel selenium compound are the same as steps (1) to (3) in Example 1.

[0085] (IV) Test methods:

[0086] (1) A selenide heterojunction catalyst (1 cm*1.5 cm) supported on nickel foam was cut and prepared as a working electrode, a saturated mercury electrode was used as a reference electrode, and a platinum sheet was used as a counter electrode.

[0087] (2) The three-electrode system was used for testing. The electrolytic cells were separated by a proton exchange membrane. The electrolyte concentration was 1 mol / L. The standard three-electrode system was used for testing. Cyclic voltammetry was used for activation before testing.

[0088] (3) Weigh 20.8 mg of HMF and add it to 17 mL of the electrolyte in step (2). Stir with a porcelain stirrer to increase mass transfer at a stirring speed of 600 rpm.

[0089] (4) The product content was detected by high performance liquid chromatography using a CHI660e electrochemical workstation. The test temperature was room temperature and the test pressure was normal pressure.

[0090] (V) Test results:

[0091] Table 1

[0092]

[0093] It can be seen from Table 1 that the order of the catalytic performance of the catalysts is: O-1>Y-1>C-1>L-1. The HMF conversion rate of the O-1 catalyst in Example 1 is 98.7%, and the selectivity of FDCA is 96.7%. Due to the different anion properties between the catalysts in the comparative example and the example, there are differences in the speed of hydrolysis and the morphology and area of ​​the formed Co(OH)2 precursor, resulting in differences in the active sites on the catalyst surface, and ultimately leading to different catalytic performance. The O-1 catalyst exhibits the best catalytic performance. This is because the catalyst O-1 has the largest specific surface area, and the catalyst formed has many randomly distributed crystal plane structures. The electronic regulation between the interfaces leads to excellent catalytic activity of the heterojunction. At the same time, it can be concluded from the linear sweep voltammetry curve that O-1 has the lowest electrode voltage, which only requires 1.42V, which will greatly reduce the coupling voltage of the hydrogen production system, which also proves that O-1 has the highest reaction activity. The order of the catalytic performance of the catalysts in Table 1 is well correlated with the size of their hydrolysis rates.

[0094] Example 2

[0095] (I) Preparation method

[0096] A method for preparing a selenide heterojunction catalyst coupled with hydrogen evolution, the specific steps are as follows:

[0097] (1) Using a typical hydrothermal method, Co(NO3)29H2O (2 mmol), NH4F (5 mmol), and CH4N2O (10 mmol) were added into a beaker containing 60 mL of ultrapure water and stirred for 15 minutes.

[0098] (2) The mixed solution of step (1) and nickel foam (3 x 4 cm, thickness 1.5 mm, mass 0.4 g) were transferred to an autoclave containing 100 mL of polytetrafluoroethylene lining, heated to 160° C. in an oven for 6 h, then cooled to room temperature, washed with water and ethanol several times, and dried in a vacuum oven (60° C.) overnight to obtain a cobalt hydroxide precursor supported on nickel foam, namely Co(OH)2 / NF.

[0099] (3) 5 mmol of selenium powder and 130 mmol of NaOH were added to a polytetrafluoroethylene liner containing 60 mL of aqueous solution in sequence, and then ultrasonicated for 5 minutes. Then, the Co(OH)2 / NF in step (2) was added. The polytetrafluoroethylene liner was then placed in an autoclave and selenized in an oven at 180°C for 4 hours. The polytetrafluoroethylene liner was then cooled to room temperature, washed with deionized water and anhydrous ethanol several times, and dried in a vacuum oven to obtain a selenide heterojunction catalyst for coupled hydrogen evolution. The obtained catalyst was recorded as O-2-180.

[0100] (II) The relevant tests are as follows:

[0101] Figure 4 This is the XRD result of Example 3. The result is the same as that of Example 1, showing the presence of CoSe2 and NiSe phases, proving the synthesis of the heterojunction.

[0102] Figure 5 This is a scanning electron microscope image of the nickel-selenium heterojunction catalyst prepared in Example 3. The result shows that the diameter of the nanorods is about 400 nm. The nanorod shape proves that the material has a large surface area.

[0103] Figure 6 The transmission electron microscopy image of the catalyst prepared in Example 3 shows the presence of obvious lattice fringes of different sizes, indicating the presence of CoSe2 and NiSe phases on the exposed surface of the catalyst.

[0104] (III) The comparative experiment is as follows

[0105] Catalysts obtained at different selenization temperatures were selected respectively, and other conditions were the same as those for comparative experiments, and the reaction results were shown in Table 2. Comparative Example 4 was a selenization temperature of 160°C, and Comparative Example 5 was a selenization temperature of 200°C.

[0106] Specifically, in Comparative Example 4, the catalyst prepared at a selenization temperature of 160° C. was subjected to an electrocatalytic HMF reaction to obtain a reaction system of Comparative Example 4, and the remaining conditions were the same as those of the catalysis in Example 2. The prepared catalyst was named O-2-160. The preparation steps of the selenide heterojunction were the same as steps (1) to (3) in the "selenide heterojunction catalyst preparation method" in Example 2.

[0107] Specifically, in Comparative Example 5, the catalyst prepared at a selenization temperature of 200° C. was subjected to electrocatalytic HMF reaction to obtain a reaction system of Comparative Example 5, and the remaining conditions were the same as those of the catalysis in Example 2. The prepared catalyst was named O-2-200. The preparation steps of the selenide heterojunction were the same as steps (1) to (3) in the "selenide heterojunction catalyst preparation method" in Example 2.

[0108] (IV) Test methods:

[0109] (1) A selenide heterojunction catalyst (1 cm*1.5 cm) supported on nickel foam was cut and prepared as a working electrode, a saturated mercury electrode was used as a reference electrode, and a platinum sheet was used as a counter electrode.

[0110] (2) The three-electrode system was used for testing. The electrolytic cells were separated by a proton exchange membrane. The electrolyte concentration was 1 mol / L. The standard three-electrode system was used for testing. Cyclic voltammetry was used for activation before testing.

[0111] (3) Weigh 20.8 mg of HMF and add it to 17 mL of the electrolyte in step (2). Stir with a porcelain stirrer to increase mass transfer at a stirring speed of 600 rpm.

[0112] (4) The product content was detected by high performance liquid chromatography using a CHI660e electrochemical workstation. The test temperature was room temperature and the test pressure was normal pressure.

[0113] (V) Test results:

[0114] Table 2

[0115] Experiment Type catalyst Conversion rate / % FDCA selectivity % 0.1Acm-2 corresponds to electrode potential (VvsRHE) Comparative Example 4 O-2-160 90.2％ 88.7％ 1.51 Example 2 O-2-180 98.7％ 96.7％ 1.42 Comparative Example 5 O-2-200 88.4％ 85.5％ 1.50

[0116] Table 2 shows the reaction results of the nickel-selenium heterojunction catalyst prepared at different selenization temperatures. The results show that when the calcination temperature, i.e., the selenization temperature, is 180°C, the selenide heterojunction exhibits the best catalytic performance, with a HMF conversion rate of 98.7% and a FDCA selectivity of 96.7%, and it has the lowest electrode potential at a current density of 0.1 Acm -2 . When the selenization temperature is too high or too low, the conversion rate will decrease. This is because too high a selenization temperature will cause the stacking and accumulation of selenides, resulting in a reduction in active area and loss of active sites, which in turn leads to a decrease in the active sites of the catalyst and a decrease in catalytic performance. There are two main reasons for the decrease in catalytic performance when the selenization temperature is too low. One is that the crystallinity of selenides decreases due to too low a temperature; the other is that too low a selenization temperature reduces the porosity of the catalyst, thereby affecting mass transfer and the utilization of active sites.

[0117] Example 3

[0118] (I) Preparation method

[0119] A method for preparing a selenide heterojunction catalyst coupled with hydrogen evolution, the specific steps are as follows:

[0120] (1) Using a typical hydrothermal method, Co(NO3)29H2O (2 mmol), NH4F (5 mmol), and CH4N2O (10 mmol) were added into a beaker containing 60 mL of ultrapure water and stirred for 15 minutes.

[0121] (2) The mixed solution of step (1) and nickel foam (3 x 4 cm, thickness 1.5 mm, mass 0.4 g) were transferred to an autoclave containing 100 mL of polytetrafluoroethylene lining, heated to 160° C. in an oven for 6 h, then cooled to room temperature, washed with water and ethanol several times, and dried in a vacuum oven (60° C.) overnight to obtain a cobalt hydroxide precursor supported on nickel foam, namely Co(OH)2 / NF.

[0122] (3) 5 mmol of selenium powder and 130 mmol of NaOH were added to a polytetrafluoroethylene liner containing 60 mL of aqueous solution in sequence, and then ultrasonicated for 5 minutes. Then, the Co(OH)2 / NF in step (2) was added. The polytetrafluoroethylene liner was then placed in an autoclave and selenized in an oven at 180°C for 4 hours. The polytetrafluoroethylene liner was then cooled to room temperature and washed several times with deionized water and anhydrous ethanol. The catalyst was dried in a vacuum oven to obtain a selenide heterojunction catalyst for coupled hydrogen evolution. The catalyst prepared under these conditions was named O-35.

[0123] (II) The relevant tests are as follows:

[0124] 1. Related performance test of the nickel-selenium compound heterojunction obtained in Example 3 of the present invention (same as Example 1)

[0125] Figure 7 This is the XRD result of Example 3. The result is the same as that of Example 1, showing the presence of CoSe2 and NiSe phases, proving the synthesis of the heterojunction.

[0126] Figure 8 This is a scanning electron microscope image of the nickel-selenium heterojunction catalyst prepared in Example 3. The result shows that the diameter of the nanorods is about 400 nm. The nanorod shape proves that the material has a large surface area.

[0127] Fig. 9 The transmission electron microscopy image prepared in Example 3 shows the presence of obvious lattice fringes of different sizes, indicating the presence of CoSe2 and NiSe phases on the exposed surface of the catalyst.

[0128] (III) The comparative experiment is as follows

[0129] Different ratios of cobalt source and urea catalyst were selected respectively, and other conditions were the same as comparative experiments, and the reaction results were shown in Table 3. Comparative Example 6 was a cobalt source: urea molar ratio of 1:2, and Comparative Example 7 was a cobalt source: urea molar ratio of 3:5.

[0130] Specifically, in Comparative Example 6, the catalyst prepared at a selenization temperature of cobalt source: urea with a molar ratio of 1:2 was subjected to electrocatalytic HMF reaction to obtain a reaction system of Comparative Example 6, and the remaining conditions were the same as those of the catalysis in Example 3. The prepared catalyst was named O-14. The preparation steps of the selenide heterojunction were the same as steps (1) to (3) in the "selenide heterojunction catalyst preparation method" in Example 3.

[0131] Specifically, in Comparative Example 7, the catalyst prepared with a molar ratio of cobalt source: urea of ​​3:5 was subjected to electrocatalytic HMF reaction to obtain the reaction system of Comparative Example 7, and the remaining conditions were the same as those of the catalysis in Example 3. The prepared catalyst was named O-35. The preparation steps of the selenide heterojunction were the same as steps (1) to (3) in the "selenide heterojunction catalyst preparation method" in Example 3.

[0132] (IV) Test methods:

[0133] (1) A selenide heterojunction catalyst (1 cm*1.5 cm) supported on nickel foam was cut and prepared as a working electrode, a saturated mercury electrode was used as a reference electrode, and a platinum sheet was used as a counter electrode.

[0134] (2) The three-electrode system was used for testing. The electrolytic cells were separated by a proton exchange membrane. The electrolyte concentration was 1 mol / L. The standard three-electrode system was used for testing. Cyclic voltammetry was used for activation before testing.

[0135] (3) Weigh 20.8 mg of HMF and add it to 17 mL of the electrolyte prepared in step 2. Stir with a porcelain stirrer to increase mass transfer at a speed of 600 rpm.

[0136] (4) The product content was detected by high performance liquid chromatography using a CHI660e electrochemical workstation. The test temperature was room temperature and the test pressure was normal pressure.

[0137] (V) Test results

[0138] Table 3

[0139]

[0140] Table 3 shows the reaction results of the nickel-selenium heterojunction catalyst prepared at different selenization temperatures. The results show that when the molar ratio of cobalt source to urea reaches 2:5, the selenide heterojunction exhibits the best catalytic performance, with a HMF conversion rate of 98.7% and a FDCA selectivity of 96.7%, and it has the lowest electrode potential at a current density of 0.1 A cm -2 . When the concentration of urea is too high or too low, the conversion rate will decrease. This is because high concentration of urea will promote the formation of Co(OH)2 nuclei. Excessive nuclei formation inhibits the growth of crystals, and smaller nuclei are easily dissolved and lost during the oxidation process due to high surface energy, which leads to a decrease in the active sites of the catalyst and a decrease in catalytic performance. Low concentration of urea will cause the pH of the solution to be too low, which is not conducive to the nucleation of crystals, resulting in lower Co(OH)2 on the nickel foam, thereby providing a lower Co source in the subsequent selenization process. This leads to a single interface of the heterojunction material, which leads to a decrease in the active sites of the catalyst and a decrease in catalytic performance.

[0141] At the same time, by comparing Example 2, Example 3, and Comparative Examples 4 to 7, it can be seen that the selenization temperature and the molar ratio of the cobalt source: urea in the method of the present invention have a synergistic effect, which can synergistically improve the relevant properties of the prepared selenide heterojunction catalyst for coupled hydrogen evolution, especially when the selenization temperature is 180°C and the molar ratio of the cobalt source and urea reaches 2:5, there is a significant synergistic effect between the two, which can significantly synergistically improve the relevant properties of the prepared selenide heterojunction catalyst for coupled hydrogen evolution.

[0142] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for preparing a selenide heterojunction catalyst coupled with hydrogen evolution, characterized in that: The steps include: (1) adding a cobalt precursor, ammonium fluoride and urea into water and mixing them uniformly to obtain a clear mixed solution; (2) transferring the mixed solution obtained in step (1) into a reaction kettle, adding pre-cleaned nickel foam, performing hydrothermal synthesis, cooling, washing, and vacuum drying to obtain Co(OH)2 / NF; (3) After adding selenium powder, alkali and clean water and ultrasonically homogenizing, the Co(OH)2 / NF obtained in step (2) is placed in the above solution and placed in a hydrothermal kettle for selenization to obtain NiSe@CoSe2 / NF, which is a selenide heterojunction catalyst for coupled hydrogen evolution.

2. The preparation method according to claim 1, characterized in that: In the step (1), the cobalt precursor: ammonium fluoride: urea: The ratio of water: mmol: mmol: mmol: ml: g of the pre-prepared and cleaned nickel foam in step (2) is 0.5-5: 1-15: 2-18: 50-100: 0.4; Alternatively, the temperature of the hydrothermal synthesis in step (2) is 100° C. to 150° C., and the time is 2 to 8 hours; Alternatively, the temperature of selenization in step (3) is 100° C. to 200° C., and the time of selenization is 2 to 10 hours; Alternatively, in step (3), the ratio of selenium powder: alkali: clean water is 5-10: 100-200: 50-100 in mmol: mmol: ml, and the molar ratio of cobalt precursor: selenium powder is 0.5-5: 5-10.

3. The preparation method according to claim 2, characterized in that: The cobalt precursor is an organic or inorganic compound containing cobalt, and the organic or inorganic compound containing cobalt includes cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt oxalate, and cobalt acetylacetonate; Alternatively, the selenization temperature in step (3) is 180°C.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The specific steps are as follows: (1) adding a cobalt precursor, ammonium fluoride and urea into water and mixing them uniformly to obtain a clear mixed solution; (2) adding pre-cleaned nickel foam to the mixed solution obtained in step (1) to obtain an aqueous solution containing nickel foam; The preparation method of the pre-cleaned nickel foam is as follows: first, the nickel foam is ultrasonically cleaned with 3 mol / L hydrochloric acid for 30 minutes, then ultrasonically cleaned with ethanol for 30 minutes, and then vacuum dried to obtain the nickel foam; (3) The aqueous solution containing nickel foam obtained in step (2) was transferred to a stainless steel heating kettle lined with polytetrafluoroethylene, and hydrothermally synthesized at 120° C. for 2-8 h, and then washed with ethanol and deionized water, and vacuum dried to obtain the precursor Co(OH)2 / NF: (4) After adding selenium powder, alkali and clean water and ultrasonically homogenizing, the Co(OH)2 / NF obtained in step (2) is placed in the above solution and placed in a hydrothermal kettle for selenization to obtain NiSe@CoSe2 / NF, which is a selenide heterojunction catalyst for coupled hydrogen evolution.

5. A nickel-cobalt-selenide heterojunction catalyst prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the selenide heterojunction catalyst as claimed in claim 5 in electrocatalytic HMF coupled hydrogen evolution.

7. Use of the heterojunction catalyst as claimed in claim 5 in electrocatalytic production of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural.

8. A method for producing 2,5-furandicarboxylic acid by electrocatalyzing 5-hydroxymethylfurfural using the nickel-cobalt-selenide heterojunction catalyst as claimed in claim 7, characterized in that: The steps include: 1) Cut the prepared nickel-cobalt-selenide heterojunction catalyst into a size of 1 cm*1.5 cm, fix it with a platinum electrode clip, and use it as a working electrode; 2) Tested under a three-electrode system, using a platinum sheet as the counter electrode, Hg / HgO as the reference electrode, an H-type cell as the electrolytic cell, 1M KOH as the electrolyte, and a proton exchange membrane between the two cells; 3) Activating the working electrode by cyclic voltammetry until it is stable; 4) HMF was added to perform a linear scan test and a test with different coulomb electron numbers, and the Faradaic efficiency of 2,5-furandicarboxylic acid was calculated.

9. The method according to claim 8, characterized in that: The reaction conditions in step 2) are as follows: the reactor temperature is room temperature, i.e., 25° C., the pressure is normal pressure, and the reaction time is 2-10 h.

10. The method according to claim 8 or 9, characterized in that: The scanning range of the linear scanning voltammetry in step 4) is 1.0V-1.6V (relative to the reversible hydrogen electrode), the scanning speed is 10mV / s, and the potential constant range of different coulombs applied in step 4) is 1.4V-1.6V (relative to the reversible hydrogen electrode).

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