A selenium heterojunction catalyst coupled to hydrogen evolution, methods, and applications in electrocatalysis of 5-hydroxymethylfurfural

Abstract

The application belongs to the technical fields of functional material preparation, catalysis and transition metal complex material, and discloses a selenium compound heterojunction catalyst coupled with hydrogen evolution, a method and application. In preparation, a cobalt source, urea, a foamed nickel and an ammonium fluoride mixed solution are mixed in a reaction, and after being hydrothermally synthesized and cooled to room temperature, the precursor Co(OH)2 / NF is obtained by washing with ethanol and water and drying. Then, selenium powder and a strong base are added into a reaction kettle, and heating is performed to obtain the heterojunction catalyst NiSe@CoSe2 / NF with high density. The obtained heterojunction material can be used for electrocatalysis of 5-hydroxymethylfurfural. When the current density is 10 mAcm ‑2 , the potential is 1.29 V, and the optimal conversion rate is more than 98%, and the catalyst has excellent catalytic activity for electrocatalysis of 5-hydroxymethylfurfural oxidation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional material preparation and catalysis, and more particularly to a selenium compound heterojunction catalyst coupled with hydrogen evolution, a method and application thereof in electrocatalysis of 5-hydroxymethylfurfural. BACKGROUND

[0002] Nuclear waste water treatment is one of the important environmental challenges worldwide. Traditional nuclear waste water treatment methods include chemical precipitation, adsorption, ion exchange, etc. These methods can remove part of the radioactive isotopes and heavy metals, but the treatment efficiency is limited and there is a risk of secondary pollution. In recent years, electrolytic water technology has attracted attention in the treatment of nuclear waste water due to its high efficiency and environmental protection. Electrolytic water technology uses electric current to pass through an electrolyte solution (such as water) to cause oxidation-reduction reactions on the electrodes, thereby achieving the decomposition and transformation of substances in the solution. Currently, hydrogen (H) isotope liquid enrichment technology mainly uses electrolysis and water rectification methods. Among them, electrolysis is a method of enriching isotopes in an electrolytic cell by electrolyzing a liquid solution containing deuterium (D) (tritium). The first method for industrial production of heavy water is electrolysis, which is based on the differences in migration rate and overvoltage between H, D and T isotopes. During the electrolysis process, the lighter hydrogen isotopes are preferentially formed into gas and released from the solution, while the heavier hydrogen isotopes remain in the solution, achieving enrichment. For example, Pan Jingshun of the China Institute of Atomic Energy designed a tritium electrolytic concentration device with nickel as the anode and stainless steel as the cathode, and the tritium recovery rate reached about 65%. Xia Xulong et al. of the China Academy of Engineering Physics conducted simulation calculations on the hydrogen-deuterium system and found that the molar fraction of semi-heavy water in the electrolytic cell increased from 2.88 x 10 -4 to 8.35 x 10 -4 , achieving obvious enrichment. During the electrolysis process, the separation coefficient between the three isotopes is large, resulting in good separation effect. However, electrolysis consumes a large amount of electricity, so developing a high-efficiency electrode material is of great significance for the application of this technology.

[0003] Platinum is an efficient electrocatalyst that can catalyze the evolution of hydrogen (H2) and deuterium (D2). However, due to the slightly larger mass of deuterium than hydrogen, its chemical reactivity is slightly lower than that of hydrogen, and hydrogen is smaller in mass and faster in diffusion speed than deuterium, so their reduction potentials are different. Generally, the evolution potential of hydrogen is more negative than that of deuterium, meaning that under the same conditions, hydrogen is preferentially generated. In the electrolysis process, the generation of hydrogen is easier, which is related to the isotope effect. However, the current electrolysis method requires high equipment, complex equipment, high energy consumption and high cost. High energy consumption prevents the further commercialization of electrolytic hydrogen production from heavy water, and the key to reducing the energy consumption of the hydrogen production system is to reduce the high overpotential of the anode oxygen evolution reaction (OER), because compared to the cathode hydrogen evolution reaction, the four-electron reaction step at the anode requires a higher theoretical potential (1.23 V). Therefore, reducing the reaction energy barrier at the anode will effectively reduce the energy consumption of the entire water electrolysis hydrogen evolution system. Most current research is still focused on the preparation and modification of reaction catalysts, and commercial catalysts such as iridium oxide and ruthenium oxide can barely meet the requirements of industrial water electrolysis, but their high price further increases the cost of the electrolysis system.

[0004] Replacing OER with electro-oxidation of small organic molecules (urea, glycerol, 5-hydroxymethylfurfural (HMF), etc.) is becoming a hot research topic in the academic community. This method not only reduces the high potential of the anode reaction, but also produces additional products with economic value, which will help reduce the cost of the electrolysis system. The electrocatalytic reaction has mild conditions and is environmentally friendly; it has strong controllability and can regulate the reaction rate, start and stop the reaction at any time, and achieve high selectivity in preparation; it transfers electrons without oxygen or external oxidants, in line with the development concept of green synthesis and "double carbon". The product of HMF electro-oxidation, 2,5-furan dicarboxylic acid (FDCA), has great commercial value. According to statistical data, the global FDCA market size was approximately $150 million in 2018, and is expected to reach $300 million by 2025, with a compound annual growth rate of 15.7% from 2019 to 2025. FDCA has a "rigid" planar structure and the multifunctionality of dicarboxylic acid side chains, and amine compounds derived from FDCA can be used as bactericides. FDCA can not only be used in the fields of medicine, pesticides and metal organic frameworks, but also is the building block of many polyesters and polyamides. Biomass-based polymers, such as polyethylene furandicarboxylate (PEF), have been the focus of attention. Studies have shown that PEF synthesized from FDCA as a monomer is superior to polyethylene terephthalate in many properties. PEF not only has no reproductive toxicity, but also has good oxygen, carbon dioxide and water barrier properties, as well as better thermal stability and mechanical properties. Therefore, the preparation of electrocatalytic HMF catalysts with high catalytic activity coupled with cathode hydrogen evolution reaction not only reduces the cost of the entire electrolysis system, but also produces raw materials with added value, which will have ideal application prospects. SUMMARY

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

[0006] The technical scheme adopted by the present application to solve its technical problems is:

[0007] A preparation method of a selenium heterojunction catalyst coupled with hydrogen evolution, comprising the following steps:

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

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

[0010] (3) adding selenium powder, alkali and clean water after ultrasonic mixing, putting Co(OH)2 / NF obtained in step (2) into the above solution, putting into a hydrothermal kettle for selenization to obtain NiSe@CoSe2 / NF, which is the selenium heterojunction catalyst coupled with hydrogen evolution.

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

[0012] Alternatively, the temperature of hydrothermal synthesis in step (2) is 100-150 DEG C, and the time is 2-8 h;

[0013] Alternatively, the selenization temperature in step (3) is 100-200 DEG C, and the selenization time is 2-10 h;

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

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

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

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

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

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

[0020] The pre-cleaned foam nickel is prepared by first ultrasonically cleaning the foam nickel with 3 mol / L hydrochloric acid for 30 minutes, then ultrasonically cleaning with ethanol for 30 minutes, and vacuum drying to obtain the pre-cleaned foam nickel;

[0021] (3) transferring the aqueous solution containing foam nickel obtained in step (2) into a stainless steel heating kettle containing a polytetrafluoroethylene liner, hydrothermally synthesizing at 120°C for 2-8 hours, and cleaning with ethanol and deionized water, and vacuum drying to obtain the precursor Co(OH)2 / NF:

[0022] (4) adding selenium powder, alkali and water, and then ultrasonically mixing the Co(OH)2 / NF obtained in step (2) into the above solution, and then placing it into 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 described above in electrocatalytic HMF coupling hydrogen evolution.

[0025] The application of the heterojunction catalyst described above in electrocatalytic 5-hydroxymethylfurfural to 2,5-furan dicarboxylic acid.

[0026] The method for electrocatalytic 5-hydroxymethylfurfural to 2,5-furan dicarboxylic acid using the nickel-cobalt selenide heterojunction catalyst described above, comprising the following steps:

[0027] 1) The prepared nickel-cobalt selenide heterojunction catalyst is cut into a size of 1 cm*1.5 cm, fixed with a platinum sheet electrode clamp, and used as a working electrode;

[0028] 2) The test is carried out in a three-electrode system, using a platinum sheet as a counter electrode, Hg / HgO as a reference electrode, an H-type cell as an electrolytic cell, and 1 mol / L KOH as an electrolyte, and the two cells are separated by a proton exchange membrane;

[0029] 3) The working electrode is activated by cyclic voltammetry until it is stable;

[0030] 4) HMF is added for linear sweep test and different coulomb electron number test, and the faradic efficiency of 2,5-furan dicarboxylic acid is calculated.

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

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

[0033] The present application has the following advantages and positive effects:

[0034] 1. The method of the present application uses one-step hydrothermal and one-step selenization to obtain a high-density selenide heterojunction catalyst, and the selenide heterojunction catalyst is used for electrocatalysis of 5-hydroxymethylfurfural to produce 2,5-furan dicarboxylic acid. The present application regulates the electronic structure of the active site through the effect of the interface electron transfer of the heterojunction, increases the adsorption capacity of HMF, and improves the efficiency of catalytic conversion. The HMF conversion rate is more than 98%, and the Faraday efficiency of 2,5-furan dicarboxylic acid is as high as 97%.

[0035] 2. The present application reduces the overall voltage of the water electrolysis system through coupling hydrogen evolution reaction. The anode potential reaches 10 and 50 mA·cm -2 The potential required for the current density is only approximately 1.29 and 1.36 V, respectively, which is significantly lower than other commercial catalysts. When the current density reaches 100 mAcm -2 , the potential difference with OER reaches 270 mV.

[0036] 3. The present application provides a simple and convenient preparation method of a selenide heterojunction catalyst. The method is simple in process, easy to operate, and short in time consumption. The method has high reactivity in electrocatalysis of HMF to produce 2,5-furan dicarboxylic acid.

[0037] 4. The selenide heterojunction catalyst prepared by the present application has more active sites than traditional epitaxial heterojunction catalysts. The highly dispersed heterojunction catalyst improves the specific surface area of the catalyst, reduces the particle size, and exposes more active sites, thereby improving the conversion rate and selectivity of the reaction.

[0038] 5. The present application is a mixed solution of a cobalt source, urea, a foamed nickel, and ammonium fluoride. After hydrothermal synthesis in the reaction and cooling to room temperature, the precursor Co(OH)2 / NF is obtained by washing with ethanol and water and drying. Then, selenium powder and a strong base are added to the reaction kettle for heating selenization to obtain a high-density heterojunction catalyst NiSe@CoSe2 / NF. The obtained heterojunction material can be used for electrocatalysis of 5-hydroxymethylfurfural. When the current density is 10 mAcm -2The potential at this time is 1.29V, and the optimal conversion rate is more than 98%, with excellent catalytic activity of electrocatalytic oxidation of 5-hydroxymethylfurfural. BRIEF DESCRIPTION OF DRAWINGS

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

[0040] Figure 2 SEM pattern of the NiSe@CoSe2 / NF catalyst in Example 1 in the present application;

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

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

[0043] Figure 5 SEM pattern of the NiSe@CoSe2 / NF catalyst in Example 2 in the present application;

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

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

[0046] Figure 8 SEM pattern of the NiSe@CoSe2 / NF catalyst in Example 3 in the present application;

[0047] Figure 9 TEM pattern of the NiSe@CoSe2 / NF catalyst in Example 3 in the present application. DETAILED DESCRIPTION

[0048] The present application is further described below in conjunction with examples, which are illustrative rather than limiting, and the protection scope of the present application cannot be limited by the following examples.

[0049] The various experimental operations involved in the specific examples are all conventional techniques in the art, and the parts not specially noted in the text can be implemented by referring to various commonly used tool books, scientific and technical literature or related instructions, manuals, etc. before the filing date of the present application.

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

[0051] (2) transferring the system obtained in step (1) to a reaction kettle, hydrothermally synthesizing, cooling, washing, centrifuging, and drying to obtain a precursor Co(OH)2 of cobalt hydroxide loaded on foamed nickel;

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

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

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

[0055] The mixed solution of step (2) and foamed nickel (3x 4 cm) are transferred to a high-pressure sterilizer containing a 100 mL polytetrafluoroethylene liner, heated in an oven at 120-180°C for 6 h, then cooled to room temperature, and dried in a vacuum oven (60°C) overnight to obtain a cobalt hydroxide precursor loaded on foamed nickel.

[0056] Every 5 mmol of selenium powder and 130 mmol of NaOH are sequentially added to a polytetrafluoroethylene liner containing a 60 mL aqueous solution and ultrasonicated for 5 minutes, then Co(OH)2 / NF in step (2) is added, and then the polytetrafluoroethylene liner is placed in a high-pressure sterilizer and heated in an oven at 180°C for 4 h, then cooled to room temperature, washed several times with deionized water and anhydrous ethanol, and dried in a vacuum oven to obtain a selenium heterojunction catalyst.

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

[0058] Preferably, the foamed nickel needs to be cleaned of surface oxides with hydrochloric acid before use, and the surface organic matter is cleaned with ethanol ultrasonication.

[0059] Preferably, the selenium reaction time is 2-10 h.

[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 method as described above obtains a highly dense selenium heterojunction catalyst.

[0062] Use of the selenide heterojunction catalyst as described above in the electrocatalytic HMF coupling hydrogen evolution.

[0063] Method for using the selenide heterojunction catalyst as described above in the electrocatalytic HMF coupling hydrogen evolution, comprising the following steps:

[0064] The selenide heterojunction catalyst prepared by tailoring is 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] A three-electrode system is used for testing, and a proton exchange membrane is used to separate the electrolytic cells. An appropriate amount of alkaline electrolyte is weighed, and a standard three-electrode system is used for testing.

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

[0067] An appropriate amount of HMF is weighed and added to the electrolyte, and a porcelain stirrer is used to increase mass transfer.

[0068] Preferably, the test temperature is 20-35℃, and the test pressure is atmospheric pressure.

[0069] The conversion rate and Faraday efficiency of HMF are tested by applying different potentials, and the relationship between the conversion rate of HMF and the number of electrons is tested by applying different electron coulombs. The test time is 2-10h.

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

[0071] Preferably, the following foam nickel needs to be cleaned with dilute hydrochloric acid before use to remove surface oxides, and ultrasonic cleaning with ethanol is used to remove surface organic matter. Specifically, the preparation method of the pre-cleaned foam nickel is as follows: first, ultrasonic cleaning of the foam nickel with 3mol / L hydrochloric acid for 30 minutes, then ultrasonic cleaning with ethanol for 30 minutes, and vacuum drying.

[0072] Example 1

[0073] (I) Preparation method

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

[0075] (1) Co(NO3)2 9H2O (1 mmol), NH4F (3 mmol), CH4N2O (6 mmol) are added to a beaker containing 60 mL of ultrapure water and stirred for 15 minutes.

[0076] (2) The mixed solution and the foamed nickel (3 x 4 cm, thickness 1.5 mm, mass 0.4 g) of step (1) were transferred into a polytetrafluoroethylene-lined autoclave containing 100 mL of water, heated in an oven at 120 °C 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 foamed nickel, Co(OH)2 / NF.

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

[0078] The relevant tests are as follows

[0079] The coexistence of CoSe2 and NiSe phases was confirmed by x-ray diffraction (XRD) patterns Figure 1 ) at 29.06°, 34.06°, 36.04°, 38.69°, 48.04°, 50.03°, 55.11° corresponding to the (101), (021), (220), (211), (410), (401), (330) crystal planes of hexagonal NiSe (JCPDS No: 18-0887), proving the existence of a NiSe crystalline phase, and 30.48°, 34.19°, 37.57°, 43.65°, 51.69°, 56.58°, 58.93°, 63.45°, 76.13° highly consistent with the (200), (210), (211), (220), (311), (023), (321), (400), (332) crystal planes of cubic CoSe2 (JCPDS No: 88-1712), without any impurity peaks observed, proving that no impurities were generated. The morphology of the NiSe@CoSe2 / NF heterostructure was characterized by scanning electron microscopy and transmission electron microscopy. Figure 2 showed that the composite material was a uniform rod-shaped nanorod, and the diameter of the nanorod was about 400 nm. In addition, high-resolution transmission electron microscopy Figure 3 ) showed that the lattice fringes of different interplanar spacings were arranged randomly, proving the formation of a heterojunction structure.

[0080] The relevant comparative experiments are as follows

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

[0082] Specifically, Comparative Example 1 is to use cobalt oxalate as the cobalt precursor to prepare the catalyst for electrocatalytic catalysis of HMF, and the rest of the conditions are the same as in Example 1. The catalyst prepared is named C-1. The preparation steps of the nickel selenium compound are the same as steps (1) to step (3) in Example 1.

[0083] Comparative Example 2 is to use cobalt acetylacetonate as the cobalt precursor to prepare the catalyst for electrocatalytic catalysis of HMF, and the rest of the conditions are the same as in Example 1. The catalyst prepared is named Y-1. The preparation steps of the nickel selenium compound are the same as steps (1) to step (3) in Example 1.

[0084] Comparative Example 3 is to use Comparative Example 3 as the cobalt precursor to prepare the catalyst for electrocatalytic catalysis of HMF, and the rest of the conditions are the same as in Example 1. The catalyst prepared is named L-1. The preparation steps of the nickel selenium compound are the same as steps (1) to step (3) in Example 1.

[0085] (IV) Test method:

[0086] (1) The selenium heterojunction catalyst supported on the nickel foam (1 cm*1.5 cm) prepared by cutting was used as the working electrode, a saturated mercury electrode was used as the reference electrode, and a platinum sheet was used as the counter electrode.

[0087] (2) The three-electrode system was tested, the electrolysis cell was separated by a proton exchange membrane, the electrolyte concentration was 1 mol / L, and the standard three-electrode system was tested, and the cyclic voltammetry was used for activation before testing.

[0088] (3) 20.8 mg of HMF was added to 17 mL of the electrolyte in step (2), and the mass transfer was increased by stirring with a porcelain stirrer at a stirring speed of 600 revolutions / minute.

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

[0090] (V) Test results:

[0091] Table 1

[0092]

[0093] As can be seen in Table 1, the order of catalytic performance of the catalysts is: O-1 > Y-1 > C-1 > L-1. The HMF conversion rate of the O-1 catalyst of Example 1 is 98.7%, and the selectivity of FDCA is 96.7%. Due to the difference in the nature of the anions between the catalysts in the comparative examples and examples, the speed of hydrolysis, the morphology and area of the Co(OH)2precursor formed, and the active sites on the surface of the catalysts are different, which ultimately leads to different catalytic performances. The O-1 catalyst exhibits the best catalytic performance, which is because the catalyst O-1 has the largest specific surface area, and the catalyst formed has many randomly distributed crystal face structures, and the electronic regulation between the interfaces leads to excellent catalytic activity of the heterojunction, and at the same time, it can be concluded from the linear sweep voltammetry curve that O-1 has the lowest electrode voltage, only 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 catalytic performance of the catalysts in Table 1 has a good correlation with the size of their hydrolysis rates.

[0094] Example 2

[0095] (I) Preparation method

[0096] A preparation method of a selenium heterojunction catalyst coupled with hydrogen evolution, the specific steps are as follows:

[0097] (1) Co(NO3)2·9H2O (2 mmol), NH4F (5 mmol), CH4N2O (10 mmol) were added to a beaker containing 60 mL of ultrapure water and stirred for 15 minutes.

[0098] (2) The mixed solution of step (1) and foamed nickel (3x 4cm, thickness 1.5mm, mass 0.4g) were transferred to a high-pressure sterilizer containing 100 mL of polytetrafluoroethylene liner, heated in an oven at 160℃ for 6h, and then cooled to room temperature. After cooling to room temperature, wash several times with clean water and ethanol, and dry overnight in a vacuum oven (60℃) to obtain a cobalt hydroxide precursor supported on foamed nickel, i.e. Co(OH)2 / NF.

[0099] (3) 5mmol of selenium powder and 130mmol of NaOH were sequentially added to a polytetrafluoroethylene liner containing 60mL of aqueous solution and ultrasonicated for 5 minutes, then Co(OH)2 / NF in step (2) was added, and then the polytetrafluoroethylene liner was placed in a high-pressure sterilizer and selenized in an oven at 180℃ for 4h, and then cooled to room temperature. After washing several times with deionized water and anhydrous ethanol, drying in a vacuum oven, a selenium heterojunction catalyst coupled with hydrogen evolution was obtained, and the obtained catalyst was marked as O-2-180.

[0100] (II) Related detection is as follows:

[0101] Figure 4 For the XRD of Example 3, the results were the same as Example 1, CoSe2, NiSe phase existed, proving the synthesis of the heterojunction.

[0102] Figure 5 The scanning electron microscope image of the nickel selenium heterojunction catalyst prepared in Example 3, the results showed that the diameter of the nanorod was about 400 nm, and the nanorod showed that the material had a large surface area.

[0103] Figure 6 The transmission electron microscope image prepared in Example 3 can be seen that there are obvious lattice fringes of different sizes, which proves that there are CoSe2, NiSe phases on the exposed surface of the catalyst.

[0104] (Three) comparative experiments are as follows

[0105] The catalyst obtained by different seleniumization temperature was selected as the comparative experiment, and the other conditions were the same. The reaction results are shown in Table 2. Comparative example 4 is seleniumization temperature of 160℃, and comparative example 5 is seleniumization temperature of 200℃.

[0106] Specifically, comparative example 4 is the catalyst prepared by seleniumization temperature of 160℃ for electrocatalytic HMF reaction, and the reaction system of comparative example 4 is obtained, and the other conditions are the same as the catalytic conditions in example 2. The prepared catalyst is named O-2-160. The preparation steps of the selenide heterojunction are the same as steps (1) to (3) in the "selenide heterojunction catalyst preparation method" in example 2.

[0107] Specifically, comparative example 5 is the catalyst prepared by seleniumization temperature of 200℃ for electrocatalytic HMF reaction, and the reaction system of comparative example 5 is obtained, and the other conditions are the same as the catalytic conditions in example 2. The prepared catalyst is named O-2-200. The preparation steps of the selenide heterojunction are the same as steps (1) to (3) in the "selenide heterojunction catalyst preparation method" in example 2.

[0108] (Four) test method:

[0109] (1) The selenide heterojunction catalyst loaded on the nickel foam prepared by cutting (1cm*1.5cm) was used as the working electrode, the saturated mercury electrode was used as the reference electrode, and the platinum plate was used as the counter electrode.

[0110] (2) The three electrode system was tested, the electrolytic cell was separated by proton exchange membrane, the electrolyte concentration was 1mol / L, and the standard three electrode system was tested, and the cyclic voltammetry was used for activation before testing.

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

[0112] (4) Use a CHI660e electrochemical workstation to detect the content of the product by high-performance liquid chromatography, with a test temperature of room temperature and a test pressure of atmospheric pressure.

[0113] (V) Test results:

[0114] Table 2

[0115] Type of experiment Catalyst Conversion / % FDCA selectivity % 0.1 A cm-2 vs RHE 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 seleniumization temperatures. The results show that when the calcination temperature, i.e. the seleniumization temperature, is 180°C, the selenium heterojunction exhibits the best catalytic performance, with a HMF conversion rate of 98.7%, a FDCA selectivity of 96.7%, and the lowest electrode potential at a current density of 0.1 Acm -2 . When the seleniumization temperature is too high or too low, the conversion rate will decrease. This is because a too high seleniumization temperature will cause the stacking and accumulation of selenium, resulting in a decrease in active area and a loss of active sites, thereby reducing the active sites of the catalyst and causing a decrease in catalytic performance. When the seleniumization temperature is too low, there are mainly two reasons for the decrease in catalytic performance, one is the decrease in selenium crystallinity at a too low temperature, and the other is the decrease in the porosity of the catalyst at a too low seleniumization temperature, thereby affecting the mass transfer and the utilization of active sites.

[0117] Example 3

[0118] (I) Preparation method

[0119] A preparation method of a selenium heterojunction catalyst coupled with hydrogen evolution, the specific steps being as follows:

[0120] (1) Use a typical hydrothermal method to add Co(NO3)2 9H2O (2 mmol), NH4F (5 mmol), and CH4N2O (10 mmol) to a beaker containing 60 mL of ultrapure water and stir for 15 minutes.

[0121] (2) Transfer the mixed solution in step (1) and the foamed nickel (3x 4 cm, thickness 1.5 mm, mass 0.4 g) into a high-pressure sterilizer containing 100 mL of a polytetrafluoroethylene liner, heat in an oven at 160°C for 6 h, and then cool to room temperature. After cooling to room temperature, wash several times with water and ethanol, and dry in a vacuum oven (60°C) overnight to obtain a cobalt hydroxide precursor supported on foamed nickel, i.e. Co(OH)2 / NF.

[0122] (3) 5 mmol selenium powder and 130 mmol NaOH were sequentially added into a polytetrafluoroethylene-lined ultrasonic cell containing 60 mL aqueous solution for 5 minutes, then Co(OH)2 / NF in step (2) was added, and then the polytetrafluoroethylene liner was placed in an autoclave for selenization at 180°C in an oven for 4 h, and 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 coupled with hydrogen evolution. The catalyst prepared under this condition is named O-35.

[0123] (II) The relevant detection is as follows:

[0124] 1. The relevant performance detection of the nickel selenide compound heterojunction obtained in Example 3 (same as Example 1)

[0125] Figure 7 For the XRD of Example 3, the results are the same as those of Example 1, and CoSe2 and NiSe phases exist, proving the synthesis of the heterojunction.

[0126] Figure 8 The scanning electron microscope image of the nickel selenide heterojunction catalyst prepared in Example 3 shows that the diameter of the nanorods is about 400 nm, and the nanorods prove that the material has a large surface area.

[0127] Figure 9 The transmission electron microscope image prepared in Example 3 can be seen to have obvious lattice fringes of different sizes, proving that CoSe2 and NiSe phases exist on the exposed surface of the catalyst.

[0128] (III) The comparative experiments are as follows:

[0129] Catalysts with different molar ratios of cobalt source to urea were selected as comparative experiments, and the other conditions were the same. The reaction results are shown in Table 3. Comparative example 6 has a molar ratio of cobalt source to urea of 1:2, and comparative example 7 has a molar ratio of cobalt source to urea of 3:5.

[0130] Specifically, comparative example 6 is an electrocatalytic HMF reaction of a catalyst prepared by selenization at a molar ratio of cobalt source to urea of 1:2, and the reaction system of comparative example 6 is obtained, and the other conditions are the same as those in Example 3. The prepared catalyst is named O-14. The preparation steps of the selenide heterojunction are the same as steps (1) to (3) in the "selenide heterojunction catalyst preparation method" in Example 3.

[0131] Specifically, the molar ratio of cobalt source to urea for the preparation of the catalyst in Comparative Example 7 was 3:5, and the reaction system of Comparative Example 7 was prepared by electrocatalytic HMF reaction under the same conditions as the catalytic conditions 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 method:

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

[0134] (2) The test was carried out using a three-electrode system, and the electrolytic cells were separated by a proton exchange membrane. The electrolyte concentration was 1 mol / L, and the standard three-electrode system was used for testing. Before testing, cyclic voltammetry was used for activation.

[0135] (3) 20.8 mg of HMF was added to 17 mL of the electrolyte in step 2, and a porcelain stirrer was used to increase mass transfer, with a stirring speed of 600 rpm.

[0136] (4) CHI660e electrochemical workstation was used to detect the content of the product by high performance liquid chromatography, and 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. High concentration of urea will promote the formation of Co(OH)2 crystal nucleus, and excessive crystal nucleus formation will inhibit the growth of the crystal. Smaller crystal nucleus is easy to dissolve and lose in the oxidation process due to high surface energy, thereby reducing the active sites of the catalyst and causing 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 the crystal, resulting in a lower Co(OH)2 on the nickel foam, which will provide a lower Co source in the subsequent selenization process. This will lead to the single interface of the heterojunction material, thereby reducing the active sites of the catalyst and causing a decrease in catalytic performance.

[0141] Meanwhile, it can also be seen from Comparative Example 2, Example 3, Comparative Examples 4 to 7 that there is a synergistic effect between the selenization temperature and the molar ratio of the cobalt source: urea in the method of the present application, which can synergistically improve the relevant performance of the prepared selenide heterojunction catalyst coupled with hydrogen evolution. In particular, 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 performance of the prepared selenide heterojunction catalyst coupled with hydrogen evolution.

[0142] Although the embodiments of the present application are disclosed for illustrative purposes, those skilled in the art can understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present application and the appended claims, and therefore the scope of the present application is not limited to the disclosed content of the embodiments.

Claims

1. A method for preparing a selenide heterojunction catalyst coupled with hydrogen evolution, characterized in that: Includes the following steps: (1) Add cobalt precursor, ammonium fluoride and urea to water and mix evenly to obtain a clear mixed solution; (2) The mixed solution obtained in step (1) is transferred to a reactor, pre-cleaned nickel foam is added, hydrothermal synthesis is performed, and after cooling, washing and vacuum drying, Co(OH)2 / NF is obtained; (3) After adding selenium powder, alkali and water and ultrasonically homogenizing, the Co(OH)2 / NF obtained in step (2) is placed into the above solution and placed in a hydrothermal reactor for selenization to obtain NiSe@CoSe2 / NF, which is the selenide heterojunction catalyst coupled with hydrogen evolution. In step (1), the cobalt precursor, ammonium fluoride, and urea are used. Water: The ratio of pre-cleaned foam nickel in step (2) is 0.5-5:1-15:2-18:50-100:0.4 mmol:mmol:mmol:ml:g; The hydrothermal synthesis in step (2) is carried out at a temperature of 100 ℃~150 ℃ for 2-8 h. In step (3), the selenization temperature is 100 ℃~200 ℃ and the selenization time is 2-10 h; In step (3), the ratio of selenium powder: alkali: water is 5-10:100-200:50-100 mmol:mmol:ml, and the molar ratio of cobalt precursor to selenium powder is 0.5-5:5-10.

2. The preparation method according to claim 1, characterized in that: The cobalt precursors include cobalt chloride, cobalt nitrate, and cobalt sulfate; Alternatively, the selenization temperature in step (3) is 180 °C.

3. The preparation method according to claim 1 or 2, characterized in that: The specific steps are as follows: (1) Add cobalt precursor, ammonium fluoride and urea to water and mix evenly to obtain a clear mixed solution; (2) Add pre-cleaned nickel foam to the mixed solution obtained in step (1) to obtain an aqueous solution containing nickel foam; The method for preparing the pre-cleaned nickel foam is as follows: 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 finally vacuum dry it to obtain the product. (3) The aqueous solution containing nickel foam obtained in step (2) was transferred to a stainless steel heating vessel with a polytetrafluoroethylene liner, and hydrothermally synthesized at 120 °C for 2-8 h. The solution was 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 water and ultrasonically homogenizing, the Co(OH)2 / NF obtained in step (2) is placed into the above solution and placed in a hydrothermal reactor for selenization to obtain NiSe@CoSe2 / NF, which is the selenide heterojunction catalyst coupled with hydrogen evolution.

4. The nickel-cobalt selenide heterojunction catalyst is prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the selenide heterojunction catalyst as described in claim 4 in the electrocatalytic HMF coupling hydrogen evolution.

6. The application of the heterojunction catalyst as described in claim 4 in the electrocatalytic production of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural.

7. The method for electrocatalyzing the production of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural using the nickel-cobalt-selenide heterojunction catalyst as described in claim 4, characterized in that: Includes the following steps: 1) The prepared nickel-cobalt selenide heterojunction catalyst was cut into 1 cm * 1.5 cm pieces and fixed with platinum sheet electrode clamps to be used as working electrodes; 2) The test was conducted in a three-electrode system, using a platinum sheet as the counter electrode, Hg / HgO as the reference electrode, and an H-type cell as the electrolytic cell. The electrolyte was 1 M KOH, and the two cells were separated by a proton exchange membrane. 3) The working electrode is activated using cyclic voltammetry until it is stable; 4) Add HMF to perform linear scan tests and tests with different coulombic electron numbers, and calculate the Faraday efficiency of 2,5-furandicarboxylic acid.

8. The method according to claim 7, characterized in that: The reaction conditions in step 2) are: reactor temperature is room temperature (25 ℃), pressure is atmospheric pressure, and reaction time is 2-10 h.

9. The method according to claim 7 or 6, characterized in that: In step 4), the scanning range of the linear scanning voltammetry is 1.0 V-1.6 V relative to the reversible hydrogen electrode, and the scanning speed is 10 mV / s. In step 4), the range of constant potentials with different coulombs applied is 1.4 V-1.6 V relative to the reversible hydrogen electrode.

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