Method for preparing alloy material with high-entropy effect through visible light in-situ reduction in aqueous solution

Abstract

The invention provides a method for preparing an alloy material with a high-entropy effect by visible light in-situ reduction in an aqueous solution, which comprises the following steps: by using an LED lamp for simulating a visible light section in sunlight as an energy source, carrying out in-situ reduction on an organic dye fluorescein serving as a photosensitizer and triethanolamine serving as an electronic sacrificial agent in the aqueous solution, and various (such as more than three) metal salt precursors are reduced at normal temperature and normal pressure, and the alloy material with the high-entropy effect is prepared. The method overcomes the defects that a traditional alloy material preparation process is complex, high in pollution and energy consumption and the like, and has the advantages of being simple in process, low in energy consumption, low in raw material cost and the like. The alloy material with the high-entropy effect is wide in application, can realize electro-catalysis nitrate reduction synthesis of ammonia, has a remarkable catalytic effect and excellent cyclic catalytic stability, and provides an application prospect for electro-catalysis nitrate reduction synthesis of ammonia by the alloy material with the high-entropy effect.

Description

Technical Field

[0001] The present invention relates to the technical fields of new materials and photo / electrocatalysis, and particularly relates to a method for in-situ reducing metal ion precursors in an aqueous solution under visible light to prepare an alloy material with a high entropy effect. Background Art

[0002] Alloy materials with a high entropy effect have been widely studied as hot catalysts in the fields of photo / electrocatalytic carbon dioxide reduction, water splitting, small molecule conversion, etc. Alloy materials with a high entropy effect can be divided into ternary alloy materials, quaternary alloy materials, and high entropy alloy materials according to the number of alloying elements, among which high entropy alloy materials usually contain more than five elements. The alloying elements in the alloy materials with a high entropy effect can be metals, non-metals, or other types of atoms, which are mixed together in an equimolar ratio or an approximate equimolar ratio to form a unique solid solution structure, showing a high degree of disorder at the microscopic level. This disorder state leads to a significant increase in the mixing entropy of the alloy materials with a high entropy effect, thereby suppressing the formation of complex intermetallic compounds and avoiding the embrittlement problem caused by increasing the number of elements in traditional alloy materials.

[0003] The development of alloy materials with a high entropy effect has experienced a process from early exploration to concept proposal and then to rapid development. At the same time, its synthesis methods are also diverse, including mechanical alloying method, arc melting method, and laser scanning ablation technology, etc. However, most of these methods have problems such as harsh reaction conditions, high energy consumption, expensive precursors (high-quality raw materials and auxiliary materials), and pollution of waste gas, waste water, and waste residue after the reaction. Summary of the Invention

[0004] Photoinduced technology is a technology that uses light energy to initiate chemical reactions or physical changes. Compared with traditional synthesis methods, by using very special light as a clean "reagent" and energy source, it is possible to provide uniform energy input to the entire reaction solution under normal temperature and pressure conditions by adjusting factors such as light intensity and wavelength to maximize the light absorption of reaction species, and the reaction process is more gentle. Therefore, photoinduced synthesis of nanomaterials is a green preparation method with broad application prospects.

[0005] Ammonia (NH 3) is an important inorganic compound with a wide range of applications in agriculture, industry, medicine, daily life, etc. In addition, as a carbon-free energy carrier, it also has advantages such as high energy density, safety, and no pollution. However, the unbalanced human nitrogen activities have led to the continuous accumulation of nitrates in nature, causing pollution and endangering human health. Electrochemical reduction of nitrate to ammonia has advantages such as mild reaction conditions and environmental friendliness, and is expected to supplement or replace the traditional Haber-Bosch industrial ammonia synthesis industry, with broad application prospects in the fields of energy conversion and environmental protection. Therefore, developing economic and efficient catalyst materials to achieve nitrate reduction to generate NH 3 is of top priority.

[0006] In order to improve the problems existing in the preparation process of high-entropy effect alloy materials in the prior art, such as harsh reaction conditions, high energy consumption, expensive precursors (high-quality raw materials and auxiliary materials), and pollution of waste gas, waste water, and waste residue after the reaction, the present invention provides a method for in-situ visible-light reduction preparation of high-entropy effect alloy materials in an aqueous solution. The method uses an LED lamp that simulates the visible light segment in sunlight as an energy source, and reduces a variety of (such as three or more) metal salt precursors in an aqueous solution including organic dye fluorescein as a photosensitizer and triethanolamine as an electron sacrificial agent at normal temperature and pressure to prepare an alloy material with a high-entropy effect. The method overcomes the disadvantages of the traditional alloy material preparation process, such as complex process, high pollution, and high energy consumption, and has advantages such as simple process, low energy consumption, and low raw material cost. The alloy material with a high-entropy effect has a wide range of uses. It can achieve electrochemical reduction of nitrate to ammonia, with significant catalytic effects and excellent cyclic catalytic stability, providing an application prospect for the electrochemical reduction of nitrate to ammonia by the alloy material with a high-entropy effect.

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

[0008] A method for in-situ visible-light reduction preparation of an alloy material with a high-entropy effect in an aqueous solution, the method comprising the following steps:

[0009] 1) Mix fluorescein, triethanolamine, water, and three or more metal salts to obtain a mixed solution;

[0010] 2) Place the mixed solution in step 1) under visible light for a light reaction to prepare the alloy material with a high-entropy effect.

[0011] According to an embodiment of the present invention, in step 1), the fluorescein is used as a photosensitizer; the molecular formula of the fluorescein is C 20 H 12 O 5 ; the CAS number of the fluorescein is 2321-07-5; the structural formula of the fluorescein is:

[0012]

[0013] According to an embodiment of the present invention, in step 1), the metal salts are selected from at least three salts formed by zinc salts and metal ions with a more positive reduction potential than zinc ions; exemplarily, the metal salts are selected from at least three of cobalt salts, nickel salts, copper salts, zinc salts, molybdenum salts, chromium salts, tantalum salts, cadmium salts, indium salts, tin salts, lead salts, bismuth salts, ruthenium salts, and platinum salts; preferably, the metal salts are three, four, or more than five of cobalt salts, nickel salts, copper salts, zinc salts, molybdenum salts, chromium salts, tantalum salts, cadmium salts, indium salts, tin salts, lead salts, bismuth salts, ruthenium salts, and platinum salts.

[0014] According to an embodiment of the present invention, in step 1), the reduction potential of the metal salt is lower than the -1.7 V potential generated by the fluorescein. Therefore, the metal salt can be reduced to metal atoms and exist as alloying elements in the alloy material.

[0015] According to an embodiment of the present invention, when the metal salts are three of cobalt salts, nickel salts, copper salts, zinc salts, molybdenum salts, chromium salts, tantalum salts, cadmium salts, indium salts, tin salts, lead salts, bismuth salts, ruthenium salts, and platinum salts, the alloy material prepared is a ternary alloy material with a high entropy effect; when the metal salts are four of cobalt salts, nickel salts, copper salts, zinc salts, molybdenum salts, chromium salts, tantalum salts, cadmium salts, indium salts, tin salts, lead salts, bismuth salts, ruthenium salts, and platinum salts, the alloy material prepared is a quaternary alloy material with a high entropy effect; when the metal salts are five of cobalt salts, nickel salts, copper salts, zinc salts, molybdenum salts, chromium salts, tantalum salts, cadmium salts, indium salts, tin salts, lead salts, bismuth salts, ruthenium salts, and platinum salts, the alloy material prepared is a quinary alloy material with a high entropy effect, i.e., a high entropy alloy material.

[0016] According to an embodiment of the present invention, in step 1), the metal salt can be an organometallic salt or an inorganic metal salt; exemplarily, the metal salt can be acetate, oxalate, phosphate, sulfate, nitrate, chloride, etc. Exemplarily, the cobalt salt is selected from cobalt chloride (for example, cobalt chloride hexahydrate (CoCl 2 ·6H 2 O)); the nickel salt is selected from nickel chloride (for example, nickel chloride hexahydrate (NiCl 2 ·6H 2 O)); the copper salt is selected from copper chloride (for example, copper chloride dihydrate (CuCl 2 ·2H 2 O)); the zinc salt is selected from zinc chloride (ZnCl 2 ); the molybdenum salt is selected from sodium molybdate (for example, sodium molybdate hexahydrate (Na 2 MoO 4 ·6H 2 O)).

[0017] According to an embodiment of the present invention, in step 1), in the mixed solution, the molar amounts of the metal elements forming the alloy material with high entropy effect are the same. Exemplarily, the metal salts are selected from at least three of cobalt salt, nickel salt, copper salt, zinc salt, molybdenum salt, chromium salt, tantalum salt, cadmium salt, indium salt, tin salt, lead salt, bismuth salt, ruthenium salt and platinum salt in equimolar amounts. When the metal salts are selected from three of cobalt salt, nickel salt, copper salt, zinc salt, molybdenum salt, chromium salt, tantalum salt, cadmium salt, indium salt, tin salt, lead salt, bismuth salt, ruthenium salt and platinum salt, the molar ratio of the three alloy elements forming the ternary alloy material is 1:1:1; when the metal salts are selected from four of cobalt salt, nickel salt, copper salt, zinc salt, molybdenum salt, chromium salt, tantalum salt, cadmium salt, indium salt, tin salt, lead salt, bismuth salt, ruthenium salt and platinum salt, the molar ratio of the four alloy elements forming the quaternary alloy material is 1:1:1:1; when the metal salts are selected from five of cobalt salt, nickel salt, copper salt, zinc salt, molybdenum salt, chromium salt, tantalum salt, cadmium salt, indium salt, tin salt, lead salt, bismuth salt, ruthenium salt and platinum salt, the molar ratio of the five alloy elements forming the high-entropy alloy material is 1:1:1:1:1.

[0018] According to an embodiment of the present invention, in step 1), in the mixed solution, the ratio of the total molar amount of the metal salts to the molar amount of the fluorescein is 1:1.5 - 4, for example 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4. The total molar amount of the metal salts refers to the sum of the molar amounts of all the metal salts in the mixed solution.

[0019] According to an embodiment of the present invention, in step 1), in the mixed solution, the concentration of the fluorescein is 0.125 - 2.5 mM (mmol / L), for example 0.125 mM, 0.25 mM, 0.5 mM, 0.75 mM, 1 mM, 1.25 mM, 1.5 mM, 1.75 mM, 2 mM, 2.25 mM or 2.5 mM.

[0020] According to an embodiment of the present invention, in step 1), in the mixed solution, the concentration of one metal salt is 0.05 - 1 mM (mmol / L), for example 0.05 mM, 0.08 mM, 0.1 mM, 0.15 mM, 0.2 mM, 0.3 mM, 0.4 mM, 0.5 mM, 0.6 mM, 0.7 mM, 0.8 mM, 0.9 mM or 1 mM.

[0021] According to an embodiment of the present invention, in step 1), in the mixed solution, the volume ratio of the triethanolamine to the water is 3 - 10:97 - 90; for example 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91 or 10:90.

[0022] According to an embodiment of the present invention, in step 1), the mixing is carried out under stirring conditions. The temperature of the stirring is room temperature, and the time of the stirring is not particularly defined, as long as the materials can be mixed evenly.

[0023] According to an embodiment of the present invention, in step 2), the photo-reaction is carried out under normal temperature, normal pressure and stirring conditions.

[0024] According to an embodiment of the present invention, in step 2), the time of the photo-reaction is 6 - 24 hours, for example, 8 hours, 10 hours, 12 hours, 16 hours, 18 hours or 20 hours.

[0025] According to an embodiment of the present invention, in step 2), the source of the visible light is not particularly defined and can be provided by a light source known in the art that can provide visible light. Exemplarily, the visible light is provided by an LED lamp, for example, provided by 4 LED lamps with a power of 50W each (4×50W).

[0026] According to an embodiment of the present invention, the main wavelength λ of the LED lamp ≥ 420nm.

[0027] According to an embodiment of the present invention, in the reaction system, triethanolamine (TEOA) serves as an electron sacrificial agent, a metal salt serves as a metal ion precursor, fluorescein serves as a photosensitizer, and the metal ion precursor (i.e., the metal salt) in the aqueous solution is directly in-situ reduced under the irradiation of visible light to generate an alloy material with good crystallinity and a stable nano-sheet structure, and this alloy material has a high entropy effect, that is, this alloy material will form a unique solid solution structure, and the alloying elements show a high degree of disorder in the microstructure, and this disorder leads to a significant increase in the mixing entropy of the alloy material, that is, a high entropy effect is obtained.

[0028] According to an embodiment of the present invention, during the photo-reaction process, triethanolamine has multiple coordinatable hydroxyl groups, which can combine with metal ions to form metal complexes M-TEOA (M represents metal ions), and there is a coordination equilibrium between metal ions, TEOA and OH- in an alkaline environment; visible light will cause the metal ions to dissociate from the M-TEOA complex precursor and form metal hydroxides with the OH- complex. At the same time, visible light will excite the photosensitizer fluorescein (Fl) to the singlet state 1 Fl * (compared with SCE, having a very negative reduction potential of -1.7V), triethanolamine can quench the triplet state 3 Fl * , but cannot quench the singlet fluorescence of the excited state 1 F1 * , resulting in electrons from the excited state 1 F1 *It is directly transferred to the metal ions, an oxidation quenching reaction occurs, and the metal ions are reduced to form an alloy material with a high entropy effect.

[0029] According to an embodiment of the present invention, the method further comprises a post-processing step, wherein the post-processing step comprises washing, drying and grinding.

[0030] According to an embodiment of the present invention, the washing is to use deoxygenated anhydrous ethanol, deionized water, and deoxygenated anhydrous ethanol to ultrasonically clean the alloy material with high entropy effect in sequence; illustratively, deoxygenated anhydrous ethanol, deionized water, and deoxygenated anhydrous ethanol are used in sequence, ultrasonically for 10-20 minutes, centrifuged for 10 minutes, and repeated 3 times. The purpose of the washing is to effectively remove triethanolamine and fluorescein.

[0031] According to an embodiment of the present invention, the drying is vacuum drying at 60-80° C. for 12-16 hours.

[0032] According to an embodiment of the present invention, the grinding is to grind the dried alloy material with high entropy effect using a mortar to obtain the alloy material with a suitable particle size.

[0033] The present invention also provides an alloy material with high entropy effect prepared by the above method.

[0034] According to an embodiment of the present invention, each alloy element in the alloy material with high entropy effect presents a highly disordered state in microstructure, that is, the atoms of each alloy element in the alloy material with high entropy effect are uniformly dispersed.

[0035] According to an embodiment of the present invention, the alloy material having a high entropy effect has a face-centered cubic structure.

[0036] The present invention also provides application of the alloy material with high entropy effect in electrocatalytic nitrate reduction to synthesize ammonia.

[0037] According to an embodiment of the present invention, the alloy material with high entropy effect is used as a catalyst in the electrocatalytic reduction of nitrates to synthesize ammonia.

[0038] According to an embodiment of the present invention, the nitrate is selected from at least one of potassium nitrate, sodium nitrate and calcium nitrate.

[0039] The present invention also provides a method for synthesizing ammonia by electrocatalytic reduction of nitrates, wherein the method is to electrocatalytically reduce nitrates to synthesize ammonia in an H-type electrolytic cell using a three-electrode system, and the method comprises the following steps:

[0040] a) Using the electrode prepared from the above alloy material with high entropy effect as the working electrode, an aqueous strong base solution containing nitrate as the catholyte, an aqueous strong base solution as the anolyte, a Hg / HgO electrode as the reference electrode, and a Pt electrode as the counter electrode, assemble an H-type electrolytic cell;

[0041] b) Apply a voltage to the three electrodes in the assembled H-type electrolytic cell to carry out an electrolysis reaction to prepare the ammonia.

[0042] According to an embodiment of the present invention, in step a), the alloy material with high entropy effect is coated on a carbon paper substrate to prepare the working electrode.

[0043] According to an embodiment of the present invention, the selection of the carbon paper substrate (such as thickness, type and source of carbon material) is not particularly defined, and it has no catalytic activity but has electrical conductivity.

[0044] According to an embodiment of the present invention, in step a), the working electrode is prepared by the following method:

[0045] Mix the above-prepared alloy material with high entropy effect, water, absolute ethanol and perfluorosulfonic acid naphthol membrane solution to prepare an alloy slurry; coat the alloy slurry on a carbon paper substrate and dry it to prepare the working electrode.

[0046] Exemplarily, 5 mg of the above-prepared powdery alloy material with high entropy effect is dissolved in a mixed solution of 0.24 mL of water and 0.24 mL of absolute ethanol, ultrasonically dispersed for 30 minutes, then 20 μL of 5% perfluorosulfonic acid naphthol membrane solution is added, and ultrasonic treatment is continued for 30 minutes to prepare an alloy slurry; 20 μL of the alloy slurry is dropped onto a carbon paper substrate (1×1.5 cm), and the working electrode is obtained after drying at room temperature.

[0047] According to an embodiment of the present invention, the main function of each component added when making the alloy slurry is to uniformly disperse and stably adhere the alloy material with high entropy effect to the carbon paper substrate, and it has no catalytic activity.

[0048] According to an embodiment of the present invention, in step a), the Hg / HgO electrode and the Pt electrode can be prepared by known methods in the art or obtained by commercial purchase.

[0049] According to an embodiment of the present invention, in step a), the catholyte comprises nitrate, strong base and water, the concentration of the strong base is 0.1 - 3 M (mol / L), for example, 0.1 M, 0.2 M, 0.5 M, 0.6 M, 0.8 M, 1.0 M, 1.2 M, 1.5 M, 1.8 M, 2.0 M, 2.3 M, 2.5 M, 2.8 M or 3.0 M; the concentration of the nitrate is 0.1 - 3 M (mol / L), for example, 0.1 M, 0.2 M, 0.5 M, 0.6 M, 0.8 M, 1.0 M, 1.2 M, 1.5 M, 1.8 M, 2.0 M, 2.3 M, 2.5 M, 2.8 M or 3.0 M.

[0050] According to an embodiment of the present invention, in step a), the nitrate is selected from at least one of potassium nitrate, sodium nitrate and calcium nitrate.

[0051] According to an embodiment of the present invention, in step a), the anolyte comprises strong base and water, the concentration of the strong base is 0.1 - 3 M (mol / L), for example, 0.1 M, 0.2 M, 0.5 M, 0.6 M, 0.8 M, 1.0 M, 1.2 M, 1.5 M, 1.8 M, 2.0 M, 2.3 M, 2.5 M, 2.8 M or 3.0 M.

[0052] According to an embodiment of the present invention, in step a), the strong base is selected from at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide.

[0053] According to an embodiment of the present invention, in step a), in the H-type electrolytic cell, the working electrode is inserted into the catholyte, and the nitrate hydrogenation reaction to synthesize ammonia occurs on its surface; the reference electrode is inserted into the catholyte; the counter electrode is inserted into the anolyte, and the oxygen evolution reaction occurs on its surface.

[0054] According to an embodiment of the present invention, in step b), the range of the voltage is between -0.5 V vs. RHE and 0.2 V vs. RHE.

[0055] According to an embodiment of the present invention, in step b), the time of the electrolytic reaction is 20 - 60 min.

[0056] Beneficial effects:

[0057] The present invention provides a method for in-situ reducing and preparing an alloy material with a high-entropy effect in an aqueous solution under visible light. The method uses an LED lamp in the visible light range of simulated sunlight as a light source at normal temperature and pressure, and utilizes green electrons to prepare the alloy material with a high-entropy effect. The method overcomes the disadvantages of the traditional alloy material preparation process, such as complex process, high energy consumption, and high pollution during the preparation process; the alloy material with a high-entropy effect obtained by the present invention can achieve a high ammonia production rate and a high Faraday efficiency in the electrocatalytic nitrate reduction reaction for ammonia synthesis, providing an application prospect for the electrocatalytic nitrate reduction reaction of the alloy material with a high-entropy effect; the alloy material with a high-entropy effect synthesized by the present invention has a face-centered cubic structure and does not undergo a phase change after the electrocatalytic reaction, and can still maintain a stable face-centered cubic structure; the alloy material with a high-entropy effect has a lattice distortion effect in its structure, and the induced stress and strain can adjust the d-band center of the alloy material with a high-entropy effect, thereby significantly improving the adsorption capacity of the alloy material with a high-entropy effect for nitrate ions, which is beneficial to achieving a high ammonia production rate and a high Faraday efficiency in the electrocatalytic nitrate reduction reaction for ammonia synthesis. Description of the Drawings

[0058] Figure 1 TEM image of the high-entropy alloy material prepared in Example 1 of the present invention.

[0059] Figure 2 EDS image of the high-entropy alloy material prepared in Example 1 of the present invention.

[0060] Figure 3 HRTEM image of the high-entropy alloy material prepared in Example 1 of the present invention.

[0061] Figure 4 XRD pattern of the high-entropy alloy material prepared in Example 1 of the present invention.

[0062] Figure 5 XRD pattern of the quaternary alloy material with a high-entropy effect prepared in Example 2 of the present invention.

[0063] Figure 6 EDS image of the quaternary alloy material with a high-entropy effect prepared in Example 2 of the present invention.

[0064] Figure 7 XRD pattern of the ternary alloy material with a high-entropy effect prepared in Example 3 of the present invention.

[0065] Figure 8 EDS image of the ternary alloy material with a high-entropy effect prepared in Example 3 of the present invention.

[0066] Figure 9 LSV graph of the electrocatalytic nitrate reduction for ammonia synthesis of the high-entropy alloy material prepared in Example 1 of the present invention.

[0067] Figure 10 Faraday efficiency and ammonia production rate curves of the high-entropy alloy material prepared in Example 1 of the present invention for reducing NO at different voltages 3 -

[0068] Figure 11 Faraday efficiency and ammonia production rate curves of the high-entropy alloy material prepared in Example 1 of the present invention for electrochemically reducing NO at -0.3V vs. RHE 3 -

[0069] Figure 12 LSV diagram of the quaternary alloy material with high-entropy effect prepared in Example 2 of the present invention for electrocatalytic nitrate reduction to synthesize ammonia

[0070] Figure 13 LSV diagram of the ternary alloy material with high-entropy effect prepared in Example 3 of the present invention for electrocatalytic nitrate reduction to synthesize ammonia Detailed implementation manners

[0071] The method of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only illustrative of and explanatory of the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0072] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; unless otherwise specified, the reagents, materials, etc. used in the following examples can all be obtained from commercial channels.

[0073] Example 1: Preparation of CoNiCuZnMo high-entropy alloy material

[0074] CoCl with a concentration of 3×10 -6 mol 2 ·6H 2 O, NiCl with a concentration of 3×10 -6 mol 2 ·6H 2 O, CuCl with a concentration of 3×10 -6 mol 2 ·2H 2 O, ZnCl with a concentration of 3×10 -6 mol 2 , Na with a concentration of 3×10 -6 mol 2 MoO 4 ·2H 2 O and 3×10 -5 ​​Put 1.5 mL of triethanolamine and 28.5 mL of deionized water into a test tube containing 1.5 mL of triethanolamine and 28.5 mL of deionized water, shake well, add a magnetic stir bar, seal the test tube with a rubber stopper, and place the test tube under 4 LED light sources with a main wavelength λ≥420 nm and a power of 50 W; turn on the magnetic stirrer and stir under light for 10 hours.

[0075] After standing the above-prepared mixed system containing the high-entropy alloy material at room temperature for 30 minutes, pour off the supernatant, then wash it successively with deoxygenated anhydrous ethanol, deionized water, and deoxygenated anhydrous ethanol by ultrasonic cleaning for 10 minutes and centrifugal separation for 10 minutes, repeat 3 times, and finally dry it overnight under vacuum at 60 °C, grind it, and collect the high-entropy alloy material.

[0076] Figure 1 This is the TEM image of the high-entropy alloy material prepared in Example 1 of the present invention. As Figure 1 shown, it can be seen from the TEM characterization test that the generated high-entropy alloy material is stacked in flakes.

[0077] Figure 2 This is the EDS image of the high-entropy alloy material prepared in Example 1 of the present invention. As Figure 2 shown, the EDS elemental mapping distribution test shows that within the selected material area, cobalt, nickel, copper, zinc, and molybdenum elements are evenly distributed in the material, indicating that the high-entropy alloy material has been successfully prepared.

[0078] Figure 3 This is the HRTEM image of the high-entropy alloy material prepared in Example 1 of the present invention. As Figure 3 shown, the HRTEM test shows a typical (111) crystal plane, indicating that the high-entropy alloy material has been successfully prepared.

[0079] Figure 4 This is the XRD image of the high-entropy alloy material prepared in Example 1 of the present invention. As Figure 4 shown, the XRD test can draw the conclusion that the generated high-entropy alloy material has typical (111), (200), and (220) crystal planes, indicating that the synthesized high-entropy alloy material has a face-centered cubic structure.

[0080] Example 2: Preparation of CoNiCuZn alloy material

[0081] Other operations are the same as in Example 1, except that: in a test tube containing 1.5 mL of triethanolamine and 28.5 mL of deionized water, add 3.75×10 -6 mol of CoCl 2 ·6H 2 O, 3.75×10 -6 mol of NiCl 2·6H 2 O, 3.75×10 -6 mol mM of CuCl 2 ·2H 2 O, 3.75×10 -6 mol of ZnCl 2 and 3×10 -5 mol of the organic dye fluorescein.

[0082] Figure 5 This is the XRD pattern of the quaternary alloy material with high entropy effect prepared in Example 2 of the present invention. As Figure 5 shown, the conclusion that can be drawn from the XRD test is that the generated quaternary alloy material with high entropy effect has typical (111), (200), and (220) crystal planes, indicating that the synthesized quaternary alloy material with high entropy effect has a face-centered cubic structure.

[0083] Figure 6 This is the EDS pattern of the quaternary alloy material with high entropy effect prepared in Example 2 of the present invention. As Figure 6 shown, the EDS element mapping distribution test shows that within the selected material area, cobalt, nickel, copper, and zinc elements are evenly distributed in the material, indicating that the quaternary alloy material with high entropy effect has been successfully prepared.

[0084] Example 3: Preparation of CoNiCu Alloy Material

[0085] Other operations are the same as in Example 1, except that: 5×10 -6 mol of CoCl 2 ·6H 2 O, 5×10 -6 mol of NiCl 2 ·6H 2 O, 5×10 -6 mol of CuCl 2 ·2H 2 O and 3×10 -5 mol of the organic dye fluorescein are added to a test tube containing 1.5 mL of triethanolamine and 28.5 mL of deionized water.

[0086] Figure 7 This is the XRD pattern of the ternary alloy material with high entropy effect prepared in Example 3 of the present invention. As Figure 7 shown, the conclusion that can be drawn from the XRD test is that the generated ternary alloy material with high entropy effect has a face-centered cubic structure and a body-centered cubic structure.

[0087] Figure 8 This is the EDS pattern of the ternary alloy material with high entropy effect prepared in Example 3 of the present invention. AsFigure 8 As shown, the EDS element mapping distribution test shows that within the selected material area, cobalt, nickel, and copper elements are evenly distributed in the material, indicating that the ternary alloy material with high entropy effect has been successfully prepared.

[0088] Example 4: Electrocatalytic synthesis of ammonia from nitrate using CoNiCuZnMo high-entropy alloy

[0089] Take 5 mg of the powdered high-entropy alloy material prepared in Example 1 and dissolve it in a mixed solution of 0.24 mL of water and 0.24 mL of absolute ethanol. After ultrasonic dispersion for 30 minutes, add 20 μL of 5% perfluorosulfonic acid naphthol membrane solution and continue ultrasonic treatment for 30 minutes to make it fully dispersed. Take 20 μL of the solution and drop it onto a carbon paper substrate (1×1.5 cm), and dry it at room temperature to obtain a working electrode.

[0090] The assembly of the electrocatalytic nitrate synthesis ammonia electrode and the preparation of the electrolyte are as follows:

[0091] Take 50 mL of 1 mol / L NaOH solution on both sides of the H-type electrolytic cell, and add 0.3 M NaNO 3 to the cathode cell. In the H-type electrolytic cell, the working electrode and the reference electrode are inserted into the cathode electrolyte; the counter electrode is inserted into the anode electrolyte. Under the conditions of a voltage range of -0.6 V vs. RHE to 0.2 V vs. RHE and a scanning rate of 5 mV / s, a linear sweep voltammetry (LSV) test of nitrate on the working electrode is carried out.

[0092] Figure 9 This is the LSV diagram of the electrocatalytic reduction of nitrate to ammonia using the high-entropy alloy material prepared in Example 1 of the present invention. As Figure 9 shown, the dashed line represents the condition where 0.3 M NaNO 3 is not added to the cathode cell (only 1 M NaOH solution), and only the hydrogen evolution reaction occurs on the surface of the working electrode. The solid line represents that after adding 0.3 M NaNO 3 (1 M NaOH + 0.3 M NaNO 3 ), the current density is more negative, indicating that the nitrate hydrogenation reaction occurs on the surface of the working electrode.

[0093] Take 50 mL of 1 mol / L NaOH solution on both sides of the H-type electrolytic cell, and add 0.3 M NaNO 3 to the cathode cell. Perform a 30-minute time-current test on the working electrode under the conditions of -0.1 V vs. RHE, -0.2 V vs. RHE, -0.3 V vs. RHE, -0.4 V vs. RHE, -0.5 V vs. RHE, and -0.6 V vs. RHE.

[0094] After the reaction is completed, take an appropriate amount of the cathode electrolyte into a 25 mL colorimetric tube, dilute it to 25 mL with 1 M NaOH, sequentially add 0.6 mL of the potassium sodium tartrate solution and the potassium mercuric iodide solution (Nessler's reagent spectrophotometry), shake well and let stand for 15 min, and measure the absorbance at a wavelength of 420 nm with a UV-visible spectrophotometer. According to the national standard Nessler's reagent spectrophotometry, use a standard ammonia water solution to make a standard curve, and obtain the ammonia production rate and Faraday efficiency of the electrocatalytic system based on the sample test results.

[0095] Figure 10 Faraday efficiency and ammonia production rate curves for the reduction of NO by the high-entropy alloy material prepared in Example 1 of the present invention 3 - As Figure 10 shown, the maximum Faraday efficiency of the electrocatalytic nitrate reduction to ammonia system using the high-entropy alloy material reached 93.8% at a voltage of -0.3 V, and the ammonia production rate reached 1137.8 μmol·h -1 cm -2 at a voltage of -0.6 V, indicating that the prepared high-entropy alloy material has excellent electrocatalytic performance for nitrate reduction to ammonia.

[0096] Figure 11 Faraday efficiency and ammonia production rate curves for the electroreduction of NO by the high-entropy alloy material prepared in Example 1 of the present invention at -0.3 V vs. RHE 3 - As Figure 11 shown, the Faraday efficiency and ammonia production rate of the electrocatalytic nitrate reduction to ammonia system using the high-entropy alloy material can remain stable with the number of cycles, indicating that the prepared high-entropy alloy material has excellent stability in electrocatalytic nitrate reduction to ammonia.

[0097] Example 5: Electrocatalytic nitrate reduction to ammonia by CoNiCuZn quaternary alloy

[0098] Other operations are the same as in Example 4, except that the quaternary alloy material with high-entropy effect prepared in Example 2 is made into a working electrode for electrocatalytic nitrate reduction to ammonia.

[0099] Figure 12 Faraday efficiency and ammonia production rate curves for the reduction of NO by the quaternary alloy material with high-entropy effect prepared in Example 2 of the present invention 3 - As Figure 12 shown, the maximum Faraday efficiency of the electrocatalytic nitrate reduction to ammonia system using the quaternary alloy material with high-entropy effect reached 81.2% at a voltage of -0.5 V, and the ammonia production rate reached 670.8 μmol·h -1 cm-2 , indicating that the prepared quaternary alloy material with high entropy effect has excellent electrocatalytic nitrate synthesis ammonia performance.

[0100] Example 6: Electrocatalytic nitrate synthesis ammonia of CoNiCu ternary alloy

[0101] Other operations are the same as in Example 4, except that the ternary alloy material with high entropy effect prepared in Example 3 is made into a working electrode for electrocatalytic nitrate synthesis ammonia.

[0102] Figure 13 It is the Faraday efficiency and ammonia production rate curve of the ternary alloy material with high entropy effect prepared in Example 3 of the present invention for reducing NO 3 - at different voltages. As Figure 13 shown, the maximum Faraday efficiency of the electrocatalytic nitrate reduction synthesis ammonia system of the ternary alloy material with high entropy effect reached 80.4% at a voltage of -0.6V, and the ammonia production rate reached 870.92 μmol·h -1 cm -2 , indicating that the prepared ternary alloy material with high entropy effect has excellent electrocatalytic nitrate synthesis ammonia performance.

[0103] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an alloy material with high entropy effect by visible light in-situ reduction in an aqueous solution, the method comprising the following steps: 1) mixing fluorescein, triethanolamine, water and three or more metal salts to obtain a mixed solution; 2) placing the mixed solution of step 1) under visible light for photoreaction to prepare the alloy material with high entropy effect.

2. The method according to claim 1, wherein: In step 1), the metal salt is selected from at least three of zinc salts and salts formed by metal ions having a more positive reduction potential than zinc ions. Preferably, the metal salt is selected from at least three of cobalt salts, nickel salts, copper salts, zinc salts, molybdenum salts, chromium salts, tantalum salts, cadmium salts, indium salts, tin salts, lead salts, bismuth salts, ruthenium salts and platinum salts; Preferably, in step 1), in the mixed solution, the molar amounts of the metal elements forming the alloy material with high entropy effect are the same; And / or, in step 1), in the mixed solution, the ratio of the total molar amount of the metal salt to the molar amount of the fluorescein is 1:1.5-4; And / or, in step 1), the concentration of fluorescein in the mixed solution is 0.125-2.5 mM; And / or, in step 1), the volume ratio of triethanolamine to water is 3-10:97-90.

3. The method according to claim 1 or 2, wherein: In step 2), the illumination reaction is carried out at room temperature, pressure and stirring conditions; And / or, in step 2), the illumination reaction time is 6-24 hours.

4. The alloy material with high entropy effect prepared by the method according to any one of claims 1 to 3. Preferably, the alloy material having high entropy effect has a face-centered cubic structure.

5. Use of the alloy material with high entropy effect as claimed in claim 4 in electrocatalytic nitrate reduction to synthesize ammonia.

6. The use according to claim 5, wherein: The alloy material with high entropy effect is used as a catalyst in electrocatalytic nitrate reduction to synthesize ammonia. Preferably, the nitrate is selected from at least one of potassium nitrate, sodium nitrate and calcium nitrate.

7. A method for synthesizing ammonia by electrocatalytic reduction of nitrates, the method comprising the following steps: a) using the electrode prepared from the alloy material with high entropy effect as claimed in claim 4 as the working electrode, using a strong alkaline aqueous solution containing nitrate as the cathode electrolyte, using a strong alkaline aqueous solution as the anode electrolyte, using a Hg / HgO electrode as the reference electrode, and using a Pt electrode as the counter electrode to assemble an H-type electrolytic cell; b) applying voltage to the three electrodes in the assembled H-type electrolytic cell to carry out an electrolytic reaction to prepare the ammonia.

8. The method according to claim 7, wherein: In step a), an alloy material having a high entropy effect is coated on a carbon paper substrate to prepare the working electrode. Preferably, in step a), the cathode electrolyte comprises nitrate, strong base and water, and the concentration of the strong base is 0.1-3M; the concentration of the nitrate is 0.1-3M; the anode electrolyte comprises strong base and water, and the concentration of the strong base is 0.1-3M. Preferably, in step a), the nitrate is selected from at least one of potassium nitrate, sodium nitrate and calcium nitrate; and the strong base is selected from at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide.

9. The method according to claim 7 or 8, wherein: In step a), in the H-type electrolytic cell, the working electrode is inserted into the cathode electrolyte, and a nitrate hydrogenation to ammonia reaction occurs on its surface; the reference electrode is inserted into the cathode electrolyte; The counter electrode is inserted into the anolyte and oxygen evolution reaction occurs on its surface.

10. The method according to any one of claims 7 to 9, wherein: In step b), the voltage range is between -0.5V vs. RHE and 0.2V vs. RHE; And / or, in step b), the electrolysis reaction time is 20-60 min.

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