A method for producing a grain boundary rich metal suitable for electrocatalytic reactions

Abstract

The application discloses a preparation method of a grain boundary rich metal suitable for an electrocatalytic reaction, and belongs to the field of metal chemistry. In the technical scheme of the application, transition metal salt substances and alkali metal salt substances are ground and stirred uniformly to obtain metal salt mixed powder; the metal salt mixed powder is heated in an atmosphere environment, and then cooled to room temperature to obtain a first heating mixture; the first heating mixture is washed with water, suction filtered and dried to remove unreacted alkali metal salt in the first heating mixture; and the first heating mixture after the above completion is subjected to secondary heating treatment in an atmosphere environment, and then cooled to room temperature to obtain a grain boundary rich metal substance. The technical scheme of the application adopts a molten salt auxiliary strategy to realize simple batch preparation of a grain boundary rich metal element / alloy under low temperature conditions.

Description

Technical Field

[0001] This invention relates to a method for preparing grain boundary-rich metals suitable for electrocatalytic reactions, belonging to the field of metal chemical engineering. Background Technology

[0002] Grain boundaries, a typical planar defect, can effectively enhance the inherent activity of nanomaterials in various electrochemical reactions. For example, grain boundaries can stabilize dislocations to create local lattice distortion regions, providing more readily available catalytic sites and optimized surface atomic and electronic properties for electrocatalytic hydrogen evolution and oxygen evolution reactions, thereby achieving suitable binding energies for reaction intermediates. Furthermore, grain boundaries can disrupt the symmetry of adjacent local spaces or modulate catalytic sites, thus regulating the binding energies of various reaction intermediates and consequently modulating the reaction selectivity of electrochemical carbon dioxide reduction, electrochemical carbon monoxide reduction, and electrochemical nitrate reduction reactions.

[0003] However, the simple and large-scale preparation of grain-bound metal elements / alloys suitable for electrocatalytic reactions is one of the bottleneck problems hindering their widespread application. Scientists have reported many methods for preparing composites of metal oxides and carbon materials, commonly including hydrothermal methods, ultrasound-assisted electrodeposition methods, and chemical synthesis methods. However, most of these methods are complex, expensive, and severely limited by the structure of the materials themselves. Summary of the Invention

[0004] To address the problems existing in the prior art, this application provides a method for preparing grain boundary-rich metals suitable for electrocatalytic reactions, which adopts a molten salt-assisted strategy to achieve simple batch preparation of grain boundary-rich metal elements / alloys under low temperature conditions.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is a method for preparing grain boundary-rich metals suitable for electrocatalytic reactions.

[0006] Includes the following steps:

[0007] 1) Grind the transition metal salt and the alkali metal salt and stir them evenly to obtain a mixed metal salt powder;

[0008] 2) After heating the metal salt mixture powder in an atmosphere, it is cooled to room temperature to obtain a single-heat mixture;

[0009] 3) Wash the mixture after heating once, filter and dry it to remove unreacted alkali metal salts from the mixture after heating once;

[0010] 4) After the first heating mixture from step 3) is completed, it is subjected to a second heating treatment in an atmosphere, and then cooled to room temperature to obtain a grain boundary-rich metal.

[0011] The optimized preparation method of the grain boundary rich metal suitable for the electro-catalytic reaction, in step 1), the transition metal salt substance is one kind of transition metal salt or a mixture of multiple transition metal salts; the alkali metal salt substance is one kind of alkali metal salt or a mixture of multiple alkali metal salts;

[0012] The alkali metal salt is an alkali metal nitrate or an alkali metal chloride salt, and the alkali metal salt includes potassium nitrate, sodium nitrate, lithium nitrate, potassium chloride, sodium chloride, lithium chloride, etc.

[0013] The transition metal salt is a transition metal nitrate, a transition metal chloride salt, a transition metal carbonate, or a transition metal sulfate.

[0014] The optimized preparation method of the grain boundary rich metal suitable for the electro-catalytic reaction, in step 2), the heating atmosphere environment is nitrogen, a mixture of nitrogen and hydrogen, argon, or a mixture of argon and hydrogen;

[0015] In step 2), the heating temperature of the metal salt mixed powder is 200-700 degrees Celsius, and the heating holding time is 0.5-5 hours.

[0016] The optimized preparation method of the grain boundary rich metal suitable for the electro-catalytic reaction, in step 4), the secondary heating atmosphere environment is nitrogen, a mixture of nitrogen and hydrogen, argon, or a mixture of argon and hydrogen;

[0017] In step 4), the secondary heating temperature of the primary heating mixture is 200-700 degrees Celsius, and the heating holding time is 0.5-5 hours.

[0018] The optimized preparation method of the grain boundary rich metal suitable for the electro-catalytic reaction, in step 3), the process of mixing, washing, filtering, and drying the primary heating mixture includes,

[0019] 301) adding the primary heating mixture into deionized water, and completely dissolving the alkali metal salt in the deionized water;

[0020] 302) filtering the product obtained after step 301) to remove the dissolved alkali metal salt;

[0021] 303) drying the remaining product in a vacuum environment at a temperature of 80 degrees Celsius for at least 12 hours.

[0022] The optimized preparation method of the grain boundary rich metal suitable for the electro-catalytic reaction, in step 2), when heating the metal salt mixed powder in the atmosphere environment, the heating rate is 10 degrees per minute;

[0023] In step 4), when performing the secondary heating treatment in the atmosphere environment, the heating rate is 10 degrees per minute.

[0024] In the step 2), when the metal salt mixed powder is heated in the atmosphere environment, the metal salt mixed powder is heated in the alumina porcelain boat;

[0025] In the step 4), when the secondary heating treatment is carried out in the atmosphere environment, the primary heating mixture is heated in the alumina porcelain boat.

[0026] The beneficial effects of the present application are:

[0027] In the technical scheme of the present application, the molten salt auxiliary strategy is adopted to realize the simple batch preparation of the grain boundary rich metal element / alloy under low temperature conditions. And the grain boundary rich metal element / alloy prepared by the technical scheme of the present application can realize the regulation of the electrochemical microenvironment on the surface of the catalyst in the electrochemical test process, thereby realizing excellent electrocatalytic performance. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The XRD pattern of the grain boundary rich iridium element;

[0029] Figure 2 The transmission electron microscope pattern of the grain boundary rich iridium element;

[0030] Figure 3 The electrocatalytic hydrogen evolution performance comparison chart of the grain boundary rich iridium element and the commercial benchmark 20wt% Pt / C;

[0031] Figure 4 The in-situ Raman spectrum of the grain boundary rich iridium element in the alkaline electrocatalytic hydrogen evolution process. DETAILED DESCRIPTION

[0032] The present application provides a preparation method of a grain boundary rich metal suitable for an electrocatalytic reaction, comprising the following steps:

[0033] 1) grinding and uniformly stirring a transition metal salt substance and an alkali metal salt substance to obtain a metal salt mixed powder;

[0034] 2) transferring the metal salt mixed powder into an alumina porcelain boat, placing it in the middle of a tube furnace, and heating and treating it in an atmosphere environment, and then naturally cooling it to room temperature to obtain a primary heating mixture;

[0035] 3) mixing, washing with water, and filtering and drying the primary heating mixture to remove unreacted alkali metal salt in the primary heating mixture;

[0036] 4) after the completion of step 3), the primary heating mixture is subjected to secondary heating treatment in an atmosphere environment, and then cooled to room temperature to obtain a grain boundary rich metal substance.

[0037] In the present application, the transition metal salt substance is a transition metal salt or a mixture of multiple transition metal salts, and can be a transition metal nitrate, a transition metal chloride, a transition metal carbonate, or a transition metal sulfate. The transition metal salt can be manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, copper nitrate, ruthenium chloride, iridium chloride, rhodium chloride, platinum chloride, manganese chloride, iron chloride, cobalt chloride, nickel chloride, copper chloride, manganese carbonate, iron carbonate, cobalt carbonate, nickel carbonate, copper carbonate, manganese sulfate, iron sulfate, cobalt sulfate, nickel sulfate, copper sulfate, etc.

[0038] In the present application, the mass ratio of the transition metal salt to the alkali metal salt is 1:200 to 1:2.

[0039] The alkali metal salt substance is an alkali metal salt or a mixture of multiple alkali metal salts, and the alkali metal salt can be an alkali metal nitrate or a chloride salt. The alkali metal salt includes potassium nitrate, sodium nitrate, lithium nitrate, potassium chloride, sodium chloride, lithium chloride, etc.

[0040] In steps 2) and 4) of the present application, the heated atmosphere is nitrogen, a mixture of nitrogen and hydrogen, argon, or a mixture of argon and hydrogen.

[0041] In steps 2) and 4) of the present application, the heating temperature and the secondary heating temperature are 200 to 700 degrees Celsius, the temperature rising speed is 10 degrees per minute, and the heating holding time is 0.5 to 5 hours.

[0042] In step 3), the process of mixing, washing, filtering, and drying the primary heating mixture includes,

[0043] 301) The primary heating mixture is added to deionized water, and the alkali metal salt is completely dissolved in the deionized water;

[0044] 302) The product obtained after step 301) is filtered, and the dissolved alkali metal salt is removed;

[0045] 303) The remaining product is dried in a vacuum environment at a temperature of 80 degrees Celsius for at least 12 hours.

[0046] The present application will be further described in detail below with reference to specific examples and accompanying drawings.

[0047] Example 1

[0048] In this example, the preparation of a grain boundary-rich iridium element is described in detail, and the specific steps include:

[0049] The 110 mg of potassium chloride, 90 mg of lithium chloride, and 20 mg of iridium trichloride were thoroughly ground in a mortar for 20 minutes, then transferred to an alumina boat and placed in a tube furnace, and the gas in the tube furnace was completely replaced with argon for 30 minutes. Then, the temperature was programmed to increase at a rate of 10 degrees per minute to 500 degrees Celsius, and maintained for 2 hours, and then naturally cooled to room temperature.

[0050] The resulting mixture was added to 200 mL of deionized water to completely dissolve the alkali metal salt, and then suction filtered to remove the dissolved alkali metal salt. The remaining product was placed in a vacuum oven and dried at 80 degrees Celsius for 12 hours. The sample obtained after drying was transferred to an alumina boat and placed in a tube furnace, and the gas in the tube furnace was completely replaced with a mixture of argon and hydrogen for 30 minutes. Then, the temperature was programmed to increase at a rate of 10 degrees per minute to 300 degrees Celsius, and maintained for 30 minutes, and then naturally cooled to room temperature after heating was complete, to obtain grain boundary-rich iridium single element.

[0051] Material morphology characteristics

[0052] As shown in FIG. 1, XRD characterization showed that the prepared material was iridium single element. As shown in FIG. 2, a transmission electron microscope image showed that the prepared material was grain boundary-rich, Figure 1 white mark line in the figure represents the grain boundary. Figure 2 Figure 2

[0053] Electrochemical performance test

[0054] 1. Preparation of catalyst ink and performance test

[0055] (1) 2 mg of catalyst was weighed and dispersed in 300 μL of anhydrous ethanol and 40 μL of a 5 wt% Nafion solution, and ultrasonicated for 1 h to obtain a uniformly dispersed catalyst ink.

[0056] (2) Test of catalyst oxygen evolution performance

[0057] Electrochemical tests were performed on a CHI 760E electrochemical workstation (CHI Instruments, China) using a three-electrode system.

[0058] A carbon rod electrode and a reversible hydrogen electrode were used as the counter electrode and reference electrode, respectively. Preparation of the working electrode: 6 μL of catalyst ink was taken with a pipette and applied to a glassy carbon electrode with a diameter of 3 mm, and naturally dried at room temperature. At this time, the loading of the catalyst on the glassy carbon electrode was 0.5 mg cm-2.

[0059] ​​During the electrocatalytic hydrogen evolution test, the linear voltammetry curve scan rate was 5 mV s⁻¹, and the data were compensated for 95% IR. The electrolyte was 1 M KOH.

[0060] When testing the time-potential curve of the catalyst at a constant current density of 10 mA cm⁻², a glassy carbon electrode coated with the catalyst was used as the working electrode, a carbon rod as the counter electrode, and a reversible hydrogen electrode as the reference electrode.

[0061] Catalyst electrochemical performance description

[0062] like Figure 3 As shown, at a reference current density of 10 mA cm⁻², the overpotential of grain boundary-rich iridium is only 7 mV, which is better than the commercial reference of 20 wt% Pt / C (37 mV).

[0063] The influence of grain boundaries on the electrocatalytic hydrogen evolution reaction

[0064] Test conditions

[0065] Operando Raman measurements were performed on a Renishaw Raman spectrometer (laser wavelength = 532 nm). Catalyst ink was dropped onto a carbon paper electrode serving as the working electrode. The working electrode was first immersed in the electrolyte before testing. Similarly, in-situ electrochemical measurements were performed using a self-made battery to obtain better signal data. A voltage was applied to the catalyst electrode for 20 minutes before data acquisition.

[0066] Test Results

[0067] Figure 4 The in-situ Raman spectroscopy showed that the grain-bound iridium elemental catalyst, under the condition of applying a voltage of 50 mV, can generate a unique reaction intermediate H3O+ compared with the condition of not applying a voltage, thereby changing the electrochemical microenvironment on the catalyst surface and accelerating the alkaline electrocatalytic hydrogen evolution reaction.

[0068] Example 2

[0069] The specific steps for preparing ruthenium rich in grain boundaries include:

[0070] 110 mg of potassium chloride, 90 mg of lithium chloride, and 20 mg of ruthenium trichloride were thoroughly ground in a mortar for 20 minutes. The mixture was then transferred to an alumina ceramic boat and placed in a tube furnace. Argon gas was introduced for 30 minutes to completely replace the gas in the tube furnace with argon. The temperature was then increased to 500°C at a rate of 10°C / min and held for 2 hours, followed by natural cooling to room temperature.

[0071] The resulting mixture was added to 200 ml of deionized water to completely dissolve the alkali metal salt, and then filtered to remove the dissolved alkali metal salt.

[0072] The remaining product is dried in a vacuum oven at 80 degrees Celsius for 12 hours.

[0073] The sample obtained after drying is transferred to an alumina porcelain boat and placed in a tube furnace, and a mixed gas of argon and hydrogen is passed for 30 minutes. The gas in the tube furnace is completely replaced with the mixed gas of argon and hydrogen, and then the temperature is programmed to rise at a rate of 10 degrees Celsius per minute to 300 degrees Celsius and maintained for 30 minutes. After heating is completed, natural cooling to room temperature is performed to obtain a grain boundary-rich ruthenium element.

[0074] Example 3

[0075] The specific steps for preparing the grain boundary-rich nickel element include:

[0076] The 110 milligrams of potassium chloride, 90 milligrams of lithium chloride, and 20 milligrams of nickel chloride are thoroughly ground in a mortar for 20 minutes, then transferred to an alumina porcelain boat and placed in a tube furnace, and argon gas is passed for 30 minutes. The gas in the tube furnace is completely replaced with argon. Then the temperature is programmed to rise at a rate of 10 degrees Celsius per minute to 500 degrees Celsius and maintained for 2 hours, and then naturally cooled to room temperature.

[0077] The obtained mixture is added to 200 milliliters of deionized water to completely dissolve the alkali metal salt, and then suction filtration is performed to remove the dissolved alkali metal salt.

[0078] The remaining product is dried in a vacuum oven at 80 degrees Celsius for 12 hours.

[0079] The sample obtained after drying is transferred to an alumina porcelain boat and placed in a tube furnace, and a mixed gas of argon and hydrogen is passed for 30 minutes. The gas in the tube furnace is completely replaced with the mixed gas of argon and hydrogen, and then the temperature is programmed to rise at a rate of 10 degrees Celsius per minute to 300 degrees Celsius and maintained for 30 minutes. After heating is completed, natural cooling to room temperature is performed to obtain a grain boundary-rich nickel element.

[0080] Of course, the above description is not a limitation on the present application, and the present application is not limited to the above examples. Changes, modifications, additions, or substitutions made by those of ordinary skill in the art within the spirit and scope of the present application should be within the protection scope of the present application.

Claims

1. A method for the production of a grain boundary rich metal suitable for electrocatalytic reactions, characterized in that: The method comprises the following steps: 1) grinding and stirring a transition metal salt substance and an alkali metal salt substance to obtain a mixed metal salt powder; 2) heating the mixed metal salt powder in an atmosphere environment using a molten salt assisted strategy, and cooling to room temperature to obtain a first heating mixture; 3) mixing, washing with water, filtering and drying the first heating mixture to remove unreacted alkali metal salt in the first heating mixture; 4) performing secondary heating treatment on the first heating mixture obtained after step 3) in an atmosphere environment, and cooling to room temperature to obtain a grain boundary rich metal; In step 2), the heating atmosphere is nitrogen or argon; In step 4), the secondary heating atmosphere is a mixture of nitrogen and hydrogen or a mixture of argon and hydrogen.

2. The method for preparing a grain boundary rich metal suitable for an electrocatalytic reaction according to claim 1, wherein: In step 1), the transition metal salt substance is a transition metal salt or a mixture of multiple transition metal salts; and the alkali metal salt substance is an alkali metal salt or a mixture of multiple alkali metal salts; The alkali metal salt is an alkali metal nitrate or an alkali metal chloride, and the alkali metal salt includes potassium nitrate, sodium nitrate, lithium nitrate, potassium chloride, sodium chloride and lithium chloride; The transition metal salt is a transition metal nitrate, a transition metal chloride, a transition metal carbonate or a transition metal sulfate.

3. The method for preparing a grain boundary rich metal suitable for an electrocatalytic reaction according to claim 1, wherein: In step 2), the heating temperature of the mixed metal salt powder is 200-700 degrees Celsius, and the heating holding time is 0.5-5 hours.

4. The method for preparing a grain boundary rich metal suitable for an electrocatalytic reaction according to claim 1, wherein: In step 4), the secondary heating temperature of the first heating mixture is 200-700 degrees Celsius, and the heating holding time is 0.5-5 hours.

5. The method for preparing a grain boundary rich metal suitable for an electrocatalytic reaction according to claim 1, wherein: In step 3), the process of mixing, washing with water, filtering and drying the first heating mixture comprises: 301) adding the first heating mixture into deionized water, and completely dissolving the alkali metal salt in the deionized water; 302) filtering the product obtained after step 301) to remove the dissolved alkali metal salt; 303) drying the remaining product in a vacuum environment at a temperature of 80 degrees Celsius for at least 12 hours.

6. The method for preparing a grain boundary rich metal suitable for an electrocatalytic reaction according to claim 1, wherein: In step 2), the heating rate is 10 degrees / minute when heating the mixed metal salt powder in the atmosphere environment; In step 4), the heating rate is 10 degrees / minute when performing secondary heating treatment in the atmosphere environment.

7. The method for preparing a grain boundary rich metal suitable for an electrocatalytic reaction according to claim 1, wherein: In step 2), when the metal salt mixed powder is heat-treated in an atmosphere, the metal salt mixed powder is held in an alumina porcelain boat and heated. In step 4), when the secondary heat treatment is performed in an atmosphere, the primary heat-treated mixture is held in an alumina porcelain boat and heated. In step 2), when the metal salt mixed powder is heat-treated in an atmosphere, the metal salt mixed powder is held in an alumina porcelain boat and heated. In step 4), when the secondary heat treatment is performed in an atmosphere, the primary heat-treated mixture is held in an alumina porcelain boat and heated. In step 2), when the metal salt mixed powder is heat-treated in an atmosphere, the metal salt mixed powder is held in an alumina porcelain boat and heated. In step 4), when

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