Carbon-supported ruthenium-doped iron-based phosphide electrocatalyst, and preparation method and application thereof

Abstract

The invention provides a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst as well as a preparation method and application thereof, and belongs to the field of electrocatalytic materials. The method comprises the following steps: mixing ruthenium trichloride, ferric trichloride and phenylphosphonic acid, and carrying out a coordination reaction to obtain an MOFs precursor; performing ultrasonic washing and purification on the obtained MOFs precursor to obtain a pure product; and placing the obtained pure product in a tubular furnace for calcination and carbonization to obtain the carbon-supported ruthenium-doped iron-based phosphide electrocatalyst. The invention also provides the carbon-supported ruthenium-doped iron-based phosphide electrocatalyst obtained by the preparation method. The carbon-supported ruthenium-doped iron-based phosphide provided by the invention has excellent electro-catalytic performance, and the overpotential for realizing electro-catalytic reduction hydrogen evolution is relatively low.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrocatalytic materials, and particularly relates to a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst, a preparation method and application thereof. BACKGROUND

[0002] With the growing demand for clean and sustainable energy, in-depth research has been conducted to develop new technologies for energy storage and conversion. In terms of energy conversion, electrocatalytic water splitting is widely welcomed due to its environmental characteristics, net zero carbon emissions and sustainable clean energy production. The electrocatalytic water splitting process involves two half-reactions, namely the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). However, such reactions require the addition of efficient and stable catalysts to reduce the high activation energy of hydrogen to improve the reaction kinetics. As the most efficient electrocatalytic hydrogen evolution catalyst, noble metal Pt has a hydrogen adsorption Gibbs free energy (ΔGH) of almost zero, thus being able to produce a very high exchange current density at a near-zero overpotential. However, the scarcity and high price of noble metals seriously restrict the commercial development and practical application of electrocatalytic materials. Therefore, it is necessary to develop efficient, stable and inexpensive catalysts for the sustainable production of hydrogen.

[0003] In recent years, a large amount of research work has been carried out at home and abroad in the preparation of new electrocatalysts, especially transition metal-based catalysts with high content, such as cobalt, iron, nickel and copper. These transition metals can be combined with different ligands to form complexes for electrocatalytic reduction of hydrogen evolution. Among them, iron and cobalt metal organic complexes are widely used for electrocatalytic reduction of hydrogen evolution. However, single metal organic complexes as electrocatalysts for electrocatalytic reduction of hydrogen evolution still have the problems of poor electrocatalytic performance and high overpotential for reaction. SUMMARY

[0004] The purpose of the present application is to provide a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst, a preparation method and application thereof. The carbon-supported ruthenium-doped iron-based phosphide provided by the present application has excellent electrocatalytic performance and a low overpotential for electrocatalytic reduction of hydrogen evolution.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions: The present application provides a preparation method of a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst, comprising the following steps: Step one: mixing ruthenium trichloride, iron trichloride and phenyl phosphonic acid to carry out a coordination reaction to obtain a MOFs precursor; Step two: ultrasonic washing and purification of the MOFs precursor obtained in step one to obtain a pure product; Step three: calcining and carbonizing the pure product obtained in step two in a tube furnace to obtain a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst.

[0006] Preferably, the molar ratio of ruthenium trichloride, iron trichloride and phenylphosphonic acid in step one is 0.125:0.5:1.

[0007] Preferably, the reaction temperature in step one is 60℃, and the reaction time is 11-14h.

[0008] Preferably, the purification step in step two includes adding EtOH, ultrasonic crushing and washing, centrifugal collection, ultrasonic crushing and washing with deionized water, and finally drying under vacuum.

[0009] Preferably, the temperature for calcining and carbonizing in step three is 900℃, the time is 2-3h, and the heating rate is 5-10℃ / min.

[0010] The application also provides a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst prepared by the above method.

[0011] The application also provides the use of the above carbon-supported ruthenium-doped iron-based phosphide electrocatalyst in the hydrogen evolution reaction of alkaline electrolytic water.

[0012] Advantages of the application In the application, phenylphosphonic acid is used as an organic ligand, iron ions (Fe 3+ ) and ruthenium ions (Ru 3+ ) are used as metal centers, a ruthenium-iron bimetallic MOFs material precursor is obtained by heating and stirring, and an iron-ruthenium phosphide is obtained after tube furnace calcination. In the application, it is difficult for ruthenium to coordinate with phenylphosphonic acid, so conditions are adjusted to make it coordinate with iron ions and phenylphosphonic acid, and only a small amount of ruthenium is needed to significantly improve the electrocatalytic performance. In the process of high-temperature carbon burning, the organic matter is in-situ derived into a carbon base, which provides long-range continuous conductive support for the active center, and the overpotential in the HER reaction process is significantly reduced.

[0013] In the application, a bimetallic MOFs precursor is prepared by co-coordinating ruthenium-iron salt with phenylphosphonic acid, and a carbon-supported ruthenium-doped iron-based phosphide is prepared. Compared with a single-metal phosphide derived from a single-metal MOFs precursor, the overpotential of the catalyst material prepared by the experimental method is significantly reduced, the Tafel slope is also significantly reduced, the reaction kinetics is significantly improved, and the purpose of improving the electrocatalytic performance is ultimately achieved. The experimental results show that when the overpotential is-0.20V vs.RHE, the electrocatalytic hydrogen evolution reaction on the surface of the ruthenium-iron metal organic complex electrode begins, and the corresponding reaction overpotential is 200mV. BRIEF DESCRIPTION OF DRAWINGS

[0014] The above and / or additional aspects and advantages of the application will become apparent and be readily understood from the following description, taken in connection with the accompanying drawings, in which: Figure 1SEM image of ruthenium iron phosphide prepared for Example 1 of the present application.

[0015] Figure 2 For Figure 1 SEM image after 2 times magnification.

[0016] Figure 3 For Figure 1 SEM image after 10 times magnification.

[0017] Figure 4 For the electrocatalytic hydrogen evolution performance chart of black product 1 of Example 1 and commercial Pt / C and material-unloaded glassy carbon electrode.

[0018] Figure 5 For the electrocatalytic hydrogen evolution performance chart of black products 1-4 obtained from Example 1 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0019] The present application provides a preparation method of carbon-supported ruthenium-doped iron-based phosphide electrocatalyst, comprising the following steps: Step one: first dissolve ruthenium trichloride and iron trichloride in deionized water for ultrasonic dissolution, the ultrasonic dissolution time is preferably 10 min, to obtain a metal ion mixed solution, then weigh the phenyl phosphonic acid and dissolve it in an ethanol solvent, after complete dissolution, add the above metal ion mixed solution to the ethanol solution of phenyl phosphonic acid to carry out coordination reaction to obtain MOFs precursor; the molar ratio of ruthenium trichloride, iron trichloride and phenyl phosphonic acid is preferably 0.125:0.5:1, and the reaction temperature in step one is preferably 60℃, and the reaction time is preferably 11-14h.

[0020] Step two: ultrasonic washing and purification of the MOFs precursor obtained in step one to obtain a pure product; the purification step is preferably that after the reaction in step one is completed, the three-necked flask is cooled to room temperature, the solid is collected by centrifugation, EtOH is added for ultrasonic crushing and washing, the solid is collected by centrifugation, this process is repeated three times, then H2O is used to repeat the above operation three times, and the product is preferably dried at 60℃ under vacuum.

[0021] Step three: under the protection of nitrogen, the pure product obtained in step two is placed in a tube furnace for calcination and carbonization, the calcination and carbonization temperature is preferably 900℃, the time is preferably 2-3h, more preferably 3h, and the heating rate is preferably 5-10℃ / min, more preferably 5℃ / min, to obtain a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst. The present application also provides the carbon-supported ruthenium-doped iron-based phosphide electrocatalyst obtained by the above preparation method.

[0022] The present application also provides the application of the above carbon-supported ruthenium-doped iron-based phosphide electrocatalyst in alkaline electrolytic water hydrogen evolution reaction.

[0023] The application utilizes organic phosphonic acid as a phosphorus source, adopts a double-metal coordination effect, synthesizes a MOFs precursor coordinated with a phosphonic acid ligand, precisely regulates the crystal phase structure of a binary metal phosphide at a molecular level, optimizes the catalytic performance of an electrode material, and realizes controllable construction of an electrocatalytic material with high intrinsic activity and high reaction selectivity. In the application, the phosphonic acid group exhibits stronger coordination ability, and the coordination mode is also more diverse. In the coordination process, the phosphonic acid group can form diversified coordination structures such as monodentate, bidentate and even polydentate. Compared with the pollution of an external phosphorus source high-temperature process and the uncontrollability of a phosphorus element doping amount, through adjustment of the number of phosphonic acid groups and the coordination mode in the organic phosphonic acid ligand, the crystal phase structure of the phosphide can be regulated and controlled, and the content ratio of the double metal, the morphology of the catalyst and other multi-scale structures can be realized, so that the high-activity ruthenium-doped iron-based phosphide can be precisely synthesized at a molecular level.

[0024] The application will be further described below in combination with examples, and those skilled in the art can more comprehensively understand the application, but the application is not limited in any way by the examples. Examples

[0025] (1) 0.5 mmol of ferric chloride and 0.125 mmol of ruthenium trichloride were weighed and dissolved in 10 mL of deionized water, and ultrasonic dissolution was performed for 10 min. Then 1 mmol of phenyl phosphonic acid was weighed and dissolved in 10 mL of anhydrous ethanol, and after complete dissolution, the metal ion mixture was added dropwise into the ethanol solution of the phenyl phosphonic acid, and then transferred into a 100 mL three-necked flask for stirring reaction at 60 DEG C in an oil bath for 12 hours. After the reaction was completed, the three-necked flask was cooled to room temperature, and the solid was collected by centrifugation. Then 35 mL of EtOH was used for ultrasonic crushing and washing, and the solid was collected by centrifugation. The process was repeated three times. Then 35 mL of H2O was used for repeating the above operation three times. Vacuum drying was performed at 60 DEG C to obtain a light brown solid of iron-ruthenium-phenyl phosphonic acid MOFs precursor material.

[0026] (2) 100 mg of the ruthenium-iron-phenyl phosphonic acid complex was placed in a 7 mL corundum boat. After N2 protection for 30 min, the sample was heated from room temperature to 900 DEG C at a heating rate of 5 DEG C / min and kept for 3 hours. After cooling to room temperature, a black product, i.e. a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst, was obtained. The black product was collected and ground for LSV detection.

[0027] (3) 20 mg of the black product 1 was weighed by using an analytical balance and placed in a 5 mL centrifuge tube. 3.6 mL of isopropanol and 0.4 mL of 5% nafion solution were measured by using a pipette and added into the centrifuge tube. Then the centrifuge tube was placed in an ultrasonic cleaning instrument, and ultrasonic treatment was performed at 40 KHz for 1 h to obtain a uniformly dispersed suspension. 20 uL of the suspension was dropped on a glassy carbon electrode with an area of 0.2 cm 2 by using a pipette in five times, and then naturally dried at room temperature.

[0028] Figure 1 SEM image of ruthenium iron phosphide prepared in Example 1 of this invention; Figure 2 for Figure 1 SEM image magnified 2 times; Figure 3 for Figure 1 The SEM image is magnified 10 times. It can be seen that the obtained material exhibits a loose porous structure. This structure not only facilitates the contact between water molecules and the active sites on the material surface, but also promotes the rapid diffusion of gaseous products generated by water decomposition, thereby improving the catalyst performance.

[0029] Comparative Example 1 (1) Weigh 0.5 mmol of ferric chloride and 0.125 mmol of ruthenium trichloride and dissolve them in 10 mL of deionized water. Sonicate for 10 min to dissolve. Then weigh 1 mmol of phenylphosphonic acid and dissolve it in 10 mL of anhydrous ethanol. After complete dissolution, add the metal ion mixture dropwise to the ethanol solution of phenylphosphonic acid. Transfer the solution to a 100 mL three-necked flask and stir in an oil bath at 60 °C for 12 hours. After the reaction is complete, cool the three-necked flask to room temperature, centrifuge to collect the solid, add 35 mL of EtOH, sonicate to break up and wash the solid, centrifuge to collect the solid, and repeat this process three times. Repeat the above operation three times with 35 mL of H2O. Dry under vacuum at 60 °C to obtain a light brown solid iron-ruthenium phenylphosphonic acid MOF precursor material.

[0030] (2) Place 100 mg of the ruthenium iron phenylphosphonic acid complex in a 7 mL corundum ceramic boat. Place it in a tube furnace, purge with N2 for 30 min, then raise the temperature of the sample from room temperature to 700 °C at a rate of 5 °C / min and hold for 3 hours. After cooling to room temperature, grind and collect the resulting black product 2 for LSV detection.

[0031] (3) Weigh 20 mg of black product 2 using an analytical balance and place it in a 5 mL centrifuge tube. Add 3.6 mL of isopropanol and 0.4 mL of 5% Nafion solution to the centrifuge tube using a pipette. Then, place the centrifuge tube in an ultrasonic cleaner and sonicate it at 40 kHz for 1 hour to obtain a uniformly dispersed suspension. Use a pipette to take 20 μL of the suspension in 5 portions and drop it onto a 0.2 cm² area. 2 The glassy carbon electrode was allowed to air dry naturally at room temperature.

[0032] Comparative Example 2 (1) Take 1 mmol of ferric chloride and dissolve it in 10 mL of deionized water, and ultrasonic it for 10 min to dissolve. Then take 0.5 mmol of phenyl phosphonic acid and dissolve it in 10 mL of anhydrous ethanol. After complete dissolution, add the metal ion mixture to the ethanol solution of phenyl phosphonic acid, and transfer it to a 100 mL three-necked flask for stirring reaction at 60°C in an oil bath for 12 hours. After the reaction is completed, cool the three-necked flask to room temperature, centrifuge to collect the solid, add 35 mL of EtOH, and ultrasonic it to break up and wash the solid. Centrifuge to collect the solid, and repeat this process three times. Then repeat the above operation three times with 35 mL of H2O. Dry at 60°C under vacuum to obtain a white solid of iron phenyl phosphonic acid MOFs precursor material.

[0033] (2) Place 100 mg of the iron phenyl phosphonic acid complex in a 7 mL corundum boat. Place it in a tube furnace, and after 30 min of N2 protection, increase the temperature of the sample from room temperature to 900°C at a rate of 5°C / min, and keep it at 900°C for 3 hours. After cooling to room temperature, grind the obtained black product 3 and collect it for LSV detection.

[0034] (3) Take 20 mg of the black product 3 and place it in a 5 mL centrifuge tube. Use a pipette to take 3.6 mL of isopropanol and 0.4 mL of 5% nafion solution and add them to the centrifuge tube. Then place the centrifuge tube in an ultrasonic cleaner, and ultrasonic it at 40 KHz for 1 h to obtain a uniformly dispersed suspension. Use a pipette to take 20 μL of the suspension and drop it on a glassy carbon electrode with an area of 0.2 cm 2 at room temperature.

[0035] Comparative Example 3 (1) Take 1 mmol of ferric chloride and dissolve it in 10 mL of deionized water, and ultrasonic it for 10 min to dissolve. Then take 0.5 mmol of phenyl phosphonic acid and dissolve it in 10 mL of anhydrous ethanol. After complete dissolution, add the metal ion mixture to the ethanol solution of phenyl phosphonic acid, and transfer it to a 100 mL three-necked flask for stirring reaction at 60°C in an oil bath for 12 hours. After the reaction is completed, cool the three-necked flask to room temperature, centrifuge to collect the solid, add 35 mL of EtOH, and ultrasonic it to break up and wash the solid. Centrifuge to collect the solid, and repeat this process three times. Then repeat the above operation three times with 35 mL of H2O. Dry at 60°C under vacuum to obtain a white solid of iron phenyl phosphonic acid MOFs precursor material.

[0036] (2) Place 100 mg of the iron phenyl phosphonic acid complex in a 7 mL corundum boat. Place it in a tube furnace, and after 30 min of N2 protection, increase the temperature of the sample from room temperature to 700°C at a rate of 5°C / min, and keep it at 700°C for 3 hours. After cooling to room temperature, grind the obtained black product 4 and collect it for LSV detection.

[0037] (3) 20 mg of the black product 4 was weighed by using an analytical balance and was placed in a 5 mL centrifuge tube. 3.6 mL of isopropyl alcohol and 0.4 mL of 5% nafion solution were measured by using a pipette and were added into the centrifuge tube. Then, the centrifuge tube was placed in an ultrasonic cleaner, and was ultrasonically treated at 40 KHz for 1 h to obtain a uniformly dispersed suspension. 20 μL of the suspension was dropped on a glassy carbon electrode with an area of 0.2 cm 2 at room temperature by using a pipette.

[0038] The carbon-supported ruthenium-doped iron-based phosphide obtained in the application was used as a catalyst material, a glassy carbon electrode was used as a current collector support, and was prepared as a working electrode. A reversible hydrogen electrode was used as a reference electrode, and a platinum sheet electrode was used as a counter electrode. A 1M KOH electrolysis device was assembled in a glass electrolytic cell, and a Chenhua 760E electrochemical workstation was used to perform linear scanning in an alkaline medium. The performance of electrocatalytic hydrogen evolution under alkaline conditions was investigated, wherein the scanning speed was 5 mV / s, and the scanning potential window was from 0.1 V as the starting voltage to 0.5 V. At the same time, the same test method was used to perform performance test of electrocatalytic hydrogen evolution under alkaline conditions on a commercial noble metal-based Pt / C catalyst as a control sample, and the test results are shown in the figure.

[0039] Figure 4 It is the electrocatalytic hydrogen evolution performance graph of the black product 1 of Example 1, a commercial Pt / C and a glassy carbon electrode without material loading. Figure 5 It is the electrocatalytic hydrogen evolution performance graph of the black products 1-4 obtained in Example 1 and Comparative Examples 1-3.

[0040] As can be seen from the figure, when the potential is 0.3 V, the decomposition current of 1M potassium hydroxide solution on the surface of the glassy carbon electrode loaded with the black product 1 reaches 10 mA·cm -2 , and the corresponding reaction overpotential is 300 mV. The overpotential of the glassy carbon electrode loaded with the black product 3 reaches 10 mA·cm -2 , and the overpotential is 418 mV. The electrode material doped with a small amount of ruthenium metal is reduced by 118 mV compared with the electrode material without doping ruthenium metal. The overpotential of the glassy carbon electrode loaded with the black product 2 and the black product 4 obtained by carbon burning at 700 ℃ reaches 10 mA·cm -2 , and the overpotential is more than 500 mV, which has no use value. It can be seen that the electrode of the doped small amount of ruthenium metal double metal organic complex prepared in the application has relatively excellent electrocatalytic performance.

Claims

1. A method for preparing a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst, characterized in that, The method comprises the following steps: Step 1: mixing ruthenium trichloride, iron trichloride and phenyl phosphonic acid to carry out a coordination reaction to obtain a MOFs precursor; Step 2: ultrasonic washing and purifying the MOFs precursor obtained in step 1 to obtain a pure product; Step 3: placing the pure product obtained in step 2 in a tube furnace to carry out calcination and carbonization to obtain a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst.

2. The method for preparing a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst according to claim 1, characterized in that, In step 1, the molar ratio of ruthenium trichloride, iron trichloride and phenyl phosphonic acid is 0.125:0.5:

1.

3. The method for preparing a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst according to claim 1, characterized in that, In step 1, the reaction temperature is 60℃, and the reaction time is 11-14h.

4. The method for preparing a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst according to claim 1, characterized in that, The purification step in step 2 comprises: adding EtOH to ultrasonic crushing and washing, centrifugal collection, again using deionized water to ultrasonic crushing and washing, and finally drying under vacuum.

5. The method for preparing a carbon-supported ruthenium-doped iron-based phosphide electrocatalyst according to claim 1, characterized in that, In step 3, the calcination and carbonization temperature is 900℃, the time is 2-3h, and the heating rate is 5-10℃ / min.

6. The carbon-supported ruthenium-doped iron-based phosphide electrocatalyst obtained by the preparation method of claim 1.

7. The use of the carbon-supported ruthenium-doped iron-based phosphide electrocatalyst of claim 6 in the hydrogen evolution reaction of alkaline electrolytic water.

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