Monatomic alloy and electrochemical preparation method and application thereof

Abstract

The invention relates to a method for electrochemically preparing monatomic alloy, which comprises the following steps: preparing ionic liquid containing a main metal precursor, the main metal is Fe, Co, Ni, Cu, Au and / or Ag, and the ionic liquid is choline chloride-based ionic liquid; preparing the main metal through a three-electrode system by taking the ionic liquid containing the main metal precursor as electrolyte; pure ionic liquid serves as electrolyte to prepare monatomic alloy through a three-electrode system, a working electrode adopts main metal, a counter electrode adopts precious metal, the precious metal is Ru, Rh, Pt, Ir and / or Pd, and the precious metal is deposited on the surface of the main metal in a replacement mode. The invention further relates to the monatomic alloy and application of the monatomic alloy as a catalyst in water electrolysis hydrogen production. According to the method, the method is simple, rapid and low in cost, the problems that main metal is easy to sinter and the catalyst is inactivated due to noble metal single atom agglomeration are solved, and the monatomic alloy electrocatalyst with high catalytic activity is obtained.

Description

Technical Field

[0001] The present invention relates to a catalyst, and more particularly to a single-atom alloy and an electrochemical preparation method and application thereof. Background Art

[0002] The development and utilization of clean and renewable energy is a key strategy to solve energy and environmental problems. Hydrogen is a clean and efficient fuel that can be produced by electrocatalytic water splitting under mild conditions and has extremely high purity. At the same time, hydrogen-oxygen fuel cells using hydrogen as fuel have many advantages over traditional thermal power devices. Promoting energy conversion efficiency depends on efficient electrocatalysts. In the past few decades, various reaction mechanisms have been studied based on metal catalysts. By forming multi-metal alloy catalysts, the electronic effect, group effect, synergistic effect, etc. produced make the performance of alloy catalysts better than that of single metal catalysts. However, only the metal atoms on the surface of the alloy participate in the reaction, and most of them are precious metals. Therefore, it is necessary to improve the utilization rate of precious metals to reduce the cost of catalysts. Single atom catalysts have 100% atomic utilization and show some properties different from single metal catalysts. By combining the advantages of alloy catalysts and single atom catalysts, one metal in the alloy is dispersed at the atomic level on the surface of another metal, thereby forming single atom alloys (SAAs), and the catalytic performance and cost are optimized by adjusting the structure and composition. SAAs catalysts are an emerging research field in energy catalysis in recent years.

[0003] SAAs catalysts have high atomic utilization efficiency, excellent interaction between metal single atoms and metal carriers, and unique electronic structure. They have attracted much attention in the field of catalysis and are expected to reduce the cost of precious metal catalysts. Single-atom alloys have been successfully prepared by methods such as initial wet co-impregnation and electrochemical replacement, and have shown great potential in the fields of oxygen reduction and carbon dioxide reduction. However, the current preparation methods of single-atom alloys are not perfect enough, and there are relatively few preparation methods for single-atom alloys with non-precious metal carriers and multiple single-atom species. Therefore, it is necessary to further broaden the scope of the preparation methods of single-atom alloys. Moreover, the currently known preparation methods of single-atom alloys have long processes and also require steps such as high-temperature reduction. Not only are they expensive, but the host metal (also known as the carrier metal) is easy to sinter, and the guest metal (i.e., the single-atom metal) is easy to agglomerate, resulting in catalyst deactivation. Summary of the invention

[0004] In order to solve the problem that the known single-atom alloy preparation methods in the prior art are expensive, the present invention provides a single-atom alloy and an electrochemical preparation method and application thereof.

[0005] According to the present invention, the method for electrochemically preparing single-atom alloys includes the following steps: S1, preparing an ionic liquid containing a main metal precursor, wherein the main metal is Fe, Co, Ni, Cu, Au and / or Ag, and the ionic liquid is a choline chloride-based ionic liquid; S2, using the ionic liquid containing the main metal precursor as an electrolyte to prepare the main metal through a three-electrode system; S3, using a pure ionic liquid as an electrolyte to prepare the single-atom alloy through a three-electrode system, wherein the working electrode uses the main metal, and the counter electrode uses a noble metal, wherein the noble metal is Ru, Rh, Pt, Ir and / or Pd, and the noble metal is deposited on the surface of the main metal in the form of replacement.

[0006] In a preferred embodiment, in step S2, the main metal is prepared by a constant potential method or a constant current method. In a preferred embodiment, the main alloy is prepared by a constant potential method or a constant current method.

[0007] In a preferred embodiment, in step S2, the working electrode is made of carbon cloth.

[0008] In a preferred embodiment, in step S2, the counter electrode is a Ni metal electrode.

[0009] In a preferred embodiment, in step S3, the single-atom alloy is prepared by cyclic voltammetry.

[0010] In a preferred embodiment, in step S2 and step S3, the temperature is maintained at 50°C to 70°C.

[0011] In a preferred embodiment, in step S2 and step S3, the voltage range is -0.6V to -1.2V.

[0012] In a preferred embodiment, in step S2 and step S3, the reference electrode is a non-mercury-silver electrode.

[0013] The single-atom alloy according to the present invention is prepared according to the above method.

[0014] According to the application of the above-mentioned single-atom alloy, it is used as a catalyst in the electrolysis of water to produce hydrogen.

[0015] The electrochemical method for preparing a single-atom alloy according to the present invention has simple steps, does not involve steps such as high-temperature reduction, is simple and fast, and is inexpensive, avoiding the problems of easy sintering of the main metal and agglomeration of noble metal single atoms leading to catalyst deactivation. The single-atom alloy obtained according to the method of the present invention uses isolated single-atom noble metals loaded on the main metal to increase the reaction active sites and reduce the synthesis cost of the electrocatalyst, thereby preparing a single-atom alloy electrocatalyst with high catalytic activity and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is a process flow chart of the method for electrochemically preparing single-atom alloy according to the present invention.

[0017] Figure 2 : is the X-ray diffraction pattern of the single-atom alloy obtained according to Example 1 of the present invention.

[0018] Figure 3 This is an atomically resolved spherical aberration electron microscope image of the single-atom alloy obtained according to Example 1 of the present invention.

[0019] Figure 4 This is a performance test diagram of the single-atom alloy obtained according to Example 1 of the present invention for producing hydrogen by electrolysis of water. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0021] like Figure 1 As shown, the electrochemical method for preparing single-atom alloys according to the present invention first includes preparing an ionic liquid containing a main metal precursor, wherein the main metal precursor can be a non-noble metal (Fe, Co, Ni, Cu) precursor, or a noble metal (Au, Ag) precursor, and the ionic liquid is a choline chloride (Choline Chloride, ChCl) based ionic liquid (Ionic Liquids, referred to as ILs). Specifically, the main metal precursor is added to the choline chloride based ionic liquid to obtain an ionic liquid containing the main metal precursor. In a preferred embodiment, the main metal precursor is Fe, Co, Ni, Cu, Au and / or Ag salt. In a preferred embodiment, the main metal precursor is NiCl2 and CoCl2. In a preferred embodiment, the choline chloride-based ionic liquid is a deep eutectic mixture (Deep Eutectic Solvents, DESs) formed by choline chloride and ethylene glycol (ChCl-Ethylene Glycol) or a deep eutectic mixture (ChCl-Urea) formed by choline chloride and urea.

[0022] like Figure 1As shown, the method for electrochemically preparing a single-atom alloy according to the present invention then includes preparing the main metal through a three-electrode system using an ionic liquid containing a main metal precursor as an electrolyte. Specifically, the main metal is prepared by a constant potential method or a constant current method. In a preferred embodiment, the main metal is an alloy material. In a preferred embodiment, the main metal is a NiCo alloy. The three-electrode system includes a counter electrode, a working electrode, and a reference electrode. In a preferred embodiment, the working electrode is made of carbon cloth, etc. In a preferred embodiment, the counter electrode is a Ni metal electrode. The electrolyte is a non-aqueous solution, and a reference electrode of a non-aqueous system is used. In a preferred embodiment, the reference electrode is a non-aqueous-silver electrode. In a preferred embodiment, the electrolytic cell of the three-electrode system is placed in a temperature-controlled magnetic stirring electric heating jacket, the temperature is maintained at 50°C to 70°C, the voltage range is -0.6V to -1.2V, and the time is 2h to 4h.

[0023] like Figure 1 As shown, the method for electrochemically preparing a single-atom alloy according to the present invention then includes preparing a single-atom alloy by a three-electrode system using a pure ionic liquid as an electrolyte, wherein the working electrode uses a main metal, the counter electrode uses a guest metal, the guest metal is a noble metal, the noble metal is Ru, Rh, Pt, Ir and / or Pd, and the noble metal is deposited on the surface of the main metal in the form of substitution. In a preferred embodiment, the working electrode uses an alloy. In a preferred embodiment, the working electrode uses a NiCo alloy. In a preferred embodiment, the counter electrode is a Pt metal electrode. Specifically, a single-atom alloy is prepared by cyclic voltammetry. In a preferred embodiment, the number of cycles is 1000. The electrolyte is a non-aqueous solution, and a reference electrode of a non-aqueous system is used. In a preferred embodiment, the reference electrode is a non-aqueous-silver electrode. In a preferred embodiment, the electrolytic cell of the three-electrode system is placed in a temperature-controlled magnetic stirring electric heating jacket, the temperature is maintained at 50°C to 70°C, the voltage range is -0.6V to -1.2V, and the time is 2h to 4h.

[0024] The method for electrochemically preparing a single-atom alloy according to the present invention then includes taking the single-atom alloy out of the electrolytic cell, washing it multiple times with deionized water, then washing it multiple times with anhydrous ethanol, and finally drying it.

[0025] like Figure 1As shown, the method for electrochemically preparing a single-atom alloy according to the present invention then includes electrolyzing water to produce hydrogen through a three-electrode system, wherein the working electrode is a single-atom alloy. Specifically, the electrochemical properties of the single-atom alloy are tested using an electrochemical workstation. In a preferred embodiment, an alkaline aqueous solution is the electrolyte. In a preferred embodiment, the electrolyte is a 1.0M KOH solution. In a preferred embodiment, the scan rate of the HER polarization curve is 2mV / s, the potential range is 0.1V to -0.3V (vs.RHE), and all polarization curves use 95% electrochemical compensation.

[0026] According to the electrochemical method for preparing single-atom alloys of the present invention, an ionic liquid containing a main metal precursor is added as an electrolyte, and a noble metal is used as a counter electrode. The noble metal is slowly dissolved in the ionic liquid and then deposited and dispersed and diluted on a carrier of the main metal to enhance the interaction between the noble metal and the main metal, which can effectively improve the catalyst performance. Compared with other processes for preparing single-atom alloy materials, the method is simpler, greatly shortens the process, is controllable, has low requirements for equipment conditions, and reduces costs to a great extent. The process is universal and can prepare different single-atom alloys by changing the types of carriers, ionic liquids and metal counter electrodes, so as to be applied to various electrochemical energy storage and conversion fields such as water electrolysis to produce hydrogen and fuel cells. The amount of noble metals in single-atom alloy catalyst materials can be effectively reduced, and the utilization rate of noble metals can be improved, thereby effectively reducing costs.

[0027] Example 1

[0028] Take 2.38g NiCl2·6H2O and 1.19g CoCl2·6H2O and add them into 30mL choline chloride-ethylene glycol ionic liquid to finally obtain a dark blue liquid.

[0029] The working electrode is carbon cloth, the counter electrode is Ni metal electrode, and the reference electrode is non-water-silver electrode. The dark blue liquid prepared above is used as the electrolyte, 30 mL is added to the electrolytic cell, and placed in a temperature-controlled magnetic stirring electric heating mantle, the temperature is maintained at 50°C to 70°C, and the NiCo alloy is prepared by constant potential method, the voltage range is -0.6V to -1.2V, and the time is 2h to 4h.

[0030] The working electrode is NiCo alloy, the counter electrode is Pt metal electrode, and the reference electrode is non-aqueous-silver electrode. Pure choline chloride-ethylene glycol ionic liquid is used as the electrolyte, 30 mL is added to the electrolytic cell, and placed in a temperature-controlled magnetic stirring electric heating mantle, the temperature is maintained at 50℃~70℃, and the single-atom alloy is prepared by cyclic voltammetry, the voltage range is -0.6V~-1.2V, and the number of cycles is 1000.

[0031] The single-atom alloy material is taken out from the electrolytic cell, washed with deionized water for several times, then washed with anhydrous ethanol for several times, and finally dried. The X-ray diffraction pattern of the obtained single-atom alloy is as follows: Figure 2 As shown in the figure, the characteristic peak of the single-atom alloy is mainly the signal of the Ni characteristic peak, and the position of the peak is shifted to the left, between the standard characteristic peaks of Ni and Co, indicating the successful preparation of the NiCo alloy. In addition, there is no characteristic peak of metal Pt in the figure, indicating that the content of Pt is very low and is dispersed in the Ni-Co alloy in the form of atoms. The atomic resolution surface spherical aberration electron microscopy image of the obtained single-atom alloy is shown in Figure 3 As shown in the figure, white bright spots (brighter contrast points) are dispersed in the lattice fringes, indicating that Pt is dispersed in the NiCo alloy in the form of single atoms (the white bright spots circled in the figure are Pt atoms), indicating the successful preparation of single-atom alloys.

[0032] The electrochemical performance of the single-atom alloy was tested using a Chenhua CHI 660E electrochemical workstation. The test was conducted in a standard three-electrode device with a 1.0M KOH solution as the electrolyte; the scan rate of the HER polarization curve was 2mV / s, the potential range was 0.1 to -0.3V (vs. RHE), and all polarization curves were compensated with 95% electrochemical compensation. The performance test of the single-atom alloy for hydrogen production by electrolysis of water is shown in the figure below. Figure 4 As shown in the figure, the single-atom alloy (i.e., the sample of the embodiment marked in the figure) has a current of 10 mA / cm 2 The hydrogen evolution overpotential at a current density of only 16 mV, which exceeds that of commercial Pt / C electrocatalysts. The mass fraction of Pt detected by inductively coupled plasma mass spectrometry is less than 3 wt.%, which is significantly lower than the mass fraction of 20 wt.% in Pt / C. This further illustrates that the single-atom alloy has higher atomic utilization and stronger catalytic activity.

[0033] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A method for electrochemically preparing a single-atom alloy, characterized in that: The method comprises the following steps: S1, preparing an ionic liquid containing a main metal precursor, wherein the main metal is Fe, Co, Ni, Cu, Au and / or Ag, and the ionic liquid is a choline chloride-based ionic liquid; S2, preparing the main metal through a three-electrode system using an ionic liquid containing a main metal precursor as an electrolyte; S3, using pure ionic liquid as electrolyte to prepare single-atom alloy through a three-electrode system, wherein the working electrode is made of main metal, and the counter electrode is made of precious metal, the precious metal is Ru, Rh, Pt, Ir and / or Pd, and the precious metal is deposited on the surface of the main metal in the form of replacement.

2. The method according to claim 1, characterized in that In step S2, the host metal is prepared by a constant potential method or a constant current method.

3. The method according to claim 1, characterized in that In step S2, the working electrode is made of carbon cloth.

4. The method according to claim 1, characterized in that In step S2, the counter electrode is a Ni metal electrode.

5. The method according to claim 1, characterized in that In step S3, a single-atom alloy is prepared by cyclic voltammetry.

6. The method according to claim 1, characterized in that In step S2 and step S3, the temperature is maintained at 50°C to 70°C.

7. The method according to claim 1, characterized in that In step S2 and step S3, the voltage range is -0.6V to -1.2V.

8. The method according to claim 1, characterized in that In step S2 and step S3, the reference electrode is a non-mercury-silver electrode.

9. A single-atom alloy, characterized in that: The single-atom alloy is prepared according to the method described in any one of claims 1-8.

10. The use of the single-atom alloy according to claim 9, characterized in that: The single-atom alloy is used as a catalyst in the electrolysis of water to produce hydrogen.

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