A method for strengthening a catalytic water decomposition OER reaction by magnetizing an electrode

Abstract

The present application belongs to the technical field of electrocatalytic hydrogen production, and relates to a method for strengthening water decomposition OER reaction by magnetized electrode. Hydrogen production by catalytic water decomposition has been a long-term effort, and the rate-limiting step of water decomposition is its OER reaction. Recently, some scholars have enhanced the effect of OER reaction by means of external magnetic field, however, the external magnetic field must add a magnetic field generating device outside the electrolytic cell, which will increase the cost of equipment; in addition, due to the long-time application of external strong magnetic field, it must produce magnetic field radiation and other shortcomings to the surrounding workers. The present application firstly selects or synthesizes conductive metal (or metal compound) magnetic material, then magnetizes the magnetic material by using an electromagnet or a permanent magnet, and then uses the magnetized magnetic material as an electrode. After magnetization, the magnetic material does not need to apply an external magnetic field and directly carries out the electrocatalytic water decomposition reaction.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic hydrogen production technology and relates to a method for enhancing the oxygen evolution reaction (OER reaction) of water by magnetizing electrodes. Background Technology

[0002] With the advancement of technology, people's demand for energy is becoming increasingly strong. However, traditional fossil fuels have limited and non-renewable reserves, making the development of new energy sources an inevitable path for social development. Hydrogen energy has high energy density, and its only byproduct is water, with no carbon emissions, making it environmentally friendly and one of the most promising new energy sources. Currently, hydrogen production methods mainly involve fossil fuel production and water electrolysis. While water electrolysis produces high-purity hydrogen, its cost is relatively high. Therefore, researchers have long been actively studying catalytic water splitting for hydrogen production. The rate-limiting step in water splitting is the oxygen evolution reaction (OER), a four-electron mass transfer process with slow kinetics. The theoretical decomposition voltage is 1.23V, but the actual decomposition voltage is often much higher (overpotential). Therefore, finding a suitable electrocatalyst is key to reducing the cost of water splitting. In recent years, researchers have discovered that the noble metals ruthenium and iridium and their oxides exhibit superior OER catalytic performance. However, these precious metals are scarce and expensive. Therefore, finding lower-cost electrocatalytic materials and methods is currently a research focus. As research deepens, people have discovered that the abundant transition metals Fe, Co, Ni and their compounds can be used as substitutes for noble metal electrocatalysts. Fe, Co, Ni and their oxides (hydroxyl radicals) are ferromagnetic materials. Taking advantage of this characteristic, researchers have recently made innovations in the electrocatalytic methods using these catalytic materials. According to reports, the external magnetic field can bring positive effects to the OER reaction. For example, Felipe A[1] et al. used NiZnFe4Ox mixed oxide as the anode. Under the application of an external magnetic field of 450mT, the intrinsic catalytic activity of OER was increased by about 40%. The research group of Professor Xu Ping of Harbin Institute of Technology[3] studied the oxygen evolution reaction (OER) behavior of nickel-based catalysts (Ni(OH)2, NiO and Ni) under the action of an external magnetic field that can be precisely controlled. They found that the overpotential of different catalysts decreased by different degrees under the action of the magnetic field. In recent years, there have been continuous reports on the enhancement of water splitting electrocatalytic reaction by external magnetic fields on different magnetic catalytic materials. Introducing magnetism into catalytic water electrolysis has become a research hotspot in the past two years.

[0003] However, the inventors believe that, according to process requirements, an external magnetic field must be added outside the electrolysis cell for water electrolysis. This not only increases the cost of the fixed equipment for water electrolysis, but also, since a strong external magnetic field must be applied for a long time during the water electrolysis process, the surrounding workers will inevitably be exposed to magnetic field radiation for extended periods, which will seriously harm their health. Therefore, to avoid the above-mentioned drawbacks, the inventors have proposed the following invention. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the main objective of this invention is to achieve magnetic enhancement of the OER reaction in water splitting without the need for an external magnetic field. This invention provides a method for enhancing the catalytic OER reaction in water splitting using a magnetized electrode.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for enhancing the electrochemical water splitting (OER) reaction by magnetizing electrodes involves first selecting or synthesizing a conductive metal (or metal compound) magnetic material, then magnetizing the magnetic material using an electromagnet or permanent magnet, and finally using the magnetized conductive metal (or metal compound) magnetic material directly or as an auxiliary anode electrode for the electrochemical water splitting reaction. After magnetization, the magnetic material can directly undergo the OER reaction of electrocatalytic water splitting without the need for an external magnetic field, thus greatly improving the catalytic efficiency of electrocatalytic water splitting.

[0007] Furthermore, in the method described above for enhancing the catalytic water splitting OER reaction with a magnetized electrode, the selected or synthesized conductive metal (or metal compound) material is a material containing Fe, Co, Ni elements or a combination thereof, and the material can be a ferromagnetic material, a ferrimagnetic material, or a paramagnetic material.

[0008] Furthermore, in the method described above for enhancing the catalytic water splitting OER reaction with a magnetized electrode, the magnetization method of the selected magnetic material can be 1: a permanent magnet is placed above, below, or on a certain side of the (formed) magnetic material, and reciprocates in one direction to do work (or the permanent magnet remains stationary while the magnetic material moves to do work), while the magnetic field strength of the magnetic material is measured with a gaussmeter. The reciprocating motion of the permanent magnet continues until the magnetic field strength of the magnetic material no longer increases (indicating that the magnet is fully charged); the magnetization method of the selected magnetic material can also be 2: the magnetic material described above is placed within the magnetic field range of an electromagnet with a certain magnetic field strength, and the magnetic material is magnetized by reciprocating current, and the magnetic field strength of the magnetic material is measured with a gaussmeter until the designed magnetic field strength is reached.

[0009] Furthermore, in the method described above for enhancing the catalytic water splitting OER reaction with a magnetized electrode, the method of using the magnetized conductive metal (or metal compound) magnetic material directly or as an auxiliary anode electrode for the electrochemical water splitting reaction is as follows: the magnetic material is processed and shaped into various forms such as plates, strips, and rods, and directly used as the anode for the electrochemical water splitting reaction; or the magnetic material is prepared onto a conductive electrode carrier (such as conductive metal electrode plates, graphite blocks, carbon cloth, nickel foam, diamond electrodes, glass electrodes, etc.) by coating, plating, or bonding to create an electrode plate containing the magnetic material, which is then used as the anode for the electrochemical water splitting reaction.

[0010] Furthermore, in the method described above for enhancing the catalytic water splitting OER reaction with a magnetized electrode, the catalytic efficiency of the OER reaction of electrocatalytic water splitting can be determined by comparing the initial overpotential before and after magnetization, where the current density for oxygen production in the OER reaction of water electrolysis is 10 mA / dm2.

[0011] The beneficial effects of the method of the present invention are:

[0012] 1. The method of the present invention overcomes the disadvantage that the external magnetic field method requires the addition of a magnetic field generating device outside the electrolysis cell of water electrolysis, which increases the cost of fixed equipment for water electrolysis and is not easy to promote.

[0013] 2. The method of the present invention overcomes the disadvantage of the external magnetic field method, which requires the application of a strong external magnetic field for a long time during the water electrolysis process, which will cause the surrounding workers to be exposed to magnetic field radiation for a long time, and will seriously harm the health of the surrounding workers. Attached Figure Description

[0014] Figures 1-4 This is a comparison of the LSV (Liquidity Stabilization Value) of the OER (Oxygen Evolution Reaction) after non-magnetization and magnetization when using different electrode materials for anodic electrolysis of water in Examples 1-4 of this invention. Wherein:

[0015] Figure 1 In Figure a, LSV curve of oxygen evolution reaction of blank nickel foam is shown, and in Figure b, LSV curve of oxygen evolution reaction of magnetized nickel foam is shown.

[0016] Figure 2 In Figure a, LSV curve of oxygen evolution reaction of blank nickel-iron foam is shown, and in Figure b, LSV curve of oxygen evolution reaction of magnetized nickel-iron foam is shown.

[0017] Figure 3In Figure a, LSV curve of oxygen evolution reaction of blank foamed cobalt-nickel is shown, and in Figure b, LSV curve of oxygen evolution reaction of magnetized foamed cobalt-nickel is shown.

[0018] Figure 4 In Figure a, LSV curves of the oxygen evolution reaction (OER) for unmagnetized Fe3O4 nanoparticle catalysts are shown, while in Figure b, LSV curves of the OER for magnetized Fe3O4 nanoparticles are shown. Detailed Implementation

[0019] To better understand the present invention, the technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0020] Example 1

[0021] 1. The magnetic material selected in this embodiment is two pieces of nickel foam (hereinafter referred to as NF), with a size of 1.5*1.0*0.1cm.

[0022] 2. Immerse an unmagnetized piece of NF in 0.5 mol / L sulfuric acid (under ultrasonic conditions) for 1 minute to remove the surface oxide layer, rinse 3 times with deionized water, and air dry for later use (the magnetic field strength of the unmagnetized NF was measured to be 0.04 mT using a gaussmeter).

[0023] 3. Take the other piece of NF (nitrogen foam), acid wash (as above), rinse three times with deionized water, and then magnetize it with a 0.3T (Tesla) permanent magnet. The magnetization method is to hold the piece of nickel foam in your hand and rub it back and forth above the permanent magnet 20-30 times. Then use a gaussmeter to measure its magnetic field strength. The magnetic strength of the nickel foam was measured to be 0.84mT (no further increase was made). Then use the magnetized NF for later use.

[0024] 4. OER Performance Testing: In an electrochemical workstation, a three-electrode system was used. The unmagnetized NF electrode and the magnetized NF electrode were used as anodes, a platinum sheet electrode as cathode, and a calomel electrode as reference electrode. The electrochemical performance of the water splitting OER reaction was tested in a 1 mol / L potassium hydroxide solution. The LSV curves of the blank NF and the magnetized NF were compared (see attached instruction manual). Figure 1 ).

[0025] From the graph, we can clearly see that the OER deposition overpotential with magnetized NF as the anode is much lower than that with unmagnetized NF as the anode (when the current density for oxygen production in the OER reaction is 10 mA / cm²). 2At that time, the oxygen evolution overpotential of the magnetized NF as the anode was 371mV, while that of the unmagnetized NF as the anode was 430mV. Moreover, under the same applied potential, its OER evolution current was significantly larger, which means that the internal magnetization greatly improved the catalytic efficiency of the magnetic material NF electrode for the electrocatalytic water splitting OER reaction.

[0026] Example 2

[0027] 1. The magnetic material selected in this embodiment is two pieces of foamed nickel iron (hereinafter referred to as FeNi), with a size of 1.5*1.0*0.1cm.

[0028] 2. Immerse an unmagnetized piece of FeNi in 0.5mol / L sulfuric acid (under ultrasonic conditions) for 1 minute to remove the surface oxide layer, rinse 3 times with deionized water, and air dry for later use (the magnetic field strength of the unmagnetized FeNi was measured to be 0.28mT using a gaussmeter).

[0029] 3. Take the other FeNi piece mentioned above, acid wash it (as above), rinse it three times with deionized water, and then magnetize it with a 0.3T (Tesla) permanent magnet. The magnetization method is to hold the piece of foamed nickel-iron and rub it back and forth above the permanent magnet 20-30 times. Then use a gaussmeter to measure its magnetic field strength. The magnetic strength of the foamed nickel-iron was measured to be 0.98mT (no further increase is made). Then use the magnetized FeNi for later use.

[0030] 4. OER Performance Testing: In an electrochemical workstation, a three-electrode system was used. An unmagnetized FeNi electrode and a magnetized FeNi electrode were used as the anode, a platinum sheet electrode as the cathode, and a calomel electrode as the reference electrode. The electrochemical performance of the water splitting OER reaction was tested in a 1 mol / L potassium hydroxide solution. A comparison of the LSV curves of the blank FeNi and the magnetized FeNi was obtained (see attached instruction manual). Figure 2 ).

[0031] From the figure, we can clearly see that the OER deposition overpotential of the magnetized FeNi anode is much lower than that of the unmagnetized FeNi anode (when the current density for oxygen production in the OER reaction is 10 mA / cm²). 2 At that time, the oxygen evolution overpotential of the magnetized FeNi as the anode was 360mV, while that of the unmagnetized FeNi as the anode was 412mV. Moreover, under the same applied potential, its OER evolution current was significantly larger, which means that the internal magnetization greatly improved the catalytic efficiency of the magnetic material catalyzing the FeNi electrode for the electrocatalytic water splitting OER reaction.

[0032] Example 3

[0033] 1. The magnetic material selected in this embodiment is two pieces of foamed nickel cobalt (hereinafter referred to as CoNi), with a size of 1.5*1.0*0.1cm.

[0034] 2. Immerse an unmagnetized piece of CoNi in 0.5 mol / L sulfuric acid (under ultrasonic conditions) for 1 minute to remove the surface oxide layer, rinse 3 times with deionized water, and air dry for later use (the magnetic field strength of the unmagnetized CoNi was measured to be 0.41 mT using a gaussmeter).

[0035] 3. Take the other CoNi piece mentioned above, acid wash (as above), rinse it three times with deionized water, and then magnetize it with a 0.3T (Tesla) permanent magnet. The magnetization method is to hold the foamed nickel-cobalt piece in your hand and rub it back and forth above the permanent magnet 20-30 times. Then use a gaussmeter to measure its magnetic field strength. The magnetic strength of the foamed nickel-cobalt was measured to be 1.12 mT (no further increase is made). Then use the magnetized CoNi for later use.

[0036] 4. OER Performance Testing: In an electrochemical workstation, a three-electrode system was used. An unmagnetized CoNi electrode and a magnetized CoNi electrode were used as the anode, a platinum sheet electrode as the cathode, and a calomel electrode as the reference electrode. The electrochemical performance of the water splitting OER reaction was tested in a 1 mol / L potassium hydroxide solution. A comparison of the LSV curves of the blank CoNi and the magnetized CoNi was obtained (see attached instruction manual). Figure 3 ).

[0037] As can be clearly seen from the figure, the OER evolution overpotential of the magnetized CoNi anode is much lower than that of the unmagnetized CoNi anode (when the current density for oxygen production in the OER reaction is 10 mA / cm2, the OER evolution overpotential of the magnetized CoNi anode is 312 mV, while that of the unmagnetized CoNi anode is 343 mV). Moreover, under the same applied potential, the OER evolution current is significantly larger, which means that internal magnetization greatly improves the catalytic efficiency of the magnetic material-catalyzed CoNi electrode for the electrocatalytic water splitting OER reaction.

[0038] Example 4

[0039] 1. Preparation of two Fe3O4 nanoparticle magnetic material electrodes: Weigh 50 mg of Fe3O4 nanoparticle catalyst and mix it with 0.3 mL of FAA-3 (anion exchange solution) ionomer. Then, add ethanol:deionized water in a 3:1 (volume ratio) ratio to the particle mixture to a final volume of 1 mL. Shake until homogeneous, then evenly spray the mixture onto a pre-prepared 1*1.5 cm carbon cloth to achieve a loading of 50 mg / cm². -2 The carbon cloth catalytic electrode was dried in an oven at 60°C for one hour and then put into use.

[0040] 2. The magnetic field strength of a Fe3O4 nanoparticle magnetic material electrode prepared according to the above method was measured to be 0.09 mT using a gaussmeter. After another Fe3O4 nanoparticle magnetic material electrode was magnetized according to the method of this invention, the magnetic field strength of its magnetized electrode was measured to be 0.72 mT.

[0041] 3. OER Performance Testing: In an electrochemical workstation, a three-electrode system was used, with the aforementioned magnetic material electrode as the anode, a platinum sheet electrode as the cathode, and mercury oxide as the reference electrode. Electrochemical performance testing of the water splitting OER reaction was conducted in a 1 mol / L potassium hydroxide solution. A comparison of the LSV curves of the blank and magnetized Fe3O4 nanoparticle magnetic material electrodes was obtained (see attached instruction manual). Figure 4 ).

[0042] As can be clearly seen from the figure, the OER deposition overpotential of the magnetized Fe3O4 nanoparticle magnetic material electrode as the anode is much lower than that of the unmagnetized Fe3O4 nanoparticle magnetic material electrode as the anode (when the current density for oxygen production in the OER reaction is 10 mA / cm²). 2 At that time, the oxygen evolution overpotential of the magnetized Fe3O4 nanoparticle magnetic material electrode as the anode was 613mV, while that of the unmagnetized Fe3O4 nanoparticle magnetic material electrode as the anode was 648mV. Moreover, under the same applied potential, its OER evolution current was significantly larger, which means that internal magnetization greatly improved the catalytic efficiency of the magnetic material catalyzing the Fe3O4 nanoparticle magnetic material electrode for the electrocatalytic water splitting OER reaction.

Claims

1. A method of magnetizing an electrode to enhance a catalytic water-splitting OER reaction, characterized by: The method first selects or synthesizes a conductive metal or metal compound magnetic material, then magnetizes the magnetic material with an electromagnet or a permanent magnet, and then directly or indirectly uses the magnetized conductive metal or metal compound magnetic material as an anode electrode for an electrochemical water decomposition reaction; the magnetic material does not need to be subjected to an external magnetic field after magnetization, and directly performs an OER reaction of electrocatalytic water decomposition, so that the catalytic efficiency of electrocatalytic water decomposition is greatly improved. The selected or synthesized conductive metal or metal compound material is a material containing Fe, Co, Ni elements or a combination thereof, which can be a ferromagnetic material, a ferrimagnetic material or a paramagnetic material.

2. The method of claim 1, wherein the magnetized electrode enhances the OER reaction of catalytic water splitting. The magnetization method of the selected magnetic material can be 1: a permanent magnet is moved back and forth above, below or on a side of the magnetic material as described above, or the permanent magnet is fixed and the magnetic material is moved, while the magnetic field strength of the magnetic material is measured by a gauss meter, and the permanent magnet is moved back and forth until the magnetic field strength of the magnetic material no longer increases; the magnetization method of the selected magnetic material can also be 2: the magnetic material as described above is placed in the magnetic field of an electromagnet with a certain magnetic field strength, and the magnetic material is magnetized by reciprocating power supply, and the magnetic field strength of the magnetic material is measured by a gauss meter until the designed magnetic field strength is reached.

3. The method of claim 1, wherein the method is characterized by: The method of directly or indirectly using the magnetized conductive metal or metal compound magnetic material as an anode electrode for an electrochemical water decomposition reaction is to process the magnetic material into various forms of electrode plates, such as plates, strips and rods, and directly use them as anodes for electrochemical water decomposition reaction; or the magnetic material is prepared on a conductive electrode carrier by coating, plating or bonding, and the conductive electrode carrier can be a conductive metal plate, a graphite block, a carbon cloth, a nickel foam, a diamond electrode or a glass electrode, to form an electrode plate containing the magnetic material, which is then used as an anode for electrochemical water decomposition reaction.

4. The method of claim 1, wherein the method is characterized by: The catalytic efficiency of the magnetic material after magnetization without an external magnetic field for directly performing an OER reaction of electrocatalytic water decomposition can be determined by comparing the initial overpotential of the current density of 10 mA / dm2 of oxygen generated by the OER reaction of electrolytic water before and after magnetization of the magnetic material with and without magnetization, respectively, by using an electrochemical workstation to track the kinetics of the reaction.

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