Method for preparing a water electrolysis catalyst electrode comprising cobalt boride nanoparticles synthesized by thermal plasma and water electrolysis catalyst electrode thereof

Abstract

The present invention provides a method for preparing a water electrolysis catalyst electrode comprising cobalt boride nanoparticles, comprising the steps of: preparing cobalt boride nanoparticles using thermal plasma; and preparing an electrode comprising the cobalt boride nanoparticles prepared in the above step.

Description

Technical Field

[0001] This invention relates to a hydroelectric system comprising cobalt boride nanoparticles synthesized by thermal plasma.

[0002] Preparation method of electrolytic catalyst electrode and its water electrolysis catalyst electrode. Background Technology

[0003] With increasing energy demand, efforts are being made to develop efficient, low-cost, and environmentally friendly alternatives.

[0004] Research on energy conversion and storage systems. In particular, the conversion of water into oxygen and hydrogen is core to this research.

[0005] Energy conversion technology has become an integral part of the storage of renewable resources in the form of chemical fuels. Previously, electricity...

[0006] Chemical hydrogen production mainly relies on conventional water electrolysis methods and the chlor-alkali industry.

[0007] In fact, water splitting is considered an environmentally friendly and economical sustainable method for hydrogen supply, therefore...

[0008] Developing more effective and stable catalyst electrode materials is considered very important. (Water electrolysis)

[0009] These can be divided into two types of half-cell reactions, one of which is the hydrogen evolution reaction that occurs at the reduction electrode.

[0010] One is the Hydrogen Evolution Reaction (HER), and the other is the Oxygen Evolution Reaction (OER), which occurs at the oxidation electrode.

[0011] From a practical perspective, developing a highly efficient and stable catalyst for the oxygen evolution reaction is crucial.

[0012] For the commercialization of hydrogen production via large-scale water electrolysis, the aforementioned oxygen evolution reaction is crucial.

[0013] Theoretically, it is more complex than the hydrogen evolution reaction and requires a large overpotential. Oxidation of noble metals such as RuO2 and IrO2...

[0014] Although physical catalysts exhibit high activity, their high cost and scarcity make them difficult to mass-produce.

[0015] Applications. Therefore, there is a need to develop alternatives to high-cost catalysts from the abundant resources on Earth.

[0016] Highly efficient catalyst technology. In particular, the oxygen evolution reaction in an acidic atmosphere severely limits the development of non-acidic catalysts.

[0017] The use of noble metal catalysts has led to the proposal of non-noble metal-based hydrogen production in an alkaline atmosphere.

[0018] catalyst.

[0019] On the other hand, the problem with the hydrogen evolution reaction is that, although non-platinum-based catalysts are being actively developed to replace expensive platinum (Pt)-based catalysts, unlike the oxygen evolution reaction, most catalysts only operate in acidic atmospheres. From the perspective of using non-precious metal systems, this difference is considered a major obstacle to the final completion of water electrolysis based on non-precious metal catalysts. Therefore, there is an urgent need to develop a non-precious metal-based hydrogen production catalyst that operates in an alkaline atmosphere.

[0020] Transition metals such as nickel, cobalt, and copper may become low-cost, high-efficiency alternatives. In particular, cobalt has attracted significant attention among non-precious metals in the oxygen evolution reaction (OER). Specifically, reports indicate that, in the case of cobalt borides, boron prevents cobalt from being oxidized to a sacrificial element, and the electron transfer from cobalt to boron can enhance the catalytic activity of cobalt, thus exhibiting excellent catalytic activity for water splitting.

[0021] On the other hand, in the past few years, its design direction has been to improve surface area and conductivity by changing the various forms or structures of catalysts such as nanoparticles, nanowires, nanosheets, and nanotubes.

[0022] Typically, nanoscale catalysts are synthesized through a multi-step (STEP) process via chemical reduction, which has the problem of requiring long synthesis times and large amounts of solvent. Summary of the Invention

[0023] Technical issues

[0024] The purpose of this invention is to provide a method for preparing a water electrolysis catalyst containing cobalt boride nanoparticles that can achieve high efficiency and excellent long-term stability (durability) at low cost.

[0025] Furthermore, a water electrolysis catalyst electrode containing cobalt boride nanoparticles is provided, which can simultaneously generate hydrogen and oxygen at the cathode or anode, respectively.

[0026] Technical solution

[0027] This invention provides a method for preparing a water electrolysis catalyst electrode containing cobalt boride nanoparticles, comprising the following steps: preparing cobalt boride nanoparticles using thermal plasma; and preparing an electrode containing the cobalt boride nanoparticles prepared in the above steps.

[0028] The aforementioned cobalt boride nanoparticles can be prepared using thermal plasma from a three-torch plasma device.

[0029] The size of the aforementioned cobalt boride nanoparticles can range from 1 nm to 20 nm.

[0030] The steps for preparing the above-mentioned electrode may include the following steps: preparing a catalyst ink containing the above-mentioned cobalt boride nanoparticles; and coating the above-mentioned catalyst ink onto the electrode.

[0031] The steps for preparing the above-mentioned catalyst ink are as follows: after mixing cobalt boride nanoparticles, propanol, deionized water and additives, the mixture is subjected to ultrasonic treatment for 50 to 70 minutes. The steps for applying the above-mentioned catalyst ink to the electrode are as follows: after applying the ultrasonically treated catalyst ink to the electrode, the electrode is dried.

[0032] The above-mentioned additive can be a tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer.

[0033] In each cm 2 The amount of cobalt boride nanoparticles contained in the electrode surface can be 1 mg to 1.5 mg.

[0034] The steps for preparing the above-mentioned cobalt boride nanoparticles may include the following steps: generating a plasma jet by injecting plasma-forming gas into a three-torch plasma jet device; injecting and vaporizing a cobalt / boron mixture into the plasma jet using a carrier gas; and recovering the cobalt boride nanoparticles by cooling the vaporized cobalt / boron mixture.

[0035] The cobalt / boron mixture described above can be prepared by mixing the cobalt and boron in a molar ratio of 1:0.5 to 1:4.

[0036] According to another embodiment of the present invention, a water electrolysis catalyst electrode prepared by the above method is provided.

[0037] The aforementioned water electrolysis catalyst can generate hydrogen and oxygen at the cathode or anode, respectively.

[0038] The effects of the invention

[0039] Using this invention, a water electrolysis catalyst electrode with excellent overpotential, current density, surface area and long-term stability can be provided. The prepared water electrolysis catalyst electrode can exhibit excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the cathode or anode.

[0040] Furthermore, the preparation method of cobalt boride nanoparticles consists of a single step (STEP), which has the advantages of not only preparing them in high yield but also shortening the preparation time and reducing the preparation cost. Attached Figure Description

[0041] Figure 1 This demonstrates the process of synthesizing nanoparticles using thermal plasma (using a three-torch plasma device).

[0042] Figure 2 A three-torch plasma jet device according to an embodiment of the present invention is shown.

[0043] Figure 3 Part (a) to Figure 3 Section (f) shows a field emission transmission electron microscope (FE-TEM) image and a selected area electron diffraction (SAED) pattern of cobalt boride nanoparticles according to an embodiment of the present invention. Figure 3 The (g) section is a graph showing the dimensions of the cobalt boride nanoparticles in Table 1.

[0044] Figure 4 X-ray photoelectron spectroscopy (XPS) charts for analyzing the chemical surface state of cobalt boride nanoparticles in Example 1.

[0045] Figure 5 Linear sweep voltammetry (LSV) plots, overpotentials, and Tafel slopes for the catalyst electrodes of Examples 1 to 3 for the oxygen evolution reaction are shown.

[0046] Figure 6 The graphs show cyclic voltammetry (CV) based on scan rate and long-term stability test graphs.

[0047] Figure 7 The linear sweep voltammetry (LSV) graphs, overpotentials, Tafel slopes, and long-term stability test graphs of the catalyst electrodes of Examples 1 to 3 of the present invention are shown. Detailed Implementation

[0048] The present invention provides a method for preparing a water electrolysis catalyst electrode containing cobalt boride nanoparticles, comprising: preparing cobalt boride nanoparticles using thermal plasma; and preparing an electrode containing the cobalt boride nanoparticles prepared in the above steps.

[0049] Embodiments of the present invention

[0050] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. First, it should be noted that, as far as possible, the same reference numerals are used to refer to the same structural element or component in the drawings. In describing the present invention, to avoid obscuring the main idea of ​​the invention, specific descriptions of related well-known functions or structures will be omitted.

[0051] In this specification, terms such as “about” and “actually” are used when referring to inherent preparation errors and permissible material errors to indicate values ​​or approximate values, and the disclosure mentions precise or absolute values ​​to aid understanding of the invention and to prevent unfair exploitation by unethical infringers.

[0052] While studying the preparation method of cobalt boride nanoparticles using a three-torch plasma jet device, the inventors confirmed that the synthesized cobalt boride nanoparticles performed excellently as a water electrolysis catalyst, thus completing this invention.

[0053] Before describing the present invention, the three-torch plasma device used in the present invention will be described first.

[0054] Figure 1 This demonstrates the process of synthesizing nanoparticles using thermal plasma (using a three-torch plasma device). Figure 2 A three-torch plasma jet device according to an embodiment of the present invention is shown.

[0055] Preferably, the generation of the three-torch plasma jet used in this invention is non-transfered. In this invention, the three-torch plasma jet device generates a DC arc discharge between a cathode made of a tungsten rod and an anode on the inner surface of a nozzle made of copper. Plasma-forming gas flows in from the rear in a swirling manner, thereby heating the plasma jet-forming gas by the arc. Cobalt boride nanoparticles can be prepared by generating a non-transferable plasma jet from which a violent plasma jet is ejected from the anode nozzle.

[0056] The aforementioned plasma jet is an ionized gas composed of electrons, ions, atoms, and molecules generated in the torch section using a DC electric arc or high-frequency inductive coupling discharge. It is a high-speed jet with ultra-high temperature and high activity, ranging from several thousand to tens of thousands of K.

[0057] Reference Figure 2The three-torch plasma jet apparatus includes: a reaction tube 100 providing space for forming a plasma jet, which is a reaction space for the raw material; multiple torches 200 formed on one side of the reaction tube to supply a heat source to the supplied initial material; a feeding unit 300 formed on one side of the torches, supplying the initial material to the torches via a powder supply line; a power supply unit 400 electrically connected to the torches and supplying power; multiple reactors 500 formed at the lower part of the reaction tube, serving as a space for accumulating the material prepared by the plasma jet, and having a quenching system formed on one side; a forming gas supply unit 600 formed on one side of the torches, supplying plasma forming gas to the torches via a plasma jet forming gas supply line; and a forming gas flow regulator 700, which regulates the flow rate of the plasma forming gas via the plasma forming gas supply line. The multiple torches are arranged at equal intervals along the direction of supplying the initial material, and the plasma jets generated in the multiple torches are arranged in a combined manner (see reference). Figure 2 ).

[0058] There can be 7 reactors. When there are 7 reactors, reactors 1 to 4 can be arranged vertically, and reactors 5 to 7 can be arranged horizontally.

[0059] Specifically, three torches 200 can be formed and arranged at equal intervals on the upper surface of the reaction tube 100.

[0060] To protect the generated heat, the torch section 200 may also be equipped with a cooling system.

[0061] At the center of the torch sections 200 arranged at equal intervals, a feeding section 300 is also formed for supplying the initial material through a powder supply pipeline.

[0062] The following describes in detail each step of a method for preparing a water electrolysis catalyst electrode comprising cobalt boride nanoparticles synthesized by thermal plasma, according to an embodiment of the present invention.

[0063] The cobalt boride nanoparticles prepared in this invention can prevent cobalt from being oxidized by boron and improve the catalytic activity of cobalt through electron movement from cobalt to boron.

[0064] The preparation method of the water electrolysis catalyst electrode according to an embodiment of the present invention includes the following steps: preparing cobalt boride nanoparticles using thermal plasma; and preparing an electrode containing the cobalt boride nanoparticles prepared in the above steps.

[0065] First, cobalt boride nanoparticles were prepared using the aforementioned thermal plasma.

[0066] In the step of preparing the above-mentioned cobalt boride nanoparticles, thermal plasma from a three-torch plasma device can be used.

[0067] Specifically, the steps for preparing the cobalt boride nanoparticles include the following steps: generating a plasma jet by injecting plasma-forming gas into a three-torch plasma jet device; injecting and vaporizing a cobalt / boron mixture into the plasma jet using a carrier gas; and recovering the cobalt boride nanoparticles by cooling the vaporized cobalt / boron mixture.

[0068] In the step of generating the plasma jet, the current of the three-torch plasma jet device is set to 100A, and the plasma forming gas is injected at a flow rate of 16L / min to 28L / min.

[0069] The plasma-forming gas mentioned above is a mixture of argon and hydrogen.

[0070] Cobalt boride nanoparticles can be prepared by using the above-mentioned mixed gas as a plasma-generating gas.

[0071] In this invention, the size of cobalt boride nanoparticles can be set by changing the flow rate of the gas generated by the plasma jet, the cooling rate of the cobalt / boron mixture melted and vaporized by the plasma jet, the potential or current intensity of the plasma, etc.

[0072] Then, the cobalt / boron mixture is injected into and vaporized in the plasma jet.

[0073] The above cobalt / boron mixture can be prepared by mixing cobalt and boron in a molar ratio of 1:0.5 to 1:4.

[0074] The aforementioned cobalt / boron mixture can be generated in three torches and supplied along the direction of the combined plasma jet, specifically at a rate of 0.5 g / min to 0.6 g / min. Furthermore, the cobalt / boron mixture can be supplied using a carrier gas, specifically argon, injected at a flow rate of 4 L / min to 6 L / min.

[0075] The final step in preparing the cobalt boride particles described above is to recover the cobalt boride nanoparticles by cooling and vaporizing the aforementioned cobalt / boron mixture.

[0076] To cool the vaporized cobalt / boron mixture described above, reactors (1 to 7) may also be equipped with a cooling system, but are not limited to this.

[0077] The cooling described above is natural cooling, and cobalt boride nanoparticles are prepared by cooling the vaporized cobalt / boron mixture.

[0078] The aforementioned cobalt boride nanoparticles can be recovered separately in reactors (Reactor 1-7), and additional recovery systems can also be formed, but are not limited to this.

[0079] The size of cobalt boride nanoparticles prepared by the above method can be 1 nm to 20 nm, preferably 1 nm to 12 nm.

[0080] If the size of the cobalt boride nanoparticles is less than 1 nm, the advantage is that it increases the active cross-sectional area of ​​the catalyst, but the preparation yield is reduced. If it is greater than 20 nm, the effect of oxygen evolution reaction or hydrogen evolution reaction is reduced due to the decrease in the active cross-sectional area of ​​the catalyst. Therefore, the above range is preferred.

[0081] As described above, cobalt boride nanoparticles are prepared in a single step (STEP), which has the advantages of short preparation time and high energy efficiency.

[0082] Finally, an electrode containing the cobalt boride nanoparticles prepared in the above steps is prepared.

[0083] The steps for preparing the above-mentioned electrode include the following steps: preparing a catalyst ink containing the above-mentioned cobalt boride nanoparticles; and coating the above-mentioned catalyst ink onto the electrode.

[0084] The step of preparing the catalyst ink containing the above-mentioned cobalt boride nanoparticles is to perform ultrasonic treatment for 50 to 70 minutes after mixing cobalt boride nanoparticles, propanol, deionized water and additives.

[0085] If the ultrasonic treatment time is outside the above range, there is a problem that the catalyst ink is not completely prepared. Therefore, the above range is preferred.

[0086] The above-mentioned additive is a tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer.

[0087] Furthermore, the step of applying the catalyst ink to the electrode involves drying the electrode after applying the catalyst ink to it.

[0088] For the above coating and drying, 4 μL of catalyst ink can be coated onto the electrode using a pipette and dried at room temperature for 40 to 50 minutes.

[0089] The aforementioned electrodes can be glassy carbon electrodes, with a density of approximately 1 cm. 2The amount of cobalt boride nanoparticles contained in the electrode surface can be 1 mg to 1.5 mg, preferably, per cm. 2 The amount of cobalt boride nanoparticles contained in the electrode surface can be 1.2 mg.

[0090] If the amount of cobalt boride nanoparticles contained on the electrode surface is outside the above range, there is a problem that the coated ink will crack after drying, and there is a problem that the coating on the electrode will not be fully formed. Therefore, the above range is preferred.

[0091] The present invention provides a water electrolysis catalyst electrode containing cobalt boride nanoparticles prepared by the above method.

[0092] In one embodiment of the present invention, the water electrolysis catalyst electrode can generate hydrogen and oxygen in the cathode or anode, respectively. Specifically, in an alkaline electrolyte (1M KOH), excellent hydrogen evolution reaction or oxygen evolution reaction can be achieved in the cathode or anode, respectively.

[0093] More specifically, in the case of the oxygen evolution reaction, compared with the reversible hydrogen electrode (RHE), it can achieve 10 mA / cm 2 An overpotential of 335 mV was achieved at a current density of 49 mV / dec and a Tafel slope of 92 mV / dec, and a Tafel slope of 1.2 mF / cm² was observed in the hydrogen production assay. 2 Low active surface area.

[0094] Furthermore, the water electrolysis catalyst electrode of the present invention can achieve ±10 mA / cm² in both the oxygen evolution reaction and the hydrogen evolution reaction. 2 It exhibits long-term stability after being maintained for 10 hours.

[0095] The present invention will now be described in more detail through the following embodiments and experimental examples.

[0096] Preparation Examples 1 to 3: Preparation of Cobalt Boride Nanoparticles

[0097] Towards Figure 2 The torch of the three-torch plasma jet device shown is supplied with plasma-generating gas to generate a plasma jet under the operating conditions described in Table 1 below.

[0098] Then, a cobalt / boron mixture (1:3 mol%) is supplied to the three-torch plasma jet device and vaporized.

[0099] Finally, solidified cobalt boride nanoparticles were prepared by cooling and vaporizing the cobalt / boron mixture.

[0100] The experiment used commercially available cobalt (1μm, 95% purity) and amorphous boron (2μm, 99.8% purity), and the operation time was 20 minutes.

[0101] Table 1

[0102]

[0103] As shown in Table 1 above, 5.85 g (yield, 58.2%) of cobalt boride particles were obtained within a 20-minute operation time.

[0104] Example 1

[0105] Catalyst ink was prepared by mixing 20 mg of cobalt boride nanoparticles prepared in Preparation Example 1, 300 μL of propanol, 700 μL of deionized water, and 10 μL of tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer (5 wt%, Tafion, Sigma-Aldrich) and sonicating for 60 minutes.

[0106] Using a pipette at 1.2 mg / cm 2 The catalyst electrode is prepared by loading (coating) the prepared catalyst ink into a pre-cleaned glassy carbon electrode and drying it in air for 50 minutes.

[0107] Example 2 and Example 3

[0108] In addition to utilizing the cobalt boride nanoparticles prepared in Preparation Examples 2 and 3, the catalyst electrode was prepared using the same method as in Example 1.

[0109] Experimental methods

[0110] The morphology and structure of cobalt boride nanoparticles were investigated using selected area electron diffraction (SAED) at an accelerating potential of 200 kV and field emission transmission electron microscopy (FE-TEM, JEM-2100, JEOL, Japan). The surface state and atomic composition were analyzed using X-ray photoelectron spectroscopy (XPS, K-Alpha, Thermo Scientific, USA).

[0111] All electrochemical properties were measured using an Autolab (PGSTAT128N potentiostat / galvanostat, Metrohm, Switzerland) with three electrodes.

[0112] A glassy carbon electrode with a diameter of 3 mm was used as the working electrode, a platinum sheet was used as the counter electrode, and Ag / AgCl / 3M KCl with a double junction was used as the reference electrode.

[0113] In this invention, all potentials are calculated using the following mathematical formula 1, with a reversible hydrogen electrode (RHE) as the reference.

[0114] Mathematical Formula 1

[0115] E RHE =E Ag / AgCl +0.1976V+(0.059×pH))

[0116] In this invention, all electrochemical electrolytes used were 1M KOH (pH 14), and all solutions were measured while continuously stirred to prevent foam buildup on the working electrode.

[0117] The oxygen evolution reaction (OER) was measured on the reversible hydrogen electrode (RHE) using linear sweep voltammetry (LSV) at a range of 0.5–2 V, with the electrode rotating at 1600 rpm and a scan rate of 10 mV / s.

[0118] The double-layer capacitance (C0) was investigated by cyclic voltammetry (CV) at scan rates of 20–120 mV / s and non-inductive current-potential ratios of 1.1 V–1.4 V at a reversible hydrogen electrode (RHE). dl An analysis was conducted.

[0119] For the determination of the hydrogen evolution reaction (HER), linear sweep voltammetry (LSV) was performed on the reversible hydrogen electrode (RHE) at 1600 rpm electrode rotation and a scan rate of 10 mV / s. Then, the double-layer capacitance (C0) was measured on the reversible hydrogen electrode (RHE) between 0.4 V and 0.6 V at the same scan rate as for the oxygen evolution reaction (OER). dl ).

[0120] Electrode rotation at 1600 rpm and 10 mA / cm2 The long-term stability was analyzed using a time electrometer at the current density and at 1M KOH.

[0121] Results and Analysis

[0122] Experimental Example 1: Analysis of Field Emission Transmission Electron Microscopy (FE-TEM) Images and Selected Area Electron Diffraction (SAED) Patterns Analysis

[0123] Figure 3 Part (a) to Figure 3 Section (f) shows a field emission transmission electron microscope (FE-TEM) image and a selected area electron diffraction (SAED) pattern of cobalt boride nanoparticles according to an embodiment of the present invention. Figure 3 The (g) section is a graph showing the dimensions of the cobalt boride nanoparticles in Table 1.

[0124] from Figure 3 Part (a) to Figure 3 Part (f) confirms that, in the field emission transmission electron microscopy (FE-TEM) image, no larger particles such as cobalt and boron, which were initially introduced, were observed in the spherical cobalt boride nanoparticles.

[0125] Furthermore, in Figure 4 Part (a) to Figure 4 No peaks for initial (unevaporated) cobalt and boron were observed in the X-ray diffraction (XRD) chart of part (d), confirming that CoB crystals were predominantly present compared to Co2B crystals.

[0126] That is, it can be seen that the injected cobalt and boron were completely vaporized by the thermal plasma.

[0127] In addition, through Figure 3 Part (a) to Figure 3 The high-resolution transmission electron microscopy (HR-TEM) image of part (f) confirms that the crystal structures of CoB and Co2 are planar.

[0128] Reference Figure 3 In part (g), it can be confirmed that the size (5 nm to 15 nm) of the synthesized cobalt boride nanoparticles decreases when the flow rate of the gas injected into the three-torch plasma device decreases.

[0129] The above results confirm that the size of the synthesized nanoparticles can be adjusted by changing the gas flow rate, and that cobalt boride nanoparticles with excellent crystallinity can be synthesized in a single step (STEP) without post-processing.

[0130] Experimental Example 2: Analysis of the chemical surface state of cobalt boride nanoparticles

[0131] Figure 4X-ray photoelectron spectroscopy (XPS) charts for analyzing the chemical surface state of cobalt boride nanoparticles in Example 1.

[0132] Figure 4 The 785.40 eV and 802.30 eV peaks shown in part (b) of the cobalt 2p-ray photoelectron spectroscopy (XPS) chart are based on Co +2 High-spin vibrations, and the 780.6 eV and 796.3 eV peaks are based on Co. +3 The core level spectra.

[0133] In particular, the Co within cobalt boride nanoparticles +3 The corresponding peak of the binding energy during the synthesis process is positively shifted by CoO or Co(OH)2, which is formed accidentally due to exposure to air.

[0134] The aforementioned positive shift in binding energy further enhances the oxygen evolution reaction catalyst performance of cobalt boride nanoparticles.

[0135] from Figure 4 The boron 1s X-ray photoelectron spectroscopy (XPS) chart in section (c) confirms that two binding energy peaks at 187 eV and 191.5 eV were observed.

[0136] The 187 eV peak is formed due to the interaction between boron and cobalt, while the 191.5 eV peak is formed due to boron oxide.

[0137] Reference Figure 3 High-resolution transmission electron microscopy (HR-TEM) images confirmed that the aforementioned boron oxide (thin hydroxide or oxide film) surrounds the surface of cobalt boride nanoparticles, which is similar to a core-shell structure.

[0138] Experimental Example 3: Oxygen Evolution Reactivity Analysis

[0139] The oxygen evolution reaction of Examples 1 to 3 was tested using a three-electrode electrochemical cell with a rotating disk electrode in 1M KOH solution.

[0140] Figure 5 Linear sweep voltammetry (LSV) plots, overpotentials, and Tafel slopes for the catalyst electrodes of Examples 1 to 3 for the oxygen evolution reaction are shown.

[0141] from Figure 5As can be confirmed in section (a), the linear sweep voltammetry (LSV) plots of all oxygen evolution reactions in Examples 1 to 3 show polarization curves, which are excellent compared to the glassy carbon electrode (GC) without a catalyst.

[0142] Furthermore, Example 1, with its larger cobalt boride nanoparticles, exhibited a lower current density than Examples 2 and 3, which had similar current densities.

[0143] Figure 5 Part (b) shows the value at 10 mA / cm 2 and 20mA / cm 2 The activity of glassy carbon electrodes in Examples 1 to 3 and without catalyst under overpotential.

[0144] from Figure 5 Part (b) confirms that Examples 2 and 3 are at 20 mA / cm 2 The following examples exhibit similar overpotentials of 355mV (0.355V) and 357mV (0.357V), while Example 1 exhibits a relatively higher overpotential of 374mV (0.374V). The Tafel slopes of Examples 1 to 3 are consistent with the Tafel equation.

[0145] The calculated Tafel slope for Example 3 was 49 mV / dec, compared to 62 mV / dec for Example 1 and 54 mV / dec for Example 2. Therefore, it can be determined that Example 3 was lower than Example 1.

[0146] Based on the above results, it can be confirmed that Example 3, with its smaller particle size, is superior to the oxygen evolution reaction compared to Examples 1 and 2.

[0147] Example 4: Electrochemical Active Surface Area (ECSA) and Stability Analysis

[0148] The electrochemically active surface area (ECSA) of Examples 1 to 3 was analyzed in the non-faraday reaction region using cyclic voltammetry (CV) at different scan rates of 20–120 mV / s.

[0149] Figure 6 The graphs show cyclic voltammetry (CV) based on scan rate and long-term stability test graphs.

[0150] from Figure 6 Part (a) and Figure 6 The slope of the scan rate-based cyclic voltammetry (CV) graph in part (b) can be used to calculate the double-layer capacitance (C0) proportional to the electrochemically active surface area. dl ).

[0151] from Figure 6 Part (c) confirms that Example 1 has 52 mF / cm 2 The double-layer capacitance of Example 3 is 92 mF / cm, which is greater than that of Example 1. 2 Double-layer capacitance (C) dl ).

[0152] As can be seen from the above results, Example 3 has a better active surface area than Example 1 and Example 2, and thus has excellent oxygen evolution reaction activity.

[0153] The long-term stability test in Example 3 was performed in 1M KOH electrolyte using 10 mA / cm 2 The analysis is performed using galvanostatic polarization.

[0154] from Figure 6 As can be confirmed in section (d), although the potential of Example 3 increased slightly from 1.58V to 1.61V within 10 hours, it exhibited stable performance.

[0155] The above results confirm that cobalt boride nanoparticles synthesized by thermal plasma through galvanostatic testing can be used as excellent and stable catalysts.

[0156] Experimental Example 5: Analysis of Hydrogen Evolution Reactivity

[0157] The hydrogen evolution reactions in Examples 1 to 3 were tested in 1M KOH solution.

[0158] Figure 7 The linear sweep voltammetry (LSV) graphs, overpotentials, Tafel slopes, and long-term stability test graphs of the catalyst electrodes of Examples 1 to 3 of the present invention are shown.

[0159] from Figure 7 It can be confirmed that Examples 1 to 3 exhibit an active hydrogen evolution reaction in 1M KOH electrolyte.

[0160] Reference Figure 7 In part (b), Example 3, which has the smallest particle in the examples, is at 10 mA / cm².2 At the given current density, it exhibits a low overpotential of 389mV (0.389V), while Examples 1 and 2 exhibit overpotentials of 421mV (0.421V) and 412mV (0.412V), respectively.

[0161] Furthermore, Example 3 exhibits a low Tafel slope of 92 mV / dec, while Examples 1 and 2 exhibit higher values ​​of 110 mV / dec and 104 mV / dec, respectively.

[0162] from Figure 7 As can be confirmed in section (c), as the overpotential decreases, the Tafel slope also decreases. As shown in the oxygen evolution reaction experimental results, Example 3, with its smaller particle size, exhibits a low overpotential and a low Tafel slope, thus demonstrating excellent hydrogen evolution reaction performance.

[0163] That is, it can be seen that Example 3 exhibits a better hydrogen evolution reaction than Example 1 and Example 2, which means that the smaller the size of the cobalt boride nanoparticles, the better the activity of the hydrogen evolution reaction.

[0164] The electrochemically active surface area (ECSA) of Example 3 was analyzed by cyclic voltammetry (CV) at scan rates from 20 mV / s to 120 mV / s.

[0165] and Figure 6 The oxygen evolution reaction (OER) capacitance (C) in part (c) dl Compared with the results, 1.2 mF / cm was confirmed. 2 The relatively low results confirm that, compared with the hydrogen evolution reaction, cobalt boride nanoparticles can serve as a superior catalyst for the oxygen evolution reaction.

[0166] Furthermore, in this invention, rotation at 1600 rpm and -10 mA / cm 2 The long-term stability of the hydrogen evolution reaction in Example 3 was tested.

[0167] from Figure 7 As can be confirmed in section (e), although Example 3 caused the potential to increase slightly from 1.58V to 1.61V within 10 hours, it exhibited stable performance.

[0168] Experimental Example 6: Activity Comparison with Various Catalysts in Similar Electrolytes

[0169] As shown in Table 2, the activities of the catalysts prepared by chemical reduction and non-electrolytic electroplating under the same electrolyte or pH conditions and the cobalt boride nanoparticles of the present invention in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) were compared.

[0170] Table 2

[0171]

[0172] *NP: Nanoparticles, NS: Nanosheets, NR: Nanorods, NB: Nanoribbons, 3DNNCNTAs: Three-dimensional Ni@[Ni] (2+ / 3+) Co2(OH) 6-7 ] x Nanotube arrays, NF: nickel foam. Most existing catalysts require multi-step (STEP) and lengthy chemical reduction processes for synthesis. However, in the present invention, highly crystalline cobalt boride nanoparticles can be prepared even at nanometers below tens of nanometers. Furthermore, the advantage of this invention is that, utilizing thermal plasma, unnecessary steps such as filtration and drying are eliminated. In particular, compared to cobalt-based catalysts such as Co2B-500, Co-NiNP / NS, and CoB / NF, the cobalt boride nanoparticles of this invention demonstrate significantly superior oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities.

[0173] Therefore, by utilizing the method for preparing a water electrolysis catalyst electrode containing cobalt boride nanoparticles synthesized by thermal plasma, and the water electrolysis catalyst electrode of the present invention, excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) can be achieved in the cathode or anode due to excellent overpotential, current density, surface area, and long-term stability. Furthermore, the cobalt boride nanoparticles can be prepared in a single step (STEP), thus not only achieving the economic benefits of shortening the preparation time and reducing the preparation cost, but also improving productivity by preparing in high yield.

[0174] The present invention has been described in detail above using preferred embodiments, but the scope of the present invention is not limited to the specific embodiments and should be interpreted through the appended claims. Furthermore, it should be understood that those skilled in the art can make various modifications and alterations without departing from the scope of the present invention.

Claims

1. A method for preparing a water electrolysis catalyst electrode comprising cobalt boride nanoparticles synthesized by thermal plasma, characterized in that, Includes the following steps: Preparation of cobalt boride nanoparticles; Catalyst ink was prepared by ultrasonic treatment for 50-70 minutes after mixing cobalt boride nanoparticles, propanol, deionized water, and additives; and The prepared catalyst ink is coated onto the electrode and then dried to ensure that the catalyst ink is adhered to the electrode. The preparation of cobalt boride nanoparticles as described above includes the following process: Plasma jets are generated by injecting plasma-forming gas into a three-torch plasma jet device. A mixture of cobalt and boron in a molar ratio of 1:0.5 to 1:4 is injected into the plasma jet using a carrier gas and vaporized. Cobalt boride nanoparticles are recovered by cooling and vaporizing the above mixture. The additive mentioned above is a tetrafluoroethylene perfluoro-3,6-dioxa-4-methyl-7-octene sulfonic acid copolymer. In each cm 2 The electrode surface is coated with 1 mg to 1.5 mg of cobalt boride nanoparticles, the diameter of which is 1 nm to 20 nm.

2. A water electrolysis catalyst electrode comprising cobalt boride nanoparticles synthesized by thermal plasma, characterized in that, It is prepared by the method described in claim 1 for preparing a water electrolysis catalyst electrode containing cobalt boride nanoparticles synthesized by thermal plasma.

3. The water electrolysis catalyst electrode comprising cobalt boride nanoparticles synthesized by thermal plasma according to claim 2, characterized in that, The above-mentioned water electrolysis catalyst electrode generates hydrogen and oxygen in the cathode or anode, respectively.

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