KR20200142463A - Electrode for Electrolysis - Google Patents

Abstract

The present invention provides an electrode for electrolysis, which can improve durability and overvoltage of the electrode by including graphene oxide in a coating layer of the electrode for electrolysis, and a manufacturing method thereof.

Description

Electrode for Electrolysis {Electrode for Electrolysis}

The present invention relates to an electrode for electrolysis capable of improving overvoltage and a method of manufacturing the same.

A technology for producing hydroxide, hydrogen and chlorine by electrolyzing inexpensive brine such as seawater is widely known. This electrolysis process is commonly referred to as a chlor-alkali process, and it can be said that the performance and reliability of technology have been proven through commercial operation for decades.

In the electrolysis of such brine, an ion exchange membrane is installed inside the electrolyzer to divide the electrolyzer into a cation chamber and an anion chamber, and the ion exchange membrane method that obtains chlorine gas from the anode and hydrogen and caustic soda from the cathode using brine as an electrolyte is currently the most widely used. This is the method being used.

Meanwhile, the electrolysis process of brine is performed through a reaction as shown in the following electrochemical reaction formula.

Positive electrode (anode) _{^{reaction: 2Cl - → Cl 2 + 2e}} - (E 0 = +1.36 V)

A negative electrode (cathode) ^{_{reaction: 2H 2 O + 2e - →}} 2OH - + H 2 (E 0 = -0.83 V)

Total _{^{reaction: 2Cl - + 2H 2 O →}} 2OH - + Cl 2 + H 2 (E 0 = -2.19 V)

In performing the electrolysis of brine, the electrolytic voltage should consider both the voltage required for the theoretical brine electrolysis, the overvoltage of the anode, the overvoltage of the cathode, the voltage by the resistance of the ion exchange membrane, and the voltage by the distance between the anode and the cathode. Among these voltages, the overvoltage caused by the electrode acts as an important variable.

Therefore, a method to reduce the overvoltage of the electrode is being studied. For example, a precious metal electrode called DSA (Dimensionally Stable Anode) has been developed and used for the anode, and the development of excellent materials with low overvoltage and durability for the cathode. Is being demanded.

Stainless steel or nickel has been mainly used as such a cathode, and recently, to reduce overvoltage, the surface of stainless steel or nickel is coated with nickel oxide, an alloy of nickel and tin, a combination of activated carbon and oxide, ruthenium oxide, platinum, etc. The method of use is being studied.

In addition, a method of controlling the composition using a platinum group element such as ruthenium and a lanthanide element such as cerium is also being studied in order to increase the activity of the negative electrode by controlling the composition of the active material. However, an overvoltage phenomenon occurred, and a problem occurred in which deterioration due to reverse current occurred.

JP2003-2977967A

An object of the present invention is to provide an electrode for electrolysis with improved overvoltage by reducing the particle size of the electrode surface coating layer.

In order to solve the above problems, the present invention includes a metal substrate layer, and a coating layer comprising a platinum group oxide, a lanthanide oxide, and a graphene oxide, wherein the coating layer is formed on at least one surface of the substrate layer. Provides an electrode for disassembly.

In addition, the present invention provides a method of manufacturing the electrode for electrolysis.

The electrode for electrolysis according to the present invention has a smaller particle size of the electrode surface coating layer than the conventional electrode for electrolysis, has excellent adhesion to the electrode substrate, and has excellent surface properties, thereby improving overvoltage.

1 is a diagram showing the results (x5k and 1k) of observation of the surface before electrode activation of Comparative Example 1 of the present invention by SEM.
2 is a diagram showing the results (x5k and 1k) of observing the surface after electrode activation of Comparative Example 1 of the present invention by SEM.
3 is a diagram showing a result (x1k) of observing the surface before electrode activation of Example 1 of the present invention with an SEM.
FIG. 4 is a diagram showing a result (x1k) of observing the surface after electrode activation of Example 1 of the present invention with an SEM.
5 is a view showing the result of observing the crack of the electrode coating layer of Comparative Example 1 of the present invention by SEM.
6 is a view showing the result of observing the crack of the electrode coating layer of Example 1 of the present invention by SEM.

Hereinafter, the present invention will be described in more detail.

The terms or words used in this specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

Electrode for Electrolysis

The present invention is a metal substrate layer; And

Including; a coating layer comprising a platinum group oxide, a lanthanide oxide and a graphene oxide,

The coating layer provides an electrode for electrolysis that is formed on at least one surface of the base layer.

The metal substrate may be nickel, titanium, tantalum, aluminum, hafnium, zirconium, molybdenum, tungsten, stainless steel, or alloys thereof, of which nickel is preferable. In the electrode for electrolysis of the present invention, when such a metal substrate is used, durability and mechanical strength of the electrode may be excellent.

In the electrode for electrolysis of the present invention, the coating layer includes a platinum group oxide, and the platinum group metal of the platinum group oxide is a transition of groups 8 to 10 similar in properties to platinum such as ruthenium, platinum, rhodium, iridium, osmium or palladium. It is metal. The platinum group oxide may be one or more oxides selected from among the white metal metals described above, and preferably may be ruthenium oxide or platinum oxide.

In the coating layer, the platinum group oxide plays a role of providing a platinum group element as an active material, and when the platinum group oxide of this kind is used, the overvoltage phenomenon is improved while the change in electrode performance is small, and a separate activation process after that Can be minimized. The platinum group oxide includes all types of oxides in which a platinum group metal element and an oxygen atom are bonded, and in particular, may be a dioxide or a tetraoxide.

In the electrode for electrolysis of the present invention, the coating layer includes a lanthanide oxide, and the lanthanide oxide is a material that provides a lanthanide element to the coating layer of the electrode for electrolysis. The lanthanide element can improve the durability of the electrode for electrolysis, thereby minimizing the loss of the platinum group element in the coating layer of the electrode for electrolysis during activation or electrolysis. Specifically, when the electrode for electrolysis is activated or electrolyzed, the particles containing the platinum group element in the coating layer become metallic elements without changing the structure or are partially hydrated and reduced to active species. In addition, the structure of the particles containing the lanthanide element in the coating layer is changed to form a network with the particles containing the platinum group element in the coating layer, thereby supporting the coating layer and suppressing the dropping of the coating layer. As a result, the durability of the electrode for electrolysis By improving the catalytic layer, it is possible to prevent the loss of platinum group elements.

The lanthanide oxides are cerium oxide, placeodymium oxide, neodymium oxide, promedium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide It may be at least one selected from the group consisting of oxides, thulium-based oxides, ytterbium-based oxides, and lutetium-based oxides, of which cerium-based oxides are preferred. The oxide includes all types of oxides in which a lanthanide element and an oxygen atom are bonded, and in particular, may be an oxide of (II), (III) or (IV).

In the electrode for electrolysis of the present invention, the coating layer includes graphene oxide. The graphene oxide plays a role in improving the electrode properties, such as the surface properties of the coating layer by changing the active phase in the coating layer.In particular, by reducing the size of the electrode particles, it improves the adhesion between the electrode and the substrate, thereby making the electrode durable. Can be improved. In addition, the graphene oxide can prevent the needle-like structure of the lanthanide compound from being revealed even after activation of the electrode by strongly bonding the platinum group oxide as the active material with the metal substrate, thereby helping to maintain the electrode active phase. The occurrence of cracks can be minimized.

The graphene oxide has a hydroxy group, an epoxy group, a carboxyl group or a carbonyl group by oxidizing some carbon atoms contained in graphene, and can be prepared by strongly oxidizing graphite. The graphene oxide is particularly suitable for forming a coating layer because it can be stably dispersed in a large amount in a solvent including water. The oxygen content in the graphene oxide used in the present invention may be 60% or less, preferably 50% or less. In addition, the average thickness of the graphene oxide used in the present invention may be 0.5 to 2nm, preferably 1 to 1.5nm. If the oxygen content and the average thickness of the graphene oxide have a value outside this range, the structure of the graphene oxide may be easily collapsed.

In the electrode for electrolysis of the present invention, the platinum group oxide and the lanthanide oxide contained in the coating layer are 1:0.01 to 1:0.5, preferably 1:0.05 to 1:0.35, more preferably 1:0.1 to 1: It can be included in a molar ratio of 0.25. When the content of the platinum group oxide and the lanthanide oxide is in such a range, the effect of preventing the loss of the platinum group element may be particularly excellent, and thus durability of the electrode may be greatly improved.

In the electrode for electrolysis of the present invention, the platinum group oxide and graphene oxide included in the coating layer may be included in a weight ratio of 1:0.0001 to 1:0.003, preferably 1:0.0005 to 1:0.002. When less than this graphene oxide is included, the effect of improving durability by graphene oxide is insignificant, and when more than this is included, the effect of improving durability does not increase significantly, which is not economical.

Method of manufacturing electrode for electrolysis

The present invention comprises the steps of applying a coating composition on at least one surface of a metal substrate; And

It includes the step of drying and heat treating the metal substrate coated with the coating composition to coat,

The coating composition provides a method of manufacturing an electrode for electrolysis comprising a platinum group precursor compound, a lanthanide precursor compound, and graphene oxide.

In the method of manufacturing an electrode for electrolysis of the present invention, the metal substrate is the same as the metal substrate of the electrode for electrolysis described above.

In the method of manufacturing an electrode for electrolysis of the present invention, the coating composition may include a platinum group precursor compound, a lanthanide precursor compound, and graphene oxide. The platinum group precursor compound and the lanthanide precursor compound are oxidized and converted into oxides in a heat treatment step after coating.

The platinum group precursor compound is ruthenium hexafluoride (RuF ₆ ), ruthenium (III) chloride (RuCl ₃ ), ruthenium (III) chloride hydrate (RuCl ₃ ·xH ₂ O), ruthenium (III) bromide (RuBr ₃ ), ruthenium (III) at least one ruthenium precursor compound selected from the group consisting of bromide hydrate (RuBr ₃ xH ₂ O), ruthenium iodide (RuI ₃ ) and ruthenium acetate salt, or chloroplatinic acid hexahydrate (H ₂ PtCl ₆ 6H ₂ O), diamine dinitro platinum (Pt(NH ₃ ) ₂ (NO) ₂ ) and platinum (IV) chloride (PtCl ₄ ), platinum (II) chloride (PtCl ₂ ), potassium tetrachloroplatinate (K ₂ PtCl ₄ ), potassium hexachloroplatinate (K ₂ PtCl ₆ ) It is preferably at least one platinum precursor compound selected from the group consisting of. When the above-listed platinum group precursor compounds are used, the platinum group oxide may be easily formed.

The lanthanide precursor compound is a cerium precursor compound, a placeodymium precursor compound, a neodymium precursor compound, a promethium precursor compound, a samarium precursor compound, a europium precursor compound, a gadolinium precursor compound, a terbium precursor compound, and dysprosium. It may be one or more selected from the group consisting of a precursor compound, a holmium precursor compound, an erbium precursor compound, a thulium precursor compound, a ytterbium precursor compound, and a lutetium precursor compound, and in particular, cerium (III) nitrate hexahydrate ( The group consisting of Ce(NO ₃ ) ₃ ·6H ₂ O), cerium (IV) sulfate tetrahydrate (Ce(SO ₄ ) ₂ ·4H ₂ O) and cerium (III) chloride heptahydrate (CeCl ₃ · 7H ₂ O) It may be one or more cerium-based precursor compounds selected from. When the lanthanide precursor compounds listed above are used, the lanthanide oxide may be easily formed.

In the electrode preparation method for electrolysis of the present invention, the coating composition comprises a platinum group precursor compound and a lanthanide precursor compound from 1:0.01 to 1:0.5, preferably 1:0.05 to 1:0.35, more preferably 1:0.1 To 1:0.25 molar ratio. According to the content ratio of the platinum group precursor compound and the lanthanide precursor compound of the coating composition, the content of the platinum group oxide and the lanthanum oxide included in the electrode coating layer to be prepared may be determined, and electrolysis using a coating composition having such a composition ratio In the case of manufacturing an electrode for use, the effect of preventing the loss of platinum group elements included in the electrode coating layer to be produced may be particularly excellent, and thus durability of the electrode may be greatly improved.

In the method of manufacturing an electrode for electrolysis of the present invention, the coating composition may include the platinum group precursor compound and graphene oxide in a weight ratio of 1:0.0001 to 1:0.003, preferably 1:0.0005 to 1:0.002. As in the case of the platinum group precursor compound and the lanthanide precursor compound, the content of graphene oxide included in the electrode coating layer prepared according to the content of graphene oxide included in the coating composition may be determined. When less than this graphene oxide is included in the coating composition, the effect of improving durability due to graphene oxide is insignificant, and when more than this, the effect of improving durability does not increase significantly, which is not economical.

In the manufacturing method of the present invention, it may include a step of pretreating the metal substrate before performing the coating step.

The pretreatment may be to form irregularities on the surface of the metal substrate by chemical etching, blasting, or thermal spraying of the metal substrate.

The pretreatment may be performed by sand blasting the surface of the metal substrate to form fine irregularities, and salt treatment or acid treatment. For example, the surface of the metal substrate may be sandblasted with alumina to form irregularities, immersed in an aqueous sulfuric acid solution, washed and dried to pretreat to form fine irregularities on the surface of the metal substrate.

The application is not particularly limited as long as the catalyst composition can be evenly applied on the metal substrate, and may be performed by a method known in the art.

The application may be performed by any one method selected from the group consisting of doctor blade, die casting, comma coating, screen printing, spray spraying, electrospinning, roll coating, and brushing.

The drying may be performed at 50 to 300°C for 5 to 60 minutes, preferably at 50 to 200°C for 5 to 20 minutes.

If the above-described conditions are satisfied, the solvent can be sufficiently removed while minimizing energy consumption.

The heat treatment may be performed at 400 to 600° C. for 1 hour or less, and is preferably performed at 450 to 550° C. for 5 to 30 minutes.

If the above-described conditions are satisfied, impurities in the catalyst layer are easily removed, and the strength of the metal substrate may not be affected.

Meanwhile, the coating may be performed by sequentially repeating coating, drying, and heat treatment so that the amount of the platinum group oxide per unit area (m 2) of the metal substrate is 10 g or more. That is, in the manufacturing method according to another embodiment of the present invention, after applying, drying and heat treating the catalyst composition on at least one surface of a metal substrate, the first catalyst composition is applied again on one surface of the metal substrate, dried, and The coating to be heat treated can be repeatedly performed.

Hereinafter, examples and experimental examples will be described in more detail to describe the present invention in detail, but the present invention is not limited by these examples and experimental examples. The embodiments according to the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art.

material

In this example, a nickel mesh substrate (Ni purity of 99% or more, 200 μm) manufactured by Jang Inheungjeo was used as the metal substrate, and as the platinum group precursor compound, ruthenium chloride hydrate (RuCl ₃ nH ₂ O) hydrate and lanthanide precursor As a compound, cerium nitrate hexahydrate (Ce(NO ₃ ) ₃ ·6H ₂ O) was used. As the graphene oxide, N002-PS (Digechem Co., Ltd.) was used.

In addition, deionized water was used as a solvent for the coating composition.

Pretreatment of metal substrates

Before forming a coating layer on a metal substrate, sand blast the surface of the substrate with aluminum oxide (White alumina, F120) at 0.8kgf/cm ² , then put it in 5M H ₂ SO ₄ aqueous solution and pretreat at 80°C for 3 minutes I did.

Example 1

Ruthenium chloride hydrate and cerium nitrate hexahydrate of the material were mixed in a molar ratio of 1:0.2, and ruthenium chloride hydrate and graphene oxide were mixed in a weight ratio of 1:0.00078, and dissolved in deionized water to prepare a coating composition. The prepared coating composition was brush coated on the pretreated metal substrate, dried at 180° C. for 10 minutes, and then heat treated at 500° C. for 10 minutes. The coating, drying, and heat treatment processes were repeated 10 times, and finally heat-treated at 500° C. for 1 hour to prepare an electrode for electrolysis with a coating layer formed thereon.

Example 2

In Example 1, except that the mixing weight ratio of ruthenium chloride hydrate and graphene oxide was 1:0.0005, an electrode for electrolysis was prepared in the same manner.

Comparative Example 1. When graphene oxide is not included in the coating layer

In Example 1, except that graphene oxide was not included in the coating composition, an electrode for electrolysis was prepared in the same manner.

Information of the electrodes prepared in Examples 1 to 2 and Comparative Example 1 is summarized in Tables 1 and 2 below.

Molar ratio of each component Example 1 Example 2 Comparative Example 1 Ruthenium chloride hydrate One One One Cerium nitrate hexahydrate 0.2 0.2 0.2

Weight ratio of each component Example 1 Example 2 Comparative Example 1 Ruthenium chloride hydrate One One One Graphene oxide 0.00078 0.0005 -

Experimental Example 1. Performance check of the prepared electrode for electrolysis

In order to confirm the performance of the electrodes prepared in Examples 1 to 2 and Comparative Example 1, a cathode voltage measurement experiment using half cells in Chlor-Alkali Electrolysis was performed. After activating the electrode under the conditions of a current density of -6A/cm ² and a temperature of 90°C, voltage was measured through a constant current of -0.62A/cm ² . A 32% NaOH aqueous solution was used as an electrolyte, a Pt wire was used as the counter electrode, and a Hg/HgO electrode was used as the reference electrode. The results are summarized in Table 3 below.

division Example 1 Example 2 Comparative Example 1 Cathode potential (V vs. SCE) -1.087 -1.089 -1.106

From the above results, it was confirmed that the electrode of the present invention in which a platinum group oxide, a lanthanum group oxide, and a graphene oxide were simultaneously included in the coating layer exhibited a lower overvoltage compared to the electrode of the comparative example which did not.

Experimental Example 2. Measurement of particle size of electrode

The particle sizes of the electrodes prepared in Example 1 and Comparative Example 1 were measured through an X-ray diffraction analyzer (Bruker AXS D4-Endeavor XRD), and the results are shown in Table 4 below.

division Example 1 Comparative Example 1 Particle size (nm) 26.5 50.7

From the above results, it was confirmed that the electrode particle size of the examples of the present invention was significantly smaller than the electrode particle size of the comparative example, and the adhesion between the electrode and the substrate was excellent.

Experimental Example 3. Observation of the surface of the electrode

Using a scanning electron microscope (FE-SEM) (Hitachi S-4800 Scanning Electron Microscope), the surfaces before and after activation of the electrodes prepared in Example 1 and Comparative Example 1 were observed with a magnification of 5000 to 1000 times. It is represented by 1 to 6.

As can be seen in FIGS. 1 to 4, the electrode of Example 1 to which graphene oxide is added has little difference in electrode shape before and after activation, but the electrode of Comparative Example 1 to which graphene oxide is not added is active after activation. Phase loss occurred, and the acicular structure of cerium oxide, a lanthanide oxide, appeared.

In addition, as can be seen in Figs. 5 and 6, the electrode of Example 1 to which graphene oxide is added is superior to the electrode of Comparative Example 1 with excellent adhesion to the nickel mesh, which is a metal substrate, and thus less cracks in the electrode layer appear. Confirmed.

From this point, it was confirmed that the durability of the electrode of the examples of the present invention was superior to that of the electrode in comparison.

Claims (10)

Metal base layer; And
Including; a coating layer comprising a platinum group oxide, a lanthanide oxide and a graphene oxide,
The coating layer is an electrode for electrolysis that is formed on at least one surface of the base layer.
The method of claim 1,
The platinum group oxide is a ruthenium oxide electrode for electrolysis.
The method of claim 1,
The lanthanide oxide is a cerium oxide electrode for electrolysis.
The method of claim 1,
The platinum-group oxide and the lanthanide oxide are contained in a molar ratio of 1:0.01 to 1:0.5.
The method of claim 1,
The platinum group oxide and graphene oxide are 1:0.0001 to 1: 0.003 of the weight ratio of the electrode for electrolysis is included.
Applying a coating composition on at least one side of a metal substrate; And
It includes the step of drying and heat treating the metal substrate coated with the coating composition to coat,
The coating composition is a method for producing an electrode for electrolysis comprising a platinum group precursor compound, a lanthanide precursor compound, and graphene oxide.
The method of claim 6,
The platinum group precursor compound is ruthenium hexafluoride (RuF ₆ ), ruthenium (III) chloride (RuCl ₃ ), ruthenium (III) chloride hydrate (RuCl ₃ ·xH ₂ O), ruthenium (III) bromide (RuBr ₃ ), ruthenium (III) at least one ruthenium precursor compound selected from the group consisting of bromide hydrate (RuBr ₃ xH ₂ O), ruthenium iodide (RuI ₃ ), ruthenium iodide (RuI ₃ ), and ruthenium acetate salt, or chloroplatinic acid hexa Hydrate (H ₂ PtCl ₆ 6H ₂ O), diamine dinitro platinum (Pt(NH ₃ ) ₂ (NO) ₂ ) and platinum (IV) chloride (PtCl ₄ ), platinum (II) chloride (PtCl ₂ ), potassium Tetrachloroplatinate (K ₂ PtCl ₄ ), potassium hexachloroplatinate (K ₂ PtCl ₆ ) One or more platinum precursor compounds selected from the group consisting of an electrode for electrolysis.
The method of claim 6,
The lanthanide precursor compound is a cerium compound, a placeodymium compound, a neodymium compound, a promethium compound, a samarium compound, a europium compound, a gadolinium compound, a terbium compound, a dysprosium compound, a holmium compound, erbium A method of manufacturing an electrode for electrolysis, which is at least one selected from the group consisting of a compound based on a thulium compound, a compound based on ytterbium, and a compound based on lutetium.
The method of claim 6,
The coating composition is a method of manufacturing an electrode for electrolysis comprising a platinum group precursor compound and a lanthanide precursor compound in a molar ratio of 1:0.01 to 1:0.5.
The method of claim 6,
The coating composition is a method of producing an electrode for electrolysis comprising a platinum group precursor compound and graphene oxide in a weight ratio of 1:0.0001 to 1:0.003.

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