Manufacturing method of electrodes for electrolysis

Abstract

To provide a method for producing an electrode for electrolysis, which suppresses deterioration of a catalyst layer or a conductive substrate during storage of the electrode for electrolysis and has excellent durability capable of being easily stored.SOLUTION: The present invention relates to a method for producing an electrode for electrolysis, which comprises an alkali treatment step of treating the electrode for electrolysis with an alkaline aqueous solution having a pH of 9 to 14. After the alkali treatment step, it is subjected to a drying step and no cleaning step is performed. The electrode for electrolysis includes a conductive substrate containing nickel, and a catalyst layer provided on the conductive substrate.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing an electrode for electrolysis. [Background technology]

[0002] Reducing energy consumption is the biggest challenge in the ion-exchange membrane chlor-alkali electrolysis process. A detailed analysis of the cell voltage in ion-exchange membrane chlor-alkali electrolysis reveals that in addition to the theoretically required voltage, there are also voltages due to the membrane resistance of the ion-exchange membrane, overvoltages at the anode and cathode, and voltages due to solution resistance and gas resistance. Among these voltages, the electrode overvoltage for the anode has been reduced to around 50 mV under normal operating conditions by applying platinum group oxides to the insoluble electrode, reaching a level at which further improvement or refinement is not possible.

[0003] On the other hand, conventionally used mild steel, stainless steel, and nickel cathodes exhibit an overvoltage of 300–400 mV under normal operating conditions. Therefore, efforts have been made to activate these electrode surfaces and reduce the overvoltage, and many technologies have been developed. Examples include plasma spraying nickel oxide to produce highly active cathodes despite the oxide surface, as well as Raney nickel plating, nickel-tin composite plating, and activated carbon-oxide composite plating on the electrode surface. All of these have been used as cathodes for hydrogen generation in caustic soda. However, further reduction of the cathode overvoltage is necessary to reduce the electrolysis voltage, and various cathodes have been proposed for this purpose, including:

[0004] For example, Patent Document 1 proposes an electrode for hydrogen generation in which a precious metal coating made of one type of precious metal, or a mixture or alloy of two or more types of precious metals, or a coating of the precious metal coating containing one or more types of base metals such as nickel, is coated on a conductive substrate such as nickel.

[0005] On the other hand, a hydrogen generation electrode using a catalyst made of platinum and cerium oxide has been proposed (Patent Document 2). The hydrogen generation electrode made of this platinum and cerium oxide catalyst has a low overvoltage and exhibits excellent performance as a hydrogen generation electrode for electrolysis of an alkali metal chloride aqueous solution. In addition, it has been proposed to provide an intermediate layer made of nickel oxide between the platinum and cerium oxide catalyst and the substrate, and further improvements in terms of cost, etc. have been investigated.

[0006] In this context, we have developed an electrode for hydrogen generation, which is formed by coating a conductive metal with a cerium-platinum mixture-based electrode active material containing at least one of cerium metal, cerium oxide, and cerium hydroxide and platinum metal, and which is characterized in that the composition of the electrode active material is cerium-rich, with a platinum molar fraction of 15 to 30 mol % and a cerium molar fraction of 70 to 85 mol % in metal equivalent (Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 57-23083 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-239882 [Patent Document 3] International Publication No. 2011 / 040464 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, various electrodes for electrolysis (electrodes for generating hydrogen) have been developed to date. However, in electrodes for electrolysis that have a catalytic layer containing a precious metal (such as a platinum group metal), a nickel-based oxide, a cerium-based oxide, or the like, and that are provided with a conductive substrate containing nickel, the catalytic layer and / or the conductive substrate can be altered depending on the storage conditions prior to use in an electrolytic cell, causing problems with the durability of the electrodes for electrolysis during electrolysis (such as an increased rate of wear of the catalytic layer and a decreased reverse current resistance), and this has necessitated strict management of the storage conditions for the electrodes for electrolysis.

[0009] Under these circumstances, an object of the present invention is to provide a method for producing an electrode for electrolysis that is excellent in durability and can be stored simply and easily, while suppressing deterioration of the catalyst layer or the conductive substrate during storage of the electrode for electrolysis. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides the following method for producing an electrode for electrolysis.

[0011] Item 1. A method for producing an electrode for electrolysis, comprising an alkaline treatment step of treating the electrode for electrolysis with an alkaline aqueous solution having a pH of 9 to 14. Item 2. The method for producing an electrode for electrolysis according to Item 1, wherein the alkaline treatment step is followed by a drying step. Item 3. The method for producing an electrode for electrolysis according to Item 1 or 2, wherein a cleaning step is not carried out after the alkali treatment step. Item 4. The method for producing an electrode for electrolysis according to any one of Items 1 to 3, wherein the alkaline aqueous solution is an aqueous solution of a hydroxide of an alkali metal or alkaline earth metal, or a carbonate of an alkali metal or alkaline earth metal. Item 5. The method for producing an electrode for electrolysis according to any one of Items 1 to 4, wherein the alkaline aqueous solution is an aqueous solution of sodium hydroxide, potassium hydroxide, or sodium carbonate. Item 6. The method for producing an electrode for electrolysis according to any one of Items 1 to 5, wherein the electrode for electrolysis comprises a conductive substrate containing nickel and a catalyst layer provided on the conductive substrate. Item 7. The method for producing an electrode for electrolysis according to any one of Items 1 to 6, wherein the catalytic layer contains any one of platinum metal, palladium-based oxide, nickel-based oxide, cerium-based oxide, ruthenium-based oxide, and iridium-based oxide. [Effects of the Invention]

[0012] According to the method for producing an electrode for electrolysis of the present invention, by subjecting the electrode for electrolysis to an alkali treatment step in which it is treated with an alkaline aqueous solution of pH 9 to 14, substances that cause deterioration (chlorine (chlorides) and oxidizing agents (substances derived from the raw materials of the catalyst layer and the external environment during storage)) contained in the catalyst layer that cause deterioration can be inactivated, thereby suppressing deterioration of the catalyst layer of the electrode for electrolysis or the conductive substrate, and making it possible to provide an electrode for electrolysis that has excellent durability. Furthermore, by subjecting the electrode for electrolysis that has been subjected to the alkali treatment step to a drying step without a cleaning step (i.e., in a state in which alkali is supported on the surface of the catalyst layer of the electrode for electrolysis), deterioration of the catalyst layer or the conductive substrate can be suppressed. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a schematic diagram of a cell used for measuring the initial hydrogen generation potential in a reference example. [Figure 2] FIG. 10 is a diagram showing cycles in a reverse current resistance test of a reference example. [Figure 3] 1 is a graph showing the time until the catalytic layer of the electrolysis electrode is altered. [Figure 4] 1 is a graph showing the time until the catalytic layer of the electrolysis electrode is altered. [Figure 5] 1 is a graph showing the hydrogen generation potential of an electrode for electrolysis. BEST MODE FOR CARRYING OUT THE INVENTION

[0014] The present invention will be described in detail below.

[0015] The production method of the present invention includes an alkali treatment step of treating the electrode for electrolysis with an alkaline aqueous solution having a pH of 9 to 14.

[0016] The alkaline aqueous solution used in the alkaline treatment step in the production method of the present invention can be used without any particular limitation as long as it is in the pH range of 9 to 14. By treating the electrolysis electrode with an alkaline aqueous solution having a pH of 9 to 14 (preferably pH 10 to 14, more preferably pH 11 to 14), it is possible to inactivate deterioration-causing substances (chlorine (chlorides) and oxidizing agents (derived from the raw materials of the catalytic layer)) contained in the catalytic layer of the electrolysis electrode.

[0017] The alkaline treatment step of the electrode for electrolysis may be carried out by immersing the electrode for electrolysis in an alkaline aqueous solution (immersion method), or by applying the alkaline aqueous solution to the surface of the electrode for electrolysis using a brush or spray (application method).

[0018] When the alkali treatment step is carried out by the immersion method, the immersion time may be appropriately adjusted, specifically, in the range of 1 minute to 50 hours, preferably in the range of 1 hour to 30 hours, and more preferably in the range of 10 hours to 24 hours. The temperature of the alkaline aqueous solution is in the range of 10°C to 100°C, preferably in the range of room temperature (25°C) to 80°C.

[0019] By immersing the electrolysis electrode in an alkaline aqueous solution, the alkali penetrates into the outer surface and / or pores of the catalytic layer of the electrolysis electrode, deactivating the substances that cause deterioration (chlorine (chlorides) and oxidizing agents (derived from the raw materials of the catalytic layer)).

[0020] When the alkaline treatment step is carried out by the application method, the method for applying the alkaline aqueous solution to the electrode for electrolysis is not particularly limited, and known methods such as application with a brush or roller, spraying, and dip coating can be used.

[0021] When the electrode for electrolysis is subjected to alkaline treatment by the coating method, the amount of solution to be applied onto the electrode for electrolysis is not particularly limited, but it is sufficient to apply an amount of solution that can inactivate the substances that cause deterioration (chlorine (chlorides) and oxidizing agents (derived from the raw materials of the catalyst layer)). For example, 2It is sufficient to apply 5 g or more of alkali to the substrate, and in this case, application may be carried out multiple times so that the total amount of alkali applied is 5 g or more.

[0022] The alkaline aqueous solution used in the alkaline treatment step of the present invention can be used without any particular problems as long as it can efficiently inactivate the deterioration-causing substances contained in the catalytic layer of the electrolysis electrode. For example, the alkaline aqueous solution may be an aqueous solution of ammonia water, an alkali metal or alkaline earth metal hydroxide, or an alkali metal or alkaline earth metal carbonate, and examples of alkali metal or alkaline earth metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide. Examples of carbonates of alkali metals or alkaline earth metals include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate. Among these, sodium hydroxide, potassium hydroxide, and sodium carbonate are preferred. The aqueous alkali solutions may be used alone or in combination of two or more. When mixed, the mixing ratio may be adjusted so that the alkali concentration falls within the range described below.

[0023] The alkaline aqueous solution used in the alkaline treatment step of the present invention can be used without any particular problems as long as it has a concentration of 0.01 to 48% by mass. The concentration is preferably 0.1 to 40% by mass, and more preferably 16 to 35% by mass. If the concentration of the alkaline aqueous solution exceeds 48% by mass, the catalytic layer of the electrolysis electrode may peel off, and if it is less than 0.01% by mass, the deactivation of substances that cause deterioration contained in the catalytic layer may not proceed sufficiently.

[0024] In the production method of the present invention, it is preferable to dry the electrode for electrolysis by carrying out a drying step after the alkali treatment step. The drying step may be carried out under drying conditions sufficient to evaporate the aqueous alkaline solution attached to the surface of the electrode for electrolysis in the alkali treatment step, for example, at room temperature for about 10 minutes to 24 hours, and is preferably carried out at a temperature of room temperature or higher and 200°C or lower for about 5 minutes to 10-odd hours.

[0025] In the production method of the present invention, it is preferable not to wash the alkali adhering to the surface of the electrode for electrolysis after the alkali treatment step and before the drying step (i.e., not to perform the washing step). By not subjecting the electrode for electrolysis that has been subjected to the alkali treatment step to the washing step, the alkali supported on the surface of the electrode for electrolysis inactivates substances that cause deterioration (chlorine (chlorides) and oxidizing agents (materials of the catalyst layer, and substances derived from the external environment during storage)), thereby contributing to suppression of deterioration of the catalyst layer. Note that, as long as alkali is supported on the electrode for electrolysis that has been subjected to the alkali treatment step, deterioration of the catalyst layer can be suppressed, and the amount of alkali supported on the electrode for electrolysis is not particularly limited, but may be, for example, 5 g / m 2 If the temperature is above this level, the substances that cause deterioration of the catalyst layer can be sufficiently inactivated.

[0026] The alkali treatment step in the production method of the present invention may be carried out immediately after the catalytic layer formation step in a typical production process for an electrode for electrolysis, or an electrode for electrolysis that has been stored for a certain period of time after the catalytic layer formation step may be subjected to the alkali treatment step. Preferably, the alkali treatment step is carried out immediately after the catalytic layer formation step.

[0027] In the production method of the present invention, the electrode for electrolysis can be either an anode or a cathode, as long as it is an electrode used for electrolysis. Preferably, it is an electrode for sodium chloride electrolysis.

[0028] The conductive substrate of the electrode for electrolysis is not particularly limited as long as it has conductivity and functions as a substrate for the electrode, and any conductive substrate used in known electrodes can be used.

[0029] The conductive substrate preferably contains a metal, and more preferably is made of a metal. Examples of metals include nickel, stainless steel, iron, copper, titanium, and steel. Among these, nickel or titanium is preferred, and nickel is more preferred. The conductive substrate is preferably made of nickel or titanium, and more preferably nickel. Suitable conductive substrates containing nickel or titanium include those made of nickel or titanium, as well as those in which the surface of stainless steel is coated with nickel or titanium. The conductive substrate may contain 20% or more by mass of nickel or titanium (particularly nickel), and preferably 50% or more by mass. More preferably, it contains 75% or more by mass, and particularly preferably 90% or more by mass.

[0030] The shape of the conductive substrate is not particularly limited, and examples thereof include a plate, a rod, a porous shape (expanded metal, punched metal, blind shape, etc.), etc. From the viewpoint of increasing the surface area of the coating provided on the conductive substrate, a porous shape, etc. is preferred.

[0031] The size of the conductive substrate is not particularly limited and may be set appropriately depending on the size of the electrolytic cell, the size of the electrodes, etc., but examples include a length of about 300 mm to 2,500 mm, a width of about 1,200 mm to 1,500 mm, and a thickness of about 0.1 mm to 6 mm.

[0032] The surface of the conductive substrate may be roughened from the viewpoint of improving the adhesion of the catalyst layer. The surface roughness Ra of the conductive substrate can be set to, for example, about 1 to 10 μm. Examples of methods for roughening the surface of the conductive substrate include blasting.

[0033] The surface of the conductive substrate may be subjected to an etching treatment from the viewpoint of improving the adhesion of the catalyst layer. Examples of the etching method include a method of immersing the conductive substrate in an acid such as hydrochloric acid. After the etching treatment, it is preferable to wash the surface of the conductive substrate with water until it becomes neutral, and then dry it.

[0034] In the electrode for electrolysis of the present invention, the catalyst layer is formed on a conductive substrate. More specifically, the catalyst layer is preferably formed on the surface of the conductive substrate.

[0035] The material used in the catalyst layer can be appropriately selected from elemental metals or metal oxides, and can generally be selected from transition metals. Furthermore, from the viewpoint of reducing overvoltage during electrolysis, it is preferable that the material contains at least platinum metal. Examples of metals that can be used in the catalyst layer include platinum metal, palladium-based oxides, ruthenium-based oxides, nickel-based oxides, cerium-based oxides, and iridium-based oxides (for example, a catalyst layer containing ruthenium-based oxides and cerium-based oxides). The catalyst layer may contain only one type of metal, or a combination of multiple metals. When multiple metals are used in combination, the ratio can be appropriately adjusted.

[0036] The state of the metal in the catalyst layer is not particularly limited. For example, it is preferable that at least a portion of platinum is contained as platinum metal, and platinum oxide, platinum hydroxide, etc. may be contained. At least a portion of palladium is contained as palladium oxide, and palladium metal, palladium hydroxide, etc. may be further contained. At least a portion of ruthenium is contained as ruthenium oxide, and ruthenium metal, ruthenium hydroxide, etc. may be further contained. At least a portion of nickel is contained as nickel oxide, and nickel metal, nickel hydroxide, etc. may be further contained. At least a portion of cerium is contained as cerium oxide, and cerium metal, cerium hydroxide, etc. may be further contained. At least a portion of iridium is contained as iridium oxide, and iridium metal, iridium hydroxide, etc. may be further contained. The above-mentioned metals may be in the form of an alloy or amorphous metal.

[0037] Furthermore, from the viewpoint of effectively suppressing a decrease in the effective surface area of the platinum group metal due to a reverse current when electrolysis is stopped while lowering the hydrogen generation potential during electrolysis, the content of the platinum group metal in the catalyst layer (i.e., the amount of the platinum group metal supported) is preferably 2 g / m 2 More preferably, 3 g / m 2 More preferably, 4 g / m 2 The higher the amount of platinum group metal supported, the greater the effect, but from an economical point of view, the upper limit of the amount of platinum group metal supported is, for example, 20 g / m 2 Examples include:

[0038] From the same viewpoint, the thickness of the catalyst layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. The thicker the catalyst layer, the more effective it is, but from an economic viewpoint, the upper limit of the thickness of the catalyst layer is, for example, 20 μm.

[0039] The method for forming a catalyst layer on a conductive substrate is not particularly limited, but as described below, the catalyst layer can be suitably formed by a method in which, for example, a solution containing any compound (chloride, nitrate compound, oxide, hydroxide, sulfate, etc.) of a platinum compound, a palladium compound, a ruthenium compound, a nickel compound, a cerium compound, or an iridium compound is applied onto the conductive substrate, and the formed coating is baked to thermally decompose these compounds.

[0040] Here, a general method for manufacturing an electrode for electrolysis (electrode for hydrogen generation) will be described. The electrode for hydrogen generation comprises a conductive substrate and a catalytic layer provided on the conductive substrate. Components contained in the catalytic layer include platinum metal, palladium-based oxides, ruthenium-based oxides, nickel-based oxides, cerium-based oxides, and iridium-based oxides. The method for forming the catalytic layer is not particularly limited, and any known method that can form a catalytic layer containing the above-mentioned components on a conductive substrate, such as thermal decomposition, powder sintering, electroplating, dispersion plating, thermal spraying, or arc ion plating, can be used.

[0041] Among these methods for forming a catalyst layer, the thermal decomposition method is preferred. In the thermal decomposition method, for example, a solution containing any compound (chloride, nitrate compound, oxide, hydroxide, sulfate, etc.) of platinum compounds, palladium compounds, ruthenium compounds, nickel compounds, cerium compounds, or iridium oxides is applied onto a conductive substrate, and the coating film is baked to form a catalyst layer on the conductive substrate.

[0042] The platinum compound is not particularly limited as long as it is thermally decomposed by firing the catalyst layer to contain platinum metal in the catalyst layer, and examples thereof include dinitrodiammine platinum, chloroplatinic acid, tetraammine platinum nitrate, hexaammine platinum hydroxide, bis(acetylacetonato)platinum, etc. One type of platinum compound may be used, or two or more types may be used.

[0043] The palladium compound is not particularly limited as long as it is thermally decomposed by firing the catalyst layer to contain palladium oxide in the catalyst layer, and examples thereof include palladium chloride, dinitrodiamminepalladium nitrate, palladium nitrate, tetraamminepalladium chloride, tetraamminepalladium hydroxide, tetraamminepalladium nitrate, tetraamminepalladium sulfate, etc. One type of palladium compound may be used, or two or more types may be used.

[0044] The ruthenium compound is not particularly limited as long as it is thermally decomposed by firing the catalyst layer to contain ruthenium oxide in the catalyst layer, and examples thereof include ruthenium chloride, ruthenium nitrate, hexaammineruthenium chloride, etc. One type of ruthenium compound may be used, or two or more types may be used.

[0045] The nickel compound is not particularly limited as long as it is thermally decomposed by firing the catalyst layer to contain nickel oxide in the catalyst layer, and examples thereof include nickel nitrate, nickel sulfate, nickel carbonate, nickel chloride, nickel acetate, etc. One type of nickel compound may be used, or two or more types may be used.

[0046] The cerium compound is not particularly limited as long as it is thermally decomposed by firing the catalyst layer to contain cerium oxide in the catalyst layer, and examples thereof include cerium nitrate, cerium sulfate, cerium carbonate, cerium chloride, cerium acetate, etc. One type of cerium compound may be used, or two or more types may be used.

[0047] The iridium compound is not particularly limited as long as it is thermally decomposed by firing the catalyst layer to contain iridium oxide in the catalyst layer, and examples thereof include iridium nitrate, iridium sulfate, iridium chloride, hexaammineiridium chloride, hexaammineiridium hydroxide, hexaammineiridium nitrate, etc. One type of iridium compound may be used, or two or more types may be used.

[0048] The metals contained in the solution used to form the catalyst layer are not particularly limited, and can be adjusted to have the molar ratio in the catalyst layer described above.

[0049] The solvent contained in the solution is not particularly limited, but is preferably one that can dissolve the metal compound used in the catalyst layer. Specific examples of the solvent include water, inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid, and acetic acid, lower alcohols such as methanol, ethanol, propanol, and butanol, and mixed solutions containing at least two of these. Furthermore, in order to suppress dissolution of the conductive substrate, a pH adjuster or the like may be added to the solution.

[0050] The total concentration of metals in the solution is not particularly limited, but from the viewpoint of suitably forming a catalyst layer so that the amount of catalyst component (platinum group metal, etc.) contained in the catalyst layer is a predetermined amount, the total concentration is preferably 2% or more, more preferably about 3 to 30%, and even more preferably about 4 to 20%.

[0051] In the step of forming the catalyst layer, the catalyst layer may be formed by using a solution containing one or more metal compounds and applying it onto the conductive substrate, or by using multiple solutions and repeatedly applying and baking them separately onto the conductive substrate to form the catalyst layer.

[0052] The method for applying the solution to the conductive substrate is not particularly limited, and known methods such as brush coating, spraying, dip coating, etc. As described above, the surface of the conductive substrate may be roughened or may be subjected to treatment such as etching, washing with water, drying, etc.

[0053] After applying the solution to the conductive substrate, it is preferable to dry the catalyst layer before firing it. Drying can be carried out under conditions sufficient to evaporate the solvent, for example, at a temperature of 200°C or less for about 5 to 60 minutes, and more preferably at a temperature of 150°C or less.

[0054] Next, the obtained catalyst layer is calcined to form a catalyst layer containing at least any one of platinum metal, palladium oxide, ruthenium oxide, nickel oxide, cerium oxide, and iridium oxide on the conductive substrate, thereby obtaining an electrode for electrolysis (electrode for hydrogen generation). The calcination can be carried out, for example, in an oxidizing atmosphere such as air (for example, in the atmosphere).

[0055] The calcination may be carried out under conditions such that the metal compound in the catalyst layer is thermally decomposed to contain the metal element or metal oxide in the resulting catalyst layer. The calcination temperature is preferably about 200 to 700°C, more preferably about 350 to 550°C. The calcination time is preferably about 5 to 60 minutes, more preferably about 10 to 30 minutes.

[0056] The above series of steps of coating, drying, and firing is repeated at least once, preferably multiple times, to form a catalyst layer on the conductive substrate. The number of times the series of steps is repeated is not particularly limited, and it is preferable to repeat the series of steps until a predetermined amount of platinum group metal or the like is supported. Furthermore, when the series of steps is repeated, the composition of the solution to be applied may be the same or different, but is usually the same.

[0057] By carrying out an alkali treatment step following the above-described method in the production method of the present invention, an electrode for electrolysis (electrode for hydrogen generation) having excellent durability can be suitably produced.

[0058] The electrolysis electrode (electrode for hydrogen generation) obtained by the production method of the present invention can be used for electrolysis. The electrolysis method is a method of electrolyzing a solution containing water (for example, water, an aqueous solution of an alkali metal chloride such as sodium chloride, or an aqueous solution of an alkali metal hydroxide such as sodium hydroxide).

[0059] For example, when the electrolysis electrode (electrode for hydrogen generation) obtained by the production method of the present invention is subjected to ion exchange membrane method salt electrolysis, the electrolyte temperature at the start of use is about 70 to 90°C, the electrolyte concentration in the cathode chamber (aqueous sodium hydroxide solution) is about 20 to 40 mass%, and the current density is 0.1 to 10 kA / m2 It can be about. [Example]

[0060] Next, the present invention will be specifically explained by way of examples, but the present invention is not limited to these examples.

[0061] (Reference example 1) In Reference Example 1, MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was used. MD-C60: Expanded metal Ni substrate, catalyst layer: Ru / Ce=4 / 1 (weight ratio)

[0062] (Reference example 2) In Reference Example 2, MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode B) in which the catalyst layer or the conductive substrate had been altered was used.

[0063] (Production Example 1) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was immersed in a 0.2% by mass sodium hydroxide aqueous solution (pH = approximately 13) at 30°C for 16 hours (subjected to the alkali treatment process), and then naturally dried at room temperature for 5 hours (drying process) to produce electrode 1.

[0064] (Production Example 2) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was immersed in a 2.5% by mass sodium hydroxide aqueous solution (pH = approximately 14) at 30°C for 16 hours (subjected to the alkali treatment process), and then naturally dried at room temperature for 5 hours (drying process) to produce electrode 2.

[0065] (Production Example 3) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was immersed in a 32% by mass aqueous solution of sodium hydroxide (pH = approximately 14) at 30°C for 16 hours (subjected to the alkali treatment process), and then naturally dried at room temperature for 5 hours (drying process) to produce electrode 3.

[0066] (Production Example 4) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was immersed in a 4.5% by mass sodium carbonate aqueous solution (pH = approximately 11) at 30°C for 16 hours (subjected to the alkali treatment process), and then naturally dried at room temperature for 5 hours (drying process) to produce electrode 4.

[0067] (Production Example 5) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was immersed in a 0.2 mass % potassium hydroxide aqueous solution (pH = approximately 14) at 30°C for 16 hours (subjected to the alkali treatment process), and then naturally dried at room temperature for 5 hours (drying process) to produce electrode 5.

[0068] (Production Example 6) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was filled with 0.2 mass% sodium hydroxide aqueous solution (pH = approximately 13) at 30°C at a ratio of 5 g / m2 to the electrode area. 2 The coating was carried out with a brush so as to obtain the above-mentioned results, and the coating was subjected to an alkali treatment step, followed by natural drying at room temperature for 5 hours (drying step), thereby producing an electrode 6.

[0069] (Production Example 7) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was immersed in a 0.2% by mass sodium hydroxide aqueous solution (pH = approximately 13) at 30°C for 1 minute (subjected to the alkali treatment process), and then naturally dried at room temperature for 5 hours (drying process) to produce electrode 7.

[0070] (Production Example 8) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was immersed in a 0.2% by mass sodium hydroxide aqueous solution (pH = approximately 14) at 30°C for 1 hour (subjected to the alkali treatment process), and then naturally dried at room temperature for 5 hours (drying process) to produce electrode 8.

[0071] (Production Example 9) MD-C60 (manufactured by Daiso Engineering Co., Ltd.) (electrode A) was immersed in a 6% by mass aqueous solution of sodium hydroxide (pH = approximately 14) at 30°C for 16 hours (subjected to the alkali treatment process), and then naturally dried at room temperature for 5 hours (drying process) to produce electrode 9.

[0072] (Reference examples 1 and 2) A reverse current resistance test was carried out using electrodes A and B. In this reference example, it was confirmed what effect would occur on the electrode performance due to the deterioration of the catalyst layer or conductive substrate of the electrolysis electrode.

[0073] (reverse current resistance test) Electrode A or electrode B was used as the working electrode, and a cell was assembled as shown in the schematic diagram in Figure 1. Next, a current of 10 kA / m 2 The sample was then subjected to cathodic electrolysis at 1 kA / m for 60 minutes to prepare the sample before testing (the current was in the direction normally used). 2 Anodic electrolysis at 9 kA / m for 45 minutes (current flow is reversed from that normally used) 2 A cycle test was conducted in which two cycles of cathodic electrolysis (current flow in the direction normally used) were repeated (see the cycle diagram in Figure 2), and the amount of catalyst loss on electrode A or electrode B after two cycles was measured using the method described below. The results are shown in Table 1.

[0074] (X-ray fluorescence analysis) The change in catalyst amount before and after the reverse current resistance test was measured by X-ray fluorescence analysis for Electrode A and Electrode B. The measurement equipment used was a Handheld XRF Analyzer DP-2000-C (Innov-x Systems, Inc.), and the catalyst amount was calculated using the calibration curve method.

[0075] TIFF0007720136000001.tif41116

[0076] As shown in Table 1, electrode B, which had a degraded catalytic layer or conductive substrate, showed a significant increase in overvoltage and a decrease in catalyst after the reverse current withstand test, compared to electrode A, which had no degraded catalytic layer or conductive substrate.

[0077] Example 1 Electrodes A, 1, 2, 3, 4, 5, 6, 7, and 8 were subjected to a storage stability test.

[0078] (Storage stability test) Each electrode was stored in saturated steam at 90°C, and the time until deterioration of the catalyst layer or conductive substrate occurred was measured. The above storage conditions are accelerated test conditions designed to accelerate the deterioration of the conductive substrate or catalyst layer, and deterioration of the conductive substrate or catalyst layer can be confirmed in approximately 1 / 20 the time required for a normal storage test. The presence or absence of deterioration of the catalyst layer or conductive substrate was determined by observing the cathode surface with a magnifying glass. The results are shown in the graphs in Figures 3 and 4.

[0079] As shown in FIG. 3, electrodes 1, 2, 3, 4, and 5 were subjected to the alkali treatment process by immersion for 16 hours in a 0.2 mass% sodium hydroxide aqueous solution (electrode 1), a 2.5 mass% sodium hydroxide aqueous solution (electrode 2), a 32 mass% sodium hydroxide aqueous solution (electrode 3), a 4.5 mass% sodium carbonate aqueous solution (electrode 4), and a 0.2 mass% potassium hydroxide aqueous solution (electrode 5). The time until the catalyst layer or conductive substrate deteriorated was 28 to 39 times longer than that of electrode A, which was not subjected to the alkali treatment.

[0080] Furthermore, as shown in FIG. 4, in electrodes 6, 7, and 8, which were subjected to the alkali treatment process using a 0.2% by mass sodium hydroxide aqueous solution by the coating method (electrode 6), by immersion in a 0.2% by mass sodium hydroxide aqueous solution for 1 minute (electrode 7), and by immersion in a 0.2% by mass sodium hydroxide aqueous solution for 1 hour (electrode 8), the time until the catalyst layer or conductive substrate deteriorated was improved by 4 to 6 times compared to electrode A, which was not subjected to the alkali treatment process.

[0081] Example 2 The hydrogen evolution potentials of electrodes A, 2, and 9 were measured.

[0082] (Measurement of hydrogen generation potential) Each electrode was used as a working electrode, and a cell was assembled as shown in the schematic diagram in Figure 1. A current density of 6 kA / m 2 The hydrogen generation potential was measured by the current interrupt method under the following conditions. The cell configuration is as follows. As a pretreatment, a current density of 4 kA / m 2 Electrolysis was carried out for 1 minute at 1000 kJ / min. The results are shown in Figure 5. The test conditions were as follows: Electrolyte: 32% by mass sodium hydroxide aqueous solution (volume approximately 300 mL) Liquid temperature: 80℃ Working electrode electrolysis area: 100mm 2 (10mm x 10mm) Counter electrode: platinum plate Counter electrode electrolysis area: 625mm 2 (25mm x 25mm) Reference electrode type: Mercury / mercury oxide electrode (Hg / HgO) (immersed in 32% sodium hydroxide aqueous solution (25°C))

[0083] As shown in Figure 5, electrodes 2 and 9, which were subjected to the alkali treatment process by immersion for 16 hours in a 2.5 mass% aqueous sodium hydroxide solution (electrode 2) and a 6.0 mass% aqueous sodium hydroxide solution (electrode 9), respectively, exhibited hydrogen evolution potentials equivalent to that of electrode A, which was not subjected to the alkali treatment process. This proves that there is no problem with electrode performance even when subjected to the alkali treatment process.

Claims

1. The method includes an alkali treatment step in which the electrodes for electrolysis are immersed in or coated with an alkaline aqueous solution having a pH of 9 to 14, thereby inactivating substances that cause deterioration and are contained in the catalytic layer of the electrodes for electrolysis; A method for producing an electrode for electrolysis, characterized in that after the alkali treatment step, the electrode is subjected to a drying step, and a washing step is not performed.

2. 2. The method for producing an electrode for electrolysis according to claim 1, wherein the alkaline aqueous solution is an aqueous solution of a hydroxide of an alkali metal or an alkaline earth metal, or a carbonate of an alkali metal or an alkaline earth metal.

3. 3. The method for producing an electrode for electrolysis according to claim 1, wherein the alkaline aqueous solution is an aqueous solution of sodium hydroxide, potassium hydroxide, or sodium carbonate.

4. 3. The method for producing an electrode for electrolysis according to claim 1, wherein the electrode for electrolysis comprises a conductive substrate containing nickel and a catalyst layer provided on the conductive substrate.

5. 5. The method for producing an electrode for electrolysis according to claim 4, wherein the catalytic layer contains any one of platinum metal, a palladium-based oxide, a nickel-based oxide, a cerium-based oxide, a ruthenium-based oxide, and an iridium-based oxide.

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