JP2018119199A - Electrode for hydrogen generation, method for producing the same, and method of electrolysis therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for hydrogen generation having sufficiently low hydrogen overvoltage in the initial stage and having excellent durability.SOLUTION: An electrode for hydrogen generation comprises a catalyst layer having principal components therein supported on an electrically conductive base material, wherein the principal components are platinum, nickel, and palladium, the catalyst layer is in the form of alloy, amorphous metal, metal oxide or metal hydroxide, impedance is 0.9 Ω or less at 0.1 Hz when a set potential is 1.0 V vs Hg/HgO and when a potential amplitude is 5 mV in an aqueous solution of 1 mol/l sodium hydroxide, and the weight of the catalyst layer is 10 g/mor more per projection area of the electrically conductive base material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode for hydrogen generation used for electrolysis of water or electrolysis of an aqueous alkali metal chloride solution such as salt, a method for producing the same, and an electrolysis method using the same.

  The water or alkali metal chloride aqueous solution electrolysis industry is a power-intensive industry, and various technological developments have been made to save energy. The energy saving means is to reduce power loss generated during electrolysis by reducing electrolysis voltage and / or improving current efficiency. For example, in the salt electrolysis industry, the current efficiency is operated at 95% or more, and there is little room for improvement. On the other hand, the electrolysis voltage is operated at around 3.0 V with respect to the theoretical decomposition voltage of about 2.3 V, and there is a lot of room for voltage reduction, and research and development for reducing the voltage are actively conducted.

  In particular, regarding the reduction of the overvoltage, since the overvoltage value depends on the electrode catalyst material and the morphology of the electrode surface, many researches and developments have been conducted on the improvement thereof. For example, as a result of vigorous research and development for reducing anode overvoltage for the ion exchange membrane salt electrolysis anode, a dimensional stability electrode with low anode overvoltage and excellent durability [eg Denora Permerek Co., Ltd. DSE chlorine-generating electrode (registered trademark)] made commercially available.

  On the other hand, many proposals have been made regarding an electrode for hydrogen generation for reducing cathode overvoltage, so-called active cathode. For example, an electrode for hydrogen generation has been proposed in which a conductive substrate surface is loaded with a substance containing organic compounds such as amino acids, carboxylic acids, and amines in addition to a combination of nickel, iron, cobalt, and indium by electroplating. (Patent Document 1). In the electrode for generating hydrogen of Patent Document 1, if the coating layer is too thin, sufficient low hydrogen overvoltage performance cannot be obtained, and if it is too thick, it is easy to peel off, so 20 μm to 300 μm is appropriate ([0011 ]).

  In recent years, a so-called zero gap type ion exchange membrane method electrolytic cell in which an anode, an ion exchange membrane and a cathode are brought into close contact with each other has been put into practical use. For example, the step width is 0.1 mm to 1.0 mm, the minor axis is 0.5 mm to 5.0 mm, the major axis is 1.0 mm to 10 mm, the plate thickness is 0.1 mm to 1.0 mm, and the opening It has been proposed to use an electrode for hydrogen generation in which an electrode catalyst is supported on an expanded metal having a rate of 48 to 60% (Patent Document 2). When the electrocatalyst is supported on such an expanded metal (also referred to as “expanded mesh”) that is thin and has a small aperture, the coating layer is too thick at 20 μm to 300 μm. These effects may not be exhibited when used in a zero gap electrolytic cell.

In recent years, an electrode for hydrogen generation using a catalyst containing platinum has been proposed. For example, the weight of the catalyst layer is optimally about 1 to 15 g / m ² , and the optimal thickness is an electrode for hydrogen generation having a thickness of about 0.1 to 10 μm (Patent Document 3 [0036]). It can also be preferably used in the zero gap type ion exchange membrane electrolytic cell described in Document 2, and research and development has been actively conducted.

  Among them, the electrode for hydrogen generation in which a catalyst layer mainly composed of platinum, nickel and palladium is supported on a conductive substrate is, for example, iron in an electrolyte solution which has been regarded as a drawback of conventional platinum-based catalysts. Due to ion poisoning, the hydrogen overvoltage does not increase, and the catalyst does not peel off or fall off due to the reverse current flowing during the electrolysis operation or stop / start operation (Patent Document 4). [0047]).

  The electrode for hydrogen generation in which the catalyst layer which has platinum, nickel, and palladium as a main component is carry | supported has a hydrogen overvoltage of 70-80 mV, for example (Table 1 of patent document 4). This can be positioned as sufficiently high performance as compared with the prior art, but from the viewpoint of environmental protection, a technology capable of further reducing hydrogen overvoltage is required.

Japanese Patent No. 3319370 Japanese Patent No. 5582002 Japanese Patent No. 5042389 JP2015-143389A

The object of the present invention is that it can be used in the water or alkali metal chloride aqueous solution electrolysis industry, etc., and is not affected by poisoning by iron ions. Platinum, nickel, and an electrode for hydrogen generation excellent in durability with no dropout, and further having a hydrogen overvoltage of less than 70 mV measured at 6 kA / m ² in a 32 wt% sodium hydroxide aqueous solution at 90 ° C. The object is to provide a method for producing an electrode for hydrogen generation in which a catalyst layer mainly composed of palladium is supported.

In order to solve the above problems, the inventor has conducted extensive studies on a hydrogen generation electrode in which a catalyst layer mainly composed of platinum, nickel, and palladium is supported. As a result, the hydrogen overvoltage is less than 70 mV. The inventors have found that an electrode for hydrogen generation in which a catalyst layer mainly composed of platinum, nickel and palladium is supported is obtained, and the present invention has been achieved. That is, the present invention is an electrode for hydrogen generation in which a catalyst layer mainly composed of platinum, nickel and palladium is supported on a conductive substrate, and the catalyst layer is made of an alloy, amorphous metal, metal oxide In a 1 mol / L aqueous solution of sodium hydroxide, set potential: 1.0 V vs Hg / HgO, potential amplitude: 0.9 Ω at 0.1 Hz, measured at 5 mV The hydrogen generating electrode is characterized in that the weight of the catalyst layer is 10 g / m ² or more per projected area of the conductive substrate.

  Hereinafter, the present invention will be described in detail.

  The electrode for hydrogen generation of the present invention is formed by supporting a catalyst layer mainly composed of platinum, nickel and palladium on a conductive substrate.

  In the hydrogen generating electrode of the present invention, platinum, nickel, and palladium can be appropriately dispersed at the atomic level in the catalyst layer in order to obtain high catalytic activity for hydrogen generation, that is, to obtain a sufficiently low hydrogen overvoltage. It is desirable that In particular, palladium has a high affinity for platinum and nickel, and therefore plays an important role in appropriately dispersing these three components.

  In order to obtain an appropriate dispersion state, the palladium content in the catalyst layer is preferably 1 mol% or more and 55 mol% or less.

  In order to obtain a more appropriate dispersion state, it is preferable that the palladium content in the catalyst layer is 4 to 48 mol%, the nickel content is 48 to 4 mol%, and the balance is platinum.

  In the electrode for hydrogen generation according to the present invention, the catalyst layer is in an alloy, amorphous metal, metal oxide or metal hydroxide state. This is because the hydrogen generation electrode of the present invention forms a catalyst layer under various thermal conditions through a metal salt compound medium, so that the state of metal oxide or metal hydroxide, alloy, amorphous metal Therefore, these states do not affect the hydrogen overvoltage performance.

  The electrode for hydrogen generation of the present invention has an impedance measured at a set potential of 1.0 V vs. Hg / HgO and a potential amplitude of 5 mV in a 1 mol / L sodium hydroxide aqueous solution at 0.9 Hz or less at 0.1 Hz. When the impedance exceeds 0.9Ω, the hydrogen overvoltage indicates 70 mV or more, and the effect of the present invention is not exhibited. Preferably it is 0.88Ω or less, more preferably 0.86Ω or less. There is no lower limit value of impedance, and the effect of the present invention is exhibited at any value as long as it is 0.9Ω or less.

  The impedance is a complex number. When the impedance is Z, the real component of Z is Z ', the value obtained by multiplying the imaginary component by minus is Z ", and the imaginary number is i, Z = Z'-iZ". In general, a graph with Z ′ on the horizontal axis and Z ″ on the vertical axis is called a Nyquist diagram, and the electrochemical characteristics of the electrode can be considered from the shape. The impedance Z varies with frequency, and is usually displayed as a graph with the logarithm of frequency on the horizontal axis and the absolute value | Z | of impedance on the vertical axis.

  The inventors examined the impedance characteristics of the electrode for hydrogen generation in which a catalyst layer mainly composed of platinum, nickel and palladium is supported, and in the frequency range of 800 Hz to 0.1 Hz, the electrolyte solution: 1 mol / L FIG. 2 shows the Nyquist diagram of impedance measured at a sodium hydroxide aqueous solution, reference electrode: Hg / HgO, counter electrode: Ni coil, measurement temperature: room temperature, set potential: 1.0 V vs. Hg / HgO, and potential amplitude: 5 mV. As shown in FIG. 4, it has been found that it consists of two semicircles. The semicircle on the left side (which is on the high frequency side) is attributed to the capacitive semicircle, and the semicircle on the right side (which is on the low frequency side) is attributed to the diffusion impedance. Published by Masayuki Itagaki, published by Maruzen Co., Ltd., p131).

  Furthermore, the impedance characteristics and the hydrogen generation overvoltage were studied repeatedly, and it was found that the semicircular arc diameter attributed to the diffusion impedance strongly correlated with the hydrogen generation overvoltage. Finally, as shown in FIG. It has been found that the hydrogen generation overvoltage of the electrode for hydrogen generation in which a catalyst layer mainly composed of platinum, nickel and palladium is supported with an impedance of 1 Hz is determined.

  The reason for this is unclear, but the inventors presume as follows. That is, the diffusion layer thickness and the diffusion constant are determined by the impedance characteristics on the low frequency side (for example, “Electrochemical Impedance Method Principle / Measurement / Analysis” written by Masayuki Itagaki, published by Maruzen Co., Ltd., p132). If it is small, the diffusion layer thickness during the hydrogen generation reaction is thin and / or the mass transfer coefficient is large. As a result, it is estimated that the hydrogen generating electrode of the present invention having an impedance of 0.9Ω or less has a hydrogen generating reaction smoothly proceeding and a particularly low hydrogen overvoltage can be obtained as compared with the conventional hydrogen generating electrode. ing.

In the hydrogen generating electrode of the present invention, the weight of the catalyst layer is 10 g / m ² or more per projected area of the conductive substrate. When the weight of the catalyst layer is less than 10 g / m ² , the effect of the present invention cannot be obtained, and the hydrogen generation overvoltage exceeds 70 mV. The reason for this is unknown, but for example, it is assumed that a catalyst layer weight of about 10 g / m ² is necessary to obtain the number of catalytic activity points necessary to express particularly excellent hydrogen overvoltage performance. ing. In order to fully exhibit excellent hydrogen overvoltage performance, the weight of the catalyst layer is preferably 12 g / m ² or more, and more preferably 14 g / m ² or more.

  Next, the manufacturing method of the electrode for hydrogen generation of this invention is demonstrated.

  The method for producing an electrode for hydrogen generation according to the present invention comprises forming a catalyst layer precursor by applying a catalyst layer forming liquid containing a platinum salt, a nickel salt, and a palladium salt on a conductive substrate, drying, and thermally decomposing. It is.

  Examples of the method for forming the catalyst layer precursor by applying the catalyst layer forming liquid on a conductive substrate, drying, and pyrolyzing include a pyrolysis method and the like.

  Here, the thermal decomposition method refers to a series of operations in which a liquid for forming a catalyst layer containing a platinum salt, a nickel salt, and a palladium salt is applied on a conductive substrate, dried, and thermally decomposed.

  Examples of the conductive substrate used include nickel, iron, copper, titanium, and stainless steel alloy, and nickel having excellent corrosion resistance with respect to an alkaline solution is particularly preferable. The shape of the conductive substrate is not particularly limited, and may generally be a shape that matches the electrode of the electrolytic cell. For example, a flat plate, a curved plate, or the like can be used.

  In addition, the conductive substrate used is preferably a perforated plate, and for example, expanded metal, punch metal, and net can be used.

  The conductive substrate is preferably roughened in advance. This is because the contact surface area can be increased by roughening, and the adhesion between the substrate and the support is improved. The surface roughening means is not particularly limited, and a known method such as sand blasting, etching with oxalic acid or hydrochloric acid solution, washing with water and drying can be used.

  The catalyst layer forming liquid used contains platinum salt, nickel salt, and palladium salt.

  As the platinum salt, chloroplatinic acid, dinitrodiamine platinum or the like can be used. In particular, it is preferable to use dinitrodiammine platinum that forms an ammine complex because the crystallite diameter of the platinum alloy after the reduction treatment can be reduced to, for example, 200 angstroms or less to increase the reaction specific surface area. This is because the thermal decomposition temperature of the dinitrodiamine platinum is as high as about 550 ° C., so that aggregation of platinum during thermal decomposition is suppressed, and a film in which platinum, nickel and palladium are uniformly mixed after thermal decomposition is obtained. It is estimated that a fine crystallite-based alloy is obtained by the treatment.

  The salt in the nickel salt or palladium salt is not particularly limited, and for example, nitrate, sulfate, chloride, carbonate, acetate, sulfamate and the like can be used.

  Further, as a solvent for dissolving platinum salt, nickel salt and palladium salt, those capable of completely dissolving these raw materials are preferable in order to increase the surface area of the supported material, such as water, nitric acid, hydrochloric acid and sulfuric acid. An organic acid such as an inorganic acid or an acetic acid solution, an organic solvent such as methanol, ethanol, propanol, or butanol, or a mixture thereof can also be used. In addition, the pH of the catalyst forming liquid may be adjusted and used for the purpose of suppressing the dissolution of the base metal in the catalyst forming liquid, and complex salts such as lysine and citric acid are added to increase the surface area of the support. However, nickel and palladium may be complexed.

  For example, the catalyst layer forming liquid may be applied to the conductive substrate using, for example, a catalyst layer forming liquid containing a platinum salt, a nickel salt, and a palladium salt using a brush. Good. In addition to brush coating, all known methods such as a spray method and a dip coating method can be suitably used.

  What is necessary is just to perform the drying temperature after application | coating at the temperature of 200 degrees C or less for 5 to 60 minutes, for example, and the drying temperature of 150 degrees C or less is preferable.

  The thermal decomposition temperature after drying may be performed for 5 to 60 minutes in the range of over 200 ° C. and 700 ° C. or less, but preferably over 350 ° C. and 500 ° C. or less. For example, when a dinitrodiamine platinum solution is used, the thermal decomposition temperature of dinitrodiamine platinum is 550 ° C., and by performing thermal decomposition at 500 ° C. or less, platinum sintering is suppressed and hydrogen overvoltage is further reduced. A working electrode can be obtained.

In the method for producing an electrode for hydrogen generation according to the present invention, in particular, the coating amount is controlled to be 13 mL / m ² or more and 31 mL / m ² or less per projected area of the conductive base material, and then the step of drying and pyrolysis is performed. It is important to repeat 4 to 8 times. When the coating amount per projected area of the conductive base material is less than 13 mL / m ² and / or when the number of times of repeating the coating, drying, and thermal decomposition steps is 9 times or more, the impedance exceeds 0.9Ω, etc. The effect of the present invention cannot be obtained. On the contrary, when the number of times of repeating the coating, drying and pyrolysis steps is less than 3, the final catalyst layer weight is less than 10 g / m ^2, and the hydrogen generating electrode of the present invention cannot be obtained.

As described above, when the coating amount of the catalyst layer forming liquid is less than 13 mL / m ² per projected area of the conductive substrate, and / or the number of times of repeating the coating, drying, and thermal decomposition steps is 9 times or more, or 3 If it is less than the number of times, the electrode for hydrogen generation of the present invention cannot be obtained, and the hydrogen overvoltage is 70 mV or more.

On the other hand, if the coating amount exceeds 31 mL / m ² , the catalyst layer forming liquid cannot be sufficiently retained on the conductive substrate, resulting in poor yield, or clogging of the holes when the conductive substrate is a perforated plate. Even if there is a manufacturing defect such as occurrence, even if the hydrogen generation overvoltage is 70 mV, the effect of the present invention cannot be sufficiently obtained.

In the present invention, the area of the hole is not considered in the projected area. For example, the projected area of a 1 m × 1 m non-porous plate is 1 m ² , and the projected area of a 1 m × 1 m perforated plate is also 1 m ² regardless of the aperture ratio.

  When a non-porous plate is used for the conductive substrate, the catalyst-forming liquid may be applied only on one side, and the applied side may be used facing the anode.

On the other hand, when a porous plate is used for the conductive substrate, the catalyst forming liquid is preferably applied on both surfaces of the conductive substrate almost evenly because the electrolysis voltage may be further lowered. For example, when applying a 20 mL / ^{m 2,} the 8~12mL / ^{m 2} was coated on one surface, or by applying the remaining 12~8mL / ^{m 2} on the other side, a 20 mL / ^{m 2} only on one side is coated, Drying and thermal decomposition can be performed, and 20 mL / m ² can be applied only to the other side in the next round.

  When the conductive base material is a perforated plate, the reason why the electrolysis voltage may be further lowered by applying it almost evenly on both sides is unknown, but can be considered as follows.

  Although the hydrogen generation reaction mainly occurs at the contact portion between the catalyst and the electrolytic solution, the contact area between the catalyst and the electrolytic solution tends to be wider when the catalyst is applied on both sides, even if the amount of catalyst is the same, than when the catalyst is applied on one side. . When the conductive substrate is a non-porous plate, the reverse surface facing the anode is shielded from the electrolysis current, and the hydrogen generation reaction is unlikely to proceed. Therefore, the catalyst-forming liquid is preferably applied to one side.

  On the other hand, when the conductive substrate is a perforated plate, the electrolysis current easily reaches the opposite surface facing the anode through the holes of the conductive substrate. It is thought that it may decrease.

After pyrolysis, a reduction treatment is performed for the purpose of reducing and alloying the support to a metallic state. Although the reduction treatment method is not particularly limited, for example, a chemical reduction method by contact with a substance having a strong reducing power such as hydrazine, formic acid or oxalic acid, an electrochemical reduction method for giving a reduction potential to platinum, nickel and palladium, etc. Can be used. As an efficient prescription, an electrochemical reduction method is preferable, and an electrochemical reduction method in water electrolysis or alkali metal chloride aqueous solution electrolysis is more preferable. The “electrolysis of water” referred to in the present invention means not “electrolysis of pure water” but “electrolysis of water containing an electrolyte such as NaOH, HCl, H ₂ SO ₄ ”.

  For example, the electrochemical reduction method is a method for applying a potential necessary for the reduction of platinum, nickel, and palladium. The standard electrode potential of platinum, nickel and palladium in aqueous solution has already been disclosed ("Electrochemical Handbook" 5th edition, Maruzen Publishing, pages 92-95), and the potential required for reduction can be estimated from the standard electrode potential. It is.

  In reducing and alloying the support after pyrolysis into a metal state, the electrochemical reduction method is one of the preferred embodiments of the present invention. The electrode before the pyrolysis and reduction treatment is also performed. It means that it is a preferable form of the electrode for hydrogen generation of this invention.

  The electrode for hydrogen generation of the present invention thus obtained generates hydrogen gas and an aqueous alkali metal hydroxide solution from above the cathode by electrolysis of water or alkali metal chloride aqueous solution, and from above the anode. Electrolysis characterized by producing oxygen gas or chlorine gas, that is, as an electrode for hydrogen generation in an application of electrolysis of an aqueous solution of alkali metal chloride such as water or salt in an electrolytic cell in which an anode is arranged with a diaphragm interposed When used, low hydrogen overvoltage can be obtained, low overvoltage characteristics can be maintained stably for a long time without special measures not to mix iron ions in the catholyte, and the catalyst can be peeled off during shutdown and restart operations. This is an electrode for hydrogen generation that does not drop off, that is, extremely excellent in hydrogen overvoltage performance and durability. Here, the diaphragm typically includes a cation exchange membrane that selectively permeates cations.

  Therefore, in the field of electrolysis industry of aqueous solutions of alkali metal chlorides such as water or salt, the required energy of the electrolysis industry can be easily reduced simply by changing the electrode for hydrogen generation to the electrode for hydrogen generation provided by the present invention. It becomes possible.

  According to the present invention, it is possible to easily obtain an electrode for hydrogen generation in which the initial hydrogen overvoltage is sufficiently low and the durability is excellent.

  The hydrogen generating electrode of the present invention does not increase the hydrogen overvoltage due to iron ion poisoning in the electrolytic solution, which has been regarded as a drawback of the conventional platinum-based catalyst. The catalyst does not peel off or fall off due to the reverse current flowing inside. Therefore, the low hydrogen overvoltage characteristic inherent in platinum can be stably maintained over a long period of time, and in particular, water or alkali that is forced to contain iron in the catholyte and reverse current that flows several times a year during shutdown and restart. The energy required for the electrolysis industry of metal aqueous solutions can be greatly reduced.

It is a figure which shows the relationship of the impedance measured value and overvoltage measured value of Examples 1-4 and Comparative Examples 1-4. 1 is a Nyquist diagram of Example 1. FIG. It is a figure which shows the frequency characteristic of the impedance of Example 1. FIG. 2 is a Nyquist diagram of Comparative Example 1. FIG. 6 is a diagram illustrating frequency characteristics of impedance in Comparative Example 1. FIG.

  The present invention will be specifically described by the following examples, but the present invention is not limited to the examples.

  In addition, each evaluation was implemented by the method shown below.

<Impedance measurement>
The impedance at 0.1 Hz of the electrode is 1260 type impedance analyzer (manufactured by Solartron) and 1287 type potentiostat / galvanostat (manufactured by Solartron). Measured with

Electrolytic solution: 1 mol / L sodium hydroxide aqueous solution Reference electrode: Hg / HgO
Counter electrode: Ni coil Measurement temperature: Room temperature Setting potential: 1.0 V vs Hg / HgO
Potential amplitude: 5mV
Although the reference electrode and the measurement electrode were liquid-coupled using a tube made of perfluoroalkoxy fluororesin, the impedance between the tip of the tube and the measurement electrode was set to 0.43 to 0.47Ω at 800 Hz. It was adjusted.

<Measurement of hydrogen overvoltage>
Water electrolysis was performed for 10 minutes under the conditions of Ni, temperature 88 ° C., and current density 6.0 kA / m ² using an electrolytic solution of 32 wt% sodium hydroxide aqueous solution (capacity: about 1 L) by the current interrupter method. The hydrogen overvoltage was measured.

Example 1
Nickel expanded mesh (1200 mm × 450 mm) was used as the conductive substrate, and as a roughening treatment, 10 wt% hydrochloric acid solution was used for etching at a temperature of 50 ° C. for 15 minutes, followed by washing with water and drying.

  Next, using dinitrodiammine platinum nitrate solution (Tanaka Kikinzoku), nickel nitrate hexahydrate, palladium nitrate dihydrate (Kojima Chemical) and water, platinum was 48 mol%, nickel was 48 mol%, A catalyst forming solution containing 4 mol% of palladium was prepared.

Next, this catalyst forming liquid was applied to the entire surface of the nickel expanded mesh using a roller at a coating amount of 20 mL / m ² , dried in a hot air drier at 80 ° C. for 15 minutes, and then aired using a box-type firing furnace. Thermal decomposition was performed at 400 ° C. for 15 minutes under the flow. This series of operations was repeated 6 times to produce an electrode.

  The catalyst-forming liquid was applied on one side by half of the total catalyst-forming liquid amount and on the other side by the remaining half.

When the weight of the final catalyst layer was measured by subtracting the weight of the original conductive substrate from the weight of this electrode, it was 16.4 g / m ² .

  Next, when this electrode was cut out and the initial hydrogen overvoltage was measured, it was 68 mV. Subsequently, the impedance at 0.1 Hz was measured. These results are shown in Table 1, and the relationship between impedance and hydrogen overvoltage at 0.1 Hz is shown in FIG.

  The Nyquist diagram of the impedance is composed of two semicircles as shown in FIG. 2, and the frequency characteristic of the impedance rises on the low frequency side as shown in FIG. High value was shown.

The weight of the catalyst layer per mL of the catalyst-forming liquid (numerical value obtained by dividing the weight of the final catalyst layer by the coating amount × the number of repetitions) was 0.14 g / m ² .

比較例１
実施例１と同様の触媒形成用液をニッケルエキスパンドメッシュにローラーを用いて全面に１０ｍＬ／ｍ^２の塗布量で塗布することと一連の操作を１０回繰り返すこと以外は、実施例１と同様に操作して電極を作製した。触媒形成用液量、一連の操作の繰返し回数の条件、最終的な触媒層の重量、０．１Ｈｚにおけるインピーダンス、初期水素過電圧を、まとめて表１に、０．１Ｈｚにおけるインピーダンスと水素過電圧の関係を図１に示した。

Comparative Example 1
The same catalyst forming solution as in Example 1 was applied to the entire surface of a nickel expanded mesh at a coating amount of 10 mL / m ² using a roller, and the series of operations was repeated 10 times in the same manner as in Example 1. An electrode was produced by operating. Table 1 summarizes the amount of catalyst forming liquid, conditions for the number of repetitions of a series of operations, final catalyst layer weight, impedance at 0.1 Hz, and initial hydrogen overvoltage. Table 1 shows the relationship between impedance and hydrogen overvoltage at 0.1 Hz. Is shown in FIG.

  The Nyquist diagram of impedance was composed of two semicircles as in Example 1, as shown in FIG. The left semicircle was the same in Example 1 and Comparative Example 1, but the right semicircle was larger in diameter than Example 1.

  Further, as shown in FIG. 6, the frequency characteristic of the impedance rises on the low frequency side as in the first embodiment, but the rise is abrupt, and the impedance of 0.1 Hz shows a higher value than that in the first embodiment. .

Example 2
An electrode was produced in the same manner as in Example 1 except that the same catalyst forming liquid as in Example 1 was applied to the entire surface of the nickel expanded mesh using a roller at a coating amount of 16 mL / m ² . Table 1 summarizes the amount of catalyst forming liquid, conditions for the number of repetitions of a series of operations, final catalyst layer weight, impedance at 0.1 Hz, and initial hydrogen overvoltage. Table 1 shows the relationship between impedance and hydrogen overvoltage at 0.1 Hz. Is shown in FIG.

  Although not shown, the Nyquist diagram of the impedance and the frequency characteristic of the impedance in Example 2 were the same as those in Example 1.

Example 3
Similar to Example 1, except that the same catalyst forming solution as in Example 1 was applied to the entire surface of a nickel expanded mesh using a roller at a coating amount of 30 mL / m ² and the series of operations was repeated five times. An electrode was produced by operating. Table 1 summarizes the amount of catalyst forming liquid, conditions for the number of repetitions of a series of operations, final catalyst layer weight, impedance at 0.1 Hz, and initial hydrogen overvoltage. Table 1 shows the relationship between impedance and hydrogen overvoltage at 0.1 Hz. Is shown in FIG.

  Although not shown, the Nyquist diagram of impedance and the frequency characteristic of impedance in Example 3 were the same as in Example 1.

Example 4
An electrode was produced in the same manner as in Example 1 except that the same catalyst forming solution as in Example 1 was applied to the entire surface of the nickel expanded mesh using a roller at a coating amount of 25 mL / m ² . Table 1 summarizes the amount of catalyst forming liquid, conditions for the number of repetitions of a series of operations, final catalyst layer weight, impedance at 0.1 Hz, and initial hydrogen overvoltage. Table 1 shows the relationship between impedance and hydrogen overvoltage at 0.1 Hz. Is shown in FIG.

  Although not shown, the Nyquist diagram of the impedance and the frequency characteristic of the impedance in Example 4 were the same as those in Example 1.

Comparative Example 2
The same procedure as in Example 1 except that the catalyst forming solution was applied to a nickel expanded mesh (60 mm × 60 mm) with a brush on the entire surface at a coating amount of 10 mL / m ² and the series of operations was repeated 8 times. An electrode was produced in the same manner as in Example 1. Table 1 summarizes the amount of catalyst forming liquid, conditions for the number of repetitions of a series of operations, final catalyst layer weight, impedance at 0.1 Hz, and initial hydrogen overvoltage. Table 1 shows the relationship between impedance and hydrogen overvoltage at 0.1 Hz. Is shown in FIG.

  Although not shown, the Nyquist diagram of impedance and the frequency characteristic of impedance of Comparative Example 2 were the same as those of Comparative Example 1.

Comparative Example 3
Except for applying the same catalyst forming solution as in Example 1 to a nickel expanded mesh (60 mm × 60 mm) with a brush on the entire surface at a coating amount of 16 mL / m ² and repeating the series of operations three times. An electrode was produced in the same manner as in Example 1. Table 1 summarizes the amount of catalyst forming liquid, conditions for the number of repetitions of a series of operations, final catalyst layer weight, impedance at 0.1 Hz, and initial hydrogen overvoltage. Table 1 shows the relationship between impedance and hydrogen overvoltage at 0.1 Hz. Is shown in FIG.

  Although not shown, the Nyquist diagram of impedance and the frequency characteristic of impedance of Comparative Example 3 were the same as those of Comparative Example 1.

Comparative Example 4
The same procedure as in Example 1 except that the catalyst forming solution was applied to a nickel expanded mesh (60 mm × 60 mm) with a brush on the entire surface at a coating amount of 13 mL / m ² and the series of operations was repeated 10 times. An electrode was produced in the same manner as in Example 1. Table 1 summarizes the amount of catalyst forming liquid, conditions for the number of repetitions of a series of operations, final catalyst layer weight, impedance at 0.1 Hz, and initial hydrogen overvoltage. Table 1 shows the relationship between impedance and hydrogen overvoltage at 0.1 Hz. Is shown in FIG.

  The impedance Nyquist diagram and impedance frequency response of Comparative Example 4 were the same as those of Comparative Example 1 although not shown.

From Table 1, the impedance measured at a set potential of 1.0 V vs Hg / HgO and a potential amplitude of 5 mV in a 1 mol / L sodium hydroxide aqueous solution is 0.9 Ω or less at 0.1 Hz, and the weight of the catalyst layer is In Examples 1 to 4, which are 10 g / m ² or more per projected area of the conductive base material, the hydrogen generation electrode has an initial hydrogen overvoltage of less than 70 mV, but the set potential in a 1 mol / L sodium hydroxide aqueous solution. : 1.0 V vs Hg / HgO, potential amplitude: impedance measured at 5 mV is greater than 0.9Ω at 0.1 Hz, and / or the weight of the catalyst layer is 10 g / m per projected area of the conductive substrate ^In Comparative Examples 1 to 4 of less than ² , the initial hydrogen overvoltage exceeds 70 mV, and it is clear that the hydrogen generating electrode of the present invention has particularly excellent performance.

Comparative Example 5
Except for applying the same catalyst forming solution as in Example 1 to a nickel expanded mesh (60 mm × 60 mm) with a brush on the entire surface at a coating amount of 35 mL / m ² and repeating the series of operations four times. An electrode was produced in the same manner as in Example 1. The amount of catalyst forming liquid, the conditions for the number of repetitions of a series of operations, and the weight of the final catalyst layer are collectively shown in Table 1 (impedance at 0.1 Hz, initial value because the catalyst loading efficiency during production was remarkably bad) Hydrogen overvoltage was not measured).

  The weight of the catalyst layer per 1 mL of the catalyst forming liquid was 0.07 g / ml, which is about half that of Example 1, and it was revealed that the catalyst supporting efficiency at the time of production was remarkably poor. Therefore, it is clear that this manufacturing method is remarkably inferior in manufacturing cost.

From the results of all of the above examples and all the comparative examples, after coating the coating amount of the catalyst layer forming liquid to 13 mL / m ² or more and 31 mL / m ² or less per projected area of the conductive substrate, Examples 1-4 produced by repeating the drying and pyrolysis steps 4 to 8 times are particularly excellent in initial overvoltage performance and excellent in catalyst carrying efficiency. In Comparative Examples 1 to 5 manufactured under conditions that deviate from the conditions, it is apparent that the initial overvoltage performance and / or the catalyst carrying efficiency is inferior.

Claims (8)

An electrode for hydrogen generation in which a catalyst layer mainly composed of platinum, nickel and palladium is supported on a conductive base material, the catalyst layer being an alloy, an amorphous metal, a metal oxide or a metal hydroxide And an impedance measured in a 1 mol / L sodium hydroxide aqueous solution at a set potential of 1.0 V vs. Hg / HgO and a potential amplitude of 5 mV is 0.9 Ω or less at 0.1 Hz, and the catalyst layer The hydrogen generating electrode is characterized by having a weight of 10 g / m ² or more per projected area of the conductive substrate. The electrode for hydrogen generation according to claim 1, wherein the palladium content in the catalyst layer is 1 mol% or more and 55 mol% or less. 2. The electrode for hydrogen generation according to claim 1, wherein the catalyst layer has a palladium content of 4 to 48 mol%, a nickel content of 48 to 4 mol%, and the balance being platinum. A method for producing an electrode for hydrogen generation in which a catalyst layer forming liquid containing a platinum salt, a nickel salt, and a palladium salt is coated on a conductive substrate, dried, and thermally decomposed to form a catalyst layer precursor, the catalyst After the coating amount of the layer forming liquid is controlled to be 13 mL / m ² or more and 31 mL / m ² or less per projected area of the conductive substrate, the drying and pyrolysis steps are repeated 4 to 8 times. The method for producing an electrode for hydrogen generation according to any one of claims 1 to 3, wherein: The method for producing an electrode for hydrogen generation according to claim 4, wherein the catalyst layer is formed by forming a catalyst layer precursor on a conductive substrate, followed by reduction treatment. 6. The method for producing an electrode for hydrogen generation according to claim 5, wherein the reduction treatment is an electrochemical reduction treatment of water or an aqueous alkali metal chloride solution. The electrode for hydrogen generation according to any one of claims 1 to 3 is used as a cathode, and water or an alkali metal chloride aqueous solution is electrolyzed in an electrolytic cell in which an anode is disposed across a diaphragm, and the cathode An electrolysis method comprising producing hydrogen gas and an aqueous alkali metal hydroxide solution from above, and producing oxygen gas or chlorine gas from above the anode. The electrolysis method according to claim 7, wherein the diaphragm is a cation exchange membrane.

Images