JPS63145790A - Highly durable low-hydrogen overvoltage cathode and its production - Google Patents

Abstract

PURPOSE:To effectively prevent the oxidation of the activated component of an electrode, by using a hydrogen storage metal capable of electrochemically occluding and discharging hydrogen for the activated metal particles in the electrode obtained by providing the electrode activated metal particles on an electrode core. CONSTITUTION:A layer 2 on which the electrode activated metal particles 3 are exposed is formed on the electrode core 1. The metal layer 2 and the activated metal particles 3 are bound with a binder (PTFE, etc.), Raney nickel, etc., are used for the activated metal particles 3, and about 5-90wt% of the particles is made of a hydrogen occluding metal. A lanthanum-nickel based alloy exemplified by LaNi5-xXxYy, etc., (0<=x<=5, 0<=y5, and X and Y are other meals) is used as the hydrogen occluding metal, and the mean particle diameter is controlled to about 0.1-100mum. The electrode is used as the cathode in the electrolysis of an aq. halogen-alkali soln., hence large amt. of hydrogen occluded in the hydrogen occluding metal is electrochemically oxidized, and the oxidation of the active component of the electrode is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a highly durable low hydrogen overvoltage cathode, particularly to a low hydrogen overvoltage cathode which exhibits extremely little deterioration in characteristics even under oxidizing conditions, and a method for producing the same.

[Background technology]

Various types of low hydrogen overvoltage cathodes have been proposed, particularly as cathodes for aqueous halide electrolysis. Among these, one of the applicants has already proposed Japanese Patent Application Laid-Open No. 54-1127.
Although the electrode disclosed in Publication No. 85 has greater effects in terms of lower hydrogen overvoltage and durability than previously known electrodes, the present inventors have conducted further studies. As a result, we found that some of the electrodes disclosed in the above publications do not always have sufficient durability, and as a result of our earnest efforts to solve this problem, we have arrived at the present invention.

Producing halogen gas from the anode chamber and caustic alkali aqueous solution and hydrogen gas from the cathode chamber by electrolysis in an alkali halide aqueous solution electrolytic cell is already a well-known industrial method for producing chlorine and caustic alkali. As the cathode of this electrolytic cell, an S cathode with a low hydrogen overvoltage as mentioned above is preferably used, but the above electrolytic cell may be stopped for various reasons during operation, and in this case, the N rotation must be restarted. The inventors of the present invention have investigated this phenomenon in depth, and found that when stopping the electrolytic cell, the anode and cathode are short-circuited with a bus bar. The generated reverse current oxidizes the cathode, and in the case of cathodes containing nickel or cobalt as active ingredients, they transform into hydroxides, reducing electrode activity and returning to the original active state even after N conversion is resumed. It was found that the hydrogen overvoltage did not return (that is, the hydrogen overvoltage increased).

In addition, even in the stopping method of stopping current supply without shorting the anode and cathode, if the cathode is immersed in high-temperature, high-concentration NaOH for a long time, if the cathode active ingredients are nickel or cobalt, they will reach a corrosion potential. (This reaction is also a type of electrochemical oxidation reaction) and the electrode activity was found to decrease.

[Disclosure of the invention]

Therefore, as a result of intensive studies to prevent this phenomenon, we found that if a hydrogen storage metal that electrochemically absorbs and releases hydrogen and has a low hydrogen overvoltage is used as part or all of the electrode active component, the above-mentioned electrical We discovered that when the tank is stopped, the large amount of hydrogen stored in the hydrogen storage metal is electrochemically oxidized, which effectively prevents the oxidation of the electrode active component, that is, the activity can be maintained for a long period of time. The invention has been completed, and the present invention provides an electrode in which electrode-active metal particles are provided on an electrode core, in which some or all of the electrode-active particles can absorb and release hydrogen electrochemically. The gist of the present invention is a highly durable low hydrogen overvoltage cathode made of metal and a method for manufacturing the above-mentioned highly durable low hydrogen overvoltage cathode described below.

Here, hydrogen storage metals that can absorb and release hydrogen electrochemically refer to metals that undergo the following electrode reaction in an alkaline aqueous solution. In other words, in the reduction reaction, hydrogen atoms generated by reducing water are transferred into the metal. It absorbs.

In the oxidation reaction, the zero reaction formula is shown below, which is a reaction in which occluded hydrogen is reacted with hydroxide ions on the metal surface to form water.

Storage-release M is a hydrogen-absorbing metal, and MH represents its hydride. For example, when salt electrolysis using an ionic membrane is performed using a cathode in which this hydrogen-absorbing metal is part or all of the electrode active particles. At the initial stage of energization, hydrogen is stored in the hydrogen-absorbing metal due to the rightward reaction of reaction formula (1), and when hydrogen storage eventually reaches saturation, hydrogen is absorbed on the surface of the hydrogen-absorbing metal by reaction (2) shown below. occurs, and the electrode reaction on the original cathode proceeds.

HO+ e 54 H2+ OH (2) On the other hand, in the event of a power outage due to a short circuit in the battery case, a large amount of hydrogen stored in the hydrogen storage metal electrochemically releases hydrogen through a leftward reaction in equation (1). That is, by electrochemically oxidizing hydrogen and applying an oxidation current, oxidation of the electrode active particles themselves can be effectively prevented.

As described above, the hydrogen storage metal that can be used in the present invention is one that can electrochemically store and release hydrogen,
Specifically, lanthanum nickel alloys such as LaN15-XxXY9 (where X is 0≦X≦5.0≦y≦5.
is another metal) or M NiN15-xxxYy (: misch metal, x,
y, X, Y are the same as above), and T i N i x (0x≦2).
There are titanium-nickel alloys represented by the above, but the hydrogen storage alloys used in the present invention are not limited to these.

Since the hydrogen overvoltage of these metals is generally low, hydrogen overvoltage can be effectively reduced by using these fine particles as an electrode active material. However, to roughly reduce the overvoltage, Raney nickel and Raney cobalt, which have lower hydrogen overvoltage, are used. It goes without saying that particles such as the above and the hydrogen storage metal may coexist.

When using the above-mentioned Raney nickel, Raney cobalt, etc. particles together, especially when the below-mentioned composite plating method is adopted as a manufacturing method, it is preferable that these particles and the hydrogen storage metal are bonded in advance with a binder.

In this case, the binder is preferably a fluororesin from the viewpoint of stability during the manufacturing process, and polytetrafluoroethylene (PTFE) and tetrafluoroethylene-hexafluoropropylene copolymer are particularly preferred.

The binder content in the mixture powder of particles such as Raney nickel and Raney cobalt, hydrogen storage metal particles and binder is preferably 0.1wt% to 10wt%, 0.1w
If it is less than t%, it will not function sufficiently as a binder,
If the amount exceeds 10 wt%, the electrode active metal particles will be coated with the binder, resulting in a decrease in electrode activity.

In this case, in order to achieve the initial objective, the hydrogen storage metal should be present in an amount of 5 to 9% by weight, especially 7% of the total electrode active metal.
Preferably, it is present in an amount of 0 to 80 wt%.

In addition, these hydrogen storage metals are known to cause brittle fracture and become pulverized due to absorption and release of hydrogen, so in order to prevent them from falling off due to pulverization, it is necessary to crush them mechanically or to pulverize hydrogen in the gas phase in advance. Metals that have been pulverized by repeated absorption and release of gases are used, and in order to prevent this from falling off, metal particles such as nickel powder and polymer powders are used as binders in addition to the Raney nickel and Raney cobalt as matrix materials. Good too.

Furthermore, microencapsulation in which the metal particles are covered with a thin metal layer by chemical plating is preferred.

Here, since the gold mC4 layer generally has micropores that communicate with the inside, the metal constituting the gJ layer does not necessarily need to have hydrogen permeability, but when considering its performance as an electrode, Those with hydrogen permeability are preferred.

As such metals having hydrogen permeability, among many metals, nickel, cobalt, iron, etc. are preferable, and palladium and the like may also be suitably used, although there are some problems in terms of cost.

Next, the thickness of the metal B film mentioned above is determined by the properties of the thin film layer (density,
(hydrogen permeation rate, amount of hydrogen dissolved), properties of hydrogen storage metal particles (hydrogen permeation rate, density), and size. In other words, the thickness of the coating layer must not be so thick that the diffusion of hydrogen therein becomes the rate-limiting step in the entire process of hydrogen absorption, storage, and release, and the thickness of the coating layer must not be so thick that hydrogen diffusion within it becomes the rate-determining step in the entire process of hydrogen absorption, storage, and release, and the thickness of the coating layer must not be so large that hydrogen diffusion within it becomes the rate-limiting step in the entire process of hydrogen absorption, storage, and release. It is necessary to have a thickness that is strong enough to withstand volume changes and suppress pulverization. Moreover, increasing the thickness more than necessary decreases the weight ratio of the hydrogen storage metal in the microencapsulated hydrogen storage metal, and decreases the hydrogen storage metal per unit volume of the microencapsulated body. Generally, the weight of the metal constituting the thin layer is 3 times the weight of the hydrogen-absorbing metal particles.
Good results can be obtained by selecting the thickness to be 0% or less, preferably about 5 to 15%.

Generally, hydrogen storage metal particles have an average particle diameter of 0.1 to 10
Since a material with a diameter of about 0μ is used, is it applicable? The thickness of jN2 depends on the metal type, but is 0.01 to 20
Finally, the thickness is preferably about 0.03 to 10. If the thickness is thinner than the above lower limit, the effect of preventing pulverization of the hydrogen storage metal will be reduced.

In addition, if the thickness is larger than the above upper limit, the hydrogen permeation rate becomes low and the object of the present invention cannot be fully achieved. Although it is related to the dispersibility of particles during electrode production, which will be described later, 0.1 l to 1 ooIL is sufficient.

Within the above range, from the viewpoint of porosity of the electrode surface, etc., preferably 0.91L to 50IL, more preferably 1μ to 30IL
It is.

A preferred embodiment of the cathode of the present invention is a cathode in which the electrode active metal particles are attached to the electrode core by plating metal.

In this case, the plated metal is provided in a layer on the electrode core,
The electrode active metal particles are partially exposed on the surface of the plated metal layer.

Furthermore, the particles used in the present invention are preferably single-surface porous in order to achieve a lower hydrogen overpotential of the electrode.

This surface porosity does not mean only that the entire surface of the particle is porous; it is sufficient that only the portion exposed from the layer made of the plated metal described above is porous.

The degree of porosity is preferably as large as possible; however, if the degree of porosity is excessively large, the mechanical strength of the layer provided on the electrode core decreases, so the degree of porosity (porositF) should be 2.
It is preferably 0 to 90%, more preferably 35 to 85%, particularly preferably 50 to 80%.

The above porosity is a value measured by a known mercury intrusion method or water displacement method.

The layer on which the electrode active metal particles are firmly provided on the metal substrate is preferably made of the same metal as part of the components constituting the particles.

Thus, a large number of the above particles are attached to the electrode surface of the cathode of the present invention, and macroscopically, the cathode surface is microporous.

In this way, the cathode of the present invention has a large number of particles containing a hydrogen-absorbing metal, which itself has a low hydrogen overvoltage, on the electrode surface, and as mentioned above, the electrode surface is microporous. The active surface of the electrode becomes larger, and the synergistic effect of these makes it possible to effectively reduce the hydrogen overvoltage.

Furthermore, in the preferred embodiment, the particles used in the present invention are firmly attached to the electrode surface by the layer made of the metal, so they are not easily deteriorated, and the sustainability of the low hydrogen overvoltage can be dramatically extended. I can do it.

The electrode core of the present invention may be made of any suitable conductive metal, such as Ti, Zr, Fe, or Ni.

V, Mo, Cu, , Ag, Mn, white metal, graphite,
A metal selected from Cr or an alloy selected from these metals may be employed. Of these, Fe, Fe alloy (Fe-N
Particularly preferred electrode cores preferably employ Ni, Ni alloys (N1-Cu alloys, Ni-Cr alloys, etc.), Cu, Cu alloys, etc. The material of the body is Fe, Cu,
These are Ni, Fe-Ni alloy, and Fe-Ni-Cr alloy.

The structure of the electrode core can be made into any suitable shape and size depending on the structure of the electrode used. Its shape is, for example, plate-like, porous, or net-like (e.g. expanded metal)
, blind shapes etc. can be adopted.

These may be shaped like a flat plate, a curved plate, or a cylinder.

In the case of the above-mentioned preferred embodiment of the present invention, the thickness of the layer is sufficient if it is 20x to 2 mm, and more preferably 25x to 1 mm, although it depends on the particle size of the particles employed. This is because, in the present invention, some of the particles described above are attached to the electrode core while being buried in the metal layer.

In order to make it easier to understand such a state, a cross-sectional view of the electrode surface of the present invention is shown in FIG. 1. As shown in FIG. A portion of the electrode active metal particles 3 are included so as to be exposed from the surface of the layer. The proportion of particles in layer 2 is preferably 5 to 80 wt%, more preferably 10 to 60 wt%. In addition to this state, the electrode of the present invention can be further improved by providing an intermediate layer made of a metal selected from Ni, Co, Ag, and Cu between the electrode core and the layer containing the particles of the present invention. Durability can be improved. The middle class is
The metal of the above-mentioned layer may be the same or different, but from the viewpoint of adhesion between the intermediate layer and the above-mentioned layer, it is preferable that the metal of the intermediate layer and the metal of the layer is of the same type. , the thickness of the intermediate layer is 5 to Lo from the viewpoint of mechanical strength, etc.
OP is sufficient, more preferably 20-80p
, particularly preferably from 30 to 501 L.

To facilitate understanding of the electrode provided with such an intermediate layer, a cross-sectional view of the electrode is shown in FIG.

1 is an electrode core, 4 is an intermediate layer, 2 is a layer containing particles, and 3 is an electrode active particle.

As a specific means for attaching the electrode active metal particles, various methods are employed, such as a composite plating method, a melt coating method, a baking method, a pressure forming sintering method, and the like.

Among these, the composite plating method is particularly preferable because it allows the electrode active metal particles to be attached well.

The composite plating method is a bath in which metal particles, for example, nickel as a component of the metal particles, are dispersed in an aqueous solution containing metal ions forming a metal layer, and plating is performed using the electrode core as a cathode. The metal and metal particles are co-electrodeposited onto the electrode core. In more detail, the particles become bipolar in the bath under the influence of the electric field, increase the local current density of the plating when they approach near the cathode surface, and when they come into contact with the cathode, the particles become bipolar due to the reduction of normal metal ions. It is thought that it is co-electrodeposited on the core by plating.

In this composite plating method, when two types of electrode active metal particles such as Raney nickel and hydrogen storage metal are used, the electrodeposition characteristics of these particles are different, and the difference between these two types of particles in the electrodeposited coating layer is Since the abundance ratio is difficult to be constant, it is preferable to bind these two types of particles in advance with a binder as described above.

For example, when a nickel layer is used as the metal layer, various nickel plating baths can be used, such as a total nickel chloride bath, a high nickel chloride bath, a nickel chloride-nickel acetate bath, a Watts bath, and a sulfamine-ugly Ni bath.

The proportion of such particles in the bath is Ig/Jl ~ 200
g/l is preferable from the viewpoint of improving the adhesion of particles to the electrode surface, and the temperature conditions during dispersion plating work are 20 to 80°C, and the current density is IA/drn.
It is preferable that it is -20A/dtn'.

It goes without saying that additives for reducing strain, additives for promoting co-electrodeposition, etc. may be added to the plating bath as appropriate.

In addition, in order to further improve the adhesion strength of the particles, electrolytic plating or electroless plating is performed to the extent that each particle is not completely coated after composite plating, or heating and baking in an inert or reducing atmosphere are performed as appropriate. You may go.

In addition to this, as described above, when providing an intermediate layer between the electrode core and the metal layer containing particles, the electrode core is first plated with Ni, Co leather, or Cu, and then the dispersion plating method described above is applied. A metal layer containing particles is formed thereon by means of melt spraying.

The various plating baths mentioned above can be used as plating baths in the case of heating, and known plating baths can also be used for Cu plating.

In this way, an electrode is obtained in which electrode active metal particles containing a hydrogen storage metal are attached to the electrode core via a metal layer.

Next, another method for manufacturing the cathode of the present invention will be explained.

The cathode of the present invention can also be manufactured by a melt coating method or a baking method. That is, a hydrogen-absorbing metal powder or a mixed powder of this and other low hydrogen overvoltage metal powder (for example, obtained by melting and pulverization) is adjusted to a predetermined particle size, and then melted and sprayed using plasma, oxygen/acetylene flame, etc. and obtain a partially exposed coating layer of these particles on the electrode core,
Alternatively, a dispersion or slurry of these particles is applied onto the electrode core and baked to obtain a desired coating layer.

The cathode of the present invention can also be obtained by preparing an electrode sheet containing a hydrogen-absorbing metal in advance and attaching it to an electrode core. In this case, the sheet is formed by mixing hydrogen-absorbing metal particles or hydrogen-absorbing metal particles and other metal particles (for example, Raney alloy showing low hydrogen overvoltage characteristics) with organic polymer particles, or by baking after forming. Of course, in this case, the electrode active particles are exposed from the surface of the sheet. The sheet thus obtained is pressed onto the electrode core and fixed onto the electrode core by heating.

The electrode of the present invention can of course be used as an electrode for ion-exchange membrane-based alkaline chloride aqueous solution electrolysis, especially as a cathode, but it can also be used as a porous diaphragm (e.g. asbestos diaphragm).
It can also be used as an electrode for aqueous alkali chloride electrolysis using.

When used as a cathode for alkali chloride electrolysis, iron dissolved from the electrolytic cell material into the catholyte may be deposited on the cathode, reducing electrode activity.
It is an effective method to deposit a non-electronically conductive material as disclosed in JP-A-57-143482 on the cathode of the present invention.

[Best mode for carrying out the invention]

(Example 1) Commercially available LaNi5 was pulverized to 500 mesh or less, and this powder was heated in a nickel chloride bath (NiCl2.6HO30
0 g/i, HBO 38 g/l) at a rate of 5 g/l, and while stirring well, composite plating was performed using the Ni expanded metal as the cathode and the Ni plate as the anode. The temperature was 40° C., the pH was 2.5, and the current density was 4 A/drrf. As a result, a black-gray composite plating layer was obtained, and the eutectoid amount of LaNi5 was 10 g/dm'.

The thickness of the plating layer is approximately 2501L, and the porosity is approximately 6.
It was 0%.

Next, this electrode was made of RuO2-TtO2 as an anode, and fluorine-containing cation exchange films (CF=CF2 and CF2=CFO (CF
2) Copolymer with 3COoCH3, ion exchange capacity 1.44 intestinal eq/g
Resistance tests against short circuits were conducted using the ion-exchange membrane (resin) as a cathode for a salt electrolytic cell. The anolyte is 3N
NaCl solution, catholyte 35% NaOH at 90℃
The following short circuit test was carried out on the third day after the start of electrolysis at a current density of 30 A/drn'.

First, the anode and cathode during electrolysis were short-circuited with a copper wire to stop electrolysis, and the electrolysis was left as it was for about 5 hours. During this time, the current flowing from the cathode to the anode was observed. Note that the temperature of the catholyte was maintained at 90°C. The copper wire was then removed and electrolysis resumed. After repeating this operation 5 times, remove the electrode and
5% NaOH 190 °C, current density 20 A/d m
The hydrogen overvoltage was measured at 0.12 V, which was almost unchanged from before the test.

(Example 2) Commercially available L a N i5 was pulverized into 25 pots or less, and this powder was heated in a nickel chloride bath (NiCM 6H20300g).
In addition, commercially available Raney nickel alloy powder (manufactured by Yoken Fine Chemicals, Ni 50 wt%, A 250 wt%, 20
0 mesh pass) was added to the plating solution at a rate of 5 g/l.

While thoroughly stirring this, composite plating was performed using an iron expanded metal as a cathode and a Ni plate as an anode. The temperature is 40°C and the pH is 2.5. Current density is 3A/drn'
And so. As a result, the eutectoid amount of L a N t 5 was 6 g/
drn', the eutectoid amount of Raney nickel alloy is 2g/dtn
A composite plating layer in which LaNt 5 and Raney nickel alloy coexisted was obtained. The thickness of this plating layer is approximately 3
00g, and the porosity was about 65%. This sample was heated to 90℃
After developing the Raney nickel alloy An by immersion in 25% NaOH solution.

The same short circuit test as in Example 1 was conducted. After the test, the hydrogen overvoltage was measured and was o, oav, which was almost the same as before the test.

(Example 3) Commercially available LaNi5 powder (30 L or less) and commercially available stabilized Raney nickel powder (manufactured by Yoken Fine Chemicals, trade name: "Dry Raney Nickel") were mixed in a high nickel chloride bath (NtSO-6H20200 g/ml), NjC intersection ・6
H20175g/text.

8 BO340g/text) each contains l Og/
After stirring well, composite plating was performed using a Ni punched metal as a cathode and a Ni plate as an anode. The temperature is 50℃, the pH is 3,0゜'rL flow density is 4
A/dm'. As a result.

A composite plating layer containing L a N i5 and stabilized Raney nickel was obtained, in which the eutectoid amount of L a N i s was 5 g/drn' and the eutectoid amount of stabilized Raney nickel was 2.
g/drrr'. Further, the thickness of this plating layer was about 250 JL, and the porosity was about 60%. Using this, the same short circuit test as in Example 1 was conducted. After the test, the hydrogen overvoltage was measured and found to be 0.07V, which was almost the same as before the test.

(Example 4) Ichita's L a N + 5 powder (15 pots or less) was added to a high nickel chloride bath (N s SO 6 H 20200 g /
Sentence, N iCl C6H20175g/fL,
10 g/liter of HBO (40 g/l) was added, and while stirring the mixture well, composite plating was carried out using an iron expanded metal plated with nickel to a thickness of 50 mm as a cathode and a Ni plate as an anode. went. The temperature was 40°C, the pH was 2.0, and the current density was 4A/drn'. As a result, the eutectoid amount of LaN15(7) was 10 g/dr.
A composite plating layer that was rf was obtained. The thickness of this plating layer was approximately 350 mm, and the porosity was approximately 65%. After conducting a short circuit test using this in the same manner as in Example 1, the hydrogen overvoltage was measured to be 0.10 V, which was almost unchanged from before the test.

(Example 5) Composite plating was performed under the same conditions as in Example 2 except that the Raney nickel alloy powder was replaced with expanded Raney nickel. As a result, a composite plating layer containing L a N s 5 and expanded Raney nickel was obtained.

The eutectoid amount of LaNi5 was 5 g/dm', and the eutectoid amount of expanded Laney metal was 3 g/drrf. The thickness of this plating layer was about 400 g, and the porosity was about 70%. A short circuit test was conducted on this in the same manner as in Example 1. The hydrogen overvoltage after the test was 0.08V, which was unchanged from before the test.

(Comparative example) According to Example 12 of JP-A-54-112785,
A Raney nickel alloy composite plated cathode was obtained. A short circuit test was conducted using this in the same manner as in Example 1. The hydrogen overvoltage before the test was o, oav, but after the test it was 0.2
It had risen to 5V.

(Example 6) LaNi5 of Example 1 was M m N 1 i,s A
Composite plating was performed in the same manner as in Example 1, except that the plating was changed to 10,5 (Mm: Mitshu Metal). As a result, 4
．． 5 0.5 eutectoid amount is 9.5 g/drrfMm
A composite plating layer of NiAn was obtained. The thickness of this plating layer is approximately 2
50μ, and the porosity was about 60%. This was subjected to a short circuit resistance test in the same manner as in Example 1. As a result, the hydrogen overvoltage was 0.15V, which was almost unchanged from before the test.

(Example 7) Ni powder and Ti powder were mixed to have a composition of T l 2 N i, and Ti2N was melted by arc melting in an argon atmosphere.
i was prepared and ground to 500 mesh or less.

6 parts of this Ti2Ni powder, 2 parts of carbonyl nickel powder, and 2 parts of PTFE powder were mixed in a pestle and molded into a sheet. The thickness of this sheet is approximately 1 mm, and the porosity is approximately 50%.
Met. This was pressed onto nickel expanded metal and then fired at 350° C. for 1 hour in an argon atmosphere to form an electrode. As a result of conducting a short circuit resistance test in the same manner as in Example 1, the hydrogen overvoltage was 0.
The voltage was 17V, which was almost unchanged from before the test.

(Example 8) An aqueous solution of methyl cellulose was added as a thickener to 5 parts of commercially available (7) La Nis (500 mesh or less) and 5 parts of carbonyl nickel powder, and the mixture was thoroughly mixed to prepare a paste. This was applied uniformly onto a nickel punched metal substrate by screening printing.
Next, this was dried in air at 100°C for 1 hour, and then baked at a vacuum width of about 1000°C for 1 hour to obtain L a N r 5 -
A metal sintered layer was formed.

The thickness of the L a N i 5-nickel sintered layer is approximately Inm
The porosity of this layer was about 50%. From the zero weight change, the amount of L a N i5 in the sintered layer was about 9 g/arrt
Met. A short circuit test was conducted using this in the same manner as in Example 1, and as a result, the hydrogen overvoltage was 0.14 V, which was almost the same as before the test.

(Example 9) 500 mesh bus L a N s 5 3% J! !
After processing in S and washing with water, adjust the pH to 6.0 with aqueous ammonia.
Pour into a commercially available nickel chemical plating solution (BEL801 manufactured by Uemura Kogyo Co., Ltd.) adjusted to ~6.5, and heat to 63~65℃.
Plating was carried out for 10 minutes.

The LaNi5 particles with a thin nickel layer attached by plating were filtered, washed with water and dried.

The average thickness of the thin nickel layer of these particles was 1 tile, and the midM ratio of the thin nickel layer to L a N i5 was 13%.

Next, according to Example 1, 5 g and 7 g of the above particles were added.

Raney nickel alloy powder (200 mesh pass) 5
Composite plating was performed using a composite plating bath containing g/l.

The amount of La Nis particles in the composite plating layer was 6 g/d, and the amount of Raney nickel alloy particles was 2 g/drn'. Further, the thickness of the composite plating layer was about 300p, and the porosity of the layer was about 65%.

Next, the above cathode was developed in a 20% NaOH aqueous solution, and a short circuit resistance test was conducted in the same manner as in Example 1. The hydrogen overvoltage of the cathode after the test was measured in the same manner as in Example 1, and it was found to be 0.08V, which was almost the same as before the test.

(Example 10) La N L 5 particles of 500 mesh passes were plated for 1 minute in the same manner as in Example 9 to form a thin nickel layer.
aN 15 particles were obtained. In this case, the average thickness of the nickel thin layer was 0.1 g, and the weight ratio of the nickel g layer to the LaNi5 particles was 1%.

Next, a cathode was manufactured using these particles in the same manner as in Example 9, and a short circuit test was conducted. The result is hydrogen overvoltage 0.085V
The hydrogen overvoltage was only 5 mV higher than before the test.

(Example 11) A cathode was manufactured in the same manner as in Example 9, except that Raney nickel alloy powder was not used.

When the same short circuit test as in Example 9 was conducted, the hydrogen overvoltage was 0.11 V, which was only 5 mV higher than before the test.

(Example 12) Raney Ni alloy with particle size of 500 mesh under (50
wt%Ni, 50wt%AIL) and LaNi5 with a particle size of 500 mesh under in a weight ratio of 4:1 (i.e., 20wt% with respect to the total electrode active metal), and PTFE Disverge E7 (Mitsui Fluorocarbon Made of chemical
Teflon 30J) was added so that the solid content of PTFE was 3 wt %, and an appropriate amount of water was added to form a paste and kneaded. This paste was dried and solidified and pulverized to obtain a mixed powder of Raney Ni and LaNl 5.

This mixed powder was soaked in a nickel chloride bath (NiCJl.-6HO).
Composite plating was performed by using Ni punched metal as a cathode and Ni plate as an anode while stirring the mixture well. Temperature is 40℃, pH is 2
．． 5. The current density was 6 A/drn'. As a result, a black-gray composite plating layer was obtained, with Raney N1 and LaN
The eutectoid amount of the i s mixture was 4 g/dm'. The thickness of this plating layer is approximately 3007 zm, and the porosity is approximately 65%.
Met. Also, eutectoid Raney Ni and L a Ni is
The weight ratio was 4:1. This sample was heated to 25% at 90°C.
Ai of Raney-Ni alloy was immersed in NaOH solution for 2 hours.
After developing RuO2-, it is used as a cathode and RuO2-
Using T t O2, a fluorine-containing cation exchange membrane (
Flemion manufactured by Asahi Glass Building, ion exchange capacity 1.44mec
Salt electrolysis was performed using I/g resin) as an ion exchange membrane, and a cathode short-circuit resistance test was conducted. The anolyte is 3.5
NNaCu solution, catholyte is 35% NaOH solution,
The following short circuit test was conducted on the second day after the start of electrolysis at 90° C. and a current density of 30 A/dm'.

First, the anode and cathode during electrolysis were short-circuited with a copper wire to stop electrolysis, and the electrolysis was left as it was for 2 hours. During this time, the temperature of the catholyte was maintained at 90°C. After 2 hours, the electrolytic cell was disconnected from the circuit, left to cool, and after it had cooled down sufficiently, the catholyte was replaced with a fresh 35% NaOH solution, the circuit was connected again, the electrodes were short-circuited, and the temperature was raised. It was left for 2 hours. The copper wire was then removed and electrolysis resumed. This operation.

After repeating the test five times, the hydrogen overvoltage was measured in a 35% NaOH solution at 90° C. at a current density of 30 A/drn', and the result was 0.09 V, which was unchanged from before the test.

(Example 13) "L a N s of 500 mesh under JmNl
Composite plating was performed in the same manner as in Example 12, except that L a N is of 145 mesh under was used instead of L a N is.

The eutectoid amount of the mixture of Raney Ni and La Ni is 4.
It was 5 g/dm'. The thickness of this plating layer is approximately 300 mm
gm porosity was approximately 60%. Also, the eutectoid Raney N
The weight ratio of f and LaNi5 was 4:1.

Using this, the same short circuit test as in Example 12 was conducted. The hydrogen overvoltage after the test was 0.09 V, which was the same as before the test.

(Example 14) Composite plating was performed in the same manner as in Example 13 except that the weight ratio of Raney Ni and LaNi5 in Example 13 was changed to 1:1. The eutectoid amount of the mixture of Raney Ni and LaNi5 was 6 g/dm'. The thickness of this plating layer is approximately 3
50 #Lm, the porosity was about 60%. Moreover, the weight ratio of eutectoided Raney Ni and LaNi5 was 4:1.

Using this, the same short circuit test as in Example 12 was conducted. The hydrogen overvoltage after the test was 0.10V, which was unchanged from before the test.

(Example tS) In a nickel chloride bath, 4 g/l of Raney Ni powder with a particle size of 500 mesh or less, and 1 g/l of LaNi 5 powder with a particle size of 500 mesh or less (7).
After stirring well, composite plating was performed using a Ni punched metal as a cathode and a Ni plate as an anode. As a result, Raney Ni and L a N r 5
A composite plating layer containing Raney Ni was obtained, and the eutectoid amount of Raney Ni was 3.
The eutectoid amount of L a N i 5 was Lg/drrf. The thickness of this plating layer was about 250 Bm, and the porosity was about 60%.
After developing the Raney Ni alloy An by immersion in a 25% NaOH solution at 0° C., the same short circuit test as in Example 12 was conducted. The hydrogen overvoltage after the test was 0.09V, unchanged from before the test.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view of the surface of an example of the electrode of the present invention;
The figures each show a partial cross-sectional view of the surface of another example of the electrode of the present invention. In the figure, 1 is an electrode core, 2 is a layer containing particles, 3 is an electrode active particle, and 4 is an intermediate layer.

Claims (17)

[Claims] (1) In an electrode in which electrode-active metal particles are provided on an electrode core, a part or all of the electrode-active metal particles are hydrogen storage metals that can electrochemically absorb and release hydrogen. Hydrogen overvoltage cathode. (2) The highly durable and low hydrogen overvoltage cathode according to claim 1, wherein some of the electrode active metal particles are particles made of Raney nickel and/or Raney cobalt. (3) The highly durable and low hydrogen overvoltage cathode according to claim 2, wherein particles made of Raney nickel and/or Raney cobalt are bonded to a hydrogen storage metal with a binder. (4) The binder is polytetrafluoroethylene and/or
or the highly durable and low hydrogen overvoltage cathode of claim 3, comprising a tetrafluoroethylene-hexafluoropropylene copolymer. (5) High durability and low hydrogen overvoltage according to claim 1 or 3, wherein the hydrogen storage metal is an alloy selected from lanthanum-nickel alloy, misch metal, nickel-based alloy, and titanium-nickel alloy. cathode. (6) The highly durable and low hydrogen overvoltage cathode according to claim 1 or 5, wherein the hydrogen storage metal is a particle coated with a thin metal layer. (7) Claim 6 in which the metal thin layer has hydrogen permeability
Highly durable low hydrogen overvoltage cathode. (8) The highly durable and low hydrogen overvoltage cathode of claim 1, wherein the electrode active metal particles are adhered to the electrode core by plating metal. (9) The highly durable and low hydrogen overvoltage cathode according to claim 8, wherein the plating metal is the same metal as a part of the components constituting the electrode active metal particles. (10) The electrode core is immersed in a plating bath in which hydrogen-absorbing metal particles capable of electrochemically absorbing and desorbing hydrogen are dispersed as at least a part of the electrode-active metal particles, and a composite plating method is applied to the electrode. A method for producing a highly durable and low hydrogen overvoltage cathode, which comprises co-electrodepositing the electrode active metal particles together with a plating metal on a core. (11) Claim 10, wherein the electrode active metal particles are hydrogen storage metal particles and particles made of Raney nickel and/or Raney cobalt bound together with a binder.
Method for manufacturing highly durable low hydrogen overvoltage cathodes. (12) Plated metal is formed in a layer on the electrode core,
12. The method for producing a highly durable, low hydrogen overvoltage cathode according to claim 10 or 11, wherein a part of the electrode active metal particles is exposed on the surface of the layer. (13) The method for producing a highly durable and low hydrogen output overvoltage cathode according to claim 10 or 11, wherein the hydrogen storage metal particles are particles coated with a thin metal layer. (14) A method for producing a highly durable and low hydrogen overvoltage cathode according to claim 13, wherein the metal thin layer has hydrogen permeability. (15) A layer containing hydrogen storage metal particles that can electrochemically absorb and release hydrogen as at least a part of the electrode active metal particles is formed by baking or melt coating, so that some of the electrode active metal particles are A method for producing a highly durable and low hydrogen overvoltage cathode, which comprises providing a cathode on an electrode core so as to be exposed on the surface of the layer. (16) Electrode active metal particles consisting of a hydrogen storage metal capable of electrochemically absorbing and desorbing hydrogen, or the metal and another low hydrogen overvoltage metal, so that a part of the particles is exposed from at least one surface. Producing a sheet containing
A method for producing a highly durable and low hydrogen overvoltage cathode, in which a surface of the sheet opposite to the particle-exposed surface is fixed to an electrode core. (17) The method for producing a highly durable and low hydrogen overvoltage cathode according to claim 16, wherein the sheet contains organic polymer particles as a sizing agent.