EP0129231B1 - Cathode à surtension basse de l'hydrogène et procédé pour la fabrication de la cathode - Google Patents
Cathode à surtension basse de l'hydrogène et procédé pour la fabrication de la cathode Download PDFInfo
- Publication number
- EP0129231B1 EP0129231B1 EP84106905A EP84106905A EP0129231B1 EP 0129231 B1 EP0129231 B1 EP 0129231B1 EP 84106905 A EP84106905 A EP 84106905A EP 84106905 A EP84106905 A EP 84106905A EP 0129231 B1 EP0129231 B1 EP 0129231B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- codeposit
- plating
- dispersant
- nickel
- slurry
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
Definitions
- the present invention generally relates to a low hydrogen overvoltage cathode for use in electrolysis of water or alkali metal halides and method for producing the same. More particularly, it relates to the preparation of a low hydrogen overvoltage cathode having low hydrogen- generating electric potential and satisfactory durability specifically suitable for electrolysis of an aqueous alkali metal halide solution.
- electrodes obtained by spray coating an iron group cathode base with nickel or tungsten carbide. powder US ⁇ A ⁇ 4 049 841
- electrodes spray coated with cobalt and zirconium US-A-3 992 278)
- electrodes comprising nickel and cobalt subjected to leaching treatment after spray coating US-A-4 024 044
- electrodes obtained by spray coating an electrode base with Raney-nickel and then leaching with alkali a sacrificial metal contained in the coating layer JP-A-122887/80
- electrodes obtained by spray coating of an alkali-resistant metal on a cathode base and depositing a platinum group metal on the surface thereof JP-A-131189/80, JP-A-158288/80
- electrodes obtained by forming an activated layer by plating method on a cathode base e.g., electrodes obtained by dispersing a platinum group metal powder into nickel US-A-4465580 and US-A-4 543 265
- a cathode base is at first considered.
- a material for the cathode base carbon.steel, stainless steel, nickel and the like are known but carbon steel is normally used from economical consideration.
- an activated layer of low hydrogen overvoltage deposited is an activated layer of low hydrogen overvoltage deposited. In this case, when corrosion of the base is feared during the course of operation at low hydrogen overvoltage, it is necessary to provide a protective layer of alkali-resistance between the base and the activated layer.
- nickel-plating bodies, copper- plating bodies and the like are normally employed and as the activated layer, it is prevailing to employ those of alkali-resistant metals designed so as to have large surface.
- alkali-resistant metals designed so as to have large surface.
- there are included a method for electroplating a Raney alloy JP-Patent Examined Publication Nos.
- GB-A-991 231 disclosed an electrode with a Raney-Ni base having activated Raney-Ni centers being covered with a thin layer of a metal of the Pt-group
- US-A-4 331 517 describes a method of electrodepositing a catalyst metal and a sacrificial metal on an electroconductive substrate wherein the substrate is inserted into a solution of Co, Ni, Ru, Rh, Pd, Os, Pt, mixtures thereof and AI, Zn, Sn and mixtures thereof. Then an electrical current passes from the plating anode to the cathode to electrodeposit metal on the substrate.
- the present invention encompasses a method for producing a low hydrogen overvoltage cathode which comprises using a codeposit plating tank in which an anode and an object to be plated of a non-perforated flat structure are positioned in parallel with each other, supplying a dispersant slurry through one side of the tank in a substantially horizontal way to thus allow it to flow in a space formed between the anode and the object, then removing the slurry through the opposite side and recirculating it back to the tank, whereby codeposit plating is applied to only one surface of the object, the dispersant comprising an alloy of a first metal selected from the group consisting of nickel, cobalt and silver, a second metal selected from the group consisting of aluminium, magnesium, zinc and tin, and third metal selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium and osmium.
- the cathode prepared according to the present invention is coated in such a manner that electroconductive fine particles of the alloy as defined above are for example dispersed in nickel or a nickel alloy, and is capable of reducing hydrogen generation electric potential by 200 to 300 mV as compared with conventional iron cathodes.
- Examples for a cathode base are iron, stainless steel, nickel and further, iron coated with nickel and a nickel alloy such as Ni-Mo, Ni-W.
- nickel or nickel alloys such as Ni-Mo, Ni-W and further, a mixture of nickel and oxides thereof may suitably be used.
- a platinum group metal selected from the group consisting of platinum, ruthenium, iridium, rhodium, palladium and osmium, and an oxide thereof may be used singly or in combination of two or more.
- Electroconductive fine particles should have electroconductivity and large surface area and be superior in resistance to caustic alkali which may be exemplified by Raney-nickel, Raney-cobalt and Raney-silver.
- Raney-nickel alloy When the Raney-nickel alloy is employed, it is necessary to leach by a known manner after formation of the coating layer. For example, adequate activity is obtained by immersing the coating layer in a 10 to 30% aqueous caustic soda solution at 40 to 60°C for more than one hour.
- the foregoing fine particles should desirably be as fine as possible and their particle size should preferably be approximately 0.149 mm (100 mesh-pass) or less, more preferably 0.074 mm (200 mesh-pass) or less, though not limited in particular.
- An amount of 0.01% or more of the platinum group metal to be held by the fine particles provides cathodes having an adequate activity. An amount exceeding 50% leads to economical disadvantage.
- the thickness of the coating layer is not specifically limited but should preferably be 800 um or less, more preferably 400 pm or less, taking into consideration economy. With a view to keeping activity for a prolonged period of time, thickness should be at least 10 pm or more, more preferably 50 11m or more.
- cathodes having less durability are caused by many vacant spaces present in the active portion or insufficiency of adhesion force among particles, i.e., shortage of mechanical strength
- cathodes having high hydrogen overvoltage are caused by lack of active area actually working or activity per unit area.
- cathodes produced by electroplating containing a sacrificial component dissolving during the electrolysis when containing the sacrificial component in great amounts to lower hydrogen overvoltage, deteriorate in mechanical strength, thereby being inferior in durability.
- a process for codeposit plating of Raney-nickel is characterized in that the mechanical strength of the active portion is great but it has been found through studies by the present inventors that it is still insufficient in long-term durability. That is, for the purpose of minimizing hydrogen overvoltage, the content of Raney alloy in a codeposit plating coating layer has to be increased, but the increased content of Raney-nickel results in a decrease in the mechanical strength of the active portion.
- a modified process of the foregoing Raney alloy codeposit plating method producing low hydrogen overvoltage cathodes is revealed by JP-A-133387/83.
- Raney alloy and a platinum group metal are admixed in powder, with which codeposit plating is made.
- it is not yet satisfactory though providing cathodes which are not only stronger in the mechanical strength, but smaller in hydrogen overvoltage, as compared with the codeposit plating using Raney alloy alone. That may be because uniform codeposit plating is difficult due to the differences in particle size, specific gravity and the like between the Raney alloy and the platinum group metals.
- the platinum group metals, different from Raney alloy shows no activity when buried in a nickel matrix.
- An apparatus for codeposit plating of Raney alloy is disclosed by, for example, JP-A-104491/80. According to the apparatus, however, it is impossible to perform codeposit plating uniformly and firmly, in cases where a cathode is a structure of a non-perforated flat plate and only one surface is subjected to codeposit plating. That is, in conventional Raney alloy codeposit plating, a dispersant slurry is flowed in a vertical way by the use of gas, a vibrating plate, a pump and the like.
- the present invention has been completed on the thought that if a dispersant slurry is flowed horizontally rather than vertically, contacting and colliding chances between dispersant slurry particles and an object to be plated should be enhanced to thereby improve the deposition of the particles onto the object.
- the cathode base usable for activated cathodes of the present invention may be in the form of a non-perforated flat plate.
- an electrolytic cell for use in the electrolysis of an aqueous alkali metal halide solution providing as a separator a cation exchange membrane, in particular, operation is often carried out for saving energy cost by reducing an anode-cathode distance to 3 mm or less, often 2 mm or less.
- non-perforated flat plate cathodes are capable of making uniform micro-distribution of current density over the cation exchange membrane and hence very desirable.
- the cathodes of the present invention obtained in such a manner as aforesaid are adapted for use as electrodes which generate hydrogen gas in, for example, the electrolysis of water or alkali metal halides.
- Fig. 1 depicts a schematic representation showing an example in which codeposit plating is effected according to the present invention.
- a dispersant is well stirred to give a uniform slurry concentration.
- a dispersant slurry (2) is supplied by a pump (3) to a codeposit plating tank (4) through one side, then removed through the other side. The removed dispersant slurry is returned back to the codeposit plating bath storage tank (1) and recirculated between the plating bath storage tank (1) and the plating tank (4).
- uniform codeposit plating is possible without recirculating the dispersant slurry between the plating bath storage tank (1) and the plating tank (4), recirculation is carried out since a large quantity of dispersant slurry is needed.
- the codeposit plating tank (4) is equipped with a cathode (6) to be plated and an anode (5), both being positioned in parallel with each other, to thus form a closed codeposit plating chamber (7).
- the cathode (6) is, needlessly, located so that the surface to be plated faces to the inside of the chamber.
- the anode (5) any known anode for use in electroplating may be used and the shape is not specifically limited, including a flat plate, a perforated plate, a net, an aggregate of nickel tips and the like.
- An amount of the dispersant contained in a codeposit plating coating in the present invention is variable according to the direction in which the object to be plated was placed, the concentration of the dispersant slurry, the average flow rate of the dispersant slurry within the codeposit plating chamber and the like.
- Fig. 2 and Fig. 3 are schematic representations showing the direction in which the object to be plated are placed.
- the object In Fig. 2, the object is located horizontal and faces upward, as in the case of Fig. 3.
- the object In Fig. 5, the object is located vertical.
- a preferred emobdiment is to locate the object substantially horizontal to face upward, as shown by Fig. 1 and Fig. 2. It is also considered to locate the object to face downward, but in this case the same plated object as in the case of Fig. 1 and Fig. 2 can not be obtained because of a decrease in a deposition-improving effect caused by gravity, unless the slurry concentration is higher than in the case of Fig. 1 and Fig. 2.
- An embodiment of locating the objects as shown by Fig. 3 is useful when two sheets of cathodes are produced at one time. That is, by locating two objects so that the backsides of the objects are in contact with each other, two sheets of hydrogen overvoltage cathodes can be produced through one operation of codeposit plating.
- codeposit plating should desirably be made with a higher slurry concentration.
- the dispersant slurry should be flowed substantially horizontal in the codeposit plating tank.
- substantially horizontal means an extent within which an increase in deposition of the dispersant particles resulting from gravity is achievable, i.e., the angle between the horizontal surface and the slurry flowing line being within 45 degrees, more preferably 30 degrees, regardless of upward or downward direction, most preferably 0 degree.
- the dispersant slurry is normally supplied through one side of the tank and removed through the opposite other side, but it is possible for the purpose of uniformization, to flow it to a reverse direction during the operation by changing an inlet and an outlet. It is further desired to position dispersing plates at an inlet and an outlet to improve uniformization.
- the slurry concentration should preferably be not less than 0.01 g/I and less than 3 g/l, more preferably not less than 0.05 g/I and less than 3 g/ I. In the case of less than 0.01 g/l, only the plated object containing a dispersant in less amounts is obtained and thus showing high hydrogen overvoltage. In the case of not less than 3 g/l, the plated object contains a dispersant in greater amounts, which shows low initial hydrogen overvoltage but is poor in the mechanical strength, thus lacking in long-term durability.
- the average flow rate of the dispersant slurry within the codeposit plating chamber should preferably be 0.05 m/sec or more, more preferably less than 10 m/sec.
- a well-known nickel plating bath may be suitably employed, including such as watts bath, all nickel chloride bath and high nickel chloride bath.
- the particle size of the dispersant is not specifically limited, but should preferably be approximately 0.149 mm (100-mesh pass) or less, more preferably 0.074 mm (200-mesh pass) or less.
- the dispersant may be comprised of an optional combination of a first metal selected from the group consisting of nickel, cobalt and silver, a second metal selected from the group consisting of aluminium, magnesium, zinc and tin, and a third metal selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium and osmium.
- the second metal is leached by being immersed in an aqueous caustic alkali solution after codeposit plating, whereby a coating layer is made porous and thus activated.
- the content of the third metal is considered from both aspects of cost and activity, but should desirably be not higher than 50 weight %. In the case of less than 0.01 weight %, an effect of increasing activity is hardly expected.
- Cathodes subjected to codeposit plating are stored for a prolonged period of time by being washed and dried.
- the second metals must be leached in an aqueous caustic alkali solution. This treatment may be made either before or after installing of the cathodes to an electrolytic cell, but the latter is preferred.
- cathodes used in the production of an aqueous alkali metal hydroxide solution by an ion exchange membrane process or an asbestos diaphragm process expanded metals, perforated plates or net structure cathodes have been commonly employed. Notwithstanding, according to the study made by the present inventors, it has been made clear that cathodes of non-perforated flat plates, only one surface of which is codeposit plated provide the best results, when served as cathodes used in a horizontal type ion exchange membrane electrolytic cell.
- the present invention is capable of production of epoch-making cells equipped with low hydrogen overvoltage cathodes, upsetting knowledge of persons skilled in the art that cells with non-perforated flat plate cathodes show high cell voltage (e.g. JP-A-174477/82, "Soda and Chlorine", 32, 281, 1981), and therefore exceedingly valuable in the industry.
- Non-perforated flat plates of carbon steel 660 mmx2,000 mm, were degreased, washed with an acid, and chemical plated with nickel to be 30 pm in thickness.
- the codeposit plating bath was removed with stirring by a pump and supplied into the codeposit plating chambers through one side to flow in a horizontal way. Codeposit plating was carried out under the conditions; temperature 50°C, current density 3 ⁇ /dm 2 , time 90 minutes and average flow rate of the slurry within the chamber 1.0 m/sec. A plating coating thus obtained was hard and uniform in thickness.
- a cathode bottom plate (carbon steel), 1800 mmx11,000 mm, used in a mercury electrolytic cell was polished smooth and then chemical plated with nickel to be 30 pm in thickness.
- the obtained plate was separated into six parts in a longitudinal way, by which the codeposit plating tank is formed substantially horizontal to allow the surface to be plated to face upward, as illustrated by Fig. 1 and Fig. 2.
- Each part was codeposit plated in the same manner and the same conditions as in Example 1.
- a plating coating was hard and was approximately uniform in thickness in every part.
- Example 2 Using this cathode, a cell was assembled and leaching treatment was performed under the same conditions as in Example 1. "Nafion 901" (Trade Mark) was positioned and the electrolysis was effected. Cell voltage was 3.45 V under the conditions; temperature 90°C, current density 50 ⁇ /dm 2 and NaOH 32%, and hydrogen overvoltage was 0.10 V.
- Nafion 901 Trade Mark
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
Claims (4)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP111573/83 | 1983-06-20 | ||
JP58111573A JPS602686A (ja) | 1983-06-20 | 1983-06-20 | 活性電極 |
JP222313/83 | 1983-11-25 | ||
JP22231383A JPS60114586A (ja) | 1983-11-25 | 1983-11-25 | 陰極の製造法 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0129231A1 EP0129231A1 (fr) | 1984-12-27 |
EP0129231B1 true EP0129231B1 (fr) | 1988-01-27 |
Family
ID=26450934
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP84106905A Expired EP0129231B1 (fr) | 1983-06-20 | 1984-06-16 | Cathode à surtension basse de l'hydrogène et procédé pour la fabrication de la cathode |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0129231B1 (fr) |
CA (1) | CA1260427A (fr) |
DE (1) | DE3469042D1 (fr) |
IN (1) | IN161189B (fr) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
IN164233B (fr) * | 1984-12-14 | 1989-02-04 | Oronzio De Nora Impianti | |
DE3612790A1 (de) * | 1986-04-16 | 1987-10-22 | Sigri Gmbh | Kathode fuer waesserige elektrolysen |
US5035789A (en) * | 1990-05-29 | 1991-07-30 | The Dow Chemical Company | Electrocatalytic cathodes and methods of preparation |
US5066380A (en) * | 1990-05-29 | 1991-11-19 | The Dow Chemical Company | Electrocatalytic cathodes and method of preparation |
US5164062A (en) * | 1990-05-29 | 1992-11-17 | The Dow Chemical Company | Electrocatalytic cathodes and method of preparation |
US5227030A (en) * | 1990-05-29 | 1993-07-13 | The Dow Chemical Company | Electrocatalytic cathodes and methods of preparation |
TW202146707A (zh) * | 2020-01-24 | 2021-12-16 | 英商億諾斯技術有限公司 | 電極總成及電解器 |
CN114774967A (zh) * | 2022-05-25 | 2022-07-22 | 江苏双良新能源装备有限公司 | 一种电解水催化网及其制备方法 |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL301623A (fr) * | 1962-12-12 | |||
CA1201996A (fr) * | 1980-04-22 | 1986-03-18 | Donald S. Cameron | Cathodes a surfaces electrocatalytiques tres rugueuses en platine/ruthenium |
US4331517A (en) * | 1981-04-02 | 1982-05-25 | Ppg Industries, Inc. | Method of preparing a cathode by high and low temperature electroplating of catalytic and sacrificial metals, and electrode prepared thereby |
-
1984
- 1984-06-16 DE DE8484106905T patent/DE3469042D1/de not_active Expired
- 1984-06-16 EP EP84106905A patent/EP0129231B1/fr not_active Expired
- 1984-06-19 CA CA000456868A patent/CA1260427A/fr not_active Expired
- 1984-06-23 IN IN454/MAS/84A patent/IN161189B/en unknown
Also Published As
Publication number | Publication date |
---|---|
CA1260427A (fr) | 1989-09-26 |
IN161189B (fr) | 1987-10-17 |
DE3469042D1 (en) | 1988-03-03 |
EP0129231A1 (fr) | 1984-12-27 |
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