JP3712220B2 - Ion exchange membrane electrolysis method - Google Patents
Ion exchange membrane electrolysis method Download PDFInfo
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- JP3712220B2 JP3712220B2 JP22609997A JP22609997A JP3712220B2 JP 3712220 B2 JP3712220 B2 JP 3712220B2 JP 22609997 A JP22609997 A JP 22609997A JP 22609997 A JP22609997 A JP 22609997A JP 3712220 B2 JP3712220 B2 JP 3712220B2
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- nickel
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- exchange membrane
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Description
【０００１】
【発明の属する技術分野】
本発明は、水素過電圧が低い活性陰極およびその製造方法に関し、とくにアルカリ金属ハロゲン化物、アルカリ金属水酸化物等のアルカリ金属塩の水溶液を高電流密度下で低水素過電圧で電気分解することができる活性陰極およびその製造方法に関する。
【０００２】
【従来の技術】
アルカリ金属ハロゲン化物水溶液またはアルカリ金属水酸化物水溶液の隔膜法、イオン交換膜法等による電気分解用の陰極として、水素過電圧が低い活性陰極が提案されている。
【０００３】
活性陰極としては、ニッケル、コバルト、白金族金属またはそれらの合金、あるいは酸化物を含有する層を、軟鋼、ステンレス、あるいはニッケル等の基体上に形成した電極が提案されており、被膜の形成方法としては、電気メッキ、無電解メッキ、分散電気メッキ、溶射、あるいは浸漬等によって表面へ析出する方法が知られている。また、水素吸蔵合金粒子を含有する被膜を形成した活性陰極が、特公昭６１−１２０３２号公報において提案されており、またニッケルまたはコバルトと他の金属からなる複合金属粒子を含有する被覆を形成することが、特公昭６１−３６５９０号公報において提案されている。
ところが、従来の活性陰極では、比較的電流密度が小さな場合には、過電圧を低下させる効果があるものの、電流密度が５ｋＡ／ｍ2 以上といった高電流密度の電気分解条件では、水素過電圧の低下が不十分であり、電解電圧が高いという問題があった。
【０００４】
【発明が解決しようとする課題】
本発明は、電流密度が５ｋＡ／ｍ2 以上の高電流密度の通電によっても水素過電圧の低下効果が十分である活性電極を提供することを課題とするものである。
【０００５】
【課題を解決するための手段】
本発明は、電極基体上に低水素過電圧の電極活性物質の被覆層を形成した活性陰極において、電極活性物質の被覆層がニッケル合金とフッ素樹脂微粒子を含有している活性陰極である。
ニッケル合金が、ニッケル−すず合金、もしくはニッケル−すず−亜鉛合金である前記の活性陰極である。
また、電極基体上に低水素過電圧の電極活性物質の被覆層を形成した活性陰極の製造方法において、ニッケル合金めっき浴にフッ素樹脂のディスパージョンを添加して分散した状態でニッケル合金を電気めっきする活性陰極の製造方法である。
また、電極基体上に低水素過電圧の電極活性物質の被覆層を形成した活性陰極を用いたイオン交換膜電解方法において、電極活性物質の被覆層がニッケル−すず合金、もしくはニッケル−すず−亜鉛合金から選ばれるニッケル合金とフッ素樹脂微粒子を含有した活性陰極を、電流密度６ｋＡ／ｍ2 〜２０ｋＡ／ｍ2 で電気分解するイオン交換膜電解方法である。
【０００６】
【発明の実施の形態】
本発明は、導電性基体上に、フッ素樹脂エマルジョンを分散しためっき浴からフッ素樹脂粒子を含んだニッケル合金層を形成したものであり、ニッケル合金層としては、ニッケル−すず合金、ニッケル−すず−亜鉛合金を挙げることができる。
これらの合金は水素発生の活性が高く、かつ表面が滑らかなめっき面を形成し、活性陰極とイオン交換膜を密着して使用しても、イオン交換膜を破損したり、傷を付ける可能性が低い陰極面を提供することができる。一方、ニッケル合金めっき層の代わりにニッケルめっき層のみを使用する場合は、活性陰極の活性が乏しく、フッ素樹脂微粒子を存在させても十分な効果を得ることができないので好ましくない。
【０００７】
本発明の活性層の量は、陰極投影面積１平方メートル当たり、５０グラム以上５００グラム以下が好ましい。５０グラム未満の場合は、活性が乏しくなり好ましくなく、５００グラムより多くしても、量に見合って活性の向上が得られなくなるので好ましくない。
【０００８】
これらの合金めっき層は、金属の表面被覆の目的で一般的に行われているニッケル合金めっきと同様の浴に、フッ素樹脂エマルジョンを分散した浴によって形成することができる。具体的には、塩化ニッケル、塩化第一すず、塩化亜鉛等を含み、これらにピロリン酸カリウム、フッ化アンモニウム等を含むめっき浴に、フッ素樹脂ディスパージョンを添加したものを用いることができる。フッ素樹脂のディスパージョンはその固形成分として、めっき浴中で０．１ないし１０ｇ／ｌの量を混合しているのが好ましい。
また、めっき浴の温度２０〜７０℃、陰極電流密度１〜２０Ａ／ｄｍ2 の条件でめっきを行うことが好ましい。
【０００９】
また、本発明においては、めっき浴を攪拌して、金属成分とともにフッ素樹脂のディスパージョンが均一に分散させることが必要である。攪拌は、攪拌機、あるいはポンプによって液を流動させる方法等によって行うことができるが、液を流動させる方法によって攪拌を行うことが好ましい。
【００１０】
また、めっき操作中には、めっき浴の成分を補給し、めっき浴の組成が変化しないように調製することが必要である。めっき液の調製は、成分物質の溶射や陽極として溶出させても良く、陽極から溶出させる場合には、陽極としては、ニッケル、ニッケルと錫の合金、ニッケルと錫等の溶解性の陽極を使用しても、不溶性の陽極を使用しても良い。溶解性の陽極を使用する場合には、板状であっても、塊状の金属を網状体に収容したものであっても良い。
【００１１】
フッ素樹脂ディスパージョンとしては、ポリテトラフルオロエチレン、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体、テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体、エチレン−テトラフルオロエチレン共重合体、ポリクロロトリフルオロエチレン、ポリフッ化ビニリデン等のディスパージョンを用いることができ、ディスパージョンの粒径としては０．０１μｍ〜０．５μｍのものが好ましい。
【００１２】
また、活性陰極の被覆中において、フッ素樹脂のディスパージョンは、０．１〜ないし２０重量％であることが好ましく、０．３重量％〜５重量％であることがより好ましい。０．１重量％未満では、フッ素樹脂の添加の効果がなく、２０重量％よりも大きい場合には水素過電圧が上昇するので好ましくない。
【００１３】
本発明の活性陰極において、ニッケル合金とポリテトラフルオロエチレンの共析物を形成することによって活性の大きな電極が得られる理由は明瞭ではないが、フッ素樹脂粒子の存在によって陰極表面での濡れ性等に影響を与え、電極表面からの水素ガスの離脱に好ましい影響を与えているのではないかと推察される。また、本発明の活性陰極には、軟鋼、ステンレス鋼、あるいはこれらにニッケル等をめっきしたもの、ニッケル等の電極基体を使用することができる。電極基体としては、平板状、エキスパンドメタル状、穿孔板状、網状、棒状等のものを使用することができる。
【００１４】
【実施例】
以下、本発明について実施例に基づき、さらに詳細に説明する。
実施例１
縦、横２０ｍｍのニッケル製エキスパンデッドメタルを水酸化ナトリウム水溶液で脱脂後、水洗いし、水で１対１に希釈した塩酸でエッチングした。水洗後、
めっき浴組成
塩化ニッケル６水塩 ３０ｇ／ｌ
塩化第一すず２水塩 １２ｇ／ｌ
ピロリン酸カリウム ２００ｇ／ｌ
グリシン ３０ｇ／ｌ
ポリテトラフルオロエチレン水性ディスパージョン ０．２ｇ／ｌ
（濃度６０重量％）
のめっき浴を調製し、ｐＨを８．０ないし８．３、浴温度を５０ないし５５℃に管理して、電流密度７．５Ａ／ｄｍ2 で３０分間のめっきを行った。
めっきの後に水洗し、濃度３２重量％の水酸化ナトリウム水溶液中において、カレントインタラプター法によって、８０℃において、水銀／酸化水銀電極を参照電極として、電流密度を変化させ、それぞれの条件下での水素過電圧を測定し、その結果を表１に示す。
【００１５】
実施例２
めっき浴組成を、
塩化ニッケル６水塩 ３０ｇ／ｌ
塩化第一すず２水塩 １２ｇ／ｌ
塩化亜鉛６水塩 ５ｇ／ｌ
ピロリン酸カリウム ２００ｇ／ｌ
グリシン ３０ｇ／ｌ
ポリテトラフルオロエチレン水性ディスパージョン ０．２ｇ／ｌ
（濃度６０重量％）
とした点を除いて、実施例１と同様の条件でめっきをして、活性陰極を作製し、実施例１と同様の条件で水素過電圧を測定し、その結果を表２に示す。
【００１７】
比較例１
ポリテトラフルオロエチレンのエマルジョンを添加しない点を除き、実施例１と同様の条件で電気めっきをし、活性陰極を作製し、実施例１と同様の条件で水素過電圧を測定し、その結果を表３に示す。
【００１９】
比較例２
ポリテトラフルオロエチレンのエマルジョンを添加しない点を除き、実施例２と同様の条件で電気めっきをして、活性陰極を作製し、実施例１と同様の条件で水素過電圧を測定し、その結果を表４に示す。
【００２１】
【発明の効果】
本発明の活性陰極は、高電流密度下での水素過電圧が低く、食塩水のイオン交換膜電解槽を高電流密度で運転した際にも、電解電圧を低くすることができるので、高電流密度下での消費電力を少なくすることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an active cathode having a low hydrogen overvoltage and a method for producing the same, and in particular, an aqueous solution of an alkali metal salt such as an alkali metal halide or alkali metal hydroxide can be electrolyzed at a high current density at a low hydrogen overvoltage. The present invention relates to an active cathode and a manufacturing method thereof.
[0002]
[Prior art]
An active cathode with a low hydrogen overvoltage has been proposed as a cathode for electrolysis by a diaphragm method, an ion exchange membrane method or the like of an alkali metal halide aqueous solution or an alkali metal hydroxide aqueous solution.
[0003]
As an active cathode, an electrode in which a layer containing nickel, cobalt, a platinum group metal or an alloy thereof, or an oxide is formed on a substrate such as mild steel, stainless steel, or nickel has been proposed. For example, a method of depositing on the surface by electroplating, electroless plating, dispersed electroplating, thermal spraying, immersion, or the like is known. Further, an active cathode having a coating containing hydrogen storage alloy particles has been proposed in Japanese Patent Publication No. 61-12032, and forms a coating containing composite metal particles made of nickel or cobalt and another metal. This is proposed in Japanese Patent Publication No. 61-36590.
However, the conventional active cathode has an effect of lowering the overvoltage when the current density is relatively small, but the hydrogen overvoltage is lowered under the high current density electrolysis conditions such as a current density of 5 kA / m 2 or more. There was a problem that it was insufficient and the electrolysis voltage was high.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide an active electrode that can sufficiently reduce the hydrogen overvoltage even when a current density of 5 kA / m 2 or higher is applied.
[0005]
[Means for Solving the Problems]
The present invention is an active cathode in which a coating layer of an electrode active material having a low hydrogen overvoltage is formed on an electrode substrate, wherein the coating layer of the electrode active material contains a nickel alloy and fluororesin fine particles.
In the active cathode, the nickel alloy is a nickel-tin alloy or a nickel-tin-zinc alloy.
Further, in the method of manufacturing an active cathode in which a coating layer of an electrode active material having a low hydrogen overvoltage is formed on an electrode substrate, a nickel alloy is electroplated in a state where a dispersion of a fluororesin is added to a nickel alloy plating bath and dispersed. It is a manufacturing method of an active cathode.
In an ion exchange membrane electrolysis method using an active cathode in which a coating layer of an electrode active material having a low hydrogen overvoltage is formed on an electrode substrate, the coating layer of the electrode active material is a nickel-tin alloy or a nickel-tin-zinc alloy. An ion exchange membrane electrolysis method in which an active cathode containing a nickel alloy and fluororesin fine particles selected from is electrolyzed at a current density of 6 kA / m 2 to 20 kA / m 2 .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a nickel alloy layer containing fluororesin particles is formed on a conductive substrate from a plating bath in which a fluororesin emulsion is dispersed. As the nickel alloy layer, a nickel-tin alloy, nickel-tin- Mention may be made of zinc alloys.
These alloys have high hydrogen generation activity and form a smooth plating surface. Even if the active cathode and the ion exchange membrane are used in close contact, the ion exchange membrane may be damaged or scratched. Can provide a low cathode surface. On the other hand, when only the nickel plating layer is used instead of the nickel alloy plating layer, the activity of the active cathode is poor, and even if fluororesin fine particles are present, a sufficient effect cannot be obtained.
[0007]
The amount of the active layer of the present invention is preferably 50 g or more and 500 g or less per square meter of the projected area of the cathode. When the amount is less than 50 grams, the activity is poor, which is not preferable. When the amount is more than 500 grams, the improvement in activity cannot be obtained in accordance with the amount, which is not preferable.
[0008]
These alloy plating layers can be formed by a bath in which a fluororesin emulsion is dispersed in a bath similar to nickel alloy plating generally performed for the purpose of metal surface coating. Specifically, it is possible to use a plating bath containing nickel chloride, stannous chloride, zinc chloride, etc., and further containing a fluororesin dispersion in a plating bath containing potassium pyrophosphate, ammonium fluoride and the like. The dispersion of the fluororesin is preferably mixed in an amount of 0.1 to 10 g / l in the plating bath as its solid component.
The plating is preferably performed under the conditions of a plating bath temperature of 20 to 70 ° C. and a cathode current density of 1 to 20 A / dm 2 .
[0009]
Moreover, in this invention, it is necessary to stir a plating bath and to disperse | distribute the dispersion of a fluororesin with a metal component uniformly. Stirring can be performed by a method of flowing the liquid using a stirrer or a pump, but it is preferable to perform stirring by a method of flowing the liquid.
[0010]
Further, during the plating operation, it is necessary to replenish the components of the plating bath so that the composition of the plating bath does not change. The plating solution may be prepared by thermal spraying of component substances or elution as an anode. When elution is performed from the anode, nickel, an alloy of nickel and tin, or a soluble anode such as nickel and tin is used as the anode. Alternatively, an insoluble anode may be used. When a soluble anode is used, it may be plate-shaped or a massive metal housed in a network.
[0011]
As fluororesin dispersion, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, A dispersion such as polyvinylidene fluoride can be used, and the particle diameter of the dispersion is preferably 0.01 μm to 0.5 μm.
[0012]
Further, in the coating of the active cathode, the dispersion of the fluororesin is preferably 0.1 to 20% by weight, and more preferably 0.3% to 5% by weight. If it is less than 0.1% by weight, there is no effect of adding a fluororesin, and if it is more than 20% by weight, the hydrogen overvoltage increases, which is not preferable.
[0013]
In the active cathode of the present invention, the reason why a highly active electrode can be obtained by forming a eutectoid of nickel alloy and polytetrafluoroethylene is not clear, but wettability on the cathode surface due to the presence of fluororesin particles, etc. It is presumed that it has a positive influence on the detachment of hydrogen gas from the electrode surface. In addition, the active cathode of the present invention can use mild steel, stainless steel, those plated with nickel or the like, or an electrode substrate such as nickel. As the electrode substrate, a flat plate shape, an expanded metal shape, a perforated plate shape, a net shape, a rod shape, or the like can be used.
[0014]
【Example】
Hereinafter, the present invention will be described in more detail based on examples.
Example 1
A nickel expanded metal 20 mm long and wide was degreased with an aqueous sodium hydroxide solution, washed with water, and etched with hydrochloric acid diluted 1: 1 with water. After washing with water
Plating bath composition Nickel chloride hexahydrate 30g / l
Stannous chloride dihydrate 12g / l
Potassium pyrophosphate 200g / l
Glycine 30g / l
Polytetrafluoroethylene aqueous dispersion 0.2 g / l
(Concentration 60% by weight)
A plating bath was prepared, and the plating was performed at a current density of 7.5 A / dm 2 for 30 minutes while controlling the pH at 8.0 to 8.3 and the bath temperature at 50 to 55 ° C.
After plating, the plate was washed with water, and the current density was changed in a sodium hydroxide aqueous solution having a concentration of 32% by weight at 80 ° C. using a mercury / mercury oxide electrode as a reference electrode at 80 ° C. The hydrogen overvoltage was measured and the results are shown in Table 1.
[0015]
Example 2
Plating bath composition
Nickel chloride hexahydrate 30g / l
Stannous chloride dihydrate 12g / l
Zinc chloride hexahydrate 5g / l
Potassium pyrophosphate 200g / l
Glycine 30g / l
Polytetrafluoroethylene aqueous dispersion 0.2 g / l
(Concentration 60% by weight)
Except for the points described above, plating was performed under the same conditions as in Example 1 to produce an active cathode, and the hydrogen overvoltage was measured under the same conditions as in Example 1. The results are shown in Table 2.
[0017]
Comparative Example 1
Except that no polytetrafluoroethylene emulsion was added, electroplating was performed under the same conditions as in Example 1 to produce an active cathode, and the hydrogen overvoltage was measured under the same conditions as in Example 1. 3 shows.
[0019]
Comparative Example 2
Except that no polytetrafluoroethylene emulsion was added, electroplating was performed under the same conditions as in Example 2 to produce an active cathode, and the hydrogen overvoltage was measured under the same conditions as in Example 1. Table 4 shows.
[0021]
【The invention's effect】
The active cathode of the present invention has a low hydrogen overvoltage under a high current density, and even when the saline ion exchange membrane electrolytic cell is operated at a high current density, the electrolytic voltage can be lowered. Lower power consumption can be achieved.
Claims (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22609997A JP3712220B2 (en) | 1997-08-22 | 1997-08-22 | Ion exchange membrane electrolysis method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22609997A JP3712220B2 (en) | 1997-08-22 | 1997-08-22 | Ion exchange membrane electrolysis method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1161475A JPH1161475A (en) | 1999-03-05 |
| JP3712220B2 true JP3712220B2 (en) | 2005-11-02 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22609997A Expired - Fee Related JP3712220B2 (en) | 1997-08-22 | 1997-08-22 | Ion exchange membrane electrolysis method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3712220B2 (en) |
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1997
- 1997-08-22 JP JP22609997A patent/JP3712220B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| JPH1161475A (en) | 1999-03-05 |
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