CN1011989B

CN1011989B - Electrode for electrolysis

Info

Publication number: CN1011989B
Application number: CN 85107379
Authority: CN
Inventors: 大江一英; 川岛幸雄
Original assignee: Dongdian Chemical Co ltd
Current assignee: Dongdian Chemical Co ltd; TDK Corp
Priority date: 1984-01-31
Filing date: 1985-08-21
Publication date: 1991-03-13
Also published as: CN85107379A

Abstract

The present invention relates to an anode formed by a conductive substrate covered with a (Ru-Sn)O2 solid solution coating, which can be used for the electrolysis of brine. The improved coating comprises 3 to 45 mol% of ruthenium oxide, 0.1 to 30 mol% of one of metal platinum, platinum oxide and iridium oxide and 50 to 96.9 mol% of tin oxide, wherein partial tin oxide can be replaced by antimony.

Description

Electrode for electrolysis

The present invention relates to the electrode that uses in the aqueous electrolysis of an alkali metal salt.

As everyone knows, ruthenium dioxide (RuO ₂) the type electrode is in the aqueous solution of alkali metal salt electrolysis, is used as anode in (typical example is the salt solution electrolysis).Japanese Patent No, disclosed electrode is the exemplary of ruthenium dioxide type electrode among the 46-21884, it does the lining base by valve metal, is covered with (Ru-Ti) O ₂Sosoloid coating and constituting.Since its long service life, industrial this type of electrode can the use as typical metal electrode.Regrettably, the anodic current efficiency that it provided is low, and it is big to analyse the oxygen amount simultaneously.

Japanese Patent No, 50-11330 have announced another kind of electrode, and its coating is to contain the 50%(mole at least) SnO ₂(Ru-Sn) O ₂Sosoloid.This class electrode also has long work-ing life, and content is about the 30%(mole) RuO ₂Enough chlorine overvoltages can be provided, but also bring some shortcomings simultaneously, wherein the aerobic overvoltage is low, analyse the oxygen amount and increase, and current efficiency is low.

For the oxygen overvoltage of the coating that increases these compositions, activator RuO ₂Content should reduce to the 20%(mole) about, yet this is unacceptable because the chlorine overvoltage can corresponding increase.

Japanese Patent No.52-28106 or U.S. Patent No. 3,776,834 disclose another kind of electrode, its (Ru-Sn-Ti) O ₂The sosoloid coating is by 14 to 20%(moles) RuO ₂, 67 to 71%(moles) TiO ₂With 9 to 19%(moles) SnO ₂Form.

It is in order to improve the oxygen overvoltage, to scribble (Ru-Ti) O thereby improve that this coating composition is set ₂The current efficiency of sosoloid electrode.It is successful that this electrode is analysed aspect the oxygen amount in minimizing, with previous being coated with (Ru-Ti) O ₂Electrode is compared and is reduced 20% approximately, but in that analyse still can not be satisfactory aspect oxygen amount and the current efficiency.

The purpose of this invention is to provide a kind of new and improved (Ru-Sn) O ₂Solid solution build electrode, it can produce bigger oxygen overvoltage, reduces and analyses the oxygen amount: improve anodic current efficiency, utilize (Ru-Sn) O simultaneously ₂The sosoloid coated electrode is in the advantage aspect chlorine overvoltage and life-span.

According to a first aspect of the invention, provide a kind of electrolysis voltage, it comprises a kind of conductive substrates, and this substrate outside surface has at least a part of number that the platinum group metal oxide catalyst coat is arranged, and it is characterized in that described coating comprises:

(1) 3 to the 45%(mole) ruthenium oxide,

(ⅱ) from metal platinum, that selects in platinum oxide and the iridium oxide is at least a, and content is 0.1 to 30%(mole).

(ⅲ) 50 to 96.9% moles stannic oxide.

According to a second aspect of the invention, provide a kind of electrode for electrolysis, it comprises a kind of conductive substrates, and its outside surface has at least a part to be covered with the platinum group metal oxide catalyst coat, it is characterized in that described coating comprises:

(ⅰ) 3 to 45%(moles) ruthenium oxide,

(ⅱ) 0.1 to 30%(mole) from metal platinum, platinum oxide and be added with the metal platinum of iridium oxide and be added with select in the platinum oxide of iridium oxide at least a,

(ⅲ) 50 to 96.9%(moles) stannic oxide wherein is no more than the 10%(mole) tin be that antimony replaces.

Fig. 1 is illustrated in the membrane type oxygen electrolyzer that has No. 1 and No. 8 sample anodes, and when saline electrolysis, the oxygen level in the anode bubbing is with the situation of active hydrogen change in concentration.

Making the used conductive substrates of electrode of the present invention can be from valve metal, such as titanium, tantalum, zirconium, niobium and preferably choose in the alloy of their titaniferous, the shape and size of substrate can be done larger change with applicable cases, but preferably use bar-shaped or tabular suitable material.

Be provided with coating on the conductive substrates, it contains (ⅰ) 3 to 45%(moles) ruthenium-oxide, (ⅱ) 0.1 to 30%(mole) metal platinum and/or platinum oxide and/or yttrium oxide and (ⅲ) 50 to 96.9%(moles) tin oxide.

This coating contains (ⅰ) 3 to 45%(moles) usually with RuO₂The ruthenium-oxide that form exists. RuO₂Content is less than the 3%(mole) time, the increase of chlorine ultra-voltage has surpassed industrial permission standard. RuO₂Content is greater than the 45%(mole) time, cause the oxygen ultra-voltage to descend, thereby increase the oxygen amount of separating out, reduce current efficiency. RuO₂Content is at 10 to 30%(moles) in the scope time, the result is relatively good.

This coating contains: (ⅱ) from metal platinum, that selects in platinum oxide and the yttrium oxide is at least a, and content is 0.1 to 30%(mole), component (ⅱ) content is lower than the 0.1%(mole) can cause that hydrogen overvoltage increases, oxygen plays that voltage reduces or the oxygen amount of separating out increases, thereby current efficiency is descended. Component (ⅱ) content is at 5 to 15%(moles) in the scope time, the result is relatively good.

Component (ⅱ) can be from metal platinum, platinum oxide, and that selects in this group material of yttrium oxide is a kind of, and two or three. Under common preparation condition, platinum and iridium are respectively with Pt and IrO₂Form exists, and therefore, component (ⅱ) generally is with Pt; Or Pt+IrO₂; Or IrO₂Form exist. As the case may be, in addition add limited amount platinum oxide, Pt and IrO₂Ratio do not have particular restriction.

This coating also contains (ⅲ) 50 to 96.9%(moles) tin oxide, be generally SnO₂Form. SnO₂Content less than the 50%(mole) can cause the oxygen ultra-voltage to reduce, analysing the oxygen amount increases, thereby current efficiency is descended. SnO₂Content is greater than the 96.9%(mole) time chlorine ultra-voltage increase and surpass the permission standard. SnO₂Content is at 55 to 85%(moles) in the scope time, the result is relatively good.

According to a second aspect of the invention, component (ⅲ), i.e. SnO₂Can contain antimony or its part and be replaced by antimony (Sb), its amount is no more than the 10%(mole of tin (Sn)) preferably be no more than the 5%(mole).

Antimony (Sb) is with Sb₂O ₃Form has partly replaced SnO as adulterant₂, in order to increase electric conductivity, the replacement amount is greater than the 10%(mole) time, impair on the contrary doping effect, and reduce corrosion stability.

Should be noted that RuO₂，SnO ₂And IrO₂And optional platinum oxide forms solid solution in coating. When having metal platinum, in general it gets involved the border of crystal grain, with the solid solution adjacency.

Usually the thickness of this coating is about 0.5 to 10 micron (μ m).

Electrode of the present invention can be by method manufacturing described in hereinafter.

For ruthenium oxide is added coating, but can use a kind of thermic to resolve into the compound solution of ruthenium oxide, for example be dissolved in the RuCl in the appropriate solvent ₃3H ₂O.After this solution coating, carry out drying and baking.

For metal platinum or platinum oxide are introduced coating, but can use a kind of thermic to resolve into the salts solution of metal platinum or platinum oxide, for example be dissolved in the halogen platinic acid in the appropriate solvent, resemble chloroplatinic acid H ₂PtCl ₆6H ₂O.This solution is coated on the titanium substrate subsequent drying and baking.

For iridium oxide is introduced coating, but can use a kind of thermic to resolve into the compound solution of iridium oxide, for example be dissolved in six chloro-iridic acid H in the appropriate solvent ₂IrCl ₆6H ₂O or iridium chloride IrCl ₆H ₂O.This solution is coated on the titanium substrate subsequent drying and baking.

For stannic oxide (can mix antimony) is introduced coating, but can use a kind of thermic to resolve into the salts solution of stannic oxide, for example, the inferior tin of halogenation, resemble tin protochloride, and stannous compound, resemble stannous carboxylic acid (as sad) salt, phosphoric acid salt, phosphorus carboxylate salt or the like, but also can use thermic to resolve into the salt of weisspiessglanz, for example be dissolved in the antimony halides in the appropriate solvent, resemble antimony chloride.After this solution coating, carry out drying and baking.

For the coating on the lining base (ⅱ) He (ⅲ) is made up of by specified proportion component (ⅰ), can one after the other be coated in the solution of above-mentioned various components respectively on the substrate surface middle drying and the baking procedure of inserting.In this multilayer coated process, have at least two kinds of above-mentioned solution to combine.

As selection, also can be prepared into single coating solution by three kinds in the solution of above-mentioned each component or four kinds are lumped together, then it is coated on the substrate surface.The method on coated substrates surface is not limited to these steps, and it is not crucial for the present invention in other words, and any step that meets the requirements all can be used.

Should be noted that owing to the antimonous hydride as the doped sno_2 agent causes significantly sacrificing because of volatilization during being baked to substrate.(below will explain) is so the amount that its adds in coating solution can be than corresponding to high several times of the stoichiometric quantity of last doped level.

Electrode of the present invention is in an alkali metal salt electrolysis, as being used as anode in the soda electrolysis.

According to the present invention, with Pt, platinum oxide and IrO ₂In at least a material selected be added to (Ru-Sn) O with predetermined amount ₂In the solid solution build coating, make a kind of new coating that is improved, be characterized in oxygen overvoltage height, it is few and anodic current efficiency is high to analyse the oxygen amount, and its characteristics are that also the chlorine overvoltage is low, and the life-span is long.Therefore, the invention provides a kind of commercial gratifying RuO ₂Solid solution build electrode.

Should be pointed out that the platinum metals beyond platinum and the iridium, for example Pd adds (Ru-Sn) O ₂The coated component of solid solution build is unsuccessful improving aspect the corrosion stability.

Be several example of the present invention below, it only does the usefulness of explanation, is not as restriction.

Example 1

Raw material is

These can be made Ru, Pt, the raw material of Ir and Sn or Sn+Sb is dissolved in respectively in the butanols, and being prepared into concentration is the material solution of every liter 100 gram metal.

Sn+Sb solution is with the 5%(mole) SbCl, add C ₁₆H ₃₀O ₄Make among the Sn.

Measure the solution of relevant raw material with transfer pipet, make it by predetermined mixed, and stirred, obtain containing the coating solution of the relevant component of different ratios.

In addition, remove to clean the thick titanium plate of 5 * 20 * 1mm, the solution of above-mentioned preparation is coated on the full surface through the plate that clean with the method for brushing with hot oxalic acid aqueous solution, subsequent drying, and in stove, toasted 10 minutes in 500 ℃ of air, with the generation thermolysis.This brushing, step dry and baking will repeat four times, till the coating of titanium plate has the composition shown in the table 1.

Make positive plate with these samples, and polarize with the scan rate measurement of potential sweep method with 240 seconds/volt.

During measurement, use the Dotite(trade mark) lead is received on the uncoated surface of sample, and except that their useful area, sample is sealed with insullac.

To these samples also in 30%(weight) the NaCl aqueous solution (being adjusted to pH=1) in and 1 mole of H ₂SO ₄In the aqueous solution, and it is 20 milliamperes/centimetre 30 ℃ and current density ²Under the condition, carry out chlorine overvoltage η Cl ₂With oxygen overvoltage η O ₂Measure.

The result of these measurements and oxygen level (O ₂Volume %) lists in the table 1 together.

For chlorine overvoltage η Cl ₂Surpassed industrial permission standard, promptly those electrodes of 100 millivolts are not measured its percentage and are analysed the oxygen amount.

It is to use fluorescence X light analysis method to measure that the coating that table 1 provides is formed.

* the example of usefulness relatively

The content of * antimony is represented based on tin (mole %).

Obviously find out from table 1 data, by Ru-Sn-Pt[of the present invention and/or Ir) electrode of system demonstrates high oxygen overvoltage, the chlorine overvoltage reduced analyse the oxygen amount to reduce.

In Fig. 1, with concentration * (by the mmole represent) mapping of the oxygen level in the anode bubbing (by volume % represents) to reactive chlorine, this experiment is that salt solution (2.5 mol NaCl) is tested in the electrolyzer at ion exchange membrane, and temperature is 55 ℃, and current density is 20 peace/decimetres ²Carry out electrolysis under the situation.Compare with the curve of No. 8 samples, it is more effective that the curve of No. 1 sample shows aspect the oxygen level of electrode of the present invention in the chlorine that reduction is separated out.

Example 2

Have identical in electrode (anode) preparation method that table 2 forms coating and the example 1, and determine its chlorine formation efficiency and resist to consume.

The method of measuring the chlorine formation efficiency is, is anode sample and diameter that 30 millimeters SUS304 disc type negative electrode is put into electrolytic solution, and electrolytic solution is to contain 0.25 mole sodium-chlor in 150 ml waters, and is placed in the sealing groove, in temperature is 30 ℃, and current density is 20 peace/decimetres ², electric weight is to carry out electrolysis under 100 coulombs of conditions.Then, solution is transferred in the iodine flask, is carried out iodometric titrationiodimetry titration, measure the concentration of hypochlorite in the solution with Sulfothiorine,

The consume experiment is the acceleration consume experiment according to Vaaler method (J.Electrochem SOC117,219(1970)).Give an example and illustrate.Containing 0.5 mole of NaCl and 2 moles of NaClO ₄The chlorine saturated solution in, under the condition of 65 ℃ and pH=3, and be 100 peace/decimetres in current density ²The Shi Jinhang electrolysis.This experiment is performed until bath voltage and reaches till 4 volts.The hours that success was turned round before record Xiayang plate was passivated is as the anodic life-span.

Symbol in the table 2 has following meaning,

Symbol work-ing life

Greater than 2500 hours

0 1500 to 2500 hours

△ 500 to 1500 hours

X was less than 500 hours

Our experience shows that this test makes the normal operation in the industrial chlorine electrolyzer of the acceleration rate of passivation want fast about 15 to 20 times.

* relatively use example

The content of * antimony Sb is the %(mole based on tin) expression.

Data in the table 2 are pointed out, the life period that electrode of the present invention is obtaining prolonging.Is high efficiency at chlorine aspect separating out.

Table 1

Sample number into spectrum is formed % (mole) η O ₂η Cl ₂O ₂%

Ru Pt Ir Sn Sb** (millivolt) (millivolt)

1????20????10????-????70????-????410????55????0.5

2????20????10????-????70????（2）????410????55????0.5

3????20????7????3????70????-????480????65????0.5

4????20????7????3????70????（2）????480????60????0.5

5＊????20????-????10????70????-????450????75????0.5

6＊????20????-????10????70????（2）????440????75????0.5

7＊????20????-????-????80????-????450????120????-

8＊????30????-????-????70????-????350????60????2.0

9＊????-????-????20????80????-????380????120????-

Table 2

Sample number into spectrum is formed (mole) Cl generation lifetime

Efficient

Ru????Pt????Zr????Sn????Sb＊＊

1 20 10 - 70 - 85

2 20 10 - 70 （2） 86

3 20 7 3 70 - 88

4 20 7 3 70 （2） 88

5 20 - 10 70 - 82

6 20 - 10 70 （2） 84

7＊????20????-????-????80????-????74????△

8＊????30????-????-????70????-????77????0

9＊ - - 20 80 - 70

10＊ 20 - 3 77 - 83

11 20 30 - 77 - 82

12＊????-????20????-????80????-????65????X

13＊????-????14????6????80????-????75????O

Claims

1, electrode for electrolysis comprises conductive substrates, and this conductive substrates has at least a part of outside surface to be covered with the platinum group metal oxide catalyst coat, it is characterized in that described coating is made up of following ingredients:

(i) ruthenium oxide of 3 to 45% (moles),

(ii) from metal platinum, platinum oxide and be added with the metal platinum of iridium oxide and be added with select in the platinum oxide of iridium oxide at least a, and contain 0.1 to 30% (mole),

The (iii) stannic oxide of 50 to 96.9% (moles).

2, according to the electrode of claim 1, wherein said substrate is selected valve metal and alloy thereof for use.

3, according to the electrode of claim 1, wherein said coating comprises;

(ⅰ) 10 to 30%(moles) ruthenium oxide.

That (ⅱ) selects from the platinum oxide that is added with iridium oxide and metal platinum is at least a, and contains 5 to 15%(moles).

(ⅲ) 55 to 85%(moles) stannic oxide.

4, according to the electrode of claim 1, wherein component (ⅱ) is the metal platinum that is added with iridium oxide.

5, the electrode used of electrolysis comprises that its at least a portion outside surface is covered with the conductive substrates of platinum group metal oxide catalyst coat, it is characterized in that described coating is made up of following ingredients:

(ⅰ) 3 to 45%(moles) ruthenium oxide,

(ⅲ) 50 to 96.9%(moles) wherein be no more than the 10%(mole) the stannic oxide that replaced by antimony of tin.

6, according to the electrode of claim 5, wherein said substrate is chosen from valve metal and alloy thereof.

7, according to the electrode of claim 5, wherein said coating comprises:

(ⅰ) 10 to 30%(moles) ruthenium oxide,

(ⅱ) 5 to 15%(moles) from the platinum oxide that is added with iridium oxide and metal platinum, select at least a,

(ⅲ) 55 to 85%(moles) stannic oxide.

8, according to the electrode of claim 5, wherein component (11) is the metal platinum that is added with iridium oxide.

9, according to the electrode of claim 5, wherein antimony replaced be no more than the 5%(mole) tin.