CA1143699A - Electrode with overlayer including oxides of platinum group, of iron group, of manganese, and of boron - Google Patents
Electrode with overlayer including oxides of platinum group, of iron group, of manganese, and of boronInfo
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- CA1143699A CA1143699A CA000343026A CA343026A CA1143699A CA 1143699 A CA1143699 A CA 1143699A CA 000343026 A CA000343026 A CA 000343026A CA 343026 A CA343026 A CA 343026A CA 1143699 A CA1143699 A CA 1143699A
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Abstract
Abstract of the Disclosure An electrode for electrochemical processes comprises an electrically conductive base topped with a layer of an active composition composed of, in wt %: metal oxide from the platinum group...5-45; at least one metal oxide from the iron and manganese group...19-94.9; boron oxide..Ø1-50.
A method of fabricating the electrode for electrochemical processes involves the deposition of an active composition on an electrically conductive base. The procedure involves the application thereto of a solution made up of a boric compound, at least one metal compound from the iron and manganese group which decomposes at a temperature between 360 and 500°C to form oxides thereof, and at least one metal compound from the platinum group which decomposes at a temperature between 360 and 500°C to form oxides thereof, and thermal treatment of said base at a temperature of 360 to 500°C. Another method of fabricating the electrode for electrochemical processes involves the deposition of an active composition on an electrically conductive base by the application thereto of a first solution of a metal compound from the platinum group which decomposes at a temperature between 360 and 500°C to form oxides thereof; thermal treat-ment of said base at a temperature of 360 to 500°C, applica-tion thereto of a second solution made up of a boric compound which decomposes at a temperature between 360 and 500°C to form oxides thereof, and thermal treatment of said base at a temperature of 360 to 500°C.
A method of fabricating the electrode for electrochemical processes involves the deposition of an active composition on an electrically conductive base. The procedure involves the application thereto of a solution made up of a boric compound, at least one metal compound from the iron and manganese group which decomposes at a temperature between 360 and 500°C to form oxides thereof, and at least one metal compound from the platinum group which decomposes at a temperature between 360 and 500°C to form oxides thereof, and thermal treatment of said base at a temperature of 360 to 500°C. Another method of fabricating the electrode for electrochemical processes involves the deposition of an active composition on an electrically conductive base by the application thereto of a first solution of a metal compound from the platinum group which decomposes at a temperature between 360 and 500°C to form oxides thereof; thermal treat-ment of said base at a temperature of 360 to 500°C, applica-tion thereto of a second solution made up of a boric compound which decomposes at a temperature between 360 and 500°C to form oxides thereof, and thermal treatment of said base at a temperature of 360 to 500°C.
Description
3~43~9 The present invention relates to electrodes for electrochemical processes, which comprise an electrically conductive substrate coated with an active composition containing metal and boron oxides. The invention may be used as an anode assembly in electrolyæing alkaline-metal chloride solutions for the production of chlorine and sodium hydroxide by the use of electrolyzers with a filtering dia-phragm. It is also suitable for electrolytic chlorate production, electroorganic synthesis, electrochemical degradation of sewage and like effluents, and the regenera-tion of etching solutions.
Until recently, graphite anodes were widely used in various electrochemical processes. The apparent advantages of such anodes are the use of readily available electrode material and their insensitivity to short-circuits. However, the graphite anodes have a high chlorine evolution potential and, in effect, a high electrolyzer voltage and are not durable, a limitation necessitating frequent dismantling of the electrolyzers to enable anode set replacements. Further-more, the graphite anodes are large and heavy, a featureincreasing the dimensions of the electrolyzers and the work areas of the electrolysis shops beyond reasonable limits.
Widely used at the present time are electrodes com-prising an electrically conductive base coated with an active composition. The electrically conductive base is fabricated from a suitable metal such, for example, as titanium, tantalum, zirconium,niobium or an alloy of these metals passivated in anode polarization. It may appear essentially in any shape, say, as a perforated or solid plate, bar, grid, or a metal-ceramic body.
Known in the art is an electrode assembly wherein anactive composition contains metal oxide or mixtures of metal -1- ~.~
~3~
oxides from the platinum group, say, ruthenium (cf. British Patent No. 1,168,558, published October 29, 1968, Inventor:
John Alan Bell, Patentee: Imperial Metal Industries~. The active surface is as thin as 3 to 10,u. The metal anodes feature improved electrochemical characteristics, constant size over a long service period, smaller dimensions and weight, high stability of the active composition, and long anode set replacement intervals, say, several years, which is generally an apparent advantage over the prior art graphite anodes.
In the aforesaid electrode for electrochemical processes comprising an electrically conductive base fabricated from passivated material and topped with a layer of active composition containing metal oxide or a mixture of metal oxides from the platinum group (platinum, iridium, ruthenium, rhodium, palladium, osmium), the active composition may include manganese, lead, cobalt, titanium, tantalum and zirconium oxides or silica amounting to less than 50 wt % of the metal oxides or mixture of the metal oxides from the platinum group (cf. British Patent No. 1,168,558 9 fully identified above)~
In such an electrode the expenditure of active composition containing, for example, ruthenium oxide is 7.5 mg/1000 ampere-hours with a current density of 0.2 A/cm2 for chlorine diaphragm electrolysis under stationary conditions, with the amount of lost active composition being determined gravi-metrically.
Also known in the art is an electrode wherein an electrically conductive base of passivated metal is topped with a layer of active composition containing metal oxides from the platinum group and metal oxides from the iron and manganese group, which do not exhibit rectification proper-ties. The active composition contains less than 50 wt % of
Until recently, graphite anodes were widely used in various electrochemical processes. The apparent advantages of such anodes are the use of readily available electrode material and their insensitivity to short-circuits. However, the graphite anodes have a high chlorine evolution potential and, in effect, a high electrolyzer voltage and are not durable, a limitation necessitating frequent dismantling of the electrolyzers to enable anode set replacements. Further-more, the graphite anodes are large and heavy, a featureincreasing the dimensions of the electrolyzers and the work areas of the electrolysis shops beyond reasonable limits.
Widely used at the present time are electrodes com-prising an electrically conductive base coated with an active composition. The electrically conductive base is fabricated from a suitable metal such, for example, as titanium, tantalum, zirconium,niobium or an alloy of these metals passivated in anode polarization. It may appear essentially in any shape, say, as a perforated or solid plate, bar, grid, or a metal-ceramic body.
Known in the art is an electrode assembly wherein anactive composition contains metal oxide or mixtures of metal -1- ~.~
~3~
oxides from the platinum group, say, ruthenium (cf. British Patent No. 1,168,558, published October 29, 1968, Inventor:
John Alan Bell, Patentee: Imperial Metal Industries~. The active surface is as thin as 3 to 10,u. The metal anodes feature improved electrochemical characteristics, constant size over a long service period, smaller dimensions and weight, high stability of the active composition, and long anode set replacement intervals, say, several years, which is generally an apparent advantage over the prior art graphite anodes.
In the aforesaid electrode for electrochemical processes comprising an electrically conductive base fabricated from passivated material and topped with a layer of active composition containing metal oxide or a mixture of metal oxides from the platinum group (platinum, iridium, ruthenium, rhodium, palladium, osmium), the active composition may include manganese, lead, cobalt, titanium, tantalum and zirconium oxides or silica amounting to less than 50 wt % of the metal oxides or mixture of the metal oxides from the platinum group (cf. British Patent No. 1,168,558 9 fully identified above)~
In such an electrode the expenditure of active composition containing, for example, ruthenium oxide is 7.5 mg/1000 ampere-hours with a current density of 0.2 A/cm2 for chlorine diaphragm electrolysis under stationary conditions, with the amount of lost active composition being determined gravi-metrically.
Also known in the art is an electrode wherein an electrically conductive base of passivated metal is topped with a layer of active composition containing metal oxides from the platinum group and metal oxides from the iron and manganese group, which do not exhibit rectification proper-ties. The active composition contains less than 50 wt % of
-2-~36~
the metal oxide from the platinum group, as referred to the weight of the metal oxide or mixture of the metal oxides, which do not exhibit rectification properties (cf. "Studies in a Chlorine Releasing Process on a Titanium Anode Having an Active Mass Containing Ruthenium Oxides", an article by I.A. Ivanter, G.P. Pechnikova and V.L. Kubasov published in the "Electrochemistry" Journal, Volume XII, No. 5, 1976 (The USSR Academy of Sciences, Moscow), pages 787 to 789).
In such an electrode the expenditure of active composition is 4 to 5.7 mg/1000 ampere-hours with a current density of 0.2 A/cm2 for chlorine diaphragm electrolysis under stationary conditions with the total number of ampere-hours during the experiment being 787-896 in the case of an active composition containing 31 wt % of ruthenium dioxide and 69 wt % of iron oxides.
A known electrode production method involves deposi-tion of an active composition containing metal oxides from the platinum, iron and manganese groups on an electrically conductive base fabricated from a passivated material, the steps comprising the application thereto of a solution of compounds of said metals which decompose at a temperature between 360 and 500C to form oxides thereof, and thermal treatment of said base. The solution of metal compounds which decompose under heat treatment may be applied repeatedly (cf. "Electrochemistry", Volume XII, No. 5, 1976, USSR Academy of Sciences, Moscow, fully identified above).
The active composition is applied to the electrically conductive base using a solution of metal compounds from the platinum, iron and manganese groups which decompose at a temperature between 360 and 500C to form oxides thereof whereupon said base is treated thermally.
With another known method a base is initially treated
the metal oxide from the platinum group, as referred to the weight of the metal oxide or mixture of the metal oxides, which do not exhibit rectification properties (cf. "Studies in a Chlorine Releasing Process on a Titanium Anode Having an Active Mass Containing Ruthenium Oxides", an article by I.A. Ivanter, G.P. Pechnikova and V.L. Kubasov published in the "Electrochemistry" Journal, Volume XII, No. 5, 1976 (The USSR Academy of Sciences, Moscow), pages 787 to 789).
In such an electrode the expenditure of active composition is 4 to 5.7 mg/1000 ampere-hours with a current density of 0.2 A/cm2 for chlorine diaphragm electrolysis under stationary conditions with the total number of ampere-hours during the experiment being 787-896 in the case of an active composition containing 31 wt % of ruthenium dioxide and 69 wt % of iron oxides.
A known electrode production method involves deposi-tion of an active composition containing metal oxides from the platinum, iron and manganese groups on an electrically conductive base fabricated from a passivated material, the steps comprising the application thereto of a solution of compounds of said metals which decompose at a temperature between 360 and 500C to form oxides thereof, and thermal treatment of said base. The solution of metal compounds which decompose under heat treatment may be applied repeatedly (cf. "Electrochemistry", Volume XII, No. 5, 1976, USSR Academy of Sciences, Moscow, fully identified above).
The active composition is applied to the electrically conductive base using a solution of metal compounds from the platinum, iron and manganese groups which decompose at a temperature between 360 and 500C to form oxides thereof whereupon said base is treated thermally.
With another known method a base is initially treated
-3-~ ~3~9'~
with a solution of a metal cornpound from the platinum group which decomposes at a temperature between 360 and 500C to form oxides thereof, the subsequent steps being the thermal treatment of said base, the application thereto of a solution of compounds of other components which decompose at a temperature between 360 and 500C to form oxides thereof, and repeated thermal treatment of said base (cf. West German Application ~o. 2,210,043, published on September 14, 1972, Inventor: A. Martinsons, Applicant: PPG Inc., U.S.A7 and West German Application ~o. 2,126,840 published on May 29, 1971, Inventor: P.P. Anthony, Applicant: PPG Inc., U.S.A.).
It is an object of the present invention to decrease the expenditure of metals from the platinum group without degrading the electrochemical characteristics of an electrode and to extend its service life.
The electrode for electrochemical processes forming the subject of the present invention comprises an electrically conductive base topped with a layer of an active composition composed of, in wt %:
metal oxide from the platinum group....... .5-45 at least one metal oxide from the iron and manganese group.................... l9-94.9 boron oxide............................... 0.1-50 To enhance electrode stability, the active composition preferably contains ruthenium and iron oxides or cobalt oxide or a mixture of manganese and cobalt oxides.
The hereinproposed method of fabricating the electrode for electrochemical processes involves the deposition of an active composition on an electrically conductive base, the 30 steps involving the application thereto of a solution contain-ing a boric compound which decomposes at a temperature between 360 and 500C to form oxides thereof, at least one metal compound from the iron and manganese group which decomposes at a temperature between 360 and 500C to form oxides thereof, and at least one metal compound from the platinum group which decomposes at a temperature between 360 and 500C
to form oxides thereof, and thermal treatment of said base at a temperature of 360 to 500C.
Desirably the solution is obtained by mixing the oxides in the following ratio, in wt %:
metal oxide from the platinum group............ .5-45 at least one metal oxide from the iron and manganese group........................ l9-94.9 boron oxide................................... 0.1-50 It is of advantage that said solution contains boric, iron and ruthenium or boric, cobalt and ruthenium or boric, cobalt, manganese and ruthenium compounds which decompose at a temperature between 360 and 500C to form oxides thereof.
Another method of fabricating the electrode for electrochemical processes in compliance with the present invention involves deposition of an active composition on an electrically conductive base, the steps including the application thereto of a first solution of a metal compound from the platinum group which decomposes at a temperature between 360 and 500C to form oxides thereof, thermal treat-ment of said base at a temperature of 360 to 500C, applica-tion thereto of a second solution containing a boric compound which decomposes at a temperature between 360 and 500C to form oxides thereof, and at least one metal compound from the iron and manganese group which decomposes at a temperature between 360 and 500C to form oxides thereof, and thermal treatment of said base at a temperature of 360 to 500C.
Desirably the solutions are obtained by mixing the 3~3q3 oxides in the following ratio, in wt %:
metal oxide from the platinum group............. .5-45 at least one metal oxide from the iron and manganese group......................... l9-94.9 boron oxide.................................... 0.1-50 To enhance electrode stability it is advantageous that the first solution contains a ruthenium compound which decomposes at a temperature between 360 and 500C to form oxides thereof, and the second solution includes boric and cobalt, or boric, cobalt and manganese or boric, cobalt and ruthenium compounds which decompose at a temperature between 360 and 500C to form oxides thereof, and at least one metal compound from the platinum group which decomposes at a temperature between 360 and 500C to form oxides thereof.
The electrodes manufactured in compliance with the hereinproposed method possess an active surface whose stability is 1.2 to 2 times that of the prior art.
The electrocatalytic properties af the electrode form-ing the subject of the present invention are essentially similar to those of the known electrodes. The electrocatalytic activity has been estimated by comparing the anode potential with a standard hydrogen electrode under chlorine diaphragm electrolysis conditions. With a current density of 0.2 A/cm2 in anode polarization the electrode potentials have been found to be within 1.34 - 1.37 V relative to a standard hydrogen electrode for a solution containing 300 g/l NaCl at 90C, except for compositions containing manganese dioxide.
The electrode forming the subject of the present invention may be fabricated as follows. A prepared base of a suitable electrically conductive material such, for example, as titanium, is treated with a solution of metal compound from the platinum group mixed with metal compound from the iron and 3~
manganese group, which also includes boric acid. Thereafter said base is thermally treated at a temperature of 360 to 500C.
In electrode production the electrically conductive base may be treated with a solution of metal compounds from the platinum group which decompose at a temperature between 360 and 500C to form oxides thereof, the subsequent steps being a thermal treatment of said base at a temperature of 360 to 500C, application of a solution of compounds of boron and metals from the platinum, iron and manganese groups which decompose at a temperature between 360 and 500C to form oxides thereof, and thermal treatment of said base.
In electrode production the electrically conductive base may also be treated with a solution containing metal compounds from the platinum group which decompose at a temperature between 360 and 500C to form oxides thereof, the subsequent steps being a thermal treatment of said base at a temperature of 360 to 500C, application of another solution of compounds of boron and metals from the iron and manganese group which decompose at a temperature between 360 and 500C to form oxides thereof, and thermal treatment of said baseO
In electrode production according to another embodi-ment of the invention the electrically conductive base may be treated with a solution containing compounds of boron and metals from the platinum, iron and manganese groups which decompose at a temperature between 360 and 500C to form oxides thereof, the subsequent steps being drying at a tempera-ture of 20 to 150C, and thermal treatment of said base at a temperature of 360 to 500C.
The appllcation of the solution and the thermal ~3~6~
treatment operations may be performed repeatedly.
Given herewith are typical examples of the practical realization of the invention.
Example Consider an electrode comprising an electrically conductive substrate representing a 30x40x2 titanium plate topped with a layer of active composition composed of, in wt %: boron oxide - 0.4, ruthenium dioxide - 31, and iron oxides - 68.6.
The production procedure is as follows. Degrease the titanium plate with 5% NaOH solution at 60C for 10 minutes and then etch it with 20% HCl solution at 100C~
To apply the active composition, prepare a solution contain-ing 7.8 ml ferrous nitrate ~l-mole solution), 1 g of ruthenium chloride solution with 19.2 wt % ruthenium concentration and 0.2 ml of boric acid solution (0.5-mole solution). Apply the solution to the prepared titanium surface and allow it to dry for 40 minutes increasing the temperature gradually from 20 to 150C. Next, allow a 20-minute waiting period at 150 and perform thermal treatment at 360C i~or 20 minutes. Repeat the operation six times. Having applied all the layers; heat the electrode at 470 for one hour. The total amount of active composition deposited on the electrode is 13.2 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm electrolysis conditions at pH = 3-5 with solution containing 300 g/l NaCl at 90C with an anode current density of 0.2 A/cm2. The anode potential relative to a standard hydrogen electrode has been found to be 1.35 V (s.h.e.). The abbrevia-tion s.h.e. stands for standard hydrogen electrode. The total number of ampere-hours during the test has been 2724.4.
No active composition losses have been observed gravimetrical-69~
ly. The anode weight measuring accuracy has been ~ 0.05 mg.
Example 2 Fabricate an electrode similar to that described in Example 1 using the above procedure. Apply the solution to the prepared titanium surface and allow it to dry at 120C
for 15 minutes. Next, perform thermal treatment at 470C
for 10 minutes, Repeat the operation eight times. The total amount of active composition deposited on the electrode is 17 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm conditions at pH = ~.5 - 5 with a solution containing 300 g/l NaCl at 90C with an anode current density of 0.2 A~cm2.
The anode potential has been found to be 1.35 V (s.h.e.) - The total number of ampere-hours during the test has been 2486. The active composition loss during the electrolyzing procedure has been 0.2 mg per 1000 ampere-hours.
Example 3 Fabricate an electrode similar to that described in Example 1 using the above procedure but omitting the pre-liminary drying step- The total amount of active composition deposited on the electrode is 11 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm electrolysis conditions at p~ = 3-4 with a solution containing 280 g/l NaCl at 90C with an anode current density of 0.2 A~cm2. The anode potential has been found to be 1.36 V
(s.h.e.). The total number of ampere-hours during the test has been 1346.2. The active composition loss during the electrolyzing procedure has been 0.9 mg~1000 ampere-hours.
Example 4 Fabricate an electrode similar to that described in Example 1 using the above procedure but omitting the pre-liminary drying step. The active composition should be ~, _ c~_ ~14369~
composed of, in wt %: ruthenium dioxide 31; iron oxides 67, and boron oxide 2. The total amount of active composition deposited on the electrode is 15.3 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm electrolysis conditions at pH = 3-4 with a solution contain-ing 280 g~l NaCl at 90C with an anode current density of 0.2 A/cm . The anode potential has been found to be 1.35 V
(s.h.e.). The total number of ampere-hours during the test has been 1605.6. The active composition losses throughout the operating procedure have been 0.56 mg/1000 ampere-hours.
Example 5 Fabricate an electrode similar to that described in Example 1 but having an active surface composed of, in wt %:
ruthenium dioxide - 31, iron oxide - 59, and boron oxide - 10.
The total amount of active composition deposited on the electrode is 10.5 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm electrolysis conditions at pH = 3-5 with a solution contain-ing 280 g/l NaCl at 90C with an anode current density of 0.2 A/cm2~ The anode potential has been found to be 1.37 V
(s.h.e.). The total number of ampere-hours during the test has been 1751. No active composition losses have been observed.
Example 6 Fabricate an electrode si,milar to that described in Example 1 using the above procedure but omitting the pre-liminary drying step with the acl,ive composition composed of, in wt %: ruthenium dioxide - 31, iron oxides - 19, and boron oxide - 50. The total amount of active composition deposited on the electrode is 13 g per 1 m2 of its surface.
In electrode production perform ~hermal treatment at a ~' -10-temperature of 500C.
The electrode has been tested under chlorine dia-phragm electrolysis conditions at: pH = 3-5 with solution containing 300 g/l ~aCl at 90C with an anode current density of 0.2 A/cm2~ The electrode potential has been found to be 1.37 V (s.h.e.~. The total number of ampere-hours during the test has been 900. The active composition expenditure during the electrolyzing procedure has been 1.2 mg/1000 ampere-hours.
ExamPle 7 Consider an electrode comprising an electrically conductive substrate representing a 30x40x2 titanium plate topped with a layer of active composition composed of, in wt %, ruthenium dioxide - 5; manganese oxide - 84.3, cobalt oxide - 10.3: and boron oxide - 0.4.
The production procedure is as follows. Prepare the titanium base using the procedure described in Example 1.
To apply the active composition, make use of solutions containing magnesium nitrate (l-mole solution), cobalt nitrate (l-mole solution), boric acid solution (0.5-mole solution)~ and ruthenium chloride solution with 19.2 wt %
ruthenium concentration. Apply a coat of ruthenium chloride solution to the prepared titanium substrate and perform thermal treatment at 370C for 10 minutes. The total amount of deposited metallic ruthenium is 1.3 g per 1 m of the surface being treated. ~ext~ apply a mixed solution o~
cobalt nitrate, manganese nitrate and boric acid prepared from the above solutions and perform thermal treatment at 380C for 20 minutes. Repeat the operation ten times. The total amount of active composition deposited on the electrode is 35 g per 1 m of its surface.
The electrode has been tested under chlorine diaphragm -~ f ,,~.,~
~36~
electrolysis conditions at pH = 3-5 with a solution contain-ing 280 g/l NaCl at 90C with an anode current density of 0.1 A~cm2. The anode potential relative to a standard hydrogen electrode has been found to be 1.5 V (s.h.e.). The total number of ampere-hours during the test has been 1070.
The active composition expenditure has been equal to 3 mg~1000 ampere-hours.
Exam~Le 8 Consider an electrode comprising an electrically conductive substrate representing a 30x40x2 titanium plate topped with a layer of active composition composed of, in wt %: ruthenium oxide - 5, cobalt oxide - 94.9, and boron oxide - 0.1 .
The production procedure is as follows. Prepare the titanium plate as described in Example 1. To apply the active composition, prepare a mixture of cobalt nitrate solutions (l-mole solution), boric acid solution (0.5-mole solution) and ruthenium chloride solution with 19.2 wt % ruthenium concentration. Apply a coat of the ruthenium chloride solu-20 tion to the prepared titanium substrate and then performthermal treatment at a temperature of 370C for 10 minutes.
The amount of deposited metallic ruthenium is 1.3 g per 1 m2 of the working area. Next, apply a mixed solution of cobalt nitrate and boric acid, prepared i rom the above solutions and perform thermal treatment at 450C Eor 20 minutes. Having applied all the layers, heat the electrode at 470C for one hour. The total amount of active composition deposited on the electrode is 30 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm 30 electrolysis conditions at pH = 4-6 with solution containing 280 g/l NaCl at 90C with an anode density of 0.2 A~/cm2. The anode potential has been found to be 1 .36 V (s.h.e.) . The 36~9 total number of ampere-hours has been 2050. The active composition expenditure has been 3 mg~1000 ampere-hours.
Example 9 Consider an electrode comprising a 30x40x2 titanium plate topped with a layer of active composition composed of, in wt %: ruthenium oxide - 45; iron oxide - 53, and boron oxide - 2. The electrode is fabricated using the procedure described in ~xample 1. Apply a coat of ruthenium chloride solution with 19~2 wt ~,, ruthenium concentration to the prepared titanium substrate and then perform thermal treatment at 370C for 10 minutes. The number of deposited metallic ruthenium is 1.3 y/m2 Of the working surface. The total amount of active composition deposited on the titanium plate is 12.5 g per 1 m2 of the anode surface.
The electrode has been t:ested under diaphragm electroly-! SiS conditions at pH = 3-4 with solution containing 300 g/l NaCl at 90C with an anode current density of 0.2 A/cm2~ The anode potential has been found 1:o be 1.35 V (s.h.e.). The total amount of ampere-hours has been 1900. The active com-position expenditure during the electrolyzing procedure has been 1 mg/1000 ampere-hours.
~ !
with a solution of a metal cornpound from the platinum group which decomposes at a temperature between 360 and 500C to form oxides thereof, the subsequent steps being the thermal treatment of said base, the application thereto of a solution of compounds of other components which decompose at a temperature between 360 and 500C to form oxides thereof, and repeated thermal treatment of said base (cf. West German Application ~o. 2,210,043, published on September 14, 1972, Inventor: A. Martinsons, Applicant: PPG Inc., U.S.A7 and West German Application ~o. 2,126,840 published on May 29, 1971, Inventor: P.P. Anthony, Applicant: PPG Inc., U.S.A.).
It is an object of the present invention to decrease the expenditure of metals from the platinum group without degrading the electrochemical characteristics of an electrode and to extend its service life.
The electrode for electrochemical processes forming the subject of the present invention comprises an electrically conductive base topped with a layer of an active composition composed of, in wt %:
metal oxide from the platinum group....... .5-45 at least one metal oxide from the iron and manganese group.................... l9-94.9 boron oxide............................... 0.1-50 To enhance electrode stability, the active composition preferably contains ruthenium and iron oxides or cobalt oxide or a mixture of manganese and cobalt oxides.
The hereinproposed method of fabricating the electrode for electrochemical processes involves the deposition of an active composition on an electrically conductive base, the 30 steps involving the application thereto of a solution contain-ing a boric compound which decomposes at a temperature between 360 and 500C to form oxides thereof, at least one metal compound from the iron and manganese group which decomposes at a temperature between 360 and 500C to form oxides thereof, and at least one metal compound from the platinum group which decomposes at a temperature between 360 and 500C
to form oxides thereof, and thermal treatment of said base at a temperature of 360 to 500C.
Desirably the solution is obtained by mixing the oxides in the following ratio, in wt %:
metal oxide from the platinum group............ .5-45 at least one metal oxide from the iron and manganese group........................ l9-94.9 boron oxide................................... 0.1-50 It is of advantage that said solution contains boric, iron and ruthenium or boric, cobalt and ruthenium or boric, cobalt, manganese and ruthenium compounds which decompose at a temperature between 360 and 500C to form oxides thereof.
Another method of fabricating the electrode for electrochemical processes in compliance with the present invention involves deposition of an active composition on an electrically conductive base, the steps including the application thereto of a first solution of a metal compound from the platinum group which decomposes at a temperature between 360 and 500C to form oxides thereof, thermal treat-ment of said base at a temperature of 360 to 500C, applica-tion thereto of a second solution containing a boric compound which decomposes at a temperature between 360 and 500C to form oxides thereof, and at least one metal compound from the iron and manganese group which decomposes at a temperature between 360 and 500C to form oxides thereof, and thermal treatment of said base at a temperature of 360 to 500C.
Desirably the solutions are obtained by mixing the 3~3q3 oxides in the following ratio, in wt %:
metal oxide from the platinum group............. .5-45 at least one metal oxide from the iron and manganese group......................... l9-94.9 boron oxide.................................... 0.1-50 To enhance electrode stability it is advantageous that the first solution contains a ruthenium compound which decomposes at a temperature between 360 and 500C to form oxides thereof, and the second solution includes boric and cobalt, or boric, cobalt and manganese or boric, cobalt and ruthenium compounds which decompose at a temperature between 360 and 500C to form oxides thereof, and at least one metal compound from the platinum group which decomposes at a temperature between 360 and 500C to form oxides thereof.
The electrodes manufactured in compliance with the hereinproposed method possess an active surface whose stability is 1.2 to 2 times that of the prior art.
The electrocatalytic properties af the electrode form-ing the subject of the present invention are essentially similar to those of the known electrodes. The electrocatalytic activity has been estimated by comparing the anode potential with a standard hydrogen electrode under chlorine diaphragm electrolysis conditions. With a current density of 0.2 A/cm2 in anode polarization the electrode potentials have been found to be within 1.34 - 1.37 V relative to a standard hydrogen electrode for a solution containing 300 g/l NaCl at 90C, except for compositions containing manganese dioxide.
The electrode forming the subject of the present invention may be fabricated as follows. A prepared base of a suitable electrically conductive material such, for example, as titanium, is treated with a solution of metal compound from the platinum group mixed with metal compound from the iron and 3~
manganese group, which also includes boric acid. Thereafter said base is thermally treated at a temperature of 360 to 500C.
In electrode production the electrically conductive base may be treated with a solution of metal compounds from the platinum group which decompose at a temperature between 360 and 500C to form oxides thereof, the subsequent steps being a thermal treatment of said base at a temperature of 360 to 500C, application of a solution of compounds of boron and metals from the platinum, iron and manganese groups which decompose at a temperature between 360 and 500C to form oxides thereof, and thermal treatment of said base.
In electrode production the electrically conductive base may also be treated with a solution containing metal compounds from the platinum group which decompose at a temperature between 360 and 500C to form oxides thereof, the subsequent steps being a thermal treatment of said base at a temperature of 360 to 500C, application of another solution of compounds of boron and metals from the iron and manganese group which decompose at a temperature between 360 and 500C to form oxides thereof, and thermal treatment of said baseO
In electrode production according to another embodi-ment of the invention the electrically conductive base may be treated with a solution containing compounds of boron and metals from the platinum, iron and manganese groups which decompose at a temperature between 360 and 500C to form oxides thereof, the subsequent steps being drying at a tempera-ture of 20 to 150C, and thermal treatment of said base at a temperature of 360 to 500C.
The appllcation of the solution and the thermal ~3~6~
treatment operations may be performed repeatedly.
Given herewith are typical examples of the practical realization of the invention.
Example Consider an electrode comprising an electrically conductive substrate representing a 30x40x2 titanium plate topped with a layer of active composition composed of, in wt %: boron oxide - 0.4, ruthenium dioxide - 31, and iron oxides - 68.6.
The production procedure is as follows. Degrease the titanium plate with 5% NaOH solution at 60C for 10 minutes and then etch it with 20% HCl solution at 100C~
To apply the active composition, prepare a solution contain-ing 7.8 ml ferrous nitrate ~l-mole solution), 1 g of ruthenium chloride solution with 19.2 wt % ruthenium concentration and 0.2 ml of boric acid solution (0.5-mole solution). Apply the solution to the prepared titanium surface and allow it to dry for 40 minutes increasing the temperature gradually from 20 to 150C. Next, allow a 20-minute waiting period at 150 and perform thermal treatment at 360C i~or 20 minutes. Repeat the operation six times. Having applied all the layers; heat the electrode at 470 for one hour. The total amount of active composition deposited on the electrode is 13.2 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm electrolysis conditions at pH = 3-5 with solution containing 300 g/l NaCl at 90C with an anode current density of 0.2 A/cm2. The anode potential relative to a standard hydrogen electrode has been found to be 1.35 V (s.h.e.). The abbrevia-tion s.h.e. stands for standard hydrogen electrode. The total number of ampere-hours during the test has been 2724.4.
No active composition losses have been observed gravimetrical-69~
ly. The anode weight measuring accuracy has been ~ 0.05 mg.
Example 2 Fabricate an electrode similar to that described in Example 1 using the above procedure. Apply the solution to the prepared titanium surface and allow it to dry at 120C
for 15 minutes. Next, perform thermal treatment at 470C
for 10 minutes, Repeat the operation eight times. The total amount of active composition deposited on the electrode is 17 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm conditions at pH = ~.5 - 5 with a solution containing 300 g/l NaCl at 90C with an anode current density of 0.2 A~cm2.
The anode potential has been found to be 1.35 V (s.h.e.) - The total number of ampere-hours during the test has been 2486. The active composition loss during the electrolyzing procedure has been 0.2 mg per 1000 ampere-hours.
Example 3 Fabricate an electrode similar to that described in Example 1 using the above procedure but omitting the pre-liminary drying step- The total amount of active composition deposited on the electrode is 11 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm electrolysis conditions at p~ = 3-4 with a solution containing 280 g/l NaCl at 90C with an anode current density of 0.2 A~cm2. The anode potential has been found to be 1.36 V
(s.h.e.). The total number of ampere-hours during the test has been 1346.2. The active composition loss during the electrolyzing procedure has been 0.9 mg~1000 ampere-hours.
Example 4 Fabricate an electrode similar to that described in Example 1 using the above procedure but omitting the pre-liminary drying step. The active composition should be ~, _ c~_ ~14369~
composed of, in wt %: ruthenium dioxide 31; iron oxides 67, and boron oxide 2. The total amount of active composition deposited on the electrode is 15.3 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm electrolysis conditions at pH = 3-4 with a solution contain-ing 280 g~l NaCl at 90C with an anode current density of 0.2 A/cm . The anode potential has been found to be 1.35 V
(s.h.e.). The total number of ampere-hours during the test has been 1605.6. The active composition losses throughout the operating procedure have been 0.56 mg/1000 ampere-hours.
Example 5 Fabricate an electrode similar to that described in Example 1 but having an active surface composed of, in wt %:
ruthenium dioxide - 31, iron oxide - 59, and boron oxide - 10.
The total amount of active composition deposited on the electrode is 10.5 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm electrolysis conditions at pH = 3-5 with a solution contain-ing 280 g/l NaCl at 90C with an anode current density of 0.2 A/cm2~ The anode potential has been found to be 1.37 V
(s.h.e.). The total number of ampere-hours during the test has been 1751. No active composition losses have been observed.
Example 6 Fabricate an electrode si,milar to that described in Example 1 using the above procedure but omitting the pre-liminary drying step with the acl,ive composition composed of, in wt %: ruthenium dioxide - 31, iron oxides - 19, and boron oxide - 50. The total amount of active composition deposited on the electrode is 13 g per 1 m2 of its surface.
In electrode production perform ~hermal treatment at a ~' -10-temperature of 500C.
The electrode has been tested under chlorine dia-phragm electrolysis conditions at: pH = 3-5 with solution containing 300 g/l ~aCl at 90C with an anode current density of 0.2 A/cm2~ The electrode potential has been found to be 1.37 V (s.h.e.~. The total number of ampere-hours during the test has been 900. The active composition expenditure during the electrolyzing procedure has been 1.2 mg/1000 ampere-hours.
ExamPle 7 Consider an electrode comprising an electrically conductive substrate representing a 30x40x2 titanium plate topped with a layer of active composition composed of, in wt %, ruthenium dioxide - 5; manganese oxide - 84.3, cobalt oxide - 10.3: and boron oxide - 0.4.
The production procedure is as follows. Prepare the titanium base using the procedure described in Example 1.
To apply the active composition, make use of solutions containing magnesium nitrate (l-mole solution), cobalt nitrate (l-mole solution), boric acid solution (0.5-mole solution)~ and ruthenium chloride solution with 19.2 wt %
ruthenium concentration. Apply a coat of ruthenium chloride solution to the prepared titanium substrate and perform thermal treatment at 370C for 10 minutes. The total amount of deposited metallic ruthenium is 1.3 g per 1 m of the surface being treated. ~ext~ apply a mixed solution o~
cobalt nitrate, manganese nitrate and boric acid prepared from the above solutions and perform thermal treatment at 380C for 20 minutes. Repeat the operation ten times. The total amount of active composition deposited on the electrode is 35 g per 1 m of its surface.
The electrode has been tested under chlorine diaphragm -~ f ,,~.,~
~36~
electrolysis conditions at pH = 3-5 with a solution contain-ing 280 g/l NaCl at 90C with an anode current density of 0.1 A~cm2. The anode potential relative to a standard hydrogen electrode has been found to be 1.5 V (s.h.e.). The total number of ampere-hours during the test has been 1070.
The active composition expenditure has been equal to 3 mg~1000 ampere-hours.
Exam~Le 8 Consider an electrode comprising an electrically conductive substrate representing a 30x40x2 titanium plate topped with a layer of active composition composed of, in wt %: ruthenium oxide - 5, cobalt oxide - 94.9, and boron oxide - 0.1 .
The production procedure is as follows. Prepare the titanium plate as described in Example 1. To apply the active composition, prepare a mixture of cobalt nitrate solutions (l-mole solution), boric acid solution (0.5-mole solution) and ruthenium chloride solution with 19.2 wt % ruthenium concentration. Apply a coat of the ruthenium chloride solu-20 tion to the prepared titanium substrate and then performthermal treatment at a temperature of 370C for 10 minutes.
The amount of deposited metallic ruthenium is 1.3 g per 1 m2 of the working area. Next, apply a mixed solution of cobalt nitrate and boric acid, prepared i rom the above solutions and perform thermal treatment at 450C Eor 20 minutes. Having applied all the layers, heat the electrode at 470C for one hour. The total amount of active composition deposited on the electrode is 30 g per 1 m2 of its surface.
The electrode has been tested under chlorine diaphragm 30 electrolysis conditions at pH = 4-6 with solution containing 280 g/l NaCl at 90C with an anode density of 0.2 A~/cm2. The anode potential has been found to be 1 .36 V (s.h.e.) . The 36~9 total number of ampere-hours has been 2050. The active composition expenditure has been 3 mg~1000 ampere-hours.
Example 9 Consider an electrode comprising a 30x40x2 titanium plate topped with a layer of active composition composed of, in wt %: ruthenium oxide - 45; iron oxide - 53, and boron oxide - 2. The electrode is fabricated using the procedure described in ~xample 1. Apply a coat of ruthenium chloride solution with 19~2 wt ~,, ruthenium concentration to the prepared titanium substrate and then perform thermal treatment at 370C for 10 minutes. The number of deposited metallic ruthenium is 1.3 y/m2 Of the working surface. The total amount of active composition deposited on the titanium plate is 12.5 g per 1 m2 of the anode surface.
The electrode has been t:ested under diaphragm electroly-! SiS conditions at pH = 3-4 with solution containing 300 g/l NaCl at 90C with an anode current density of 0.2 A/cm2~ The anode potential has been found 1:o be 1.35 V (s.h.e.). The total amount of ampere-hours has been 1900. The active com-position expenditure during the electrolyzing procedure has been 1 mg/1000 ampere-hours.
~ !
Claims (17)
1. An electrode for electrochemical processes comprising an electrically conductive base topped with a layer of active composition composed of, in wt %:
metal oxide from the platinum group ... 5-45 at least one metal oxide from the iron and manganese group ... 19-94.9 boron oxide ,.. 0.1-50
metal oxide from the platinum group ... 5-45 at least one metal oxide from the iron and manganese group ... 19-94.9 boron oxide ,.. 0.1-50
2. An electrode as claimed in claim 1, wherein said active composition contains ruthenium oxide.
3. An electrode as claimed in claim 1, wherein said active composition contains iron oxide.
4. An electrode as claimed in claim 1, wherein said active composition contains cobalt oxide.
5. An electrode as claimed in claim 1, wherein said active composition contains both manganese and cobalt oxides.
6. A method of fabricating an electrode for electro-chemical processes, involving deposition of an active com-position on an electrically conductive base, the steps comprised in the procedure being application thereto of a solution con-taining a boric compound which decomposes at a temperature between 360 and 500°C to form boron oxides, at least one metal compound from the iron and manganese group which de-composes at a temperature between 360 and 500°C to form oxides thereof, and at least one metal compound from the platinum group which decomposes at a temperature between 360 and 500°C to form oxides thereof, and thermal treatment of said coated base at a temperature of 360 to 500°C.
7. A method as claimed in claim 6, wherein the solution is obtained by mixing oxides in the following ratio, in wt %:
metal oxide from the platinum group ... 5-45 at least one metal oxide from the iron and manganese groups ... 19-94.9 boron oxide ... 0.1-50
metal oxide from the platinum group ... 5-45 at least one metal oxide from the iron and manganese groups ... 19-94.9 boron oxide ... 0.1-50
8. A method as claimed in claim 7, wherein said solution contains boric, iron and ruthenium compounds which decompose at a temperature between 360 and 500°C to form oxides thereof.
9. A method as claimed in claim 7, wherein said solution contains boric, cobalt and ruthenium compounds which decompose at a temperature between 360 and 500°C to form oxides thereof.
10. A method as claimed in claim 7, wherein said solution contains boric, cobalt, manganese and ruthenium compounds which decompose at a temperature between 360 and 500°C to form oxides thereof.
11. A method of fabricating an electrode for electro-chemical processes, involving deposition of an active com-position on an electrically conductive base, the successive steps of applying thereto a first solution of a metal compound from the platinum group which decomposes at a temperature between 360 and 500°C to form oxides thereof, followed by thermal treatment of said base at a temperature of 360 to 500°C, followed by application thereto of a second solution comprising a boric compound which decomposes at a temperature between 360 and 500°C to form oxides thereof, and at least one metal compound from the iron and manganese group which de-composes at a temperature between 360 and 500°C to form oxides thereof, and finally by thermal treatment of said coated base at a temperature of 360 to 500°C.
12. A method as claimed in claim 11, wherein both solutions are obtained by mixing oxides in the following ratio, in wt %:
metal oxide from the platinum group ... 5-45 at least one metal oxide from the iron and manganese group ... 19-94.9 boron oxide ... 0.1-50
metal oxide from the platinum group ... 5-45 at least one metal oxide from the iron and manganese group ... 19-94.9 boron oxide ... 0.1-50
13. A method as claimed in claim 12, wherein the first solution contains a ruthenium compound which decomposes at a temperature between 360 and 500°C to form oxides thereof.
14. A method as claimed in claim 12, wherein the second solution contains boric and cobalt compounds which decompose at a temperature between 360 and 500°C to form oxides thereof.
15. A method as claimed in claim 12, wherein the second solution contains boric, cobalt and manganese compounds which decompose at a temperature between 360 and 500°C to form oxides thereof.
16. A method as claimed in claim 13, wherein the second solution contains at least one metal compound from the platinum group which decomposes at a temperature between 360 and 500°C
to form oxides thereof.
to form oxides thereof.
17. A method as claimed in claim 16, wherein the second solution contains boric, cobalt and ruthenium compounds which decompose at a temperature between 360 and 500°C to form oxides thereof.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000343026A CA1143699A (en) | 1980-01-04 | 1980-01-04 | Electrode with overlayer including oxides of platinum group, of iron group, of manganese, and of boron |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000343026A CA1143699A (en) | 1980-01-04 | 1980-01-04 | Electrode with overlayer including oxides of platinum group, of iron group, of manganese, and of boron |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1143699A true CA1143699A (en) | 1983-03-29 |
Family
ID=4115965
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000343026A Expired CA1143699A (en) | 1980-01-04 | 1980-01-04 | Electrode with overlayer including oxides of platinum group, of iron group, of manganese, and of boron |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1143699A (en) |
-
1980
- 1980-01-04 CA CA000343026A patent/CA1143699A/en not_active Expired
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