Classifications

• • 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
  • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
  • C25B11/077—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the compound being a non-noble metal oxide
  • C25B11/0775—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the compound being a non-noble metal oxide of the rutile type
• • 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
  • C25B11/093—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 at least one noble metal or noble metal oxide and at least one non-noble metal oxide

Definitions

• the present invention relates to a new type of coating intended for constituting the active surface of a metal electrode made at least superficially of titanium or a titanium alloy and optionally containing a core of a better conducting material than titanium, for example of copper, aluminum, iron or alloys of these metals.
• Electrodes provided with a coating having catalytic properties according to the present invention may be used in various electrochemical processes such as cathodic protection, desalination or purification of water, electrolysis of water or hydrochloric acid, production of current in a fuel cell, reduction or oxidation of organic compounds of the electrolytic manufacture of per salts, but they are particularly useful as anodes in the electrolysis of aqueous solutions of alkali metal halides, particularly sodium chloride, both in diaphragm cells and mercury cells where they catalyze the discharge of chloride ions which is brought about at a re markably low and practically constant overpotential throughout the whole life of the electrode. Under the conditions ruling in these cells, wear of the coating is insignificant, and this assures a practically unlimited life for the anodes and avoids the burdensome operations of opening the cells and renewing the coatings.
• alkali metal halides particularly sodium chloride
• An object of the present invention is to provide an electrocatalytically active coating which is particularly well adherent to its metallic support and is resistant to electrochemical corrosion.
• a new type of coating for metal electrodes which coating comprises a compound ABO, having a rutile-type structure, where A is an element in the trivalent state selected from the group rhodium, aluminum, gallium, lanthanum and the rare earths, while B is an element in the pentavalent state selected from the group antimony, niobium and tantalum, the compound ABO, being associated with an oxide of the type M where M is ruthenium and/or iridium.
• Rh and Al have always given better results, so they are preferred.
• a solution A containing 0.5 g-atom ruthenium/liter was prepared by dissolving ruthenium trichloride (RuCl .xI-I O) in n-hexanol
• a solution B containing 0.5 g-atom rhodium/liter was prepared by dissolving rhodium trichloride (RhCl .xI-l O) in 'n-hexanol
• a solution C containing 1 g-atom antimony/liter was prepared by dissolving antimony pentachloride (SbCl in nhexanol.
• the amount of material thus deposited was approximately 4.5 g/m.
• the coating which contained 2 g-atom Ru to l gatom Rh and l g-atom Sb, showed excellent adherence to the substrate, as was shown in stripping tests with adhesive tape applied by pressure.
• the first relates to the over-potential for liberation of chlorine. It is measured at an anodic current density of 10 kA/m
• the second relates to the consumption of noble metal as a function of the amount of chlorine liberated.
• the measurement of over-potential is carried out by immersing the plates in brine containing 250 g NaCl/kg, saturated with chlorine at C and at a pH of approximately 2. Under these conditions, the plates referred to in this example show an initial overpotential of approximately 165 mV and then an overpotential of 210 mV and 248 mV after a production of 67 and 210 tons of chlorine/m respectively, while positively polarized under a current density of 10 kA/m In another test the consumption of noble metal from these plates was evaluated by using them as anodes in a cell with a flowing mercury cathode containing brine saturated with chlorine and sodium chloride at a temperature between and C with a constant anodecathode potential.
• Example 2 ABO.2MO where A Rh, B Nb and M Ru To 6 ml of solution A of Example 1 were added 3 ml of solution B of Example 1, 1.5 ml ofa solution D containing l g-atom niobium/liter obtained by dissolving niobium pentachloride (NbCl in n-hexanol, and 39.5 ml of n-hexanol.
• the average weight of the coating thus obtained was approximately 3.7 g/m it contained 2 g-atom Ru to 1 g-atom Rh and l g-atom Nb.
• the adherence to the substrate was very good.
• the plates thus coated showed over-potentials of approximately 245 mV at an anodic current density of kA/m
• the amount of chlorine already produced was 81 tons/m which corresponds to a consumption of noble metal equal to 26 mg/ton of chlorine.
• Example 3 ABO.,.2MO where A A1, B Sb and M Ru
• a solution E containing 1 g-atom aluminum/liter was prepared by dissolving aluminum trichloride (AlCl in n-butanol.
• the plates thus coated showed an initial over-potential of 156 mV at an anodic current density of 10 kA/m
• the amount of chlorine already produced was 125 tons/m which corresponds to a consumption of noble metal equal to mg/ton of chlorine.
• Example 4 ABO .2MO where A Rh, B Sb and M I
• a solution F containing 1 g-atom of iridium/liter obtained by dissolving chloroiridic acid (H lrCl .xH O) in n-hexanol were added 2.8 ml of solution B of Example 1, 1.4 ml of solution C of Example I and 43.0 ml of n-hexanoln
• the application of this composition, in 10 coats, to plates of etched titanium and the heat treatments were carried out as in Example 1.
• the weight ofthe coatings thus obtained was approximately 6 glm they contained 2 g-atomlr to l g-atom Rh and 1 g-atom Sb.
• the adherence to the substrate was excellent.
• the plates thus coated showed initial overpotentials of approximately 200 mV at an anodic current density of 10 kA/m
• the plates had produced more than 172 tons of chlorine/m
• the limit of useful life of the electrode had not yet been reached and the consumption test was continued, but it was already apparent that the consumption of noble metal would be less than 23 mg/ton of chlorine produced.
• Example 5 ABO .4MO where A Rh, B Sb and M lr To 1.6 ml of the solution F of Example 4 there were added 0.8 ml of solution B of Example 1, 0.4 ml of solution C of Example 1 and 47.2 ml of n-hexanol.
• the weight of the coatings thus obtained was approximately 3 g/m they contained 4 g-atom lr to l g-atom Rh and l g-atom Sb.
• the adherence to the substrate was excellent.
• the plates thus coated showed overpotentials of approximately 230 mV at an anodic cur rent density of 10 kA/m
• the plates had produced more than 198 tons of chlorine/m
• the limit of useful life of the electrode had not yet been reached and the consumption test was continued, but it was already apparent that the consumption of noble metal would be less than 11 mg/ton of chlorine produced.
• Example 6 ABO .2MO where A Rh, B Sb and M Ru lr To 5.5 ml of the solution A of Example 1 there were added 1.4 ml of the solution F of Example 4, 4.2 ml of the solution B of Example 1, 2.1 ml of the solution C of Example 1 and 36.8 ml of n-hexanol.
• the weight of the coatings thus obtained was approximately 7 g/m they contained 4 g-atom Ru to 2 g-atom Ir, 3 g-atom Rh and 3 g-atom Sb; the adherence to the substrate was excellent.
• Example 7 ABO .2MO where A Rh, B Sb and M M; Ru lr To 2.1 ml of the solution A of Example 1 there were added 2.1 ml of the solution F of Example 4, 3.2 ml of the solution B of Example 1, 1.6 ml of the solution C of g-atom Ir 1 and 41.0 ml of n-hexanol.
• the weight of the coatings thus obtained was approximately 6 glm they contained 2 g-atom Ru to 4 g-atom Ir, 3 g-atom Rh and 3 g-atom Sb; the adherence to the substrate was excellent.
• Example 8 ABO .2MO where A Rh, B Sb and M Ru To 15.2 ml of the solution A of Example 1, there were added 7.6 ml of the solution B of Example 1, 3.8 ml of the solution C of Example 1 and 23.4 ml of nhexanol.
• the average weight of the coatings thus obtained was approximately 12.0 g/m they contained 2 g-atom Ru to 1 g-atom Rh and 1 g-atom Sb. The adherence to the substrate was very good.
• the plates thus coated showed an initial overvoltage of approximately 1 12 mV and then ofl60 mV after the liberation of 225 tons of chlorine/m of anodic surface at an anodic current density of kA/m At this time, the limit of useful life of the electrode had not yet been reached and the consumption test was continued, but it was already apparent that the consumption of noble metal would be less than 29 mg/ton of chlorine produced.
• Example 9 ABO .4MO where A Rh, B Ta and M Ru
• a solution G containing 0.5 g-atom/liter was prepared by dissolving ruthenium trichloride RuCl x11 0 in isopropanol, a solution H containing 0.5 g-atom/liter by dissolving rhodium trichloride RhCl xH O in isopropanol and a solution 1 containing 1 g-atom Ta/liter by dissolving tantalum pentachloride TaCl in methanol.
• the average weight of the coatings thus obtained was approximately 9.9 g/m they contained 4 g-atom Ru to 1 g-atom Rh and l g-atom Ta. The adherence to the substrate was very good.
• the plates thus coated showed an initial overvoltage of approximately 190 mV and then of 198 mV after the liberation of 55 tons of chlorine/m of anodic surface at an anodic current density of 10 kA/m After production of 138 tons of chlorine/m the limit of useful life of the electrode had not yet been reached and the consumption test was continued, but it was already apparent that the consumption of noble metal would be less than 41 mg/ton of chlorine produced.
• Example 10 ABO .4MO where A Al, B Ta and 5 M Ru To 10 ml of the solution A of Example 1, there were added 1.25 ml of solution E of Example 3, 1.25 ml of the solution I of Example 9 and 37.5 ml of n-hexanol. The application of the composition, in 10 coats, to plates of etched titanium and the various heat treatments were carried out as in Example 1.
• the average weight of the coatings thus obtained was approximately 6.8 g/m they contained 4 g-atom Ru to l 'g-atom Al and l g-atom Ta. The adherence to the substrate was very good.
• Example 1 When used as anodes under the conditions specified in Example 1 the plates thus coated showed an initial overvoltage of approximately 145 mV, at a current density of 10 kA/m When submitted to the consumption test under the same conditions as in Example 1, the plates had produced more than 131 tons of chlorine/m of anodic surface. At this time, the limit of useful life of the electrode had not yet been reached and the consumption test was continued, but it was already apparent that the consumption of noble metal would be less than 26 mg/ton of chlorine produced.
• Example 11 ABO .2MO where A 0.9 Rh 0.] Yb, B Sb and M Ru
• a solution .1 containing 1 g-atom Sb/liter was prepared by dissolving antimony pentachloride in isopropanol and a solution K containing 0.1 g-atom Yb/liter by attacking ytterbium oxide Yb O with hydrochloric acid and dissolving in isopropanol.
• the average weight of the coatings thus obtained was approximately 8.0 g/m they contained 2 g-atom Ru to 0.9 g-atom Rh, 0.1 g-atom Yb and 1 g-atom Sb.
• the adherence to the substrate was excellent.
• Example 1 When used as anodes under the conditions specified in Example 1 the plates thus coated showed an initial overvoltage of approximately 122 mV at an anodic current density of 10 kA/m When submitted to the consumption test under the same conditions as in Example 1, the plates had produced more than 103 tons of chlorine/m of anodic surface. At this time, the limit of useful life of the electrode had not yet been reached and the consumption test was continued, but it was already apparent that the consumption of noble metal would be less than 41 m-g/ton of chlorine produced.
• a metallic electrode for electrochemical processes A i an l t in th trivalent state selected from the comprising a metal support and on at least a portion of group consisting f Rh d All said support a conductive coating consisting essentially 20 of a compound ABO; with a structure of the rutile- 3.

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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)
• Oxygen, Ozone, And Oxides In General (AREA)
• Chemically Coating (AREA)
• Inert Electrodes (AREA)

Applications Claiming Priority (1)

Publications (1)

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Cited By (5)

Family Cites Families (4)

• 1971
  • 1971-07-09 LU LU63506A patent/LU63506A1/xx unknown
• 1972
  • 1972-06-02 CH CH821172A patent/CH551218A/fr not_active IP Right Cessation
  • 1972-06-13 IT IT25613/72A patent/IT956522B/it active
  • 1972-06-30 JP JP6510772A patent/JPS564634B1/ja active Pending
  • 1972-06-30 FR FR7223924A patent/FR2145485B1/fr not_active Expired
  • 1972-07-03 US US00268552A patent/US3849282A/en not_active Expired - Lifetime
  • 1972-07-05 AT AT575672A patent/AT319898B/de not_active IP Right Cessation
  • 1972-07-07 BR BR4512/72A patent/BR7204512D0/pt unknown
  • 1972-07-07 NL NLAANVRAGE7209520,A patent/NL172083C/xx not_active IP Right Cessation
  • 1972-07-07 DE DE2233485A patent/DE2233485C3/de not_active Expired

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