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
• • 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
  • C25B11/042—Electrodes formed of a single material
  • C25B11/043—Carbon, e.g. diamond or graphene

Definitions

• tungsten carbide-activated electrode Another known method for producing a tungsten carbide-activated electrode consists in that active tungsten carbide with graphite powder is cold-pressed to the electrode (H. Böhm, Chem.-Ing.-Techn. 49 (1977, 328).
• the cathodes produced in this way only result in relatively low cathodic current densities, which suggests an unfavorable structure of the electrodes.
• an electrode in particular a cathode for the electrolytic decomposition of hydrochloric acid is also known, which has a coating containing tungsten carbide.
• this coating which is applied to the carrier by flame spraying, contains metallic cobalt or nickel in addition to tungsten carbide.
• the carrier is a green body formed from a binder-containing graphite powder, the carrier having a binder content of 10 to 40% by weight. Because a binder is added to the filler grains of the green body, there is also a layer of binder on its surface after the carrier has been produced, so that in this case there is no need to apply an additional binder layer.
• the support may be a porous diaphragm made of graphite.
• the tungsten compound is expediently applied to the carrier using a binder.
• a tungsten oxide powder which has been produced from para-ammonium tungstate via a precipitation reaction to tungstic acid and subsequent decomposition in air at approximately 550 ° C. or direct thermal decomposition of para-ammonium tungstate and whose specific surface area is greater than 10 is advantageously used for application to the carrier m 2 / g.
• the procedure is expediently carried out in such a way that the support with the tungsten oxide thereon is brought to reduce the tungsten oxide under a hydrogen atmosphere or a hydrogen inert gas atmosphere and is heated to a temperature of 370 to 580 ° C.
• the flowing gas is generally 1 to 3 l hydrogen / h per cm 2 cross-sectional area of the vessel in which the carrier is located.
• the heating takes place continuously in 1 to 3 hours from 20 ° C.
• the tungsten oxide (W0 3 ) is reduced to a mixture of different oxide phases with the composition WO X (0.33 ⁇ x ⁇ 3).
• the sample is expediently carried out in an inert gas atmosphere (e.g. about 21 / h flowing argon per cm 2 cross-sectional area of the vessel) in about 0.7 to 2 hours at 1 to 2 ° K / min Heated up to 620 ° C.
• an inert gas atmosphere e.g. about 21 / h flowing argon per cm 2 cross-sectional area of the vessel
• the carrier with the tungsten oxide located thereon is then heated in the temperature range from 620 to 950 ° C. at a temperature rise of approximately 1 ° K / min under a flowing CO / CO 2 atmosphere.
• the volume ratio of the CO to CO 2 is expediently about 10: 1, the volume flow about 1.5 I / h per cm 2 cross-sectional area of the vessel.
• the carburization time should last at most until all tungsten oxide has been converted into tungsten carbide. In order to achieve the highest possible electrochemical activity of the electrode, however, it may be expedient not to convert the tungsten oxide applied completely into tungsten carbide, but to leave a portion, albeit very small, of tungsten oxide.
• the carrier with the tungsten carbide layer formed is kept at 750 ° C. under flowing hydrogen gas in order to reduce any carbon present on the carrier surface.
• Electrodes produced by the method according to the invention consist in its use as a cathode in an electrolysis cell for carrying out the sulfuric acid hybrid cycle process or as a cathode in an electrolysis cell for the anodic oxidation of SO 2 exhaust gases with simultaneous cathodic H 2 production.
• Argon (20 l / h) was then passed through the quartz tube and the compacts were further heated up to 500.degree.
• the heating rate was 2.5 ° K / min.
• the compacts were heated from 580 ° C with a temperature increase of 1.4 ° K / min to 760 ° C, whereby a gas mixture of CO and C0 2 (CO / C0 2 volume ratio 9: 1; volume flow up to 15 l / h) was passed through the pipe.
• the finished electrodes with the tungsten carbide-activated surface were examined electrochemically at 80 ° C. in 50% by weight H 2 SO 4 .
• the cathodic current density of the hydrogen evolution was recorded as a measure of the activity of the electrode.
• a current density of 210 mA / cm 2 was achieved under the test conditions mentioned.
• the electrode was operated under the aforementioned conditions for 1000 hours and remained practically without weight loss.
• a carrier made of electrographite was coated with a 20% (w / w) solution of phenolic resin Spread binder in methanol. The resulting very thin binder layer was then coated uniformly with tungsten oxide powder (170 mg / cm 2 ).
• the WC1 6 was first heated to about 240 ° C in a stationary argon / hydrogen atmosphere and then the graphite disc was quickly inductively heated to about 650 ° C.
• the gas flow was then started from bottom to top and an argon / hydrogen gas mixture (4% hydrogen content) was passed through the quartz tube at a rate of 10 l / min.
• the exhaust gases were neutralized with NaOH in a wash bottle downstream of the quartz tube.
• the WC1 6 vapor with the H 2 of the carrier gas on the surface of the graphite disc was reduced to tungsten metal and the surface was coated.
• a layer thickness of about 10 ⁇ m was generated in two minutes, regardless of the roughness of the surface of the graphite disc.
• a coating time of about 3 minutes a layer thickness of 15 1 1 m was achieved.

Landscapes

• 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)
• Carbon And Carbon Compounds (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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• 1982
  • 1982-06-15 DE DE3222436A patent/DE3222436C2/de not_active Expired
• 1983
  • 1983-06-08 EP EP83105608A patent/EP0096837B1/de not_active Expired
  • 1983-06-08 AT AT83105608T patent/ATE29155T1/de not_active IP Right Cessation
  • 1983-06-14 CA CA000430334A patent/CA1203722A/en not_active Expired
  • 1983-06-15 JP JP58106009A patent/JPS596388A/ja active Pending
• 1985
  • 1985-06-05 US US06/741,637 patent/US4702784A/en not_active Expired - Fee Related

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