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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

• metal suicide the metal being one of Pt, Pd, Ir, Eh, Cr, Co, Ni, Ru, Ti, V, Zr, Nb, Hf, Ta and V.
• the invention consists in a catalytically active anode comprising at its surface an at least semiconductive water- insoluble metal silicate.
• the anode is made by dispersing the metal silicate in a non-conductive binder, and applying the dispersion to a conductive substrate.
• the silicate is reduced sufficiently to improve its electrical conductivity.
• the binder is hydrophobic, for example polytetrafluoroethylene, but the dispersion as a whole should not be excessively hydrophobic.
• the metal silicate may have a spinel or olivine structure, both of which are reported to have been synthesised.
• the olivine is convenient. It is preferably cobalt orthosilicate (Co SiO. )
• the substrate is preferably in the form of an electrically conductive sheet (foraminate or otherwise), slit metal or mesh, preferably of nickel. If of iron, the substrate preferably contains under 1.5% (more preferably under -0.3%) of carbon.
• the weight ratio of binder to metal silicate is from l-3 > more preferably from 1:5 > to 1:20 and the dispersion is preferably applied to give a coating of from 5 m 9 to 50mg of the metal silicate per square centimetre of the substrate.
• the invention extends to a catalytically active anode made as set forth above, and to an electrolytic cell including a cathode and such an anode. The invention further extends to a method of electrolysis using this cell, especially of aqueous solutions, e.g. aqueous alkali. The invention will now be described by way of example. MAKING AN ANODE
• transition metal silicates include precipitation from sodium silicate solution, and gelling using tetraethyl orthosilicate, it was found that solid state sintering gave the best results.
• Cobalt nitrate was ground with a stoichiometric amount of silica with a pestle and mortar.
• the mixture of cobalt nitrate and silica was transferred to an evaporating basin, gently heated to allow the nitrate to dissolve in its own water of crystallis- ation and then vigorously heated by bunsen burner to dry and decompose the nitrate to its oxide.
• the resultant powder was o , ground again and then heated at 1000 C for 24 hours, to promote the reaction 2Co0 + SiO —>Co SiO..
• the product was ground again, washed with 5M KOH and then with concentrated HN0 to remove any unreacted silica or cobalt oxide, then washed with water, dried, ground again and put in a dry sample bottle. That the product was cobalt silicate (olivine structure) was confirmed by X-ray powder diffraction.
• the electrode so formed was dried and cured for 1 hour at 300 C. Initially a cobalt silicate: polytetrafluoroethylene ratio of 10:3 was used, but as this proved to be too hydrophobic, the present electrode used a ratio of 10:1, giving a cobalt silicate loading of 21 mg/ /cm2.
• ELECTROLYSIS An aqueous solution of 5 KOH was electolysed at 40 C in a cell having a nickel mesh cathode and the above anode. (The anode had previously been anodised for 2 hours at 2V vs the dynamic hydrogen electrode, to activate it, possibly by forming higher oxides on its surface and hydr ⁇ phiusing it. ) The current was held at 1 amp. Oxygen was evolved at the anode, at which the voltage vs. the dynamic hydrogen electrode rose from an initial' 1700mV, neglecting early fluctuations, to 174 ⁇ mV after 40 days, possibly due to formation of a poorly conductive nickel oxide at the interface between screen and cobalt silicate. An identical cell (but with cobalt silicate loading of l4 mg/cm ) was run at 25 C, 50 C and 70 C at up to 2-g-A/cm . At
• iron silicate might be corroding at up to 6 mg/cm /week at

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)
• Silicates, Zeolites, And Molecular Sieves (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (5)

• 1980
  • 1980-04-10 JP JP50073480A patent/JPS56500377A/ja active Pending
  • 1980-04-10 GB GB8011904A patent/GB2048945A/en not_active Withdrawn
  • 1980-04-10 WO PCT/GB1980/000063 patent/WO1980002163A1/en not_active Application Discontinuation
  • 1980-10-23 EP EP80900603A patent/EP0035017A1/de not_active Withdrawn

Patent Citations (5)

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