DE2905180A1 - ELECTRODE FOR WATER ELECTROLYSIS - Google Patents

Abstract

Electrode for the electrolysis of water, consisting of an armouring metal gauze with a powder, pressed on and sintered, consisting of a graphite/polytetrafluoroethylene mixture with an impregnation serving as catalyst and containing platinum metal oxides.

Description

Electrode for water electrolysis

The invention is based on an electrode according to the preamble of the claim 1.

Electrodes as well as processes for their manufacture are mainly of the technology developed for fuel cells (e.g. Carl Berger, Handbook of Fuel Cell Technology pp. 401-406, Prentice Hall 1968; H.A. Liebhafsky and E.J.

Cairns, Fuel Cells and Fuel Batteries, pp. 289-294, John Wiley & Sons, 1968). The requirement for precisely defined reaction zones is complex Construction and special treatment processes for such fuel cell electrodes.

For water decomposition, the electrodes described above are in Their structure is too complicated and their production methods too complex and expensive. This is particularly true with regard to manufacturing methods for large industrial plants for the economical production of hydrogen.

Electrodes for water decomposition cells have already been proposed (e.g. U.S. Patent 4,039,409). To accelerate the electrochemical reactions they are usually doped with catalysts.

The electrodes described leave both with regard to their mechanical and chemical properties leave much to be desired.

The same applies to the catalysts used.

The invention is based on the object of an electrode for water electrolysis indicate which with good mechanical and chemical stability, high electrical conductivity and good permeability to water and gas has a long service life as well as the property has the ability to catalytically accelerate the water decomposition reaction in an optimal way, and a method for their production.

According to the invention, this object is achieved by the features of the claim 1 and claim 3 solved.

It has been shown that it is advantageous as an electrode material to use a porous, permeable composite material based on graphite and as Catalyst to use an impregnation consisting of platinum metal oxides.

Above all, ruthenium oxide and iridium oxide, alone, in mixtures with one another or with one further platinum metal oxide each proven.

The invention is explained in more detail using an exemplary embodiment.

Embodiment: 12.75 g (corresponding to 85% by weight) graphite powder grain sizes from 0 to 0.1 mm were mixed with 2.25 g (corresponding to 15% by weight) of polytetrafluoroethylene powder (e.g. "Teflon" 702 N from Du Pont de Nemours) in a ball mill under toluene while Ground for 6 h. The suspension of graphite and tetrafluoroethylene particles thus obtained in toluene was dried to a solid mass in a drying cabinet for 3 h.

Then the dried mass was broken, ground and again sifted through a sieve with round holes 0.25 mm in diameter.

A tissue was made into a cylindrical flat die Tantalum wire (Wire diameter 0.09 mm; 1024 meshes per cm2) inserted and with the aforementioned Powder mixture up to max.

covered approx. 2 mm. It is due to an even distribution of the powder to pay attention. The powder was then put under pressure by means of a press of 140 bar for 50 sec at room temperature, with a compact, with the metal mesh firmly connected disc was obtained.

Finally, the pressed disc was under an argon atmosphere according to The following program is subjected to a sintering process: Heating: 20 to 375 ° C at 2 ° C / min Hold: 3750 ° C for 1Y2 h Cooling: 375 to 20 ° C at 2 ° C / min Die Disc produced in this way was then immersed in an alcoholic one for 10 seconds Solution dipped, which 12 rel. Wt .-% ruthenium chloride (RuCl3) and 88 rel. Wt% Contained iridium chloride (IrCl3). After draining for 1 minute, the disc became oxidized for 10 min at a temperature of 3750C in air. This process of Dipping and oxidizing were repeated a total of 5 times. In the end, the Disk oxidized again for 4 h at a temperature of 37,500 in air.

The invention is not restricted to the exemplary embodiment. That Metal mesh used for reinforcement can be made from wire with a diameter of 0.05 to 0.2 mm be constructed. Furthermore, the powder mixture can be within the limits of 60 to 95% by weight graphi @ and 5 to 40 wt .-% tetrafluoroethylene @ariiert who @@@. burch change @ mixing ratio customized will. Sintering and oxidizing can take place at 340 to 4000C. The mixing ratio for the catalyst, 10 to 70% by weight of RuO2 and 90 to 30% by weight [I1> O2 can be.

The method can be used in a particularly advantageous manner during production of electrodes for high-performance water decomposition apparatus for the production of hydrogen use.

Thanks to its simplicity and economy, it is excellently suited for the production of serial, large-area electrodes for large-scale industrial plants.

The electrodes produced in this way are characterized by high chemical resistance and a favorable decomposition voltage.

Claims (3)

P a t e n t a n s p r ü c h e 1. Electrode for water electrolysis, on the basis of a composite material, characterized in that it consists of a reinforcing metal mesh (net) with pressed and sintered powder from a Graphite / tetrafluoroethylene mixture with an impregnation made from a mixture of There is platinum metal oxides as a catalyst. 2. Electrode according to claim 1, characterized in that the catalyst from a mixture of 10% by weight to 70% by weight Ru02 and 90% by weight to 30% by weight IrO2 exists. 3. A method for producing an electrode according to claim 1, characterized marked that on a fine-meshed fabric (net) made of metal wires one out Graphite and tetrafluoroethylene existing powder mixture pressed, the pellet sintered under an argon atmosphere at a temperature of 340 to 4000C and then dipped in an alcoholic solution of platinum metal chloriaen, dried and with a temperature of 340 to 4000C is oxidized in air.