DE2304380A1 - ELECTRODES WITH A DELAFOSSITE SURFACE - Google Patents

Description

Patent attorney H / D (521) 5088 ■

Dr. Michael.Hann January 30, 1973 63 Giessen ■ "'"

Ludwigstrasse 67

PPG Industries, Inc., Pittsburgh, Pennsylvania, USA

ELECTRODES WITH A DELAFOSSITE SURFACE

Priority: February 1, 1972 / USA / Serial No. "222,501

For numerous electrochemical reactions, such as the electrolysis of brines, hydrochloric acid and Sulfates, electroplating, electrolytic Extraction, electrolytic production of metal powders, electrolytic cleaning, electrolytic pickling and electrochemical generation of electrical Power is required for non-consumable anodes. Graphite anodes have heretofore been used for such purposes, particularly for the electrolysis of brines and the electrolysis of hydrochloric acid. In

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More recently, electrodes have been developed for such processes which have a suitable electrically conductive base or substrate and an electrocatalytic one Have a coating thereon, Typically; such electrocatalytic coatings form the Platinum group metals such as platinum, osmium, iridium, ruthenium, palladium and rhodium and theirs Oxides.

Has it been found now _? that a particularly suitable electrode for carrying out electrochemical reactions is obtained when a delafossite surface is applied to a suitable electrically conductive substrate or base. Belafossite are oxides, of high electrical conductivity from the stoichiometric formula

where in this formula A platinum, palladium, silver or Copper is. B is typically chromium »iron, cobalt, rhodium, aluminum, gadolinium, scandium, indium, thallium». Lead, ruthenium and the lanthanide *. B can also be any metal ion that has a constant +3 formal reality and with the DeIafossit structure compatible. is. "

Delafossite also close non-stoichiometric

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bindings that match the ^! stoichimetric deIafossites are isostructural. A suitable electrically conductive substrate is an electrically conductive substrate that is substantially unaffected by the electrolyte.

As already stated, the electrodes according to the invention have a delafossite surface on an electrically conductive substrate. The Delafossite have a unique crystal structure, which _{is similar to that of the natural mineral delafossite (CuFeO 2} ), whereby the small differences in the crystal structure are due to the slightly different radii of the ions,

Delafossite results in particularly satisfactory electrode materials, because they have a high electrical conductivity, which is comparable to that of metals, with a high resistance to chemical attack, comparable to that of refractory metal oxides, unite. For example, this is the electrical conductivity (bulk electrical conductivity) of compressed powders of platinum and palladium delafossite in the size range from about 10 to 10 (ohm-centimeters). Such platinum and palladium delafosites are additional also resistant to attack by strong acids, such as Aqua regia at 70 C and also against nasal chlorine.

The Delafossite are a family of oxides made up of two or more metals, the oxide being a rhomboetic one

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Has a structure with a hexagonal crystal habit similar to _{that of the mineral delafossite CuFeO 2.} Delafossite can also be characterized by the fact that its crystals have a space group of 166, a Shoenflies group of D-,> a full one

Standard symbol of R «- (R, - 3, two over m) and an international symbol of R * (R, slash 3, m). Such oxides and their crystallography are particularly in the articles by WJ * Croft et al., Acta Crystallogr., Volume 17, page 313 (1964) j W. Gessner, Z. Anorg, AlIg. Chem., Vol. 35 * 2, page 145 (1966); H. Hahn et al. Z. Anorg. AlIg. Chem., Vol. 279, p. 281 (1955); W. Dannhauser et al, J. Amer. Chem. Soc, Vol. 77, p. S96 (1955); H. Wiedersich et. Al, Mineral Mag., Volume 36, page 643 (1968); A. Krause et al, Z. Anorg. AlIg. Chem., Vol. 228, p. 253 (1936); A-. Pabst, Amer. Mineral, Vol. 31, p. 539 (1946) and AH Muir et al, J. Phys. Chem. Solids ·, Volume 28, page 65; RD Shannon et al, Chemistry of Noble Metal Oxides. I. Synthesis and Properties of ABp ₂ Delafossite Compounds, Inorganic Chemistry, Volume 10, page 713 (1971); CI Prewitt et al, Chemistry of Noble Metal Oxides. II. ^{Crystal Structures i:} öf PtCoO ₂ , PdCoO ₂ , CuFeO ₂ and AgFeO ₂ , Inorganic Chemistry, Volume 10, page 719 (1971); DB Rogers et al, Chemistry of Noble Metal Oxides. III. Electrical Transport Properties and Crystal Chemistry of ABO ₂ Compound with the Delafossita Structure, Inorganic Chemistry, Volume 10, page 723 (1971); U.S. Patent 3,498,931, U.S. Patent 3,514,414, and U.S. Patent 3,414,371. .

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As a general rule, the delafossite are further characterized by the fact that the A ions corresponding to the copper in the mineral delafossite have an effective ionic radius corresponding to two oxygen coordinations, that is, the effective ionic radii im. Range from 0.45 to 0.68 Angstroms. In the case of the particularly good electrically conductive platinum and palladium Delafossite, the A ions have effective ionic radii in the range from 0.58 to 0.61 Angstroms. The B ions, which correspond to the iron ions in the mineral delafossite, have an ionic radius that corresponds to an octahedral coordination, that is, the effective atomic radii are in the range of about 0.50 to about 1.05 Angstrom units. includes the equivalent term "crystal ionic radius".

Muir et al _t , op. cit., reports that the mineral delafossite (CuFeO ”) is rhombohedral with hexagonal planes. The structure consists of stacked hexagonal layers. The iron ions have an octahedral coordination, whereas the copper ions have a -

. have linear double oxygen coordination. the

■ Oxygen ions are three of a tetraether Surrounded by iron ions and a copper ion, three formula weights von CuFeO «result in an EJementaraelle des Minerals delafossite.

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■ The term "unit cell" is understood to mean any parallel opipiped, which is the smallest repeating unit that contains all the essential features for identifying the crystal. The unit cell determines the symmetry of the system to which a crystal belongs. The unit cell is determined by the length of the edges and the angles they enclose. The edges of a unit cell are called the lattice constant (unit translations in the pattern). If you start from any starting point in the grid and travel a distance that corresponds to and parallel to the edge of a cell, or some combination of such movements, you arrive at a point where all of the surrounding structure has the same shape and orientation has like the starting point. Because of the arbitrary nature of the definition of the unit cell, any ion can be entirely in one cell, or alternatively, it can split into two, four, or eight unit cells. In addition, the neighbor of any ion to the

■ same unit cell or to the neighboring unit cell belong..

-. C. T. Prewitt, R.D. Shannon and D.B. Rogers op. Cit. '· report that. the synthetic platinum · ?, cobalt delafossite (PtCoO-) the crystallographic structure of the Delafo * ssit-

• Type owns. For use in the electrodes according to of the invention are both stoichiometric and

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the non-stoichiometric platinum-cobalt delafosites especially suitable.

The platinum-cobalt delafossite is also reported to have a crystal structure which is similar to _{that of the natural mineral delafossite (CuFeO 2).} Each oxygen ion is coordinated by four tetrahedrisch Kationstn _$ wherein a platinum ion is located at a corner of the Tetra Heder and each represents a cobalt ion to the other corners of the Tetra Heder. Di-e. ^. Atin ions are linearly coordinated by two oxygen ions. The cobalt ions are octahedral coordinated by oxygen ions. The platinum ions are in a hexagonal bipyramidal coordination with oxygen ions at the apexes and platinum ions on the six äquatorialen.Stellungen, whereby platinum-platinum interaction is possible.

The Delafossite crystal structure and the relationships between the platinum-cobalt-delafossite, the palladium-delafossite and the mineral-delafossite (CuFeO ₉ ) are explained in more detail by referring to the figures. The figures show the following:

FIG. I is a graphical representation of the X-ray diffraction values found in the literature for the mineral delafossite (CuFeO ₉ ) presented in Table I. FIG.

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FIG. II is a graphic representation of the X-ray diffraction _{values given in the literature for platinum-cobalt-delafossite (PtCoO 9} ) and summarized in Table 2. '.

Figure III is a graph of the X-ray diffraction _{values reported in the literature for palladium-cobalt delafossite oxide (PdCoO 9} ) and summarized in Table 3 '.

IV is a graphic representation of the X-ray diffraction values given in the literature for palladium-chromium-delafossite (PdCrO ₉ ) and compiled in Table 4.

Fig. V is a graph of the X-ray diffraction _{values reported in the literature for palladium-rhodium-delafossite (PdRhO 9} ) and summarized in Table-5.

Figures IV, which are the values given in the literature and summarized in Tables 1 to 5 reproduce are to the same scale as the abscissa plotted and have a common ordinate. The abscissa gives I / Io, the specified ratio of the Intensity of the reflected beam to the incident beam. The ordinate cL gives the specified distance between the levels, calculated from Bragg's equation, which will be explained in more detail later. ■. ■

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Fig. I was based on the values of Salier and Thompson, - Phys. Rev. Volume 44, page 644 (1935) reported in A.S.T.M. X-Ray Powder Diffraction File 12-752 and in Ta'belle 1 reproduced, created. Figures II, III IV and V were based on the values of R. D. Shannon et al Inorganic Chemistry, Volume 10, pages 713, 717, op cit. and reproduced here in Tables 2, 3, 4 and 5 created.

Figure 6 is an x-ray diffraction of palladium-cobalt. Delafossite (PdCoO «) made for use as an electrode material in Example 1.

Figure VII is an X-ray diffraction of platinum-cobalt delafossite (Pt "Ca o ^?)" For use as a Electrode material in Example 2 was prepared.

Figure VIII is an X-ray diffraction of platinum-cobalt delafossite (Pt _{n Q} Co _{n 7} ,, 0 _o ) suitable for use as a. Electrode material in Example 3 was prepared.

The crystallographic units of platinum and palladium delafossite give a unique family of X-ray diffractions identified by peaks at "d" spacings from 5.9072 to .6.0229 angstroms, 2.9728 to 3.0137 angstroms, a doublet with a spacing between peaks of • 0.06-0.07 Angstroms with the first peak at 2.4260 to 2.3609 angstroms and the second peak of the doublet

»At 2.5884 to 2.5141 angstroms, a peak at 2.1460

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- ίο -

to 2.2643 angstroms and another peak at 1.6483 to 1.7104 Angstroms are characterized. For the mineral delafo'ssite only values of 2 θ degrees are available in excess, known to be about 30, i.e. for d spacings of less than 2.86 Angstroms. The mineral delafossite (CuFeO-) has the doublet at 2.58 and .2.50.8 Angstroms and on the peaks at 2.238 and 1.658 Angstrom. The differences in the results of the .-- ' X-ray diffraction between the individual members of the delafossite family is due to the slightly different Cation radii 'traced back'.

For the mineral delafossite (CuFeO ") are in table and in FIG. I the values of the X-ray diffraction are given or shown graphically. The results of the X-ray diffraction on delafossites of platinum group metals are shown in Tables 2 through 5 and den'graphical representations of the figures H-V reproduced. It is pointed out once again that the Values for Tables 1 to 5 and the graphic representations I - V are taken from the literature. These figures are idealized and show family relationships and trends. From Figures I to V is no keynote (background noise) and no randomness (randomness) that normally occur in x-ray examinations.

When observing and recording X-ray examinations become samples of the delafossit powder

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230A380

- li -

Subjected to x-rays from a copper target. The methods for such an investigation are in the chapter of the book by Klug and Alexander, X-Ray Diffraction Procedures, John X ¹ JiIey & Sons, Inc., New York (1954), pages 235-318, especially pages 270-318 and at Newfield, X-Ray Diffraction Methods, 'John Wiley & Sons, Inc., New York (1966) pp. 177,207.

As Klug and Alexander and also Newfield indicate, will X-rays at a wavelength of 1.5405 Angstrom units are caused to focus on a sample of the Apply powder. The X-rays are diffracted by the sample. The diffracted x-rays are Particularly intense at certain angles (θ), which leads to the formation of peaks in the leaves of the diffractometer or from lines in diffraction photographs. These high intensity peaks are caused by x-rays coming from parallel planes in the Crystal "are reflected", whereby it comes to an understanding. The wavelength of the X-rays, the distance between the planes in the crystal and the angle (θ) are, according to Bragg's equation, in the following relationship: >

2d sin θ = ni.

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In. In this equation, d is the distance between the planes of the crystal, η is an integer, -4 »is is the wavelength of the X-rays and θ is both the simple angle of the X-rays and the Reflection angle of the x-ray beams.

Diffraction values are used in the X-ray examination obtained with the help of a diffractometer, the one has a direct reading in 2 θ. The value (180 minus 2 θ) is the angle between the incident ray and the reflected beam. ·

Table I shows the diffraction values of the X-ray analysis for the mineral delafossite (CuFeO-). Particularly noteworthy is the doublet at 2.58 and 2.508 Angstroms and the peaks at 2.238 and 1.658 Angstroms.

For the diffraction values of the X-ray examination of powdery delafossites of metals of the platinum group have some similarities. First is a particularly strong peak at a value of "d" about 5.9072 to 6.0229 to be observed. Then it can be seen in Figures II to V that a strong doublet occurs, the peaks from each other through, about 0.06 up to about 0.07 angstroms are separated with larger ones Separation of the peaks and larger differences in the intensities in delafossites of the platinum group with larger unit cells and closely spaced peaks and of almost the same intensity for Delafos site the platinum group with a more compact unit cell.

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'.' ■ '■ - 13 -

* For the platinum-cobalt delafossite (PtCoO ₂ ) the peaks of the doublet are at 2.4260 and 2.3609 Angstroms. For palladium-cobalt delafossite (PdCoO ₂ ), the two peaks of the doublet are around 2.4272 and 2.3616 angstroms, whereas for palladium-chromium delafossite the two peaks are 2.5065 and 2.4375 angstroms and for palladium -Rhodium delafossite (PdRhO ₂ ) the two peaks are around 2.5884 and 2.5141 Angstroms. Also noteworthy is the increasing difference in intensity between the two members of the doublet as it progresses from the Delafossites with the more compact to those with the less compact unit cells. The first peak of the doublet corresponds to a distance between the planes of about 2.42 Angstroms (PtCoO ₂ ) to about 2.58 Angstroms (PdRhO «), while the second peak corresponds to a distance between the planes of about 2.36 Angstroms (PtCcO ₂ ) until about

. 2, .51 Angstrom (PdRhO ₀ ).

e.

There is also a strong peak at about 2.1460 to about 2.2644 Angstroms. ¹ This peak is around 2.14 Angstroms for the more compact unit cell of platinum-cobalt-delafossite, at a distance of 2 * 1448 angstroms for palladium-cobalt-delafossite '(PdCoO ₂ ), at a distance of 2.2088 for palladium -Chrome-delafossite (PdCrO ₂ ) and at 2.26 Angstroms for the slightly less compact unit cell of platinum-rhodium-delafossite ()

Of interest is also a weak doublet in the area of 2.0185 and 1.9814 angstroms with intensities of

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0.30 or 0.40 for the more compact platinum-cobalt delafossite. As the unit cell increases in size, this particular doublet becomes more spread out and less intense. For the only slightly less compact palladium-cobalt delafossite, the doublet occurs at "d" spacings of 2.0165 and 1.9715, respectively Angstrom, the weaker of the two members has an intensity of about 0.15. For the palladium-chromium delafossite (PdCrO ₂ ), the weaker of the two members of the doublet has an intensity of about 0.02 and the doublet occurs at 2 , 0753 and 2.0089 Angstroms, respectively. For the even less compact palladium-rhodium-delafossite (PdRhO ₂ ), the terms of the doublet occur at 2.1198 and 2.0088 Angstroms, both of which have intensities of less than Have 0.05.

For the more compact crystals of the platinum group delafossite there is a peak at around 1.76 to 1.81 Angstroms. For platinum-cobalt deiafossite (PtCoO-), this peak is around 1.7655 and has an intensity of around "0.30." 7616 angstroms is observed and has an intensity of about 0.30. For the slightly less compact palladium-chromium delafossite (PdCrO ₂ ), the peak occurs at about 1.8084 angstroms and has an intensity of less than 0.05.

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Table 1

X-ray examination of a powder made from copper-iron-delafossite (CuFeO ₂ )

2.86 35

2.58. .18

2.508 100

2.238 . 25th

2.083.6

1.902 * ".. ■ '. 9

1.658 ■. 35

1.512 x 40

. , 1.434. ■. /, 20

1.336 18

1.295. 12th

1.253 10

1.184. ■ 6

1.119 ^: '10

1.108 6

1,040 18

0.984 '16

0.965 10

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Table 2 ''

X-ray examination of platinum-cobalt-delafossite (PtGoO ₀ ) _:

I / Io

5.9450 90

2.9728 100

2.4260 '70

.2,3609 90

2.1460 x 70

- 2.0185 .. '. · ■ 30

1.9814 40 '.

1.7655 ^: 30

1.6483 60

1.4856 x 20

1.4415 _: 40

1.4135 30

'1.3751 · "15

1.3513. 10

1.2764. '' 30

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Table 3

X-ray examination of a powder of palladium-cobalt-delafossite (PdCoO ₀ ).

I / Io

2.9072 45

2.9559.90

2.4272 80

2.3616 100

2.1448 85 2.0165 .15

1.9713 : \. -50

1.7616 30

1.6445. . 85

1.4788. . . . -35

1.4373 '70

1.4149 ■ 65

1.3762 .15

1.3474. 15th

1.2762 65

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- is -

Table 4

X-ray examination of a powder of palladium- 'CÜtrom-belafossit: (PdCrO ₀ )

I / Io

6.0229 20 3.0137 65

2.5065. 30 2.4375 '100

2.2088. '. 40

2.0753. 2 2.0089 · '. _ "· -10

1.8084 x 5

1.6864 '30

1.5074. 5 1.4722; 15th

1.4614 '20

1.3791 2

1.3151 '■ 15

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Table 5

X-ray examination of palladium-rhodium-delafossite (PdRhO _n )

I / Io

6.0209 "3.0130 2.5884 2.5141 2.2644 2.1198 2.0088 1.7104 1.5071 1.4874 1.5106 1.3503 1.2945

'

90

10

100

95

85 15 70 85 80 60

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Finally, with regard to the X-ray examinations, a peak of medium intensity at about 1.6453 to about 1.7104 Angstroms should be pointed out. This peak has an intensity of about 0.30 for palladium-chromium-delafossite and of about 0.85 for palladiura-cobalt-delafossite (PdCoO ₀ )

and palladium-rhodium delafossite (PdRhO ₂ ). It is at. "• 1.6453 angstroms for platinum-cobalt delafossite (PtCoO ₇ ), at-about 1.6445 angstroms for palladium-cobalt delafossite, at about 1.6854 angstroms for palladium-chromium delafossite and at about 1.7104 angstroms for palladium-rhodium-delafossite .-- '

The chemical nature of the Delafossite will now be discussed again. The Delafossite are oxides or oxy compounds of two or more metals and correspond to the following general formula.

SUBSCRIPTION ₂ . .

When considering this formula, it must be taken into account that also non-stoichiometric connections, the imperfections in their structures can be used in accordance with the invention. Such non-stoichiometric Delafossite with errors in their structure have the formula

^A x ^B y ^Ö 2> ^where either χ or y or both are less than 1 and can be, for example, about 0.070 to 1.00. Such delafosites can also be used with good effect in the invention.

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The metal ion represented by A in the formula can be any monovalent metal ion having an effective ionic radius of from about 0.45 Angstrom units to about 0.68 Angstrom units. Such monovalent ions are copper (Cu +) 'with an effective ionic radius of 0.47 angstroms, palladium (Pd ⁺ ) with an effective ionic radius of about 0.59 angstroms, platinum (Pt ⁺ ) with an effective ionic radius of about 0.60 angstroms and silver (Ag ⁺ ) with an * effective ionic radius of about 0.67 Angstroms. Two or more such monovalent cations can also exist in the same delafossite crystal. The preferred delafosites are those in which the monovalent cation has an effective ionic radius of about 0.58 to 0.61 Angstroms, such as palladium (+1) and platinum ( +1). '

The cation represented by B in the formula is most often chromium, iron, cobalt, rhodium, aluminum, Gadolinium, scandium, indium, thallium, lead, ruthenium and the lanthanides (La, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu and Y). B is typically a trivalent cation with an effective ionic radius from about 0.50 angstroms to about 1.05 angstroms and most of the time about 0.50 angstroms to about 0.89 angstroms. The preferred trivalent cations are those with one effective = ion radius from about 0.50 to about 0.70 Angstroms, such as cobalt (Co +) with an effective ionic radius

3 of about 0.52 Angstroms, Chromium (Cr +) with an effective

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ion radius of 0.62 Angstrom and rhodium (Rh +) with an effective ionic radius of about 0.70 angstroms. The! Cation B can, however, be any metal ion '· if it has a constant +3 valence and an effective ionic radius of 0.50 to 1.05 angstroms. Such metal ions include Group III A metals such as scandium, yttrium and the lanthanides; titanium from group IV A; Vanadium from group VA; Group VI A metals such as chromium, molybdenum, and tungsten; Iron, cobalt and nickel; Ruthenium, rhodium and palladium; Metals from group III B such as aluminum, Adoiiniurn, Indium, and Thallium; Tin and lead from group IVB and antimony and bismuth from group V B.

The platinum delafosites include the stoichiometric oxygen compounds of platinum and cobalt with the Delafossite structure (PtCoO ₉ ) and also the non-stoichiometric oxygen compounds of platinum and cobalt with the Delafossite structure. Such non-stoichiometric Delafossite have the formula

"· ■ Pt _1. Co _n 09

1-fn 1-n ^z

2 3 ■ ·

where η has a value between 0.5 and 0.8.

As additional components in the Deia fossites, in particular in the platinum delafossites, small amounts of other metal ions occur, such as ions of Scandium, titanium, vanadium, chromium, manganese, iron, cobalt or nickel. If so, the delafossit has

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- 23 following formula ■

where χ is about 0.70 to 1.00, "y is about 0.70 to 1.0.0, and ζ is less than 0.11. Typically, ζ is about 0.004 to about 0.11, and. M i $ t Sc , Ti, V, Cr, Mn, Fe, Co or Ni.

The platinum-cobalt-delafossite, which is used as electrodes * Surface is particularly suitable according to this invention has the formula

14η 1-n

in the η a value of about 0.50 to ettra. Has 0.8,

Palladium delafosites, which are particularly suitable as electrode surfaces, correspond to the formula

PdMO ₂

where M is cobalt, chromium, rhodium, ruthenium, lead or a lanthanide (including yttrium) or a mixture thereof. Examples of very particularly suitable palladium delafossites are palladium-cobalt delafossite (PdCoO ₉ ), palladium-chromium delafossite

3098327109b

(PdCrO ₉ ), palladium-rhodium-delafossite (PdRhO ₉ ), the palladium-delafossite of chromium and rhodium (PdCrO ₉ / PdRhO ₉ ), the palladium-delafossite of cobalt and rhodium (PdCoO ₉ / PdRhO ₉ ), the palladium Delafossite from ruthenium (PdRuO ₉ ), the palladium delafossite from lead (PdPbO ₉ ) and the palladium delafossite from lanthanides.

The silver and copper delafossite have a higher specific electrical resistance or a lower electrical conductivity than the platinum and palladium delafossite. The Silver Delafossite have the formula

AgMO ₂

in · the M cobalt, gadolinium, scandium, "indium and Is thallium. Compressed powder of silver delafossites have an electrical conductivity (bulkelectrical conductivity) of about 10 to about 10 (Ohm centimeter)

The copper delafossite, such as copper-iron delafossite (CuFeO ₉ ), natural delafossite (CuFeO ₉ ), copper-aluminum delafossite (CuAIo ₉ ) and copper-cobalt delafossite (CuCoO ₉ ) are also used for the production of electrode surfaces suitable according to the invention. Although the copper and silver delafossite have a higher resistivity than the platinum and palladium

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Delafossite, they can be used as coatings for the electrodes, e.g. in one thickness of about 0.00254 microns (100 micro inches).

The electrodes according to the invention are in most cases an electrically conductive substrate or Base link with a 'delafossite surface One such embodiment of the invention is the delafossite in direct contact with the base member and the electrolyte.

In addition, the silver and copper delafossite and the platinum and palladium delafossite can also be used to create an electrically conductive coating on the electrically conductive base or substrate, the delafossite surface being a has a further outer coating of a suitable electrocatalytic material, such as a spinel, such as this, for example, in the previous US application Serial No. 106,840 dated Jan. 15, 1971. Instead of the spinel, a perovskite or a perovskite bronze can also be used, such as this e.g. in the previous US application serial no. 121,693 dated March 8, 1971. Alternatively, as outer coating over the delafossit coating other electrocatalytic materials can be used, such as Ruthenates, ruthenides, rhodites, rhodates and the like.

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■ - 26 -

It is also possible between the delafossite surface and the electrolyte a porous layer of a substantially non-reactive material such as Titanium dioxide, vanadium oxide, tantalum oxide, uranium oxide, To arrange niobium oxide, hafnium oxide, zirconium oxide, silicon dioxide and the like. Such external Coatings, the mechanical resistance of the Delafossit surface is improved even further. aside from that the porous outer coatings create a large surface area for catalytic reactions at the electrode formed products oc * - »r of the starting materials. Preferred these outer oxide coatings are formed "in situ", as this will be explained in more detail later.

Different · ■ substances can be mixed with the Delafossit materials. For example, one can use conductive

. Materials such as perovskite, perovskite bronzes, platinum group metals, platinum group oxides, and mixed Carbides, nitrides, oxides and borides, which are resistant to the electrolyte, in a mixture with the DeIafossit use. Such materials may be present for better conductivity or reactivity to surrender. Alternative materials are

. the oxides of titanium, tantalum, niobium, hafnium, tungsten, aluminum, vanadium, silicon and other film-forming Metals. These additives also improve the shelf life of the Delafossite. To the Delafossite To bind the substrate, any oxides can be used that are "in situ" during the manufacture of the upper

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surface are formed and which are essentially opposite are not reactive to the electrolyte.

The electrodes with a Delafossit coating according to the invention also include an electrode which consists entirely of delafossite, but such electrodes are usually used for economic reasons Not used. Electrodes according to the invention, dia a Delafossit surface or coating, are therefore preferred on a suitable electrically conductive substrate. The delafossite surface can be only 8 angstroms thick. For practical reasons, however, a Delafossit surface is used that has at least one thickness or Thickness of 1.52 microns (micro inches) with thicknesses of at least 3.81 to 5.08 microns (150 to 200 micro inches) are preferred. However, the delafossite surfaces need not be thicker than about 6.35 to 7.62 microns (250 to 300 * micro inches). Although a delafossite * Coating thicker than 7.62 microns, e.g., 20.32 microns (800 micro inches), may be used any adverse effects can be observed, but there is no further benefit from the use so thick coatings achieved.

Under a "suitable electrically conductive substrate or base "becomes a substrate with an electrical resistivity within the economic Limits meant, with this substrate also being essentially non-reactive with the electrolyte

i ·. , 1 Ϊ.

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and the products of electrolysis. For the electrolysis of brines, for example, a suitable Electrically conductive substrate does not react with solutions of sodium hydroxide or sodium chloride and are also not attacked by wetting chlorine.

Suitable electrically conductive substrates are, for example, rectifier valve metals. The rectifier metals are those metals that form an oxide film under anodic conditions. To the rectifier metals include e.g. titanium, tantalum, niobium, hafnium, tungsten, aluminum, zirconium, vanadium and their alloys. In most cases are for economic reasons Titanium or xitan alloys are used as the substrate for the base member of the electrodes in this invention. It however, other materials such as graphite or carbon can also be used. You can also use a laminate one Judge details with a less expensive metal, like iron or steel with a delafossite coating the rectifier metal.

Alternatively, titanium hydride or another electrically conductive, anodically stable hydride can be used as the electrically conductive one Substrate can be used in the electrode of this invention. Such a hydride can be the only component of the substrate or it can rest on the other material in the form of a flat structure.

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230A380

Alternatively, the hydride can be a hydride surface of a metal such as a titanium substrate with a titanium hydride layer between the metallic substrate and the delafossite surface.

A layer of an electrically conductive material, which has a better conductivity than the delafossite and is resistant to the electrolyte, can also be arranged between the delafossite and the substrate. Such an intermediate layer can be formed from a metal of the platinum group, such as, for example, from metallic ruthen, rhodium, palladium, osmium, iridium, platinum or their alloys. Particularly suitable alloys for this purpose are, for example, platinum-palladium alloys, in particular those containing about 3 to about 15% by weight of platinum, and also platinum-iridium alloys, especially those containing about 2 to about 50% by weight of iridium Alternatively, such an intermediate layer can be an oxide of a metal from the platinum group, such as ruthenium oxide (RuO ₉ ), rhodium _{oxide (Rh 9} Oo), palladium oxide (PdO ₉ ), osmium oxide (OsO ₉ ), iridium oxide (Ir ₉ O- ) Platinum Oxide (PtP ₉ ) or Mixtures thereof Such mixtures can include mixtures of platinum oxide and palladium oxide containing from about 3 to about 15 weight percent platinum oxide or platinum oxide and iridium oxide mixtures containing from about 2 to about 50 weight percent iridium oxide In connection with the metals of the platinum group or their oxides can contain

309832/1096

in addition, oxides of other metals are used, such as the oxides of titanium, zirconium, hafnium, Vanadium, niobium, tantalum, tungsten and aluminum. If there are such interlayers, they have typically from about 0.51 to about 3.05 microns (20 to 120 micro inches) thick, with thicknesses from about 1.52 to 3.05 microns are preferred. The intermediate layers can also be thinner and, for example, only 0.13 microns (5 micro inches) thick when applied evenly are so that they result in a pore-free coating. Further it is possible to use thicker intermediate layers, but this is not an essential one Preferential connected.

If with an electrode with a ^ elafossitoberflache on a substrate the substrate with the delafossite forming an electrically insulating barrier after prolonged ·. Operating times at high current densities, there may be a layer between the substrate and the delafossite a less reactive material that is more resistant to the electrolyte than the substrate, to be ordered. Less reactive materials are understood to mean materials that are not • Form an electrically insulating barrier or participate in the formation of such a barrier if they are between the Delafossit and the substrate are arranged. Such less reactive materials can be those already mentioned Be precious metals or their oxides. Alternatively

309832/1096

Platinum-cobalt-delafossite (PtCoO ₂ ), palladium-chromium-delafossite (PdCr (O or Palladiura-Fdiodium-delafossite (PdRhO ₉ )) can be used as less reactive materials to form an intermediate layer between a palladium-cobalt · 'delafossite ( PdCoO ₂ ) coating and a titanium substrate. When such interlayers are used, they are typically 0.51 to 3.05 microns thick, with 1.52 to 3.05 microns being preferred. When the interlayers are evenly applied and are pore-free, they can also be thinner, e.g. 0.13 microns thick, Thicker coatings are also possible.

The electrodes with delafossite surfaces according to the invention can be used for any electrochemical process with a non-consumable electrode. Under "non-consumable ¹¹ is meant that the electrode is not dissolved by the electrolyte and is not redeposited on the opposite electrode The electrodes of the invention can be used, for example, for the electrolysis of brines, sulfates, hydrochloric acid, phosphates, etc. Alternatively, the electrodes are useful in processes in which cations are deposited on a cathode, such as in the electrowinning of Metals, electrolytic refining, electroplating, electrophoresis, electrolytic cleaning and electrolytic pickling. Copper,

309832/1096

Nickel, iron manganese, brass, bronze, cadmium, gold, Indium, silver, tin, zinc, cobalt, chromium and similar metals can be electroplated onto cathodes. Alternatively metal powder can be produced by applying cation deposited on a suitable cathode using the electrodes of this invention. the Electrodes according to the invention can also be used for the electrolytic cleaning of aqueous solutions, of Sodium phosphate, sodium carbonate and the like are used. You can also use the electrolytic Pickling of suitable materials that · cathodically

■ ■. ·. ■ ·

compared to the anodes according to the invention, to use organic compounds electrolytically to oxidize. For example, the electrolytic oxidation of propylene to propylene oxide or propylene glycol can be used perform with the electrodes of this invention. You can also use metal structures, such as hulls protect cathodically using the anodes of this invention. With each of the above indicated cases for the use of the electrodes according to the invention, the cell contains a pair of electrodes with an anode and .ein cathode, at least one Member of the pair of electrodes has a delafossite surface, one electrode has an opposite polarity has and means are present to apply an external voltage or electromotive force between the anode and the Keeping the cathode upright, and with the anode facing der'Kathode is positively charged and an electric current

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- 33 -

is caused to flow from one member of this pair of electrodes to the other member.

In addition, the electrode of this invention can be used in fuel cells. When using the electrode with the delafossite coating in fuel cells, these electrodes will be permeable to the flow of the electrolyte. Such electrolyte permeability can be achieved by an electrically conductive porous substrate having a delafossite material deposited thereon, or by dispersion of delafossite particles in a suitable inert medium, or by other methods known in the art. Such fuel cells with electrodes according to the invention have, in addition to this electrode, an electrode of opposite polarity which is arranged at a distance from the electrode coated with delafossite, a device for feeding the electrolyte into the space between the electrodes in order to internally apply an electromotive force between electrodes generate, and a device for receiving the electric power that is generated in. the fuel cell.

The electrodes according to the invention can be produced; by synthesizing the delafossite and then applying it to a suitable electrically conductive substrate or support. Delafossite can be produced by oxidation at low temperatures and high pressures, such as a hydrothermal reaction. Also can

309832/1098 f

they can also be obtained by oxidation at high temperatures and high pressures by solids conversions and by Oxidation at low temperatures and low pressures in an oxidizing flux. Alternatively, it is possible to use Delafossite at low pressure and low temperatures in an anion exchange reaction to manufacture.

Delafossite which are useful in the present invention can be produced, for example, by the methods described in the following references; RD Shannon et al, Chemistry of Noble Metal Oxides, I. Syntheses and Properties, of ABO ₉ Delafossite Compounds, Inorganic Chemistry, Volume 10, page 713 (1971); U.S. Patent 3,498,931; U.S. Patent 3,514,414 and U.S. Patent 3,414,371.

Hydrothermal syntheses of Delafossite are carried out at a relatively low temperature under oxidizing conditions. The hydrothermal method can be used, for example, for the production of platinum-cobalt delafossite, copper delafossite and silver delafossite. The method requires the heating of two oxides in water in a closed inert tube, such as a platinum or gold tube (at high pressure, eg about 3000 atmospheres and a temperature of about 500 to 700 C for about 24 S _t reasons).

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2304330

The platinum, palladium and pluckers delafossite can be produced in a reaction at relatively low pressures and low temperatures, caused by an exchange of ions and 'the formation of a solid or molten salt as a by-product is characterized. In this method, the halide of platinum, or palladium Copper and the oxide of the second metal to form delafossite and a halide of the second Metal implemented. Alternatively, the halide or the metal and the halide of the first metal and a lithium oxy compound of the second metal (such as lithium chromate, lithium cobaltate or lithium rhodate) to be reacted with the formation of delafossite and lithium halide.

The anion exchange reaction is carried out in an evacuated sealed silica tube at a temperature carried out from about 500 ° C to about 800 ° C. The halide salts obtained as a by-product are after Formation of delafossit removed by leaching, e.g. with water. If metallic platinum, palladium or copper remains or if the chloride of the noble metal remains, these residues will through Leaching with a suitable solvent such as hydrobromic acid or aqua regia removed.

.Delafossite can also be finely powdered by diffusion mixed oxides can be produced at high temperatures. Copper delafossite can be obtained by a

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such implementation in the solid state at atmospheric Pressure and at a temperature of about 1000 C. The platinum and palladium delafossite require a temperature above 700 C and a pressure of about 3000 atmospheres for the delafossite to pass through to get an implementation in the solid state.

The silver delafossite can be made in an oxidizing flux. With this method A flux is made from silver nitrate and potassium nitrate and it becomes a chromate, rhodate or Cobaltate added to this flux. The mixture is sealed and heated to an elevated temperature, e.g. heated above 350 C for a period of more than about 100 hours. In this way it becomes a solid Obtain solution of nitrate and delafossite. The nitrate ■ can be removed by leaching with water.

The delafossite produced by one of these methods can either be used as such for an electrode or preferably serve as a surface or coating of an electrode made of a suitable base or substrate material.

Usually this is "electrically conductive base or" Substrate material a rectifier metal such as titanium. Such a substrate can be in the form of a flat, plate-like structure or it can also be in the form of a perforated plate or an expanded

309832/1091

2304390

Latticework.es (expanded mesh). Alternatively can it exist in the form of fine wires, rods or other shapes, such shapes being the drain of the Allow gases formed from the volume between the anode and the cathode into spaces behind the anode.

When a titanium member is used as the substrate material, this titanium member can be used for its use Prepare as an electrode by degreasing it before the delafossit coating is deposited and then etching. Degreasing can be done by any known method, e.g. under Use of detergents, abrasives or organic degreasing agents. Then the defatted can Titanium substrate with hydrofluoric acid, hydrochloric acid or similar materials. The etching is used to remove the naturally occurring Remove the oxide film and replace it with a thin hydride film.

The delafossite can be applied to the etched titanium surface in various ways. So can for example, a slurry of Delafossit in a solvent such as ethanol, butanol, benzyl alcohol, Manufacture phenol, benzene, cumene and the like. Such a slurry can be applied to the titanium surface, e.g. apply with a paintbrush or a brush.

309832/1098

After each spread, heat is applied to decompose or volatilize the solvent. The slurry may also contain finely divided materials such as silicon, titanium, zirconium, hafnium, Vanadium, niobium, tantalum, molybdenum, tungsten or other materials that are capable of being "in situ" during the process of evaporation or decomposition of the solvent to form an oxide. Usually will a chloride is used as such a finely distributed material, such as titanium trichloride.

Alternatively, one can prepare a slurry of dßlafosite, a metal, an organic solvent such as ethanol, butanol, benzyl alcohol, Pherfol, benzene, cumene, polyene and the like, and a silica compound or a metal compound which is soluble or dispersible in the organic solvent , such as a resinate. Such a slurry can be spread onto the titanium using, for example, about 4 to about 8 spreads and heating after each spread causes the organic constituents to decompose or volatilize. Alternatively, other methods can also be used for applying the delafossit to the substrate, such as joining by pressing or cathodic electrophoresis.

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230A380

In the above procedures for coating the titanium substrate with the delafossite, the Veneering of a titanium or a silicon compound but such connections are not required for the electrode to function. the However, oxidation products of such compounds as titanium dioxide or silicon dioxide impart der-Delafossitoberflache an additional physical Strength and durability. Alternatively, oxides of zirconium, hafnium, vanadium, niobium, tantalum, Molybdenum or tungsten on the surface of the electrode "in situ" to improve the durability and durability of the electrode surface.

The invention is explained in more detail in the following examples.

: Example 1

One makes one from a titanium substrate, a coating from a palladium-cobalt delafossite (PdCoO-) and an electrode made of metallic platinum between the titanium and the delafossite,

The delafossite is made from 2.6642 g of palladium chloride (PdCl ₂ ) and 2.2482 g of cobalt oxide by thoroughly grinding the chloride and oxide into one

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"2 'hours evacuated sucked quartz tube of an outer diameter of 10 mm, filling a length of 12.7 cm and heated therein for 1 hour at 110 ⁰ G ,. after which closes the quartz tube. Then, heating the sealed quartz tube at 850 ⁰ C , keeps it at this temperature for 15 minutes, then lets the temperature drop to 700 ^° C. and continues heating at this temperature for 65 hours 200 ml of water> then with acetone and dry it to obtain 2.4 g of a gray metallic product with a particle size ranging from 0.03 to 0.5 and from 1 to 7 microns.

This powder is examined by X-ray diffraction in a Philips diffractometer. A voltage of 35 kilovolts and a current of 15 milliamperes are used for the X-ray tube, and a voltage of 1265 volts for the detector. The radiation from a copper target is used and a divergence diaphragm of 1 °, a beam diaphragm of 0.1524 mm and a scattering diaphragm of 1 ° are used. The detector is allowed to rotate with a time constant of 2 seconds at 2Θ ^β 2 per minute and the test specimen at 2Θ - 1 ° per minute. The measured values shown in the following table (6) and in FIG. VI are obtained.

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- 41 Table 6

I / Io

5.925 x 40

4,572. 5

3.448 '5

2.957 90

2.566-10

2, '440 60

2.362 100

2.252 x 5

2.148. 40 ·

1,759 ίο

1.646 50

1.480 ίο

1.438 20

1.415 30

1.350 \ 5

1.325 5

1.277 "20

1.273 x 20

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A titanium strip 14.6 cm long, 9.5 mm wide and thick is washed of 3.175 mm with a under the trademark "Comet" commercial household cleaning agents containing abrasives, rinse it in distilled water, immerse it in 1% hydrofluoric acid for one minute and place it then 23 hours in 12N hydrochloric acid of 27 C.

. A solution of 10 g of one calculated as metal is made 7.5% by weight of platinum-containing platinum resinate of the Engelhard "0-5X" type in 9 g of toluene and carries this solution in three layers on the etched titanium strip. After each application of the two In the first layers, the strip is heated to 500 ° C. in 5 minutes at a rate of 50 ° C. and

. keep it at this temperature for 10 minutes. After applying the third layer, heat the strip at a speed of 50 C in 5 / minutes to one A temperature of 550 C. It is also kept at this temperature for 10 minutes.

From 0.5 g of the palladium-cobalt delafossite (PdCoO ”), 1 g of a _{4.5% by weight titanium solution prepared by adding 3.4 g of titanium chloride (TiCl 3} ) to 20 g of ethanol and 1.0 g of ethanol are prepared a mud and uses it to apply six coats with a brush to the titanium strip as described. After each coating, the strip is heated to 100 ⁰ C und'30 minutes at this temperature. After applying the

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23Q4380

Finally, the strip is heated in vacuo at a rate of 100 ° C. in 10 minutes to 400 C, after which it is kept at this temperature for 40 minutes.

After applying the last layer, check the Electrode in one. Beaker chlorate cell. A 500 ml beaker is used as the chlorate cell, which contains a saturated saline solution and in which the platinum-coated titanium cathode is replaced by a Teflon spacers are located at a distance of 9.5 mm from the anode. Electrolysis is carried out

2 at a current density of 53.82 amperes per dm and a «

Cell voltage of 3.5 volts. At a current density of 53.82 amps:
of 0.08 volts.

2 at a current density of 53.82 amps per dm and one

V (
2
The cell has a chlorine overvoltage of 53.82 amperes per dm

The anode is placed in a common laboratory chlorine diaphragm cell a. The cell has an iron mesh cathode that is 9.5 mm away from and from the anode separated by asbestos paper. The electrolysis of a saline solution containing 315 g of NaCl per liter is carried out

2 a current density of 53.82 amperes per dm and a temperature of about 90 ° C. The cell has a voltage at the beginning of 3.64 volts and a chlorine overvoltage of 0.08 volts. After an electrolysis time of 816 hours it has a Voltage of 3.92 volts and a chlorine overvoltage of 0.33 volts.

309832/1096

Example 2

It is made from a titanium substrate and the delafossite

Pt ,. _o Co _{n O} 0_ an electrode as a coating layer. U, ο Ό , ο ί

Delafossit is produced by anion exchange from platinum chloride, cobalt oxide (CoO) and cobalt oxide (Co ₃ O). The cobalt oxides are used in the form of a mixture consisting of 0.9048 g Co ₃ O and 0.1274 g CoO. They are in the form of a powder with a grain size of less than 325 mesh. They are pounded in a mortar to even greater fineness. The powder mixture is placed in a quartz tube with an outer diameter of 10 mm and a length of 10.16 cm, vacuumed, closed, heated to 700 ^° C. and kept at this temperature for 25 hours. Mai receives a mixed phase consisting of a black powder and light blue crystals. This material is ground, filled into another quartz tube, vacuumed for 3 hours, heated to 710 C, kept at this temperature for 18 hours and then for more 15 hours at a temperature between 700 ⁰ C and 710 ⁰ C, cools the quartz tube, and, takes out the material. it pounds it in a mortar, there ml beaker into a 150 and sets 100 ml of water to it. the mixture is filtered to The resulting sludge is passed through a filter funnel made of sintered glass at 25 ° C. The insoluble residue is washed twice with 25 ml of water and then with acetone to give a gray-black

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Solid, which one, x * ie described in Example 1, - - ■ examined by X-ray scattering. An X-ray diagram is obtained with the values shown in Table 7 and Fig. VII measured values shown.

Table 7

I / Iö

5.901 90

3,292 ■. 10

2.968 100

2,428 30

2,364 70

2,146 40

2.077 5

2.020 10 1.979 '80

1,764 10

1.648 40

1.549 5

1.445 60

1.441 20

1.414 10

1.374 5

1,350 10

1.321 5

1.277 10

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One cleans a strip of titanium with a length of. 14.6 cm, a width of 9.5 mm and a thickness of

. 3.175 mm with the household cleaning agent "Comet", etches it for 5 minutes in a 2 percent by volume hydrofluoric acid solution and then for 22 hours at 27 ° C in 12-n

. Hydrochloric acid.

0.25 g of the above-described platinum-cobalt belafossite (Pt _{Q g} Co ₀ 3O ₂ ), 0.5 g of a 4.2% strength by weight solution of titanium chloride (TiCl ₃ ) in ethanol and 0.5 g are prepared • Ethanol make a sludge and use it to apply five coats to the titanium strip with a brush. After each of the coatings 1 to 4, the strip is heated to 100 ^° C. and held for 30 minutes. After the last coat has been applied, the strip is heated in an evacuated tube to a temperature of 5 'and held for 30 minutes.

in a vacuum tube then to 500 C. This is also the case

The electrode is first tested in a beaker cell. A 400 ml capacity is used as the beaker cell Beaker. This contains the anode to be tested and, a platinum-coated titanium cathode removed 9.5 mm from this by a vain Teflon spacer. A saturated saline solution is used as the electrolyte, which is per liter Contains 315 g of table salt. After 18 hours the electrode shows a voltage of 3.15 volts with a current density of 26.91

2
Amps per dm - and a voltage of 3.8 volts at one

2 current density of 53.82 amps per dm. At a current density

309832/1096

2
of 53.82 amperes per dm, the voltage against a calomel electrode is 1.12 volts and the chlorine overvoltage is 0.06 volts. ,

The electrode is then placed in a laboratory chlorine diaphragm cell a. The cell contains an iron mesh cathode, which extends to the anode at a distance of 9.5 mm and kept separated from it by asbestos paper

will. At a current density of 53.82 amps per dm and

a temperature of the electrolyte of 90 ⁰ C at the beginning of the cell has a voltage of 3.58 volts and a Chlorüjerspannung of 0.06 volts. After 104 days of operation, the cell has a voltage of 3.70 volts and a chlorine overvoltage of 0.08 volts.

Example 3

A titanium substrate and the Delafossite Pt _Q qGOq. 73q ° 2 ^a ^ ^s distorted layer an electrode made «

The platinum-cobalt delafossite is produced by the anion exchange process in such a way that 5.322 g of platinum chloride (PtCl ₂ ), 1.9622 g of cobalt oxide (Co ~ 0.) And 0.882 g of cobalt oxide (CoO) are milled to a grain size of crushed less than 325 meshes, mixes, pour the mixture into a quartz tube with an outer diameter of 12 mm and a length of 12.7 cm, the tube

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2 hours at 25 ° C and 16 hours at 125 ° C evacuated and then sealed. The tube containing the powder is then heated to 700 ° C., kept at this temperature for 70 hours, then rapidly cooled to room temperature, whereupon it is opened. Its contents consist of a gray metallic solid, solid blue crystals and a green solid. The entire product is comminuted by grinding to a particle size of less than 32-5 meshes, the comminuted product is filled into a second quartz tube with an outer diameter of 12 mm and a length of 12.7 cm, and the tube is suctioned at 25 ° C. for 1 hour and 3 hours at 135 ° C deflated, it closes, it is heated to 700 ⁰ C, keeping it at this temperature for 47 hours. Then cool it down to room temperature and open it. It contains blue and green crystals on its cooled end and also a gray metallic solid. Comminuting the gray metallic solid to a particle size of less than 325 mesh, washed twice at 25 C with 25 ml of distilled water, then twice with acetone and dried at 70 ⁰ C. Thereafter, the powder holding 16 hours at 25 ° C Vacuum. The light gray crystalline metallic substance obtained is examined by X-ray spectroscopy in the manner described in Example 1. The X-ray diagram is shown in FIG. VIII. Apart from only minor differences, it is essentially identical to the X-ray diagram known _{from the Delafossit literature Pt Q} gCo _{Q gCL.}

309832/109 «

Mäii etches the titanium strip as described in Example 1 and carries 0.19 from a sludge composed of 0.25 g of platinum-cobalt delafossite, 0.50 g of a titanium resinate solution, calculated as metal, containing 4.2% by weight of titanium g of toluene and 0.06 g of phenol consists of five layers of coating. Heating the layers 1 to 4 at a rate of 50 ⁰ C in 10 minutes to 425 ⁰ C, and the fifth layer is also at a rate of 50 ⁰ C in 10 minutes to 500 ⁰ C. All layers can hold '10 minutes at their respective maximum temperature.

The electrode obtained is tested in the manner described in Example 1 in a beaker chlorine cell. at

a current density of 53.82 amperes per dm and a temperature of the electrolyte of 60 C, the cell has a chlorine overvoltage of 0.07 volts and against a calomel electrode an electrode voltage of 1.125 volts.

The anode is then placed in a common laboratory chlorodiphragma cell of the type described in Example 1 and also carries out the electrolysis as in the example 1 described at a current density of 53.82 amps per

2 "

dm through. The cell initially has a voltage of 3.65 volts and a chlorine overvoltage of 0.07 volts. After a The electrolysis lasts 744 hours, the cell has a voltage of 3.85 volts and a chlorine overvoltage of 0.28 volts.

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23Q4380

Example 4

An electrode is made from a titanium substrate and the palladium-rhodium delafossite (PdRhO ₉ ) as a coating layer. The delafossite is produced by the anion exchange process from lithium rhodanate (LiRhO-), metallic palladium and palladium chloride (PdClp. The lithium rhodanate (LiRhO ₉ ) is obtained from rhodium oxide (Rh ₉ O.,) and lithium carbonate (Li ₀ CO.,). Rhodium oxide (Rh ₉ O-) is obtained if rhodium chloride (RhCl- · 3H ₀ O) is heated with a supply of air for 42 hours at 790 ° C. To produce lithiurium rhodate, the rhodium oxide is ground and 1.0367 g of it is mixed with 0.3660 g of lithium carbonate (Li ₂ CO ₃ ), put the powder mixture in an alundum dish, heat it to 1040 C, keep it at this temperature for 66 hours, comminute the product obtained to a particle size of less than 325 meshes and check it by X-ray spectroscopy The X-ray diagram is essentially identical to that from the literature on lithium manganate (LiMnO ₉ ) in the case of the X-ray diagram.

The Delafossit is prepared by mixing 1.0817 g of lithium rhodanate (LiRhO ₉ ), 0.4068 metallic palladium and 0.6672 g of palladium chloride (PdCl ₂ ), the mixture is comminuted by grinding, the powder is placed in a quartz tube from an outer diameter of 9 cm filled ram and a length of 12.7, the pipe sucks 1 hour at 25 ° C and 3 hours at 110 ⁰ C deflated, the tube closes, heated to 790 C and 75 hours at this temperature keeps .

309832/1098

The product obtained is crushed, placed in a second quartz tube with an outer diameter of 9 mm and a length of 12.7 cm, the tube is vacuumed, heated to 180 ^° C., kept at this temperature for 18 hours, and closed , heats it to 775 ° C and keeps it at that temperature for 48 hours. The product obtained is washed four times with distilled water and once with acetone.

A 14.3 cm long, 9.5 wide and 3.175 mm thick titanium strip is cleaned and etched as described in Example 1 and four layers of a sludge made from 0.2 g of PaXladium-Rhodium-Delafossite (PdRhO ₂ ) are painted on it. , 0.4 g of a titanium resinate containing 4.2% by weight of titanium, 0.05 g of phenol and 0.15 g of toluene, with a brush. After each of the coatings 1 to 3 by heating the strip at a rate of 5O ⁰ C in 10 minutes to 450 ⁰ C, followed by keeping it for 10 minutes at this temperature. After the last layer has been applied, it is heated to 500 ° C in 10 minutes, also at a rate of 50 ° C. The strip is also kept at this temperature for 10 minutes.

One examines the electrode made in this way as an anode such as described in a beaker chlorate cell. At a

2 current density of 53.82 amperes per dm and a temperature of the electrolyte of 60 ⁰ C, the electrode has a chlorine overvoltage of 0.07 volts.

309832/1096

The anode is placed in a common laboratory chlorine diaphragm cell of the type described in Example 1 and conducts the electrolysis as described in Example 1 at a current density of 53.82 amps

2
per dm through. At the beginning, the cell has a voltage of 3.69 volts and a chlorine overvoltage of 0.07 volts. After electrolysis of 1320 hours, the cell has a voltage of 3.71 volts and a chlorine overvoltage of 0.15 volts.

Example 5

An electrode is made from a titanium substrate and the palladium-chromium-delafossite (PdCrO_) as a coating. The delafossite is made after the anion exchange. are made from palladium metal, palladium chloride and lithium chromate. Lithium chromate is obtained by reacting lithium carbonate (Li ₂ CO-) with chromium oxide (Cr ₂ O-). This one grinds ⁰ a mixture of 3.6945 g of lithium carbonate

) and 7.6010 chromium oxide (Cr ₂ O ₃ ), put the powder in an alundum bowl and heat it for 4 hours to 330 ^° C. and 12 hours to 930 ° C. The product obtained is ground and then heated for 23 hours 930 ⁰ C, it grinds and heated again in 23 hours 1040 ⁰ C. the dark green product obtained is grinds and examined, as described in Beispiel.1, röntgenspektroskopisch. To

309832/1096

it has the same crystal shape in its X-ray diagram like the LiM 0 «.

1.8190 g of lithium chromate (LiCrO ₂ ), 1.0670 g of palladium metal and 1.7761 g of palladium chloride (PdCl ₂ ) are put through

• grinding a powder having a grain size of less than 325 mesh forth, are the powder mixture in e.in quartz tube of an outer diameter of 10 mm and a length of 12.7 cm, the pipe sucks for 16 hours at 130 ⁰ C evacuated, closes it, heats it to 800 ⁰ C for 46 hours and cools it. The product obtained is ground, filled into a second quartz tube with an outer diameter of 10 mm and a length of 12.7 cm, the quartz tube is vacuumed for 5 hours at 130 ° C., closed and heated to 800 ^° C. for 64 hours, which means that it is heated ^{to 800 °} C. for a total of 110 hours.

The product obtained is ground to a grain size of "less than 325 meshes, and it is washed at 25 ^° C. with distilled

ο water, then wash it twice more with acetone at 25 C and

it dries.

A titanium strip 14.6 cm in length, 9.5 mm in width and 3.175 in thickness is cleaned and etched mm in the manner described in Example 1.

A solution of 10 g of a platinum resinate of the type containing, calculated as metal, 7.5% by weight of platinum is prepared Engelhard "0-5X" in 9 g of toluene so that the solution Contains 3.9% by weight of platinum, calculated as metal, and applies four coatings to the titanium strip from this solution.

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The strip is heated after each application of coatings 1 to 3 at a rate of 50 ° C in 5 minutes to 400 ° C and after application of the fourth coating, at a speed -; from 50 ° C in 10 minutes, to 500 ° C_and_hold._Ahn in in each case 10 minutes at the respective maximum temperature.

A slurry is prepared from 0.2 g of palladium-chromium delafossite (PdCrO ₂ ), 0.4 g of a titanium resinate containing 4.2% by weight of titanium, 0.05 g of phenol and 0.15 g of toluene and uses it to apply four layers of coating to the titanium strip with a brush. Heating the electrode in each case after the application of the coatings 1 to 3 at a rate of 50 ⁰ C in 10 * minutes at 450 C and after application of the last coating, also at a rate of 50 ⁰ C in 10 minutes, at 500 ⁰ C and keeps it in any case for 10 minutes at the respective maximum temperature.

The electrode is then tested as an anode in a beaker chlorate cell as described in example 1. at

■; Ο

the anode has a current density of 53.82 amperes per dm

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- 55 Example 6

It provides with a titanium substrate coated thereon a platinum layer, a further layer of the platinum-cobalt Delafossit (Pto qCoq 8 ^ 2 ^ ^unc * ^e ^ ^ner this layer of porous titanium dioxide bedeckendeaSchicht • an electrode side.

The platinum-cobalt delafossite is produced by reacting platinum chloride (PtCl “) with cobalt (II + III) oxide (Co ₃ O ₄ ) and cobalt (II) oxide (CoO) in such a way that 7.9842 g of platinum chloride (PtCl ₂ ), 3.6123 g of cobalt (II + IIl) oxide (Co ₃ O ₄ ) and 1.1241 g of cobalt (II) oxide (CoO) in a mortar to a Crush and mix powder with a grain size of less than 325 meshes, fill the powder into a quartz tube with an outer diameter of 10 mm and a length of 12.7 cm and heat it in a vacuum for 18 hours at 130 ° C., after which the tube is closed . "

The closed quartz tube is heated to 700 ° C. for 46 hours, the resulting product is removed from the quartz tube, it is ground, and then placed in a second quartz tube. mm an outer diameter of 10 and a length of 12.7 cm, the tube is heated in a vacuum for 8 hours 130 ⁰ C, closes it and then heated it to 700 ⁰ C. 64vStunden

Take the resulting product out of the tube, it is washed five times at 25 ° C with distilled water, then washed twice at "25 ° C with acetone, it is dried in an air stream at 70 ⁰ C,

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crushes it in a mortar to a grain size of less than 325 mesh and crushes it further by adding one hour in a hammer mill sold under the trademark "Mixer Mill" with a. Boron carbide hammer treated.

After examination with an electron microscope, the material obtained has grain sizes in the range between 0.02 and 7.5 microns. The grain size distribution lies within two different size ranges. In the The main thing is that the grain sizes are between 0.02 and 0.3 microns and between 1.5 and 6.0 microns. in the In the area of fine particles, the mean grain size is 0.1 micron, in the area of the larger. Particle it is 2.5 Micron.

A titanium trelf 14.6 cm long, 9.5 mm wide and 3.175 mm thick is cleaned and etched, as described in Example 1, and eight layers of 0.25 g of the Delafossite Pt _Q gCOg gO_, 0.12 g titanium tetrachloride are painted on it (TiCl,) in butanol, 0.75 g butanol and 0.15 g phenol. Heating the strip after each coating at a rate of 50 ⁰ C in 5 minutes to A25 ° C.

A sludge is then prepared from titanium tetrachloride (TiCl,) in butanol, which, calculated as metal, contains 2.25% by weight of titanium, and this sludge is spread in four layers on the delafossite surface of the titanium strip. The strip is heated to 110 ^° C. for 1 to 3 20 minutes and then for 10 minutes after the coatings have been applied

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to 425 ° C. After the last coating has been applied, it is heated to HO ^{0 C for 20 minutes and to 500 0} C for 15 minutes.

The electrode produced in this way consists of a titanium substrate as a base, a coating layer made of platinum-cobalt delafossite and a dies.e covering outer layer of titanium dioxide. Place the electrode in a beaker chlorate cell as a Anode one. At a current density of 53.82 amperes per dm h ^ t the anode has a voltage of 1.175 volts against a Calomel electrode and a chlorine overvoltage of 0.12 volts.

Example 7

A titanium substrate is used as a base, a coating of platinum-cobalt-delafossite _{Pt A 0 Οο Λ Q} 0 _o

U, ο U ₁ ö /

and an outer layer of titanium dioxide applied thereon to produce an electrode.

A titanium strip 14.6 cm long, 9.5 mm wide and 3.175 mm thick is cleaned in the manner described in Example 1, and then, from a sludge made from 0.5 g of the platinum-cobalt delafossite (Pt _{A o} Co " _{o o o} ), 0.25 g of titanium tetrachloride

UjO UjO Z

(TiCl ₇ ), 0.75 g butanol and 0.15 g phenol six over

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2104380

on trains and heated dan strip of any coating first 30 minutes .110 C and then 15 minutes at 400 ⁰ C.

A solution of titanium tetrachloride in butanol containing 2.1% by weight of titanium based on the metal is prepared and four coatings are applied from this solution to the delafossite surface of the electrode. After each of the coatings 1 to 3 by heating the electrode is first 20 minutes HO ⁰ C and for 10 minutes at 425 ⁰ C. After the fourth coating is heated it first 20 minutes and then 110 C 15 minutes 500 ⁰ G.

One tests the one from the titanium substrate, one coating from the platinum - cobalt - delafossite and one outer coating made of porous titanium dioxide electrode as described in Example 1 as an anode in a beaker chlorate cell. At a current density

2
of 53.82 amperes per dm, the anode has a voltage of 1.160 volts against a calomel electrode and a chlorine overvoltage of 0.10 volts.

The anode is placed in a laboratory chlorine diaphragm cell of the type described in Example 1 and performs the electrolysis according to Example 1 at a

Current density of 53.82 amperes per dm. The cell has a voltage of 374 volts at the beginning and a chlorine overvoltage of 0.10 volts. After electrolysis For 74 days, the cell has a voltage of 3.94 volts and a chlorine overvoltage of 0.17 volts.

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Example 8

A titanium substrate is used as a base, a coating of platinum-cobalt-delafossite (? T " _o Co ~ _O 0")

U, O UjO L

and one inserted between the substrate and the delafossit coating!
Electrode.

Zug inlaid layer of ruthenium dioxide (RuO ₉ ) a

A titanium strip 14.6 ctn long, 9.5 mm wide and 3.175 mm thick is degreased, cleaned and etched in the manner described in Example 1 and five layers of 1.5 g of ruthenium trichloride (RuCl ₃ ^ H ₂ O) in sludge containing 9 g of ethanol. The strip is air-dried for 10 minutes after each of the first four coats and then heated to 300 ° C. for 10 minutes with a supply of air. The last coating is first air-dried for 10 minutes, but is then heated for 45 minutes with a supply of air to 450 C.

From 0.5 g of the platinum-cobalt delafossite (Pt _{n ß} Co _{n ß} 0 _o ) according to Example 6, 1.0 g of a titanium tetrachloride (TiCl-) solution containing 4.2% by weight of titanium in Butanol, 0.2 g of phenol and a drop of nonylphenoxypolyoxyethylene ethanol ("IGEPAL CO-530") produce a sludge and apply six coatings to the strip. After each coating by heating the strip at first 20 minutes 110 ⁰ C and then 15 minutes at 400 ° C.

309832 / $ 109

The strip is then coated with a layer of a solution of titanium tetrachloride (TiCl,) in butanol, calculated as metal, containing 2.1% by weight of titanium and heated first to 110 ° C. for 20 minutes and then to 500 ° C. for 15 minutes. The electrode obtained by this process has a uniform gray appearance.

The electrode is tested for that described in Example 1

Way as an anode in a beaker chlorate cell. at

The anode has a current density of 53.82 amperes per dm a voltage of 1.147 volts against a calomel electrode and a chlorine overvoltage of 0.09 volts.

The electrode is then used as an anode in a laboratory chlorine diaphragm cell of the type described in Example 1 and the electrolysis is carried out as in

Example 1 described at a current density of 53.82

2 '

Amps per dm . The cell initially has a voltage of 3.60 volts and a chlorine overvoltage of 0.09 volts. After 936 hours of electrolysis, the cell has a voltage of 3.72 volts and a chlorine overvoltage of 0.07 volts.

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230A380

Example 9

An electrode is produced using a titanium substrate as the base, a coating of palladium-cobalt delafossite (PdCoO ₂ ) and a layer of ruthenium dioxide (RuO _{2) sandwiched between the substrate and the delafossite coating.}

A titanium strip 14.6 cm long, 9.5 mm wide and 3.175 mm thick is degreased, cleaned and etched in the manner described in Example 1 and four layers of 1.5 g rutheniurate dichloride (RuCl ₃ * 3H ₂ O) in sludge containing 9 g of ethanol. Dry the strip after each of the first three coatings 10 minutes in air and then heating it in an air-open furnace to a temperature of 300 ⁰ C, it stops at the one 10 minutes. Dry the strip after the fourth coating is also 10 minutes in the air, but then heating it in an air-open oven at 450 ⁰ C and holding it for 45 minutes at this temperature.

From 0.2 g of the palladium-cobalt delafossite (PdCoO ₂ ) according to Example 1, 0.4 g of a titanium resinate containing 4.2% by weight of titanium, 0.15 g of toluene and 0.05 g of phenol are prepared produced a mud and applied six coatings from it to the titanium strip. After each of the first five coatings by heating the strip at a rate of 5O ⁰ C in 5 minutes at 425 ⁰ C. After

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last coating by heating the strip at a rate of 50 ° C in 5 minutes at a temperature of 500 ⁰ C, it stops at the one 15 minutes.

They are made of a titanium substrate, a coating of palladium-cobalt delafossite and one between The ruthenium dioxide layer embedded in the substrate and the delafossite coating acts as an anode into a beaker chlorate cell according to Example 1.

2 At a current density of 53.82 amps per dm, the anode has a voltage of 1.141 volts against a Calomel electrode and a chlorine overvoltage of 0.08 volts,

The anode is inserted into a chlorine diaphragm cell of the dimensions customary in the laboratory and the Electrolysis according to Example 1 at a current density of

2
53.82 amps per dm. At the beginning, the cell has a voltage of 3.48 volts and a chlorine voltage of 0.08 volts. After a period of electrolysis of 576 hours, the cell has a voltage of 3.49 volts and a chlorine overvoltage of 0.07 volts.

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Example 10

One sets one with a titanium substrate as a base and a palladium-ruthenium-delafossite (PdRuCL) Electrode.

You degrease, clean and etch a 14.6 cm long, 9.5 now wide and 3.175 thick titanium strip such as described in the example!

A mixture is prepared from 0.4055 g of metallic palladium (Pd), 0.6749 g of palladium chloride (PdGl), 1.5813 g of ruthenium trichloride (RuCl) and 4.4528 g of lantham oxide (La-O ₃ ), it is crushed thoroughly, there are in a quartz tube of an outer diameter of 12 mm and a length of 12.7 cm, heating the tube in a vacuum for 4 hours at 25 ° C for 16 hours to 7O ⁰ C and 4 hours at 120 C, it sucks then evacuated and lock it. The sealed tube is heated to 775 ° C. and held at this temperature for 70 hours. Do you open it? Rohr, takes the resulting product from it, grinds it and puts it in a second quartz tube. One then draws the second quartz tube at 25 C for 3 hours and 4 hours at 120 ° C deflated, it closes, it is heated to 72o ⁰ C and holding it for 42 hours at this temperature.

You let the tube cool down, open it, take it out of it resulting product and washes it five times with water,

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"then once with 1N hydrochloric acid, again twice with water and finally once with acetone. The product is made with titanium chloride in butanol a mud and applies it to the etched titanium strip. The electrode consists of one Titanium substrate with a coating of a palladium-ruthenium-delafossite and titanium dioxide.

It should be emphasized that the invention is based on the embodiment shown and described in specific detail ^; Shapes should not be restricted, but all other possible embodiments as well as variants and modifications that are possible within the scope of the following claims.

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Claims (34)

- 65 claims 1. Electrode, characterized by an electrically conductive one Carrier and a coating layer thereon which contains a delafossite. 2. Electrode according to claim 1, characterized in that the carrier is made of a rectifier metal (valve metal) consists. 3. Elektro.nach claim 2, characterized in that the carrier is made of titanium. 4. Electrode according to claim 1, characterized in that the carrier consists of graphite. 5. Electrode according to claim 1, characterized in that 'which contains delafossite palladium. 6. Electrode according to claim 1, characterized in that the delafossite contains platinum. 7. Electrode according to claim 1, characterized in that between the layer containing the delafossite and the support is provided with a layer of a material that conducts electrical current better than the delafossite. 309832/1098 - ft r. * ti - 66 - 8. Electrode according to claim 1, characterized in that between the layer containing the delafossite and the carrier is a layer of a material, that is more resistant to the electrolyte than the carrier. '9 .. Electrode according to claim 1, characterized in that the platinum-cobalt-delafossite, ' the palladium-cobalt-delafossite, the palladiura-chromium-delafossite, the palladium-rhodiura-delafossite, the palladium- Ruthenium delafossite, the Palladiura lead delafossite,. the palladiura-yttrium-delafossite, the palladium-lanthanide-delafossite, the silver-cobalt-delafossite, the silver-gadoliniura-delafossite, the silver-scandium-delafossite, the silver-thaHium-delafossite, the silver-indiura-delafossite, the Copper-cobalt delafossite or plucking iron delafossite is used. 10. Electrochemical one equipped with a pair of electrodes Device, characterized in that one of the . contains a delafossite on both electrodes. 11. An electrochemical device according to claim 10, wherein the anode is characterized by an electrically conductive support with a coating containing a delafossite. . 308833/109 « 12. Electrochemical device according to claim 10, characterized by an external means with which
an electromotive force is brought into effect between the pair of electrodes. 13. Electrochemical device according to claim 10, characterized by an internal means with which
an electromotive force is brought into effect between the pair of electrodes. 14. Electrochemical device according to claim 10, characterized in that the carrier consists of a
Valve metal. 15. Electrochemical device according to claim 14, characterized in that the rectifier metal Titan used. 16. Electrochemical device according to claim 11, da-. characterized in that the support is made of graphite consists. 17. Electrochemical device according to claim 10, characterized in that the delafossite is palladium contains. 18. Electrochemical device according to claim 10, characterized in that the delafossite contains platinum. 309832/1096 19. Electrochemical device according to claim 10, characterized in that between the delafossite containing-layer and the carrier is a layer of a material that has the electrical Conducts electricity better than the Delafossit. 20. Electrochemical device according to claim 10, characterized characterized in that between the layer containing the delafossite and the support a Layer is made of a material that is more resistant to the electrolyte than the carrier. 21. Electrochemical device according to claim 10, characterized in that the Delafossit is used Platinum-cobalt-delafossite, the palladiutn-cobalt-delafossite, the palladium-chromium-delafossite, the palladium-rhodium-delafossite, the palladium-ruthenium-delafossite, the paliadium-lead-delafossite, the palladium-yttrium-delafossite, the palladium-lanthanide-delafossite, the silver-cobalt-delafossite, the silver-gadolinium-delafossite, the silver-scandium delafossite, the silver . ThallLum delafossite, the silver indium delafossif, the Copper-cobalt delafossite or copper-iron delafossite used. 22. A method for carrying out an electrochemical reaction, wherein a pair of electrodes in an electrolyte 309832/1096 . used and an electrical potential is established between the pair of electrodes, thereby characterized in that one of the two electrodes contains a delafossite. 23. The method according to claim 22, characterized in that the delafossite contains palladium. 24. The method according to claim 22, characterized in that the delafossite contains platinum. 25. The method according to claim 22, characterized in that the electrical potential is applied from the outside. 26. The method according to claim 22, characterized in that the electrical potential is applied from the inside. 27. ^ The method according to claim 22, characterized in that der.Delafossit is contained in a coating applied to an electrically conductive carrier. 28. The method according to claim 27, characterized in that the carrier consists of graphite. . · 29. The method according to claim 27, characterized in that the carrier made of a rectifier metal (valve metal). 309832/109 « 30. The method according to claim 29, characterized in that the carrier consists of titanium. 31. The method according to claim 27, characterized in that that between the layer containing the delafossite and the. Carrier inserted a layer of a material that conducts the electric current better than the Delafossit. 32. The method according to claim 27, characterized in that between the layer containing the delafossite and a layer of a material is inserted into the carrier which is more resistant to the electrolyte than the carrier is. 33. The method according to claim 22, characterized in that the delafossite is the platinum-cobalt delafossite, the Palladium-cobalt delafossite, palladium-chromium de-lafossite, the palladium-rhodium-delafossite, the palladium-ruthenium-delafossite, the palladium-lead-delafossite, the palladium-yttrium-delafossite, the palladium-lanthanide-delafossite, the silver-cobalt-delafossite, the silver Gadoliniura delafossite, the . Silver scandium delafossite, the silver thaüaium delafossite, the silver-Indian delafossite, the copper-cobalt-delafossite or the copper-iron delafossite is used. 309832/1096 34. A palladium-ruthenium oxide with the crystal structure of a Delafossite. 309832/1096