ELEKTROD FOR ELEKTROKEMISKA PROCESSER SAMT SETT FOR FRAMSTELLNING AV DENSAMMA

1402414 Coated electrodes IMPERIAL CHEMICAL INDUSTRIES Ltd 30 Aug 1972 [16 Sept 1971] 43190/71 Heading B2E [Also in Divisions C7 and Hl] An electrode for electrochemical processes, e.g. anode in a mercury cathode cell electrolysing alkali metal chloride solution, electrocatalysis in a fuel cell, electrosynthesis or cathodic protection, comprises a support of film-forming metal (Ti, Ta, Zr, Nb, W) or alloy thereof, and a coating thereon consisting of an electrocatalytic, conducting matrix in which is embedded a non-conducting particulate or fibrous refractory material, e.g. ThO 2 , TiO 2 or alumino-silicate particles of 1-50 micron size, or glass, ZrO 2 , Al 2 O 3 or SiO 2 (such as quartz wool) fibres not exceeding 1mm in length. The matrix may be of one or more Pt group metals and/or oxides with or without non-noble metal (excluding Au, Ag, Hg or Pt group metal) oxides e.g. of Ti, Zr, Nb, Ta, W, Sn, Ge or Sb. The coating may be formed on the chemically cleaned support by spraying thereon at least one layer of a paint composition comprising thermally decomposable compounds of the or each metal forming the finished coating in a liquid vehicle, depositing the particulate or fibrous refractory material onto the layer of paint composition while still in the fluid state, drying the paint layer by evaporating its liquid vehicle, and firing the coated support at 250-800‹C to convert the compounds into the matrix. A plurality of layers may be applied, each dried and fired as above, when refractory fibres of mean length greater than 50 microns are deposited only onto the first layer or first two layers while still in the fluid state. Alternatively the refractory material, particularly non-fibrous particles, may be mixed into the paint composition before it is applied to the support. Suitable thermallydecomposable compounds are halides and halo-acid complexes, resinates and alkoxides of the Pt group metals; and alkoxides, alkoxyhlides (Cl, Br or F) and resinates of the filmforming metals, e.g. alkyl orthopoly- or halo- (Cl, Br or F) titanates. A exemplified paint composition is RuCl 3 and tetrabutyl orthotitanate in n-pentanol. For forming a Pt group metal matrix, a reducing agent e.g. linalool (3, 7-dimethyl-1, 6-octadien-3-ol) is included in the paint composition. For forming a preponderantly oxide matrix, each layer is fired in an oxidising atmosphere e.g. air.