Method of producing an oxygen generating electrode

A method of producing an oxygen generating electrode, comprising the steps of:

• preparing a base material having at least a surface thereof made of titanium alone or a titanium alloy with a roughness of 5 to 100 .mu.m according to surface roughness (R.sub.z) measured by JIS B0601;
• forming a primary coating on the surface of the base material;
• and
• forming a catalyst layer on the primary coating, the catalyst layer containing an oxide of a platinum group element as a main component, and wherein
• said primary coating is composed of
• (1) a titanium oxide coating and an oxide mixture layer, wherein (a) the titanium oxide coating is made of a titanium oxide only and includes a first titanium oxide layer formed by electrolytically oxidizing the surface of the base material in an electrolyte solution to which no titanium ions have been provided, and a second titanium oxide layer formed on the first titanium oxide layer by a thermal decomposition method which involves applying a solution containing a titanium compound to the electrolytically prepared oxide layer, and (b) the oxide mixture layer includes at least one layer formed on the titanium oxide coating;
• consists of a mixture of tantalum oxide and iridium oxide;
• and has a thickness of 0.1 to 10 .mu.m;
• the proportion of tantalum oxide of the oxide mixture is 50 to 90 mole % in terms of tantalum metal-reduced chemical equivalent, or
• (2) a titanium oxide coating and an oxide layer, wherein (a) the titanium oxide coating is made of a titanium oxide only and includes a first titanium oxide layer formed by electrolytically oxidizing the surface of the base material in an electrolyte solution to which no titanium ions have been provided, and a second titanium oxide layer formed on the first titanium oxide layer by a thermal decomposition method which involves applying a solution containing a titanium compound to the electrolytically prepared oxide layer, and (b) the oxide layer is formed on the titanium oxide coating and consists of tantalum oxide, or
• (3) a titanium oxide coating, an oxide layer and an oxide mixture layer, wherein (a) the titanium oxide coating is made of a titanium oxide only and includes a first titanium oxide layer formed by electrolytically oxidizing the surface of the base material in an electrolyte solution to which no titanium ions have been provided, and a second titanium oxide layer formed on the first titanium oxide layer by a thermal decomposition method which involves applying a solution containing a titanium compound to the electrolytically prepared oxide layer, and (b) the oxide mixture layer is formed on the titanium oxide coating and consists of tantalum oxide, the oxide mixture layer including at least one layer formed on the oxide layer and consisting of a mixture of tantalum oxide and iridium oxide, and having a thickness of 0.1 to 10 .mu.m;
• the proportion of tantalum oxide of the oxide mixture is 50 to 90 moles % in terms of tantalum metal-reduced chemical equivalent;
• and
• said first titanium oxide layer is formed by immersing the base material in an electrolyte, and then carrying out an electrolytic oxidation process using a quantity of electricity of 3 mAh/cm.sup.2 or less at a potential of 0.5 to 15 V with respect to the normal hydrogen electrode potential, thereby forming a layer of a titanium oxide having a thickness of 1 to 20 nm on the surface of the base material.