Precious metal oxide catalyst for water electrolysis

A composite catalyst comprising precipitated iridium oxide particles deposited on or at the surface of inorganic oxide particles present in a quantity of less than 20 wt. % based on the total weight of the composite catalyst prepared by a process which comprises the steps of:

• a) making a mixture by dissolving an iridium precursor compound and optionally a ruthenium precursor compound in an aqueous solution containing inorganic oxide particles,
• b) adjusting the pH of the mixture to be in the range of 6 to 10 to precipitate out iridium oxide particles and optionally ruthenium oxide particles such that the iridium oxide particles and optionally the ruthenium oxide particles are deposited or dispersed on or at the surface of the inorganic oxide particles,
• c) separating and drying the inorganic oxide particles having the precipitated iridium oxide and optionally ruthenium oxide particles deposited thereon or dispersed around, and
• d) heat treating the inorganic oxide particles at temperatures in the range of 300 to 800° C. to obtain the composite catalyst,
• wherein the iridium oxide particles comprise iridium(IV)-oxide, iridium(III)-oxide or mixtures thereof.