Preparation of oxygen evolving electrodes with long service life under extreme conditions

Among the numerous base metals tested for DSA type electrodes (e.g., titanium and its alloys, zirconium, niobium etc.), tantalum is a potentially excellent substrate owing to its good elec. cond. and corrosion resistance, and the favorable dielec. properties of its oxide. Nevertheless, a DSA type electrode fabricated on a tantalum substrate would be very expensive due to the high cost of the metal. To prep. an anode combining the excellent properties of tantalum at reasonable price, a new material was developed in the authors' lab. This consists of a common base metal (e.g., Cu) covered with a thin tantalum coating. This tantalum layer was obtained by molten salt electroplating in a LiF-NaF-K2TaF7 melt at 800 Deg. Thus, an anode metal/Ta/Ta2O5-IrO2 with a surface load of 22 g m-2 IrO2, submitted to the severe test conditions used exhibits a standardized lifetime 10-fold greater than one made with ASTM grade 4 titanium base metal. Thus, this type of electrode might be advantageously employed as an oxygen evolution anode in acidic solns. [on SciFinder (R)]