Titanium as a carrier metal

Titanium as a carrier metal Titanium (or a similar metal such as tantalum, etc.) cannot work directly as anode because a semiconducting oxide layer inhibits any electron transport in anodic direction ( valve metal ). But coated with an electrocatalytic layer, for example, of platinum or of metal oxides (see below), it is an interesting carrier metal due to the excellent corrosion stability in aqueous media, caused by the self-healing passivation layer (e.g. stability against chlorine in the large scale industrial application of Dimension Stable Anodes DSA , see below). 

A cathodic current is in principle possible, but in case of hydrogen evolution, titanium will be destroyed by hydride formation. 

Protection layers between the titanium metal and the electrocatalytic coating, for example, of substoichiometric titanium oxides (see Ebonex above), increase the stability by shielding the metal, for example, to avoid the formation of insulating titanium dioxide layers on the metal [35]. The preparation of such electrodes with optimal properties usually needs the special know-how of commercial suppliers. 

It has to be considered that titanium - at least without special protection layers - will be attacked by several chemicals for example, fluorides, fluorine-containing substances, such as tetrafluo-roborates BF4, or oxalates, and possibly by other organic acids, which may be formed during anodic oxidation reactions. An application of titanium in nonaqueous media is not suitable (instability of the passivating oxide layer). 

other metal oxide coatings are possible, for example, electrochemically deposited manganese dioxide. Moreover, further electrocatalytically active oxides are research objectives, for example, oxides with spinel structure such as CoMu204 [36]. 

---