Why Titanium Electrodes is Efficient in Electrochemical Process?

Why Titanium Electrodes is Efficient in Electrochemical Process?

The choice of titanium was based on the fact that it exhibits unusually high resistance to corrosion. This material is especially known for its outstanding resistance to chlorides and other halides generally present in most process streams. Its resistance is greater in the presence of oxidizing conditions, thus when Ti becomes anode (highly oxidizing conditions) there is no danger of corrosion and unwanted consumption of the material. Moreover, it is not a harmful element to human health and it is not attacked by alkali hydroxides and acids which are produced to some extent during the electrolysis of natural water.

Titanium falls in the category of partially passive metals and alloys and has been used successfully in previous electrochemical disinfection researches. When it is coated with lead dioxide (PbO2), ruthenium oxide (RuO2), and/or mixed iridium oxide (MIO) it is upgraded into the fully passive metals category or the so-called Dimensionally Stable Anodes (DSA).

Similar to stainless steel, resistance to direct dissolution of the anode is achieved by the formation of an electrically conductive oxide film over the surface of the metal. The composition of this film varies from TiO2 at the surface to Ti2O3 to TiO at the metal interface. It is produced with the pass of current and oxidizing conditions promote the formation of TiO2.

The oxide film formed on titanium is more protective than that on stainless steel, and it often performs well in media that cause pitting and crevice corrosion in the latter -e.g., seawater, wet chlorine, organic chlorides-. Since the thickness of the thin oxide film increased slowly with time, additional voltage increase was needed in order to establish a constant current density; consequently, a larger quantity of energy was consumed.

It has been demonstrated that this TiO2 film allows anodic electrochemical reactions to take place. Following this assertion and the evidence of less chlorine being detected, it could be assumed that with this cell more reactive species such as H2O2, [O], ·OH, and ·HO2 are being generated in comparison with the other reactors. Which electrochemical reactions are taking place to depend on factors such as the half-cell potential, the concentrations of the ions present in the water, and the physical state of the electrolysis products. The lower the half-cell potential of the reaction, the easier for the reaction to take place.