Electrowinning Titanium Electrode
What is Electrowinning?
Electrowinning is an electrolytic process that deposits high purity metal on the cathode by applying external electrical. In the electrowinning process, metal reduction and reaction occur on the cathode, and water is decomposed at the anode surface to release oxygen. The latter reaction is known as the oxygen evolution reaction (OER). Although these two reactions are the main redox reactions in the electrowinning process, there are some other reactions happening on the surface of the electrodes. Proton reduction, also known as hydrogen evolution, takes place at the cathode surface. This reaction is undesirable since it consumes electrons and reduces the metal deposition current efficiency. In spite of the higher standard reduction potential of proton than metal, the hydrogen evolution proceeds at significantly lower rates under the electrowinning operating conditions. This is the result of the high hydrogen evolution overpotential on the surface of the metal, which makes this reaction difficult to occur. Co-deposition of some other elements, such as cobalt and copper, which have low overpotential for the hydrogen evolution reaction, decreases the electrowinning current efficiency.