Overvoltage and depolarization in molten AgCl, AgBr and AgI

✍ Scribed by I.G. Murgulescu; S. Sternberg; L. Medintev; C. Mustetea

• Publisher: Elsevier Science
• Year: 1963
• Tongue: English
• Weight: 767 KB
• Volume: 8
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(63)80006-7

✦ Synopsis

By means of an oscillographic measuring assembly, the applied voltage V, the ohmic voltage drop ZR md the back emf E,, were measured for the electrolysis of AgCl, AgBr and AgI.

The abrupt drops of voltage which occur at the current cut-off are proportional to the current intensity and they represent just the ohmic voltage 1R. For the temprature range 45o6oo"C the back emf E, is not dependent on the current density (in the range 0.1-2 A/cm*) and is practically equal to the emf E,, of the reversible formation cell Ag/AgHal (melt)/Hal (C).

It was concluded that the electrochemical discharge of silver and halogen ions occurs without activation overvoltage. The absence of overvoltage in molten salts may be due to the high temperatures at which the electrode processes occur as well as to the unhydrated state of the ions. For higher temperature E, is dependent on current density: at high densities (2 A/cm*) the voltage E* is equal to +!?, but at lower densities the value of J.$, is 400-500 mV lower than E,. The results obtamed for high temperatures show the existence of intense depolari~tion caused by desorption of the halogen from the carbon electrode or its diffusion in the melt.