OXYGEN REACTIONS AT THE SINGLE-CRYSTAL LAF3 ELECTRODE INTERFACE

Oxygen-sensitive electrode systems incorporating single-crystal LaF3 h ave been investigated by cyclic and inversion voltammetry. The reducti on of oxygen has been observed at the LaF3/Me air interfaces (Me = W, Mo, Cr, Nb) at E = -0.8 to -2.1 V, as have the coupled reactions of me tal oxidation, which disappear in a nitrogen atmosphere. It is demonst rated that the presence of oxides at the electrode surface either cata lyzes the ionization of oxygen (LaF3/W, LaF3/Nb, LaF3/Cr) or inhibits oxygen reactions (LaF3/Mo, LaF3/Cr, LaF3/Nb) until they are eliminated completely. It is established that the treatment of the LaF3/W and La F3/Mo interface with moist air or of the LaF3 surface with an alkali s olution (LaF3/Cr) temporarily reduces the over-voltage for oxygen redu ction, while preserving the irreversibility of the electrode systems t oward oxygen-involving reactions.