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.