Abstract
Pyrochlore structure oxides described by the formula 
, where 
, 
, 
and
, have been evaluated for oxygen electrocatalysis. In alkaline electrolyte between room temperature and 110°C, these materials display significantly lower polarizations than any other catalyst for 
evolution and are among the best for
reduction. Rotating ring disk experiments have not detected soluble 
as an intermediate during 
reduction. It has been established that reasonable activity maintenance is achievable over relatively long periods (500–1800 hr).