Abstract
Thin film electrodes of 
, 
, 
, and 
delafossite‐type oxides are good electrocatalysts for 
reduction and 
evolution in
. 
reduction activity correlates with the noble metal cation 
, while 
evolution activity correlates with the transition metal cation 
. Electrodes were prepared by rf sputtering from metal alloy targets. The as‐sputtered films are amorphous. The delafossite phase forms on annealing in air or 
at 700°–850°C. Thin films are metallic with 
.