O 2 Electrocatalysis on Thin Film Metallic Oxide Electrodes with the Delafossite Structure

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 .