Silver-modified La0.6Ca0.4CoO3 composites for molecular oxygen reduction and evolution reaction are prepared by a chemical reduction process using N2H4 as the reducing agent at room temperature. The La0.6Ca0.4CoO3 catalysts are modified with silver content that vary from 0.3 to 30 wt.% without damaging their microstructure. The electrochemical behavior of La0.6Ca0.4CoO3 catalysts with different silver loadings is studied on classical bilayer gas diffusion electrodes. The electrocatalytic properties of these composites are evaluated by polarization curves and electrochemical impedance spectroscopy in alkaline electrolyte. The silver loading is found to have a significant impact on the electrode performances, which facilitate or block the electrochemical processes of the gas diffusion electrodes. The binary catalyst electrodes exhibit higher electrocatalytic activities than that of the electrodes with only La0.6Ca0.4CoO3 as the catalyst. In this paper, the best performance was achieved when the silver loading was 3.0 wt.%. (C) 2010 Elsevier B.V. All rights reserved.