Oxides of compositions Li(1−0.5x)Fe(1.5x+1)Mn(1−x)O4 (0≤1−x≤1) with a spinel structure have been characterized by XRD analysis and Mössbauer spectroscopy. The surface properties of the materials have been studied by OCP, pHz and XPS measurements. The influence of the substitution of Fe by Mn on the electrocatalytic activity of the electrodes has been analyzed in terms of Tafel slopes and proposed cationic distribution. The oxygen evolution reaction depends on both OCP and pHz, and it is very sensitive to the iron/manganese ratio in the octahedral sites of the spinel structure.