A series of spinel-type oxides LiMn2-xCoxO4 (X = 1.0, 1.2, 1.4, 1.6) are synthesized by an improved amorphous citric precursor (ACP) method. Their specific surface areas are measured by the Brunauer-Emmet-Teller (BET) method, and their particle agglomerates are studied by scanning electron microscopy (SEM). Their electrocatalytic performances are characterized by the polarization curves of gas-diffusion electrodes that employ the oxides. The activity decreases with increasing X values.