The dual catalysts system, in which nano-manganese oxide (nano-MnOx) is electrodeposited on multiwall carbon nanotube (MWCNT) modified glassy carbon (GC) electrode, efficiently catalyzes 4-electron O-2 reduction in alkaline media through the redox-mediation of O-2 to O-2(-) (superoxide ion) by functional quinone groups on the MWCNT surface and the subsequent disproportionations of O-2(-) to O-2 and HO2- (hydrogen peroxide) and further HO2- to O-2 and OH- catalyzed by nano-MnOx.