Graphene oxide electrocatalyst on MnO(2) air cathode as an efficient electron pump for enhanced oxygen reduction in alkaline solution

Graphene oxide (GO) was deposited on the surface of a MnO(2) air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO(2) air cathode (GO-MnO(2)). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO(2) compared to the MnO(2) cathode. The GO-MnO(2) was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm(−2), in contrast to MnO(2), which produced a maximum power density of 9.2 mW cm(−2). The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO(2) surface are responsible for the increased rate of this step, whereby GO and ERGO accelerate the process of electron donation to the MnO(2) and to adsorbed oxygen atoms.