Facile construction of manganese oxide doped carbon nanotube catalysts with high activity for oxygen reduction reaction and investigations into the origin of their activity enhancement.

MnOx-doped carbon nanotube (MnOx-CNTs) catalysts for the oxygen reduction reaction (ORR) were fabricated using a simple electrochemical deposition method. MnOx-CNTs (0.85 wt % MnOx) could exhibit an improved electrocatalytic activity, long-term stability and excellent resistance to crossover-effect compared to Pt/C catalysts. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction analysis confirm that the MnOx in the MnOx-CNTs exists in an amorphous state. Moreover, compared to the catalytic performances of MnOx on other substrates, the MnOx-CNTs exhibit a high ORR activity. X-ray photoelectron spectroscopy results suggest that the electron transfer, from the CNTs to the Mn ions occurs and the high positive charge is generated on the MnOx-CNT surface. This is believed to be origin of the catalytic activity observed in the ORR using MnOx-CNTs.