Carbon Nanotube‐Modified MnO 2 : An Efficient Electrocatalyst for Oxygen Reduction Reaction

In this work, manganese dioxide/carbon nanotube (MnO 2 /CNT) have been synthesized by sonochemical‐coprecipitation method and demonstrated that it could be an effective electrocatalyst for oxygen reduction reaction (ORR). Moreover, the effect of CNT inclusion with MnO 2 was also investigated for ORR. The physical and electrochemical properties of the MnO 2 /CNT were examined by powder X‐ray diffraction (XRD), Fourier Transform Infrared (FT‐IR) spectroscopy, Brunauer‐Emmett‐Teller (BET), Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy/Energy Dispersive X‐ray (FESEM/EDX), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Mott‐Schottky and Rotating Disk Electrode (RDE) analysis. CV showed higher currents for the ORR in MnO 2 /CNT than CNT; however, ORR current dropped when the MnO 2 loading was increased from 20–40 %. The EIS analysis showed that charge‐transfer resistance for MnO 2 /CNT was significantly lower compared to the MnO 2 indicating that MnO 2 has good contact with CNT and the composite possess high electrical conductivity. Mott‐Schottky results demonstrated that incorporation of CNT into MnO 2 resulted in producing larger electron density in n‐type MnO 2 /CNT compared to MnO 2 which is liable for efficient electron donation from the Mn 3+ to adsorbed oxygen in the rate determining step. RDE results showed that MnO 2 /CNT follows 4e − transfer pathway, indicating its ability to act as an effective ORR electrocatalyst.