PEDOT:PSS/MnO2/rGO ternary nanocomposite based anode catalyst for enhanced electrocatalytic activity of methanol oxidation for direct methanol fuel cell

Abstract

In this work, a non-precious anode catalyst material PEDOT:PSS/MnO2/rGO ternary nanocomposite was synthesized by hydrothermal route followed by in situ oxidative polymerization. The morphology and structure of the synthesized samples were investigated by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). From the morphological investigations of the ternary nanocomposite, it is confirmed that PEDOT:PSS coated MnO2 nanorods are wrapped by rGO nanosheets. Brunauer-Emmett-Teller (BET) measurements confirm the porous structure and high surface area (190 m2/g) of the ternary nanocomposites. Electrochemical and electrocatalytic activities of PEDOT:PSS/MnO2/rGO coated ITO electrodes towards methanol oxidation were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) in 0.5 M NaOH as supporting electrolyte. Anodic and cathodic electron transfer coefficient (α and β) and heterogeneous rate constant (ks) of the ternary nanocomposite coated electrode were found to be 0.51, 0.45 and 0.055 s−1, respectively. The higher electrocatalytic activity i.e. higher oxidation current density (56.38 mA/cm2) and lower onset potential (0.32 V) of the ternary nanocomposite towards methanol oxidation may be due to synergistic effects of excellent conductivity of rGO nanosheets and porous nanostructure of PEDOT:PSS coated MnO2 nanorods. Long term stability holding of current density 50 mA/cm2 upto 1 h and higher cyclic stability (current retention factor 83%) upto 700th cycles imply that PEDOT:PSS/MnO2/rGO ternary nanocomposite can be the potential alternative of platinum based anode catalyst in direct methanol fuel cell.