Synthesis and electrocatalytic performance of MnO2-promoted Ag@Pt/MWCNT electrocatalysts for oxygen reduction reaction

Abstract

Two forms of crystalline MnO₂ were synthesized by a hydrothermal method, and MnO₂-doped Ag@Pt/MWCNT composites were prepared by ultrasonic treatment for oxygen reduction reaction in proton exchange membrane fuel cells (PEMFC). The morphology of the electrocatalyst samples was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). We found that the Ag@Pt/MWCNTs catalyst exhibited a core–shell nanostructure and the two forms of MnO₂ were α-MnO₂ and β-MnO₂. The electrochemical properties of the electrocatalyst samples were studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in an acidic medium. The results demonstrated that Ag10%@Pt10%/MWCNTs-α-MnO₂20% had the largest electrochemical activity area (85.83 m² g⁻¹) of all electrocatalysts and the oxygen reduction reaction on the electrocatalyst proceeds through a 4e⁻ reduction pathway.