Pt-supported C-MnO2 as a catalyst for polymer electrolyte membrane fuel cells

C-MnO2 is an alternative catalyst support in polymer electrolyte membrane fuel cells. In this study, C-MnO2 was prepared by hydrothermal method using KMnO4 as the Mn source. Meanwhile, Pt/C-MnO2 electrocatalyst was prepared by impregnation chemical reduction using ethylene glycol as reducing agent and H2PtCl6 as Pt precursor. The structure and morphology of C-MnO2 and Pt/C-MnO2 were characterized by X-ray diffraction energy-dispersive spectroscopy and transmission electronic microscopy analyses. Electrochemical performance was investigated by cyclic voltammetry analyses. A rotating disk electrode (RDE) was used to examine catalytic oxygen reduction reactions (ORRs) to explore the oxygen reduction of Pt/C-MnO2. The Pt/C-MnO2 exhibited better activity and stability than those of Pt/C. In contrast to Pt/C, MnO2 possessed unique characteristics; the oxide functions as an effective Pt support and hence enhances ORR activity and durability. The RDE results for the ORR indicated that the main reaction of the Pt/C-MnO2 catalyst was the direct reduction of O-2-H2O. This reaction is similar to the mechanism of the Pt/C catalyst and both with a four-electron charge transfer. The results of the single cell polarization experiment and the ON-OFF cycling test revealed that MnO2 improves proton exchange membrane fuel cells performance and durability. This paper also investigated the mechanism through which MnO2 promotes oxygen reduction. [GRAPHICS] .