MnO₂ supported Pt nanoparticels with high electrocatalytic activity for oxygen reduction reaction

We report the hydrothermal synthesis of manganese dioxide (MnO₂) and its application as platinum nanoparticles (PtNPs) support for oxygen reduction reaction (ORR). The prepared MnO₂ samples with different hydrothermal reaction time were systematically investigated by X-ray diffraction (XRD) and scanning electronic microscopy (SEM), conforming that the crystalline structure of samples was transferred from γ phase to β phase, and the morphology was changed from microspheres to nanorods, respectively. The ORR activity of the samples was evaluated by rotating ring-disk electrode (RRDE) method and the optimized sample was further utilized as PtNPs support to form a new nanocomposite used as ORR catalyst. We show that the 1 wt.%Pt@MnO ₂ has a promising performance toward the electrochemical catalytical reduction of oxygen, which an overall quasi 4-electron transfer in ORR, as well as a limiting reduction current of 0.71 mA was achieved. In comparison with commercialized Pt@C and other Pt-based catalysts, the MnO₂ supported PtNP exhibited remarkable mass activity (per unit mass of Pt), as high as 7.07 mA μg^-1, in alkaline solution. We demonstrate that the hydrothermal synthesized MnO₂ may offer useful applications as reliable, cost-effective and morphology controllable support for PtNP as efficient ORR catalysts.