Mno₂-Novel Metal Composite: Shape-Controlled Synthesis And Its Electrocatalytic Activity

In this work, Manganese dioxide （MnO₂） nano-materials weresynthesized via an alcohol assisted sol-gel method, X-ray diffractionmeasurement （XRD）, scan electron microscopy （SEM）, high resolutiontransmission electron microscopy （HRTEM） and Tg-DTA testing were appliedto characterize the structure of MnO₂and their synthesis mechanism. The keyfactor to control the micro morphology of as-prepared MnO₂material has beenfound as the concentration of K⁺contained in the xerogel of manganese oxide.In the case of high concentration of K⁺, the MnO₂is trend to form α-MnO₂nanowires （aspect ratio＞1000）, conversely, α-MnO₂nanoparticles is themajor products. In addition, the concentration of K⁺in xerogel was adjustedby the usage of DI water in the process of washing and filter. On the otherhand, Pt/C catalysts with20wt%loading efficiency were synthesizedsuccessfully, and a series of MnO₂-Pt/C catalysts with different MnO₂content was fabricated via doping by certain amount of MnO₂materials. The energydispersive spectrdmeter （EDS） characterization has been applied into analysisthe dispersion of MnO₂in Pt/C catalysts.In this work, electrochemical properties of novel metal catalyst Pt/C andMnO₂-Pt/C composite catalysts were tested in acidic electrolyte, theperformance of Pt/C forward oxygen reduction reaction （ORR） was enhancedby doping a low amount of MnO₂materials. However, it seemed a highcontent of MnO2in Pt/C would decrease the performance of Pt/C. Thegeneration amount of H₂O₂occurred during ORR was significantly reduced byMnO₂doping, which could be determined by rotation ring-desk electrodetesting （RRDE）. Furthermore, the transferred electron number of ORR on thesurface of MnO₂-Pt/C reached to3.98, which was much higher than that onthe surface of Pt/C, and this phenomenon can be leaded from the synergisticeffect between Pt/C and MnO₂, which play the role of co-catalyst.