Study On Anodic Electrocatalysts Of Direct Methanol Fuel Cells Based On Manganese Oxide

Due to the limited reserves of un-renewable fossil resources on the earth, it isnecessary to develop novel energy generators and energy conversion devices tomaintain the sustainable development of the society. Direct methanol fuel cells(DMFCs), fed on methanol, have received great attention recently for their merits ofhigh power efficiency, low pollution and low noise. Electrocatalyst is one of the mostimportant parts in fuel cells, and high cost-effective catalyst is always the goal.Combining nano-sized noble metal Pt with transitional metal oxide is a common wayto achieve that goal.Based on the unique physical and chemical properties of MnOx, together withtheir abundant reserves and cheap price, we prepared several MnOx-basedelectrocatlysts and characterized their electrocatalytic oxidation toward methanol. Themain points are summarized as follows:（1）A new Pt-based electrocatalyst with one dimensional tubular Mn3O4-C ascatalyst support was synthesized via a dual-sacrificial template strategy. Themorphology, structure and component of the catalyst were characterized bytransmission electron microscopy, X-ray diffraction, and energy dispersivespectroscopy, respectively. The electrochemical performances of the Pt/Mn3O4-Ccatalyst were investigated by cyclic voltammetry. The results demonstrate that Ptnanoparticles with an average size of1.8nm are uniformly dispersed on the tubularMn3O4-C, and the Pt/Mn3O4-C catalyst exhibits excellent electrocatalytic activity andstability towards methanol oxidation. It might be attributed to the uniform dispersionof Pt nanoparticles on Mn3O4-C and the synergetic catalytic effect of Pt and Mn3O4.（2）Nitrogen-doped hollow carbon spheres (N-HCS) were used as carbon supportsto prepare hollow sphere-like MnO2-NC through the reaction between C and KMnO4.Then Pt was deposited onto the surface of MnO2-NC to synthesize the electrocatalystPt/MnO2-NC. The microstructure and morphology of the as prepared catalysts werecharacterized by scanning electron microscopy, transmission electron microscopy,energy dispersive spectrometer and X-ray diffraction. The electrocatalyticperformances towards methanol oxidation were measured by cyclic voltammetry andchronoamperometry. The results indicate that Pt/MnO2-NC has the highest forwardanodic peak current density (as high as1675mA mg-1), almost3and4.5times higher than that of Pt/N-HCS and commercial E-TEK Pt/C catalyst. In addition, Pt/MnO2-NCshows the best electrochemical stability among them.(3)By taking advantages of the special structure of nitrogen-doped hollow carbonspheres and the synergistic catalytic effect between Pt and Mn3O4, we prepared thehollow sphere like Pt/Mn3O4-NC catalyst. The characterization of scanning electronmicroscopy, transmission electron microscopy, energy dispersive spectrometer andX-ray diffraction demonstrate that the Pt/Mn3O4-NC catalyst has a good hollow spherelike morphology, and Pt nanoparticles have an average size of2.1nm. Theelectrocatalytic properties of Pt/Mn3O4-NC for methanol oxidation were characterizedby cyclic voltammetry and chronoamperometry. The results show that Pt/Mn3O4-NC isan effective catalyst for methanol oxidation, which has a4and5times higher forwardpeak current density than that of commercial E-TEK PtRu/C and Pt/C, respectively. Inaddition, Pt/Mn3O4-NC shows the best electrochemical stability among them.