Synthesis Of Monodisperse Hollow Carbon Spheres And Their Application In DMFCs

Directed methanol fuel cells （DMFCs） have received considerable attentionbecause they are environmental friendly and can directly convert methanol toelectricity through electrooxidation. Platinum （Pt） has been the most effective metalfor methanol oxidation, but pure Pt is not efficient due to poisoning of carbonmonoxide that formed during the methanol electrooxidation reaction. To address thepoisoning by CO, modification of Pt with foreign metals （e.g., Ru, Ni, Co, Mo, andSn） is necessary. The PtRu binary alloy catalysts have been widely used as thecatalysts for DMFCs in the world. In addition, hollow carbon spheres （HCSs） are avery attractive support for PtRu nanoparticles due to their unique structure andexcellent properties such as low density, high specific surface area, and large porevolume. In this thesis, we have developed and investigated monodisperse HCSssupported PtRu nanoparticles as electrocatalysts, the main research as follows:（1） Discrete and highly dispersible hollow carbon spheres were prepared byusing a confined nanospace pyrolysis method, in which the polystyrene latex particles（200±20nm）were stepwisely coated with a phenol-formaldehyde polymer （PF）inner shell and a silica outer shell, and monodisperse HCSs were obtained afterpyrolysis of this spherical composite （PS@PF@SiO₂） and subsequent elimination ofthe outer silica shell. The diameter of HCSs was390±10nm and the surface areawas around226.6m2g1.（2） The electrocatalysts, PtRu nanoparticles supported on HCSs, were preparedby the impregnation and reduction method with sodium borohydride. Uniform andwell-dispersed PtRu nanoparticles with a narrow particle size distribution （2⁴nm）were observed and depended on the total metal loadings. The ICP-AES resultsindicated that the total metal loadings were11.00wt%for PtRu/HCS-1,15.75wt%for PtRu/HCS-2, and19.52wt%for PtRu/HCS-3in the final catalysts.（3） The electrooxidation of methanol on the supported catalysts was investigatedat room temperature by electrochemical impedance spectroscopy （EIS）, potentiostaticcurrent–time （i-t）, and cyclic voltammetry （CV）. The results showed that the catalystwith PtRu loading of15.75wt%（PtRu/HCS-2） possessed the highest catalytic activitythan the other PtRu catalysts. The peak current for PtRu/HCS-2was650.01mA mg–1Pt, the stability of PtRu/HCSs was PtRu/HCS-2> PtRu/HCS-3> PtRu/HCS-1.