Study On Pt-based Electrocatlysts Supported On Carbon Nanotubes For Direct Methanol Fuel Cells

Direct methanol fuel cell (DMFC) uses methanol as fuel, which solves the problems in hydrogen storage, transportation. The main factors postponing the commercialization of DMFC are the high cost of Pt, relative low catalytic acitivity and poor long-time stability of anodic and cathodic catalysts et al. In this thesis, the goal of studies focus on improving the long-time stability of electro-catalysts, optimizing support material, and developing new electrocatalysts. Therefore, we studied electro-catalysts modified by polymer inonic liquids film, carbon nano-tube functionalization and Pt-based alloy catalysts in details. The main results obtained in this thesis are presented as follows:1. PILs/Pt/1-AP-MWCNTs nanocatalysts were prepared via in-situ polymerization of [Vmim]Br monomer mixed with Pt nano-particles supported on 1-AP-functionalized MWCNTs. The Pt catalysts with (PILs/Pt/1-AP-MWCNTs) and without (Pt/1-AP-MWCNTs) PIL film were characterized by Fourier transform infrared spectrometer (FT-IR), transmission electron microscopy (TEM), and so on. The electrocatalytic properties and long-time stability of PILs/Pt/1-AP-MWCNTs and Pt/1-AP-MWCNTs for methanol oxidation were investigated by cyclic voltammetry (CV). The results show that there is obvious growth and migration of Pt nanoparticles of Pt/1-AP-MWCNTs after i-t scan for 6 h by TEM, PILs/Pt/1-AP-MWCNTs have high catalytic activity as well as excellent long-time performance compared to Pt/1-AP-MWCNTs due to the presence of PIL film.2. Pt nano-pariticles supported on 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) functionalized MWCNTs were prepared by microwave-assisted reduction process in ethylene glycol. The products were characterized by Ramen spectroscopy, TEM. The electrocatalytic properties for oxygen reduction have been investigated by cyclic voltammetry on rotating disk electrode. Pt/MWCNTs-PTCDA catalyst shows much better distribution, much smaller particles size of Pt nanoparticles, higher electrochemically active surface area, and higher electrocatalytic activity towards oxygen reduction reaction compared to Pt nanoparticles deposited on pristine MWCNTs. These results indicate that PTCDA-functionalized MWCNTs are promising support for oxygen reduction.3. Pt-rich catalysts were prepared by chemically etching, based on Pt-Cu nano-particles supported on MWCNTs via NaBH4 reduction in ethylene glycol in one pot. TEM, energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were employed to characterize the morphology of catalysts and elements composition of catalysts. The results indicate that Cu still remain in catalysts and the core is composed with Pt-Cu alloy. The electrocatalytic properties of catalysts for oxygen reduction have been investigated by cyclic voltammetry on rotating disk electrode. The chemically eched Pt-Cu/CNTs catalysts show higher electrochemically active surface area, and higher electrocatalytic activity towards oxygen reduction compared with Pt nanoparticles deposited on pristine MWCNTs (Pt/CNTs), Pt-Cu/CNTs (without etching) catalysts.