Biotemplated Synthesis Of Carbide Nanowires And Their Supported Pt Nanop Articles As Electrocatalysts For Fuel Cells

As we know, catalyst support materials play a vital role in improving the catalytic activity in fuel cells and reducing the Pt usage to lower the cost of catalysts. Therefore, the development of new catalyst supports with improved activity and durability of Pt catalyst is highly desirable.In this dissertation, we report a novel biotemplated synthesis of one-dimensional (ID) carbide nanowires as catalyst supports. Platinum (Pt) nanoparticles are highly dispersed on the surface of the ID carbide nanowires via sodium borohydride reduction method (NaBH4) and urea-assisted ethylene glycol reduction method (HD-EG), respectively, narrowly distributed and well crystallized. Moreover, the relationships between the ID carbide nanowires and methanol electrooxidation properties also have been studied. The main work is as follows:NbC nanowires (NbC NWs) have been successfully synthesized by a bamboo-based carbon-thermal method and used as a potential platinum catalyst support for direct methanol fuel cells (DMFCs). The NbC NWs show a highly oriented growth behavior, high electrical conductivity, and outstanding oxidation resistance. The Pt nanoparticles with the average size of about6nm were highly dispersed on the surface of the NbC NWs via sodium borohydride reduction method. Compared with conventional Pt/C (Vulcan XC-72) catalyst, the forward peak current density of Pt/NbC NWs is766.1mA mg-1Pt, substantially higher than that of the Pt/C catalyst (221.7mA mg-1Pt), and Pt/bamboo charcoal catalyst (53.5mA mg-1Pt). In addition, the onset and peak potentials of the Pt/NbC NWs catalyst shows a larger negative shift compared to the Pt/C catalyst and Pt/bamboo charcoal catalyst. Meanwhile, the Pt/NbC NWs catalysts possess excellent electrochemical stability, which could be attributed to little change of electrochemical surface area during methanol oxidation.In addition, the TiC NWs have been synthesized via a simple biotemplating method using natural nanoporous cotton fibers as both the carbon source and the template. The Pt nanoparticles deposited onto the TiC NWs by HD-EG method are small (ca.3nm), narrowly distributed and well crystallized. The electrocatalytic performance of the Pt/TiC NWs, Pt/C and Pt/CFs catalysts, which were evaluated by CVs and CA in electrolytes of0.1M H2SO4and1M CH3OH. Our studies demonstrate that Pt/TiC NWs catalyst exhibited attractive electrocatalytic properities, such as higher electrochemical active surface area (ECSA), much improved electrocatalytic activity and long-term durability toward MOR in comparison with the Pt/Vulcan XC-72catalyst and Pt/CFs catalyst. The ECSA of the Pt/TiC NWs is estimated to be203.83m2g-1, much higher than that of the Pt/C (140.12m2g-1) and Pt/CFs (16.96m2g-1). Additionally, after500cycles, no recordable loss of ECSA on Pt/TiC NWs is observed, while～43%and～50%loss of ECSA on Pt/C and Pt/CFs are observed. That is the direct evidence that Pt/TiC NWs has superior stability in comparison with Pt/C and Pt/CFs catalysts.