Graphene And Carbon Nanotube Based Electrocatalyts For Oxygen Reduction Reaction

Fuel cells are attracting considerable interest as a future power source due to their high energy conversion efficiency, ambient operating conditions and environmental benefits. At present, the high cost and low stability are the common problems encounted by the commercial platinum-carbon catalyst, hence it is important to develop novel catalysts with high electrocatalytic performance. In this dissertation, two resolution routes are developed to enhance the properties of cathode catalysts while decrease their cost, including the usage of novel carbon support and the exploration of metal-free catalyst. The main contents are summarized as follows:1. With graphite powder as raw material, graphite oxide was synthesized by the modified Hummers method. The electrocatalysts of graphene-supported Pt-Co alloyed nanoparticles (Pt-Co/graphene) have been conveniently prepared by the simultaneous reduction of the mixture of graphene oxide and Pt(IV), Co(II) ions by microwave-polyol reduction followed by H2 treatment at 300℃. The Pt-Co nanoparticles are highly and homogeneously dispersed on the graphene, and the composition of Pt and Co could be modulated by changing the ratio of the corresponding precursors. The monometallic Pt/graphene catalyst presents higher electrocatalytic activity and similar stability in comparison with the commercial Pt/C, which may come from the advantage of graphene. The low price, high conductivity of graphene and the modulated metal composition provide us a platform for the optimization of the electrocatalytic performance of these catalysts.2. A novel metal-free electrocatalyst, i.e., boron-doped carbon nanotubes (BCNTs), has been developed for oxygen reduction reaction (ORR). In alkaline medium, the electrocatalytic activity of BCNT increases with increasing boron dopant, and the BCNTs catalyst present better performance than the pure CNTs. Comparing the nitrogen-doped carbon nanotubes (NCNTs), with the similar content of doping, BCNTs show lower catalytic potential but large catalytic current when the reduction reaction of oxygen occurs on the surface of the catalysts. The numbers of electrons transferred of doping carbon nanotubes are greater than pure CNTs, as well. The results show that the catalytic performance of the carbon nanotubes could be improved by the N-doped or boron-doped for oxygen reduction reaction.