Investigation On Preparation Of Graphene Oxide Supporting Catalysts And Their Catalytic Performance In Oxygen Reduction

Graphene has attracted tremendous attention from both the experimental and theoretical scientific communities, because of its unique nanostructure and extraordinary properties. Besides potential applications in nano devices, graphene also is a good candidate for catalyst support. In this thesis, graphene oxide (GO) was prepared and used as catalyst supports to prepare WC/GO catalysts. Another research is to study the loading and dispersion of GO sheets into porous carbon materials, The GO/carbon porous materials could stand heat treatment at high temperature. So this research opens a new way for supporting nano-catalysts by graphene oxide. Additionally, the electrocatalytic activity and stability of above catalysts in oxygen reduction reaction (ORR) were systematically investigated.In this thesis, the preparation of GO and the optimization of the preparation parameters were investigated. To prepare high-quality GO, new measures were taken on the basis of Hummers method reported in literature. A step of preoxidation treatment was added, in which the mixture of graphite, concentrated H2SO4 and NaNO3 was hold in 80oC water bath for 1 hour. Resultantly, the GO with higher oxidation degree was obtained. The obtained GO samples were characterized by XRD, SEM, FT-IR, TGA-DSC and Raman spectroscopy.This thesis focused on the preparation of GO supported catalysts. GO solution was prepared by ultrasonically treating graphite oxide in water. Then, the GO solutions were mixed with chloroplatinic acid (H2PtCl6) solution and metatungstic acid (H2WO3) solution, respectively. PtCl62- and WO32- were adsorbed by the functional groups in the GO sheets. After drying, the samples were treated by pure H2 and CH4/H2 mixture gases, respectively, and then Pt/GO and WC/GO catalysts were obtained. XRD and SEM/EDX results show that Pt/GO catalysts with higher Pt content had larger Pt particl sizes, while the WC particle sizes in the WC/GO catalysts were insensitive to the WC contents. There probably exists some interaction between the treated GO support and WO32-, which is beneficial to the dispersion of WC particles on the surface of the treated GO. In addition, it was found that GO sheets regraphitized during heat treatment at high temperature. The electrochemical activites of Pt/GO and WC/GO catalysts with different Pt and WC contents were evaluated by cyclic voltammetry method. The results show that higher Pt content results in larger Pt particles due to agglomeration, which led to the worse activities of Pt/GO catalysts. However, the catalytic properties of WC/GO catalysts increase steadily with the increase of WC content. Moreover, WC/GO catalysts exhibited better electrocatalytic performance than Pt/GO catalysts under the investigated conditions.Aiming at the problem of agglomeration and regraphitization of GO, GO sheets were loaded into porous carbon materials. It was found that most of the GO sheets stick to the walls and some GO sheets hang between the walls of the porous materials. This novel graphene/carbon material with porous structure after treatment in NH3 showed good electrocatalytic activities for ORR. As catalyst support, this novel catalyst may possess good catalytic performance.