Preparation And Performances Of G-C₃N₄or Graphene Based Catalysts

Carbon and carbonitride materials are considered as novel types of non-metallic materials which can be widely used in the field of pollution control. Owing to their remarkable large surface area and strong adsorption capacity, carbon and carbonitride materials are widely used as substrates for metal catalytic materials, served for increasing the adsorption of target reactants and promoting cat alytic reaction. Metal materials are relatively expensive, and easily dissolved in the reaction process, resulting in harming the environment. If we can use non-metallic, such as carbon and carbonitride materials to replace metal materials completely, will expect to achieve catalytic reaction and reduce the cost of pollution control process efficienlly as well as improve the environmental security of the process. By means of compositing and doping, the novel carbon and carbonitride catalytic materials were prepared. The prepared catalytic materials achieved improved applications in the field of photocatalysis and thermocatalysis. These results are expected to develop efficient, low-cost and environment-friendly carbon and carbonitride catalytic materials, as well as to promote their applications in the field of pollution control. The following several parts of work have been done in this dissertation:In order to study the photocatalytic performance of g-C3N4and its composite materials, a hybrid photocatalyst composed of graphite carbon nitride (g-C3N4) and titanium dioxide (TiO2) was fabricated. The hybrid photocatalyst had excellent photogenerated charges separation capacity between g-C3N4and TiO2. The efficiency of phenol degradation using g-C3N4/TiO2was96.6%in60min under irradiation with a Xe lamp. The kinetic constant of phenol degradation using g-C3N4/Ti02was0.053min-1, which were2.41and3.12times of pristine g-C3N4and TiO2, respectively.g-C3N4needed to be composited with other photocatalysts, can only reduce but to avoid using metal materials. Therefore, in order to achieve metal-free catalytic reaction, nitrogen-doped graphene (N-Gr) was fabricated through hydrothermal reduction method. The nitrogen content of N-Gr was4.5%. Without the light irradation, when the reaction temperature was100℃, the conversion rate of benzyl alcohol was25.3%and the TON of benzaldehyde was0.15×10-2mol g-1in5h reation with20wt%catalyst loadings, which means N-Gr had catalytic capability in catalytic oxidation of benzyl alcohol, layed the foundation for further research. Comprehensive analysis found that oxygen-containing functional groups may have capability in catalytic oxidation of benzyl alcohol. In order to increase the amount of oxygen-containing functional groups of carbon materials, graphite oxide (GO) with plenty of oxygen-containing functional groups was fabricated through improved Hummers method. The results showed that GO had better capability in catalytic oxidation of benzyl alcohol compared with N-Gr under the same reaction conditions, and the conversion rate of benzyl alcohol was100%and the TON of benzaldehyde was0.41×10-2mol g-1. Further research found that the catalytic activity related to the mass rate of carbon and oxygen as well as the oxygen-containing functional groups of GO. When the mass rate of carbon and oxygen was more than3.01, the catalytic activity of GO decreased dramatically. And the catalytic activity of GO mainly attributed to the synergistic effect of hydroxyl and carboxyl functional groups of GO.In conclusion, g-C3N4、N-Gr and GO were fabricated as novel catalytic materials in this study. These catalytic materials were mainly composited of carbon and carbonitride materials with less or without metal phase. By means of compositing and doping. the improved efficiency and reduced cost of degradation of pollutants were achieved.