The Fabrication And Functionalization Of Carbon Nanomaterials And Their Application For Oxygen Reduction Reaction

In the 21st century, the energy crisis becomes more and more serious. Fossil fuels become less and less. If we continue to empty the resources endlessly, our future generation will not enjoy. Meanwhile, in order to lessen the smog problem, it is imperative to cut the use of fossil fuels. The existing lead-acid and lithium ion batteries are not suitable for the power battery in electrical vehicles due to their low capacity. The 13th five-year plan has pointed out new energy vehicle is one of the most important parts of the civil economy. The power battery is the key factor. Hence, it is in high emergency to develop high-capacity batteries such as fuel cells and metal-air batteries. Fuel cells are more possible for large-scale application. However, due to the high price,limited reserves and poor catalytic stability, commercial Pt/C has extremely limited the application of fuel cells. Hence, it is in high demand to develop not only low price but also good catalytic activity and stability ORR catalysts to replace commercial Pt/C. A large amount of studies have proved that heteroatoms doped carbon nanomaterials may replace commercial Pt/C for their excellent ORR performance. In this thesis, carbon nanomaterials including graphene-. carbon nanotubes and MOF derived carbon are chosen as starting materials to improve ORR activity by doping?surface oxidation and mesoporous surface area.The thesis can be divided into three parts. These three parts depicted the improvement of ORR performance by three different experimental ways from three different aspects, respectively. In the first part, nitrogen and sulfur co-doped graphene is synthesized successfully by a one-pot method by directly annealing GO and thiourea. The nitrogen content is as high as 7.8%(at%) while the sulfur content is as high as only 1.41%(at%). However, NSG700 has the best ORR activity. In the second part, NST-CNT(1:3) is fabricated by hybrid acid treatment at 700 ? for 2 h. After the ORR tests, NST-CNT(1:3) is found to have an obvious improvement than pristine CNTs. Fundamentally, the incorporated oxygen-containing groups modificated onto the surface of CNTs can activate the surface solubility of CNTs. In the third part, nonporous MOF derived mesoporous carbon can also be good ORR catalysts. As confirmed by the BET and pore size distribution, nonporous MOF derived mesoporous carbon has more mesopores than carbon derived from porous MOF. Meanwhile, the specific surface area contributed by mesopores is also bigger. More specific surface area can expose more catalytic sites. More rich mesoporous structure can afford more channels for oxygen molecule and OH" diffusion. These advantages both facilitate the ORR reaction rate.