Preparation Of Graphene Nano Sheets And Nitrogen-Doped Carbon Nano Cages And Their Applications

Graphene nano sheets (GNS) and carbon nano cages (CNCs) are two kinds of important carbon nano materials. GNS is commonly used in nano-electronic devices, solar cells and catalysts for fuel cells, whereas CNCs, due to their unique hollow and graphitic structures, have great potential in applications such as energy storage, nano-electronic devices, fuel cells and drug carriers. At present, how to prepare high quality GNS in large scale is still a big problem. In fuel cell applications, GNS as a support material is expected to improve the durability of Pt catalyst. Current catalysts involving the use of Pt for fuel cells are still of high cost. Previous research results have suggested that N doping carbon materials possess electrochemical catalytic activity for the oxygen reduction reaction (ORR). Thus, the preparation of carbon nanomaterials with a high N content and a high specific surface area has become a hot research topic.Considering the above mentioned technical issues, this thesis focuses on continuous preparation of GNS and highly N-doped CNCs, and their applications as the catalysts of fuel cells. First, the GNS were prepared by a spray pyrolysis method, using carbonyl iron as the catalyst precursor and pyridine as the carbon source under different iron/carbon ratios and reaction temperatures. GNS were used as a Pt catalyst support, and the durability of the catalyst was investigated. Solid CNCs were synthesized by thermal pyro lysis of carbonyl iron, acetylene and ammonia. They were heat treated with the addition of NH4CI to remove the enclosed iron particles, and further with the addition of ammonia to induce N doping. Finally, the CNCs with a high N content (5.3 at%) and high specific surface area (1344 m2 g-1) were prepared. The N-doped CNCs were employed to work as a metal-free catalyst for ORR, and found to exhibit a similar electrochemical catalytic activity and a much better durability than a commercial Pt/C catalyst in acidic electrolyte.The present results are expected to promote continuous preparation and commercial applications of GNS and the use of N-doped CNCs as an important metal-free catalyst in fuel cells.