Studies On Synthesis And Catalytic Properties Of Nitrogen-Doped Graphene-Fe₃O₄

Graphene, a new type nano-material, is widely used in nanoelectronics,electronic sensors, transistors, solar cells, and catalysts owing to its unique structure and excellent physical properties, e.g., high specific surface area, high thermal conductivity, high carrier mobility, and super Young's modulus. However, graphene is not easy to composite with other materials since it has no band gap. Doping with nitrogen atoms is an effective strategy to open the band gap of graphene, enabling graphene to be used in a wide field of nano-devices. This is the main purpose of this work.Firstly, nitrogen doped graphene was generated by hydrothermal method, using ammonia and formamide, respectively, as the nitrogen source. Through regulating the reaction conditions, the optimal conditions of nitrogen doped graphene were obtained. For taking ammonia as nitrogen source: the ratio of graphite oxide and ammonia was 1:24, the reaction temperature was 160?, the reaction time was 12 hours, the percentage of the nitrogen atoms was 9.08%, pyridine nitrogen was the main form of nitrogen existing; For taking formamide as nitrogen source: the ratio of graphite oxide and ammonia was 1:100, the reaction temperature was 140?, the reaction time was 12 hours, the percentage of the nitrogen atoms was 5.67%,pyrrole nitrogen was the main form of nitrogen existing. In addition, we also got the nitrogen doped graphene taking urea as nitrogen source according to literature 42 reported methods. Combining these experimental results by different nitrogen source, the nitrogen-doped graphene mechanism was interpreted.Secondly, we separated the nitrogen-doped graphene from the reaction system by adding iron oxide to the nitrogen-doped graphene. Nitrogen-doped grapheneferroferric oxide was successfully synthesized by using hydrothermal method. In this method, we used graphene oxide and urea-iron as the reaction material,ammonia as the reducing-doping agent, ethylene glycol as the reducing agent, and polyvinylpyrrolidone(PVP) as the dispersant. The reaction temperature was set to be 200 ? and the reaction time was up to 12 hours. The composite material was characterized by infrared spectrum, X-ray diffraction spectrum, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscopy, etc. The results showed that ferroferric oxide was in the nitrogendoped graphene, most of particle sizes were less than 200 nm. X-ray photoelectron spectroscopy demonstrated that the percentage of carbon atoms was 70.34%, the percentage of nitrogen atoms was 5.43%, the percentage of oxygen atoms was21.23%, and the percentage of iron atoms was 3%.Finally, oxidation of toluene was carried out by using nitrogen doped graphene-ferroferric oxide as the catalyst and using hydrogen peroxide as the oxidant. Six aspects including reaction temperature, reaction time, solvent, the amount of hydrogen peroxide, the amount of catalyst, the catalyst types were tested to investigate the influences of the toluene oxidation reaction. The optimized conditions were as follows: the reaction temperature was 60?, reaction time was12 h, acetic acid was the solvent, toluene and hydrogen peroxide ratio was 1: 4,catalyst was 0.2g.