Synthesis,Structure Desigen And Application Of Novel Carbon Materials Via Organic Dehalogenation

Porous carbon materials show important applications on energy storages and environment protection.For the preparation of porous carbon materials,the choice of carbon sources is mostly confined to O,N-contained organics such as biomasses and resins.Halogenated polymers is seldom used as carbon precursors.However,halogen-contained polymers can go through special dehalogenation.In detail,halogens in polymers can combine with hydrogen on adjacent carbon atoms to form hydrogen halide.The process would promotes the formation of sp² hybrid carbon atoms,which is in great significant of highly conductive carbon materials.In these thesis,halogen-containing polymers were choosen as carbon source to synthesize several different novel porous carbon materials combined with hard template and self-template methods.The effects of carbon sources on the conductivity of materials were studied.And the applications on energy storage and environment protection of these porous carbon materials are explored.The main researches and innovative achievements are listed as follows:1.The study of dehalogenation and its template method for three dimensional porous carbon.Firstly,choosing polyvinyl chloride and polyvinyl alcohol which have similar structure as the research objects to study the dehalogenation process.The thermogravimetric-mass spectrometric analysis shown that the pyrolysis of O-contained PVA would produce large aoount of small organics such as CO₂,CH₄,C₂H₆,while the pyrolysis of polyvinyl chloride mostly produce sp²-hybrid carbon-contained products due to its special dehalogenation.The cheracterizaiton enable lower defects,stronger crystallinity of the PVC-derived carbon.Then,with different organics as precursors,several pyrolytic carbon materials were synthesized.The conductivity test revealed that the carbon materials obtained by pyrolysis of halogen-containing organic compounds have better conductivity.Furthermore,a three-dimensional porous carbon material was synthesized with PVC as carbon source and magnesium oxide nanoparticles as inorganic template.By adjusting the mass ratio of MgO to PVC,the specific surface area and pore volume of synthesized materials can be controlled,and influence to the performance for supercapacitor was studied.Via introducint ammonia during cabonization,the material possesses high doping of active nitrogen.And its supercapacitor performance was further improved,which is superior to the commercial activated carbon?YP-50?.2.Self-template method for three dimensional graphene foam via dehalogenation of polymer.With a hollow polyvinylidene chloride microsphere-assembled polymer clay as carbon source,a three-dimensional porous graphene foam was synthesized.Because of its unique three-dimensional structure and the good supporting effect by bubbles in hollow microspheres,the polymer clay would not collapse during carbonization,which enables the synthesized graphene foam to possess similar size,shape and microstructure with its precursor.Combining with the excellent plasticity of polymer clay,this material can be used to synthesize three-dimensional graphene foams with various shapes and sizes.The graphene foam has abundant macroporous structure?20-100?m?with a low density as low as 16 mg/cm³.Due to highly sp²-hybridation,the material shows good conductivity?2.9 S/m?and thermal stability.The unique three dimensional structure enable it to support more than 20,000times its weight.In addition the material exhibits excellent hydrophobicity and shows outstanding performance on the application of oil adsorption.The maximum adsorption capacity of the material reaches 144 g/g.3.The application study of graphene foam for absorption of viscous crude oil.Crude oil is difficult to be adsorbed at room temperature by adsorbents because of its high viscosity.Therefore,it is necessary to raise the temperature of oil to decrease its viscosity.In this work,the graphene foam obtained from carbonization of polymer clay was quickly heated under a small voltage due to its excellent electrical conductivity.The heated graphene foam can increase the temperature of its surrounding crude oil and reduce the viscosity.Then,the warmed crude oil is efficiently absorbed by the graphene foam.Besides the joule-heating,the graphene foam can also be heated by irradiation of sun to absorbe viscous crude oil according to its good optical absorption characteristics.Absorbtion experiment shows that the graphene foam adsorbed crude oil to 67%of its pore volume with an adsorption capacity of 41 g/g after 12hours'irradiation under the one sun's intensity.Due to the excellent thermal stability of graphene foam,the adsorbed oil in graphene foam is easily removed by combustion,thus making the foam can be reused for several times.4.The application study of graphene foam for thermal energy storage.A phase change composite material was prepared by filling the stearic acid into polymer clay-derived graphene foam matrix.The thermal conductivity of the composite material was increased by two times compared with pure stearic acid which achieves fast thermal response.The unique three-dimensional porous structure of graphene foam improves the shape stability of phase change materials,so that no stearic acid leakage will occur after melting.Due to the excellent optical absorption properties,the composite material also exhibits this characteristic with an optical absorption efficiency of nearly 90%.Under the irradiation of sunlight,the composite material can be quickly heated and store thermal energy by melt of stearic acid,thus successfully realizing the photothermal conversion and storage of solar energy,which has good application potential.5.Benzen ring assited sol-gel method for synthesis of three dimensional porous carbon.A sol-gel method was proposed to synthsize mesoporous carbon materials.Inspired by the above research,benzyl alcohol,a small molecule with benzene ring structure,was added to the sol.This stable benzene ring structure is difficult to decompose at high temperature,which is beneficial to the sp²-hybridization of carbon atoms,and ultimately improves the conductivity of the prepared carbon materials.The synthesized mesoporous carbon material show good electrochemical activity for supercapacitors.Furthermore,a nitrogen and oxygen doped hierarchical porous carbon material was synthesized by introducing the intense decomposition of nitrate.The material has a high specific surface area?1213 m²/g?and a large number of pores about 50 nm and 2.4 nm.Nitrogen and oxygen were also doped in this process.The carbon material shows an outstanding performance for supercapacitors and delivers a mass specific capacitance of 415 F/g at a current density of 1 A/g.