Preparation Of Coal Tar Pitch-based Porous Carbons And Their Application In Supercapacitors And Photocatalysis

Coal tar pitch（CTP）,featuring low ash content,high carbon content,low price and wide sources,is a by-product of the coking process.CTP is prepared into a functional carbon material that not only reduces production costs,but also enables the high value-added utilization of CTP.In this thesis,CTP was used as the carbon source,and fluidized catalytic cracking oil（FCCO）was used as an additive to improve the plasticity of CTP,to prepare porous carbons（PCs）materials,which were applied to supercapacitors and photocatalytic degradation of phenol containing wastewater.The specific research contents of this thesis are as follows:CTP was modified by FCCO to improve the rheological properties and plasticity of CTP system.The condensed aromatic hydrocarbons in the modified CTP are not prone to excessive accumulation at high temperatures,which is favorable for the reaction with KOH to prepare PCs with high a specific area.In this experiment,the effects of activation temperature,the ratio of KOH to carbonized product,and the amount of FCCO added on the specific surface area,pore structure,and morphology of PCs were systematically investigated.The results show that PC-700-3-20 exhibited a high specific surface area(1991 m² g^-1)and developed pore structure under the optimal preparation conditions.PC-700-3-20 possessed a specific capacitance of 329F g^-1 at a current density of 0.5 A g^-1 in a three-electrode system,and the capacitance still delivered a capacitance of 220 F g^-1 as the current density increased to 20 A g^-1.The capacitance retention rate was 95.7%at a current density of 5 A g^-1 after 10000cycle measurements,indicating that the material had excellent stability.Assembled symmetrical supercapacitor based on PC-700-3-20 exhibited a competitive energy density of 5.9 Wh kg^-1 at a power density of 125 W kg^-1,and 92.8%capacitance retention after 10000 cycles.Hierarchical porous carbons（HPCs）were prepared by using Ni（NO₃）₂ as the graphitization catalyst to be supported on the improved CTP through hydrothermal pretreatment,and then through the carbonization and activation process.The introduction of Ni strengthens the hot transfer,enhances the reactivity,and trails off the difficulty of the reaction.The experiments show that the specific surface area,average pore size,degree of graphitization and electrochemical performance of HPCs prepared by Ni modification were better than those prepared without Ni modification.The specific surface area of Ni_0.3HPC-700-20 prepared under optimal conditions was2254 m² g^-1 possessing the largest number of mesopores with an average pore diameter of 2.31 nm.The increase of mesopores helps to improve the ion transport speed at high current density.The specific capacitance of Ni_0.3HPC-700-20 was 368 F g^-1 at the current density of 0.5 A g^-1 in the three-electrode system,and the capacitance retention rate was 73.3%at 20 A g^-1.The symmetric supercapacitors assembled based on Ni_0.3HPC-700-20 exhibited high energy densities in KOH and Na₂SO₄ electrolytes,among which the energy density was 8.47 Wh kg^-1 at the power density of 125 W kg^-1in KOH electrolyte,the energy density was 27.45 Wh kg^-1 at the power density of 253W kg^-1 in Na₂SO₄electrolyte.After 10000 cycle measurements,the gravimetric specific capacitance losses of Ni_0.3HPC-700-20 in KOH and Na₂SO₄ electrolytes were0 and 11.1%,respectively.PCs and Bi₂WO₆ were fabricated into PC/Bi₂WO₆ composites by hydrothermal synthesis.The introduction of PCs improved the responsiveness of PC/Bi₂WO₆composites to visible light,and the recombination ability of PC/Bi₂WO₆photogenerated electrons and holes decreased,and the photocatalytic activity was enhanced.Under the optimal preparation conditions,the degradation rate of phenol by PC_0.05/Bi₂WO₆ was 93.2%within 240 min,while the degradation rate of phenol by pure Bi₂WO₆ was only 46.3%.This thesis has 59 figures,14 tables,and 129 references.