Synthesis Of Petroleum Asphalt Based Functional Carbon Materials And Its Application In The Field Of Supercapacitors

As a byproduct of vacuum distillation of crude oil,petroleum asphalt has been well known to everyone because of its low cost and abundant source.The annual output of petroleum asphalt in China is over 503 million tons in 2019.Note that,in most instances,the petroleum asphalt has been directly used as paving materials for road construction or burned as fuel.In a manner of speaking,the petroleum asphalt is still faced to the low levels of utilization.Actually,petroleum asphalt is considered as a potential ideal raw material for large-scale production of carbon materials with high added value because of its rich in polycyclic aromatic hydrocarbons and other advantages.Meanwhile,porous carbon and carbon matrix composites show great application prospects in the field of energy storage due to their excellent physical and chemical properties.Therefore,it is necessary to develop an economic and environmental process to prepare high-performance porous carbon materials and carbon matrix composites from petroleum asphalt.Is this thesis,a method is developed for in situ synthesis of N,S co-doped hierarchical porous graphene（N,S-h PGNs）by using dual-functional g-C3N4 templates.This synthesis strategy avoids the template removal,and solves the problems of complex process,time-consuming,environmental pollution and so on.The well-developed specific surface area(1093 m² g^-1)and large pore volume(5.97 cm³ g^-1)as well as enriched N,S heteroatoms endow the N,S-h PGNs with large accessible surfaces for ion absorption,rapid paths for ion/electron transfer and sufficient space for charges storage.As a result,the N,S-h PGNs electrodes deliver a high capacity of 302 F g^-1 at the current density of 1 A g^-1 and an excellent cycling stability with 97%capacitance retention even after 20000 cycles at 10 A g^-1 in KOH electrolyte.More encouragingly,the as-fabricated supercapacitors display a high energy density of 10.42Wh kg^-1 at the power density of 250 W kg^-1,outperforming other recently reported carbon materials derived from low-cost petroleum asphalt.It is worth pointing out that the petroleum asphalt usually contains a certain amount of sulfur atoms.However,little attention has been paid to dealing with this issue in most of reported works.Inspired by the hydrodesulfurization process,an in-situ sulfur-fixation strategy has been developed to controllably prepare Mo₆S_9.5/carbon nanosheets composites.Importantly,this synthetic protocol can realize the anchoring of S atoms derived from petroleum asphalt to the great extent through doped into carbon skeletons and bonded with Mo atoms,which avoids the exhaust gas pollution during the fabrication process.The optimized Mo-based/CNs with in-situ generated Mo₆S_9.5 species exhibits a high capacitance of 512 F g^-1 at 1 A g^-1 and the assembled asymmetric supercapacitors can deliver a high energy density of 30.8 Wh kg^-1 at a power density of 800 W kg^-1 and superb electrochemical stability.In conclusion,we developed a facile and economic approach to in-situ synthetize N,S co-doped hierarchical porous carbon nanosheets by using self-decompositon template and N source,as well as petroleum asphalt as both C and S sources.In addition,we also successfully developed a facile sulfur-fixation approach to turn cheap petroleum asphalt into high value-added products.More importantly,this strategy realizes the anchoring of S atoms derived from petroleum asphalt to the great extent as well,which not only avoids the exhaust gas pollution during the fabrication process but also makes full use of resources,which provides an effective method to maximize the utilization of sulfur in petroleum asphalt.