Experimental Study On High-value Carbon Materials Manufactured From Liquid Hydrocarbon Based On Radio Frequency Inductively Coupled Plasma(ICP)

Liquid waste,including aromatic hydrocarbons in tar compounds and n-dodecane in the extract of nuclear waste,is a kind of valuable resource without effective disposal in the industry and our life.Non-thermal plasma technology has the characteristics of high energy density,controllable plasma parameters and numerous applications.Radio frequency inductively coupled plasma?ICP?is one of non-thermal plasma technologies and widely utilized in the preparation of nanomaterials from hydrocarbons.ICP plasma assisted chemical vapor deposition?ICPECVD?is an appropriate method to prepare carbon materials with specific morphology and structure,such as graphene.Due to excellent electrical conductivity of graphene,it is doped in catalytic electrode materials for hydrogen evolution reaction?HER?to further improve the added value of carbon materials.In this study,the n-dodecane decomposition by using ICP system is performed,then the reaction characteristics and the performance of catylytic materials are sufficiently investigated.In addition,after doping the obtained carbon materials with transition metal disulfides?TMDs?,the catalytic properties of the composites for hydrogen evolution reaction are studied,and the theoretical support is provided by DFT quantum mechanics calculation.The main contents and conclusions of this dissertation are as follows:?1?Carbon materials and gaseous products prepared by n-dodecane decomposition in radio frequency inductively coupled plasma are characterized and analyzed by various technological means of SEM,Raman spectroscopy and gas chromatography.The morphology and structure of graphene are influenced by plasma input power,gas ratio,n-dodecane injection rate and reaction temperature.At the optimized condition of 500 W,H₂/Ar=5:10,30L/min,and 800?,the graphene is observed with interweaved nano-layers and the length ranging from 500 nm to 1m.In the outlet gas of n-dodecane decomposition,the gaseous products below C₂ mainly consist of CH₄,C₂H₂,C₂H₄,C₂H₆ and H₂.The proportion of gas components is affected by hydrogen flow rate.?2?SEM,EDS,Raman spectroscopy,HR-TEM and XPS are used to characterize the surface structure and electrochemical workstation is utilized to test the performance of the catalytic composite materials.MoS₂ in Ni/VGNS/MoS₂ composites grows in the structure of interweaved layers and pores of graphene,accompanied by partially granular and linear structure,and a large number of S-edge structures is found to provide active sites.Meanwhile,electrochemical tests show that Ni/VGNS/MoS₂ composites have better HER catalytic performance and catalytic stability than MoS₂ and other materials.Its charge-discharge resistance is only 3.8?,and its electrochemical active areas are similar to MoS₂.?3?Models of Ni/VGNS/MoS₂ and Ni/MoS₂ are established and DFT quantum mechanics calculations are carried out to study the intermediate mechanism of Volmer-Heyrovsky reaction and Volmer-Tafel reaction.The results show that excellent electrical properties of graphene make it possible to transport electrons rapidly at its contact with metal electrodes,thus it effectively reduces the barrier height of electron migration between metal electrodes and catalysts.Meanwhile,comparing to Ni/MoS₂,the highest Gibbs free energy barrier in MoS₂/VGNS/Ni is the lowest.And the free energy barrier of Volmer-Heyrovsky reaction is lower than that of Volmer-Tafel reaction,so the Volmer-Heyrovsky reaction dominates the hydrogen evolution reaction.