Preparation And Electrocatalytic Properties Of Carbon Nanomaterials By DC Arc Method

A direct current(DC)arc method has many advantages in carbon nanomaterial synthesis,such as high efficiency,good safety,good reliability,high chemical activity,extremely fast cooling rate and controllable reaction atmosphere.Therefore,carbon nanomaterials,including FLG,carbon nanoballs,and SWCNHs had been synthesized by the method.However,the growth mechanism of carbon nanomaterials synthesized by DC arc method is still unclear due to complex electromagnetic and high temperature properties.Given the superior natures of carbon nanomaterials prepared by DC arc method,such as high conductivity,high catalytic activity,high specific surface area,and good chemical and thermal stability,etc.,they can be used as catalysts or as support of catalysts for CO2RR and ORR.However,its catalytic activity and durability need to be further improved.In order to solve the basic scientific issues of the growth mechanism of carbon nanomaterials sunthesized by DC arc method and the efficient utilization of carbon nanomaterials as catalysts,this thesis has carried out the following works:(1)By using Ar,H₂,and N₂ as buffer gases,FLG,ASCNs,and SWCNHs were prepared in the inner wall deposition by DC arc method.Ar,N₂,and H₂ were the key to the formation of ASCNs,SWCNHs,and FLG,respectively.Based on the above results obtaining the growth mechanism of carbon nanomaterials,argon played a quenching role in the preparation of ASCNs;C-N promoted the formation of SWCNHs;hydrogen terminated carbon suspension bonds to facilitate FLG forming.In order to explore deeply the growth mechanism of FLG,a hydrogen-induced edge growth model was proposed by combining experiment with numerical simulation results.(2)By using Ar/H₂,Ar/N₂,and H₂/N₂ as buffer gases,FLG,ASCNs,SWCNHs,carbon nanocages,and polyhedral graphite were prepared in the inner wall deposition by DC arc method.In the mixed atmosphere,graphene islands with different amounts of C-H due to the different hydrogen concentration leads to the growth of carbon nanocages with good structural stability and polyhedral graphite.(3)SWCNHs with different nitrogen content were prepared by DC arc method and considered as supporters of Pt for ORR catalysts.In order to investigate the durability of catalyst,ORR performance was tested after 1000 CV cycles again.By comparing ORR performances before and after 1000 CV cycles of the four catalysts,Pt/SWCNHs with the nitrogen content of 2.9%not only exhibited excellent catalytic performance,but also showed the superior durability.(4)SWCNHs-A,SWCNHs-N,and SWCNHs-O with different nitrogen and oxygen contents were fabricated by DBD plasma under N₂,O₂,and air,and then were considered as catalysts for Na-CO₂ batteries.Among these catalysts,SWCNHS-A showed higher catalytic activity of CO₂RR due to the good adsorped capacity of CO₂and the synergistic catalysis of nitrogen and oxygen functional groups.ASCNs with different sp²/sp³ ratios were obtained by DBD plasma under Ar with different treatment times.The increased proportion of sp³ carbon of modified ASCNs led to the redistribution of surface charge,thus improving the performance of CO₂RR,and meanwhile sp²/sp³ ratio of 1.9 presented the best CO₂RR performance.The above results play a significant role in invesitgating the growth mechanism of carbon nanomaterials sunthesized by DC arc method.Meanwhile,it can promote the basic research of carbon nanomaterials as catalysts for Na-air/CO₂ batteries and catalyst carriers for fuel cells to move towards practical application.