Preparation And Modification Of Carbon-based Materials Derived From Petroleum Vacuum Residue And Research Of Their Oxygen Reduction Performance

Petroleum vacuum residue,as a by-product of crude oil processing,has an annual output of hundreds of millions tons.It is of great significance to develop new ways to realize the high value-added utilization of petroleum vacuum residue.Since the petroleum vacuum residue is rich in carbon elements,it can be used as a carbon source to prepare different carbon-based nanomaterials.Carbon-based nanomaterials have demonstrated excellent catalytic activity in the field of electrocatalytic oxygen reduction reduction because of its unique electronic properties,adjustable nanostructures and other characteristics.In this paper,a series of porous carbon and its composite materials were prepared by using petroleum vacuum residue as the carbon source combined template method,and the influence of the preparation process on the catalyst was studied.A variety of characterization methods were used to analyze the synthesized porous carbon-based materials and their ORR performance was investigated.The main research contents are as follows:1.Porous carbon materials were prepared by high-temperature carbonization and acid etching with the petroleum vacuum residue as a carbon source and nano-iron oxide as the template.By optimizing the reaction conditions in the preparation process,including the screening of petroleum vacuum residue from different source,the selection of the kind of template agent,the amount of template agent and the carbonization temperature,it was determined that when Kuwait vacuum residue is used as the carbon source and nano-Fe2O3 is used as the template,the mass ratio of them is 1:4 and the carbonization temperature is 800?,porous carbon materials with good ORR performance can be obtained.The specific surface area of the porous carbon material prepared under the optimal conditions was 638.4 m2 g-1,and the N content was 1.17 at%.As an oxygen reduction catalyst,it shows good catalytic activity in alkaline electrolyte,and has outstanding stability and resistance to methanol poisoning,which is superior to commercial Pt/C.2.Using petroleum vacuum residue as carbon source,nano-iron oxide as a template,ferric nitrate and urea as external iron and nitrogen source,a Fe,N co-doped porous carbon material containing Fe3C particles was prepared.The effects of different doping elements,doping amount and heat treatment temperature on the structure and properties of the final product were studied.A typical Fe3C/Fe,N co-doped porous carbon material(Fe3C/Fe,N-PCR)has a specific surface area of 509.3 m2 g-1,a pore volume of 2.43 cm3 g-1,and an N content of 4.34 at%.As an ORR electrocatalyst,it exhibits excellent catalytic activity.The onset potential and half-wave potential were 1.02 V and 0.86 V,which were better than Pt/C catalyst 30 mV and 20 mV,respectively.In addition,the Fe3C/Fe,N-PCR catalyst showed excellent stability and methanol tolerance.After the i-t test of 50000 s,the current retention rate was 93.5%.This high oxygen reduction performance is attributed to the synergistic effect between the structure and composition of Fe3C/Fe,N-PCR catalysts:large specific surface area and hierarchical porous structure are conducive to electrolyte infiltration and mass-charge transport during the reaction,the increase in micropores can host more active sites,and the rich variety of active sites can enhance the catalytic activity.In this work,the doped porous carbon-based nanomaterials were prepared by using petroleum vacuum residue as the carbon source,and applied to the electrocatalytic oxygen reduction reaction,which provides an idea for the high value-added utilization of petroleum vacuum residue and the design and preparation of efficient non-noble metal carbon-based ORR catalyst.