Preparation And Electrochemical Properties Of Composite Porous Carbon With Waste Biomass And Mn/Fe/Co Compounds

Carbon materials are widely used in the field of electrochemistry because of their abundant resources,good chemical stability,excellent electrical conductivity,and easy construction of three-dimensional network structures.In recent years,new carbon materials such as graphene and carbon nanotubes have emerged in an endless stream,but the preparation methods of these materials are particularly complicated,the synthesis conditions are harsh,the cost is high,and the environment is more likely to be seriously polluted.At present,new carbon-based composite materials carrying transition metals and their nitrogen oxides have been widely used in the field of electrochemistry.In this paper,the waste biomasses of litchi shell,pig bone and passion fruit shell,which are rich in resources,green and cheap,are selected as carbon precursors and modified with metal salts.The materials are pored by different methods to enhance the porosity and specific surface area,and a new type of carbon-based composite material with stable structure and excellent performance was obtained.detailed The morphology,structure,formation mechanism and electrochemical performances?such as oxygen reduction catalytic performance,lithium ion battery performance,etc.?were researched in detail.The main contents of this article are as follows:?1?The waste lychee shell was taken as carbon precursor,and the material was pre-oxidized with KMnO₄ as oxidant to obtain a pre-treated carbon in which MnO₂nanoparticles were embedded in the carbon layer.The deficiency of the pretreatment material increased due to the embedding of MnO₂ and the initial pores formed.After calcination with melamine at a high temperature of 800°C,MnO₂ was further reacted with the carbon precursor and reduced to MnO nanoparticles embedded in the carbon layer.Under high temperature condition,melamine was pyrolyzed to produce NH ₃,and the material was subjected to the secondary poring of nitrogen doping,and a MnO nanoparticles embedded three-dimensional porous carbon composite material?MnO@NLEFC?with a specific surface of 782.22 g cm^-2 was obtained.As a negative electrode material for lithium ion batteries,the research results show that MnO@NLEFC composite has high specific capacity,stable cycle performance and excellent rate performance.At a current density of 2 A g^-1,the reversible capacity after1000 cycles is 515.5 mAh g^-1.In addition,at an ultra-high current density of 20 A g^-1,it still provides a high reversible capacity of 309.2 mAh g^-1 after 1000 cycles.?2?The waste pig bone was taken as the biomass carbon source and the characteristics of high natural calcium content of pig bone was used,pre-carbonization was completed at 400°C,then it was grinded into¹0?m fine powder carbon and nitric acid was taken to remove calcium from the bone to obtain a porous carbon precursor.Then,anhydrous FeCl₃ was used as the iron source,and melamine was used as the nitrogen source.After mixing,it was calcined at 900°C to carry out nitrogen doping,iron doping and secondary pore formation to obtain a three-dimensional porous carbon material.Its specific surface area is 998.5 m² g^-1,and inlaid with FeN₃nanoparticles.The material was used as an electrochemical catalyst for oxygen reduction at an alkaline medium.The research results show that the initial potential and limiting current density of the material are 0.986 V and 6.436 mA cm^-2,respectively,and the initial potential of platinum carbon is 0.963 V,the limiting current density of platinum carbon is 5.637 mA cm^-2.This indicates that the synthesized carbon-based composite material has excellent oxygen reduction electrochemical catalytic performance.?3?The waste passion fruit peel was taken as the biomass carbon source,and ZnCl₂ was used as the pore-forming agent to improve the surface and pore structure of the carbon material,and the modified porous carbon with larger specific surface was obtained.The zinc chloride,anhydrous ferric chloride and cobalt acetate tetrahydrate were uniformly dispersed into the internal structure of the passion fruit shell by hydrothermal treatment at 200°C,and the material was heat treated at 850°C.A Fe-Co-CPBC carbon-based nanocomposite was obtained.As an oxygen reduction electrochemical catalyst,the research results show that the starting potential of the material is 0.956 V and the half-wave potential is 0.841 V.The performance is close to that of platinum carbon,but the cycle performance and resistance to methan ol of the material are far superior to those of commercial platinum carbon materials.