Properties Of Carbon Metal Oxide Composites As Supercapacitor Electrodes

In order to solve the problem of energy storage and conversion,it is of great significance to design and develop new and efficient electrochemical energy storage devices.Supercapacitors,characterized by high power density,fast charge/discharge rates,long cycling life,have evolved into an important class of new-type energy storage devices.Among them,the preparation of electrode materials is the key to the development of supercapacitors.Carbon electrode based on biomass has become a research hotspot in this field because of its wide source,low price and developed pore structure.This work proposes a strategy for fuel gas production and biochar upgrading by catalytic CO₂gasification using pine sawdust(PS)as raw material.On this basis,the properties of a series of carbon-metal oxide composites were synthesized and studied by using the composite modification strategy.The main contents are summarized as follows:(1)The effects of PS char gasification conditions(including reaction temperature,reaction time and introduced nickel dosage)are investigated.The fuel gases are composed of CO_2,CO,H₂ and CH₄,along with the combustion energy up to 4.27 MJ/kg _PS-char.With the introduction of nickel catalyst in the gasification process,the capacitance of the prepared carbon-metal oxide composite electrode(the capacitance up to 130.4 F/g at 5 A/g,even to 234.0 F/g at 1 A/g)is 222.2%higher than that of the raw PS char.(2)Based on the above,the effects of manganese or iron components on CO₂gasification of biomass and the properties of carbon-metal oxide composites prepared were investigated,and the results showed that:(a)The specific capacitance of the carbon-manganese oxide composite materials can reach 229.9 F/g at 1 A/g when manganese(mass ratio of biomass to manganese is 1:0.02)is introduced.After 10000cycles of charge and discharge test,the capacitance retention rate reaches 93.5%;(b)The specific capacitance of the carbon-iron oxide composite materials can reach 197.6 F/g at 1A/g with the introduction of iron(mass ratio of biomass to iron is 1:0.03);(c)Similarly,the C-Ni/Fe oxide,C-Ni/Mn oxide and C-Fe/Mn oxide composites prepared all show good capacitance properties.This is mainly due to the corresponding formation of NiO,Fe₂O₃ or Mn₃O₄ single or binary metal oxides in the electrode sample,thus enhancing the pseudo capacitance effect of the material and improving the charge storage capacity of the material.The strategy of utilizing catalytic CO₂ gasification technology to convert biomass into electrode materials for supercapacitors provides theoretical guidance for the design and development of new electrode materials for supercapacitors,which is of great significance for the low carbon conversion and high value utilization of biomass resources.