Study On Preparation And Electrochemical Performance Of Biomass Activated Carbons Derived From Pine Nut Shell And Pig Manure

The increasing energy crisis and the environmental pollution severely limit the sustainable development of the world,so it is urgent to seek an alternative,low-cost,green and pollution-free clean energy source.As a high-power and low-cost green energy storage device,the supercapacitor is an important part of the sustainable energy utilization.The pine nut shell,as a by-product of the pine nut processing industry,has a large output,but most of the pine nut shell is buried or incinerated to cause the resource waste and the environment pollution.In addition,that fix carbon content in the pine nut shell is high and the ash content is low,so that pine nut shell is a good precursor for preparation activated carbon.With the development of the breeding industry,the numbers of livestock manures are increasing gradually.The accumulation of the livestock manures will not only pollute the environment,occupy the resources,but also pose a certain threat to the health of the human body.Preparation activated carbon from livestock manures,can realize the high valued utilization of livestock manures.Moreover,there are few reports on the use of pine nut shell-based activated carbon and pig manure-based activated carbon as the electrode materials of supercapacitor.Three different activation methods: KOH activation,H₃PO₄activation and steam activation,were selected to prepare pine nut shell-based activated carbon electrode materials.The relationships among activation methodes,pore structure and electrochemical performance of activated carbons were studied.The results showed that the pine nut shell-based activated carbon prepared by KOH activation has 3D porous network structure and hierarchical pore structure,and the pine nut shell-based activated carbon prepared by H₃PO₄activation has hierarchical pore structure and large channel.The pine nut shell-based activated carbon prepared by steam activation has hierarchical pore structure.The specific surface area of pine nut shell-based activated carbon prepared by KOH activation is 1471 m² g^-1,which is significantly higher than that of the pine nut shell-based activated carbon prepared by H₃PO₄activation(1107 m² g^-1)and the pine nut shell-based activated carbon prepared by steam activation(956 m² g^-1).At the current density of 1A g^-1,the specific capacitance of pine nut shell-based activated carbon prepared by KOH activation is 232 F g^-1,which is much higher than the specific capacitance of activated carbon prepared by the other two activation methods.The highest specific capacitance value of pine nut shell-based activated carbon prepared by KOH activation is mainly due to its 3D pore structure,and the effectof pore structure on improving the electrochemical performance of electrode materials is greater than that of specific surface area.Moreover,the equivalent series resistance of pine nut shell-based activated carbon prepared by KOH activation is lowest of 0.62 ?,and the capacitance retention rate is highest after 10000 cycles at the current density of 5 A g^-1 up to 98.5%.The symmetrical supercapacitor was assembled by pine nut shell-based activated carbon prepared by KOH activation,which shows a high energy density of 23.45 Wh kg^-1,at a power density of 450 W kg^-1.Pig manure-based activated carbon was prepared by KOH activation method.The morphology,structure,adsorption and electrochemical properties of pig manure activated carbon prepared at different activation conditions were compared and the optimum activation conditions were obtained as follows: alkali carbon ratio of 4:1,activation temperature of 800? and activation time of 1.5h.The pig manure-based activated carbons prepared at different activation conditions all have hierarchical pore structure and similar pore size distribution.The activated carbon prepared at the alkali carbon ratio of 4:1,activation temperature of 800? and activation time of 1.5h has the highest specific capacitance of 133.15 F g^-1,and the energy density of the supercapacitor assembled by the activated carbon can reach 6.87 Wh kg^-1.The excellent electrochemical performance of activated carbon prepared at alkali carbon ratio of 4:1,activation temperature of800? and activation time of 1.5h is mainly attributed to its large specific surface area.In addition,its trace mineral and metal element content all can improve the electrochemical performance of the electrode material.In this paper,biomass-based activated carbon was prepared from pine nut shell and pig manure two different biomass materials,and used as the electrode materials of supercapacitor,which provide reference value for realization the high-value utilization of biomass waste.