Preparation Of Hierarchical Porous Carbon Based On Agarose And Its Application In Supercapacitors

Porous carbon has received continuous attention from researchers and the industry due to its three-dimensional network structure and its huge application potential in future energy storage devices（such as electrochemical supercapacitors,lithium-ion batteries,solar cells,and fuel cells）.However,the synthesis methods of porous carbon are usually cumbersome,the raw materials are expensive,and the template is often toxic.These obstacles limit the large-scale production of porous carbon.The porous carbon derived from polysaccharides,a kind of natural raw materials is not only harmless to the environment and low in price,but also does not require a template to generate pores,which makes it an ideal material for preparing porous carbon.In this paper,we propose a new method for preparing porous carbon by using agarose as a raw material,and by the characteristic that it can naturally form a hydrogel when mixed with an activator in an appropriate proportion.In addition,we also studied the regulation of the activation temperature on the pore structure of porous carbon.It was found that the pore size of porous carbon would first reduce with the increase of activation temperature,and then enlarge.The difference in pore structure leads to different electrochemical properties.For example,when the content of agarose to potassium oxalate（K2C2O4）equals 1:3 and the activation temperature is 700℃,the porous carbon prepared has the highest specific surface area(1754.9 m² g^-1),and exhibits the highest variable capacitance(166.0 F g1 at 0.125 A g^-1).When increasing the content of K2C2O4 and temperature to 1:6 and 800℃,respectively,the porous carbon prepared contains the most mesopores and macropores,which makes it have the best rate performance(70.9 F g^-1 at 10 A g^-1).The regulation of temperature on the pore structure is mainly achieved by affecting the decomposition reaction of the activator.The types,yields and states of decomposition product generated from the activator at various temperatures are different,resulting in porous carbon with different pore structures,which ultimately leads to differences in electrochemical performance.The preparation method of the porous carbon we proposed and the regulation of the pore structure have very important guiding significance for the material design and production process of porous carbon.