梯级孔生物质活性炭的制备及其电容特性研究

Preparation of Hierarchical Pore Biomass Activated Carbons and Their Capacitance Characteristics

以柚子皮为原料,采用预先炭化-KOH活化工艺制备生物质活性炭,并将其用作超级电容器电极材料。采用低温氮气吸附、扫描电镜(SEM)、透射电镜(TEM)及X射线光电子能谱(XPS)等方法表征生物质活性炭的孔结构、表面形貌等微观结构和表面化学性质,利用恒流充放电、循环伏安、漏电流等手段探究生物质活性炭用作电极材料的电化学特性。研究表明:柚子皮经预先炭化-KOH活化处理可以制备出比表面积为1 347~2 269m^2/g,总孔容达0.642~1.283cm^3/g,中孔比例为23.83%~48.90%的高品质生物质活性炭。该生物质活性炭具有发达的比表面积、"大孔-中孔-微孔"三维贯通梯级孔结构,且表面富含羰基、酚羟基及羧基等含氧官能团,是一种比较理想的超级电容器电极材料。生物质活性炭电极材料在KOH电解液中具有优异的电容特性,在50mA/g电流密度下的比电容最高可达243F/g,5 000mA/g电流密度下的比电容仍可保持为175F/g,且具有优异的循环稳定性,循环1 000次后比电容保持率高达93.34%,漏电流仅为0.006 3mA。生物质活性炭优异的电化学特性与其发达的比表面积、"大孔-中孔-微孔"三维贯通梯级孔结构、合理的孔径分布及独特的富氧表面化学性质密切相关。

Biomass activated carbons used as electrode materials for supercapacitors were prepared from shaddock peel via preliminary carbonization coupled with KOH activation.The microstructures including pore structure and surface morphology and the surface chemistry property of biomass activated carbons were characterized by low temperature N 2 adsorption,scanning electron microscope(SEM),transmission electron microscope(TEM)and X-ray photoelectron spectroscopy(XPS).The electrochemical characteristics of biomass activated carbons applied as electrode materials were also investigated using galvanostatic charge-discharge,cyclic voltammetry and leakage current.The results show that high quality biomass activated carbons with specific surface area of 1 347-2 269 m 2/g,total pore volume of 0.642-1.283 cm 3/g,mesopore percentage of 23.83%-48.90%were obtained from shaddock peel through preliminary carbonization coupled with KOH activation routes.The as-prepared biomass activated carbons exhibited well-developed specific surface area with“macropore-mesopore-micropore”three dimensional interconnected hierarchical pore structure and contained some oxygen-containing functional groups such as carbonyl,phenolic hydroxyl and carboxyl on the surface of these activated carbons,which might become a promising electrode materials for supercapacitors.Biomass activated carbon electrode materials exhibited an excellent capacitance characteristics and superior cycling performance in KOH aqueous electrolyte.The maximum gravimetric specific capacitance of biomass activated carbon electrode materials was as high as 243 F/g at a current density of 50 mA/g and still remained 175 F/g even at a current density of 5 000 mA/g,the leakage current was only 0.006 3 mA and 93.34%of the initial specific capacitance was retained after 1 000 cycles.The superior electrochemical performances of biomass activated carbons were strongly depended on their well-developed specific surface area,macropore-mesopore-micropore three dimensional interconnected hierarchical pore structure,reasonable pore size distribution as well as unique oxygen-enriched surface chemistry property.