Fe_(3)O_(4)/腐殖酸铵基炭复合材料的制备及其电化学性能

Preparation and electrochemical properties of Fe_(3)O_(4)/ammonium-humate based carbon composites

制备Fe_(3)O_(4)/炭复合材料,既可以有效解决Fe_(3)O_(4)颗粒团聚和导电性差的问题,又能充分利用Fe_(3)O_(4)的高容量,从而提供优异的电化学性能。以煤系腐殖酸铵和氯化铁为原料,采用水热-炭化工艺制备Fe_(3)O_(4)/腐殖酸铵基炭复合材料(Fe_(3)O_(4)/SHAC-X),借助扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、低温氮吸附和X射线光电子能谱(XPS)等分析手段,对样品的微观形貌、孔结构以及表面化学组成进行表征,并利用恒流充放电、循环伏安、交流阻抗等电化学测试技术评价其作为超级电容器电极材料的电化学性能。结果表明:Fe_(3)O_(4)/SHAC-X的孔隙结构以中孔为主,随着FeCl_(3)·6H_(2)O用量的增加,所制样品的中孔孔容和平均孔径逐渐增加。Fe_(3)O_(4)颗粒的负载量和分布特性与FeCl_(3)·6H_(2)O用量紧密相关,Fe_(3)O_(4)/SHAC-3的Fe含量最高,Fe_(3)O_(4)颗粒分散性较好、颗粒尺寸均一;相应电极材料在3 mol/L KOH电解液中存在明显的赝电容效应,且电化学阻抗较小,成型密度较高(1.48 g/cm^(3)),在42.5 mA/g电流密度下的体积比电容高达253 F/cm^(3)。Fe_(3)O_(4)/SHAC-2具有良好的倍率性能,当电流密度从42.5 mA/g增加到4250 mA/g时,其电容保持率高达73.1%;循环稳定性较好,在2125 mA/g的电流密度下经过10000次恒流充放电之后,其电容保持率为88.3%。研究有利于推动煤系腐殖酸的洁净高效利用,并对Fe_(3)O_(4)/炭复合材料的研究应用具有借鉴意义。

The preparation of Fe_(3)O_(4)/carbon composites can not only effectively solve the problems of the agglomeration and poor electrical conductivity of Fe_(3)O_(4)particles,but also take advantage of the high capacity of Fe_(3)O_(4),and provide some excellent electrochemical properties.In this study,the Fe_(3)O_(4)/ammonium-humate based carbon composites(Fe_(3)O_(4)/SHAC-X)were prepared by hydrothermal-carbonization process using coal-based ammonium humate and ferric chloride as raw materials.Scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),nitrogen adsorption/desorption and X-ray photoelectron spectroscopy(XPS)were used to characterize the morphology,pore structure and surface chemistry of the samples.The electrochemical properties of the corresponding supercapacitor electrode materials were evaluated by constant current charge-discharge,cyclic voltammetry and alternating-current impedance measurements.The results show that the pore structure of Fe_(3)O_(4)/SHAC-X mainly consists of mesopores,the mesopore volume and average pore size increase gradually with the increase of the dosage of FeCl_(3)·6 H_(2)O,which are also closely related to the mass loading and distribution characteristics of Fe_(3)O_(4)particles.The Fe_(3)O_(4)/SHAC-3 has the highest Fe content among three samples,and the Fe_(3)O_(4)particles exhibit good dispersivity with uniform particle size.The corresponding electrode material has obvious pseudocapacitance effect in the 3 mol/L KOH electrolyte,showing a small electrochemical impedance and high volumetric capacitance of 253 F/cm~3 at the current density of 42.5 mA/g based on its high forming density(1.48 g/cm~3).Moreover,the Fe_(3)O_(4)/SHAC-2 displays a better rate performance,delivering a high capacitance retention of 73.1%with the current density increasing from 42.5 to 4250 mA/g.The specific capacitance can still maintain 88.3%after 10000 cycles at 2125 mA/g,indicating a superior cycle performance.This work is conducive to promote the clean and efficient utilization of coal based humic acid,and also has reference significance for the research and application of the Fe_(3)O_(4)/carbon composites.