Studies In Carbon-based Electrode Materials For Electrochemical Capacitors

Securing our energy future is the most important problem that humanity faces inthis century. Burning fossil fuels is not sustainable, and wide use of renewableenergy sources will require a drastically increased ability to store electrical energy.Electrochemical capacitors (ECs) were attracting more attention recently. It hassome advantages, such as, large capacity, low leakage current, simple charge ordischarge, high specific power and long cycle life. In this paper, supercapacitorelectrode materials were prepared by a variety of methods. The structure andmorphology of carbon materials were characterized systematically by a variety ofmeans such as nitrogen adsorption, high-resolution transmission electronmicroscopy (TEM), field emission scanning electron microscope (SEM), X-rayphotoelectron spectroscopy (XPS). Using cyclic voltammograms, glavanostaticcharge/discharge and electrochemical impedance tests, the electrochemicalproperties of carbons materials have been investigated. Relating thephysicochemical and structural parameters of materials to electrochemicalproperties of the carbon materials, we draw a lot of enlightening arguments. Themain contents are as follows:(1) Nitrogen-doped mesoporous carbons have been successfully synthesizedfrom soya bean dreg by chemical activation. Through SEM, TEM, XPS, XRD, N2adsorption methods, the morphological, structural, textural and frameworkproperties of the obtained soya-based carbon materials are extensively studied,clearly demonstrating the connection between the content of nitrogen and thecapacitive performance. The surface areas and the quantity of nitrogen content ofthe as-prepared carbons can be adjusted by controlling the activation temperatureand KOH dosage, which mainly influence the electrochemical properties of thecarbons. The highest specific capacitance reached~410F/g at1mol/L H2SO4electrolyte and~504F/g at30%KOH electrolyte, which was attributed to thesynergistic effects between nitrogen-containing compounds and the large specificsurface area of the carbons. This capacitance value is much higher than the otheractivated carbons reported previously in the literature. So the as-prepared carbons inthis work are very promising for supercapacitor applications.(2) In this experiment, a series of microporous-mesoporous hierarchical porouscarbons (HPCs) were prepared by using phloroglucinol and formaldehyde as carbonsource and F127as template, followed by KOH activation. The effects of KOHdosage and activation temperature on the pore structure and morphology of HPCswere investigated intensively. The HPCs synthesized through chemical activationby KOH could reach a high surface area of2060m2g-1. The electrochemicalproperties of HPCs were mainly investigated in organic electrolyte. Electrochemicaltests show that, compared to mesoporous carbon materials reported previously inliteratures, HPCs prepared in this work possess better electrochemical performance.