Electrochemical Properties And Applications Of Carbon Nanomaterials And Their Composites

Nanocarbons,such as graphene,carbon nanotubes,and expanded graphite feature different morphology and surface functional groups.They are thus expected to have different properties and applications.Herein,surficial properties and chemical properties of several nanocarbons including graphene nano platelets（GNPs）,multiwalled carbon nanotubes（MWCNTs）,graphene oxide（GO）,aminated graphene（NH₂-G）,expanded graphite（EG）have been studied together with their composites of EG,as well as their electrochemical applications.We investigate systematically electrochemical sensing characteristics and supper capacitive performance of these nanocarbons.Their composites with EG are also constructed.The detailed content ia as followed:（1）Using Fe（CN）₆^3-/4-as probe molecules,cyclic voltammograms of 5 mM Fe（CN）₆ ^3-/4-on MWCNTs,GO,GNPs,NH₂-G,and EG as well as their composites with EG were examined.Electrochemical sensing applications of these nanocarbons and their composites with EG towards positively and negatively charged inorganic ions(Pb²⁺and NO₂^-)as well as two neutral organic colorants（here sunset yellow and tartrazine）are conducted and compared.The sensitive electrochemical sensing of Pb²⁺,NO^-₂ as well as neutral sunset yellow and tartrazine have been then realized on EG,the composite of EG with MWCNTs and the composite of EG with GNPs,respectively.The possible interactions between these target compounds with nanocarbons or the composites are finally discussed under the help of scanning electron microscopy,Raman spectroscopy,and fourier transform infrared spectroscopy.The results indicated that EG shows higher accumulation ability than other nanocarbons towards Pb²⁺ions due to a large amount of delocalized electrons existing in EG flakes;The existence of a large number of delocalized electrons in EG flakes facilitates the accumulation of Pb²⁺ions;A synergistic effect among EG and MWCNTs is believed to be occurred and responsible for the improvement of the oxidation current of NO₂^-ions;The conjugated all-carbon structures of EG and GNPs facilitates the adsorption of pigment on the composite of EG/GNPs.Based on the remarkable signal enhancement effect of EG,sensitive monitoring of these charged and non-charged species on different nanocarbons or the composites are then achieved.（2）Using 0.5 M Na₂SO₄ as the electrolyte,the supercapacitive performance differences of different electrode materials were studied by cyclic voltammetry and galvanostatic charge-discharge methods.It was found that the composites with EG can increase the rate performance of GO,GNPs,and NH₂-G;MWCNTs with 3D porous structure and high specific surface area,NH₂-G with N-doped heteroatoms resulting in a higher specific capacitance,good capacitance stability.The specific capacitance retention ratio of MWCNTs and NH₂-G can be maintained at more than 80% after 500 cycles,indicating that these two materials have excellent capacitance performance and are suitable to be employed as electrode materials to construct supercapacitor.