Electrochemical Partial-Exfoliation Of Graphene And Its Composites With Polyaniline

A convenient and feasible method of cyclic voltammetry (CV) was adopted in 2.0 mol/L H2SO4 and 0.1 mol/L sodium dodecyl benzene sulfonate (SDBS) solutions, respectively to partial-exfoliate graphene from carbon fiber electrode (CC), to afford HCC and SCC with graphene sheets tightly anchored on the carbon fiber electrode. In order to improve hydrophilicity and electric conductivity of SCC, advanced cyclic voltammetry was conducted in 1.0 mol/L KNO3 of phosphate buffer solution (pH=6.86) for its secondly partial-exfoliation to prepare SNCC. The influence of CV potential on the parital-exfoliation was studied. The morphologies and electrochemical performances of CC, HCC, SCC and SNCC were studied by scanning electron microscope (SEM) and CV. It was found that the partial-exfoliation was facilitated in SDBS solution. There were graphene flakes standing on surfaces of SCC, which interconnected to form porous morphology. The electrochemical performance of SNCC was greatly improved by the secondary partial-exfoliation due to the improved hydrophilicity.In-situ electrochemical polymerization of aniline was carried out on CC, HCC, SCC and SNCC by CV from an aqueous solution containing aniline and H2SO4 to prepare PANI/CC, PANI/HCC, PANI/SCC and PANI/SNCC, respectively with different polymer loading which was controlled by scan times. The morphologies of the polymers were investigated by SEM which revealed that the PANI existed as nanofibers in PANI/CC, PANI/HCC, PANI/SCC and PANI/SNCC. The electrochemical activities and and stability were studied by CV. Galavanostatic charge-discharge (CP) measurements were conducted to investigate capacitive performances of the electrodes while their specific capacitance were calculated as well. The influences of polymer loading on the specific capacitances were studied. Due to the graphene anchoring on carbon fiber electrode through partial-exfoliation in SDBS, the polymer loading can be increased up to 5.52 mg in PANI/SCC and 7.10 mg in PANI/SNCC without peeling off, due to the interaction of graphene and PANI. While the maximum polymer loading can only be 2.89 mg in PANI/CC and 3.25 mg in PANI/HCC. The specific capacitance of PANI/SCC was only 440 F/g, duo to SDBS residue on the SCC surface. After secondary partial-exfoliation, the hydrophilicity of SNCC was improved and so the electrochemical performance of PANI/SNCC was siginficantly improved. The PANI/SNCC displayed a specific capacitance of 566 F/g at the current density of 1 A/g. The graphene anchoring on carbon fiber electrode is also helpful to compensate volume expansion/contraction of polymer during charge and discharge, therefore, the cyclic charge/discharge stability of PANI/SCC and PANI/SNCC were improved. After 1000 cycles, PANI/SNCC can maintain 81.56% of its capacitance.