Time filter

Source Type

Vermisoglou E.C.,Institute of Nanoscience and Nanotechnology Demokritos | Giannakopoulou T.,Institute of Nanoscience and Nanotechnology Demokritos | Romanos G.,Institute of Nanoscience and Nanotechnology Demokritos | Boukos N.,Institute of Nanoscience and Nanotechnology Demokritos | And 5 more authors.
Applied Surface Science | Year: 2017

Benzidine, a compound bearing aromatic rings and terminal amino groups, was employed for the intercalation and simultaneous reduction of graphite oxide (GO). The aromatic diamine can be intercalated into GO as follows: (1) by grafting with the epoxy groups of GO, (2) by hydrogen bonding with the oxygen containing groups of GO. Stacking between benzidine aromatic rings and unoxidized domains of GO may occur through π-π interaction. The role of benzidine is influenced by pH conditions and the weight ratio GO/benzidine. Two weight ratios were tested i.e. 1:2 and 1:3. Under strong alkaline conditions through K2CO3 addition (pH ∼10.4–10.6) both intercalation and reduction of GO via amino groups occur, while under strong acidic conditions through HCl addition (pH ∼1.4–2.2) π-π stacking is preferred. When no base or acid is added (pH ∼5.2) and the weight ratio is 1:2, there are indications that reduction and π-π stacking occur, while at a GO/benzidine weight ratio 1:3 intercalation via amino groups and reduction seem to dominate. The aforementioned remarks render benzidine a multifunctional tool towards production of reduced graphene oxide. The effect of pH conditions and the GO/benzidine weight ratio on the quality and the electrochemical properties of the produced graphene-based materials were investigated. Cyclic voltammetry measurements using three-electrode cell and KCl aqueous solution as an electrolyte gave specific capacitance values up to ∼178 F/g. When electric double-layer capacitors (EDLC) were fabricated from these materials, the maximum capacitance in organic electrolyte i.e., tetraethyl ammonium tetrafluoroborate (TEABF4) in polycarbonate (PC) was ∼29 F/g. © 2016


Vermisoglou E.C.,Institute of Nanoscience and Nanotechnology Demokritos | Giannakopoulou T.,Institute of Nanoscience and Nanotechnology Demokritos | Romanos G.E.,Institute of Nanoscience and Nanotechnology Demokritos | Boukos N.,Institute of Nanoscience and Nanotechnology Demokritos | And 4 more authors.
Applied Surface Science | Year: 2015

Microwave irradiation of graphite oxide constitutes a facile route toward production of reduced graphene oxide, since during this treatment both exfoliation and reduction of graphite oxide occurs. In this work, the effect of pristine graphite (type, size of flakes), pretreatment and oxidation cycles on the finally produced expanded material was examined. All the types of graphite that were tested afforded materials with high BET surface areas ranging from 940m2/g to 2490m2/g, without intervening an activation stage at elevated temperature. SEM and TEM images displayed exfoliated structures, where the flakes were significantly detached and curved. The quality of the reduced graphene oxide sheets was evidenced both by X-ray photoelectron spectroscopy and Raman spectroscopy. The electrode material capacitance was determined via electrochemical impedance spectroscopy and cyclic voltammetry. The materials with PEDOT binder had better performance (~97F/g) at low operation rates while those with PVDF binder performed better (~20F/g) at higher rates, opening up perspectives for their application in supercapacitors. © 2015 Elsevier B.V.

Loading Institute of Nanoscience and Nanotechnology Demokritos collaborators
Loading Institute of Nanoscience and Nanotechnology Demokritos collaborators