Determinant influence of the electrical conductivity versus surface area on the performance of graphene oxide-doped carbon xerogel supercapacitors

Abstract

A series of resorcinol formaldehyde based carbon xerogels were synthesized under identical conditions using different graphene oxide loads. The gelification reaction was carried out using a stable aqueous suspension of graphene oxide, yielding organic gels with graphene oxide concentrations ranging from 1.2 to 2.5%. After the carbonization, xerogels with medium surface area (650 m 2 /g) and a highly improved electrical conductivity were obtained. Specific capacitance of 120 F/g of one electrode at very high scan rate of 500 mV/s were achieved, as well as power densities above 30 kW/kg, which is a significant improvement of 180% with respect to the pristine xerogels. Carbonized xerogels were further steam activated to yield activated carbon xerogels with surface areas of up to 1800 m 2 /g. The use of activated xerogels improves slightly the specific capacitance at low scan rates only, and there is a sharp decrease above 20 mV/s, resulting in a worse performance than graphene oxide doped carbonized xerogels. The electrical conductivity of the graphene oxide-doped carbon xerogels decreases upon activation, which means that the influence of the electrical conductivity on a carbon xerogel is greater than its specific surface area, which it is is the first time it is observed for porous carbons.

Characterization of Hierarchical Porous Carbons Made from Bean Curd via K2CO3 Activation as a Supercapacitor Electrode

“…ESR of HPC‐0, HPC‐5, HPC‐10, and HPC‐15 are almost identical (within experimental error) in two different solutions (Table S2). ESR varies around 0.5 Ω in both solutions, which is considered quite low, thus highlighting the consistency of electrode performance and the practical applicability of the synthesis route we reported here (Table S2) . In the medium to high frequency region, small semicircle arc appears in HPC‐5, HPC‐10, and HPC‐15 cases in both solutions, which corresponds to the presence of R ct at the electrode|electrolyte interface (insets of Figure (a) and Figure (b)) .…”

“…ESR varies around 0.5 Ω in both solutions, which is considered quite low, thus highlighting the consistency of electrode performance and the practical applicability of the synthesis route we reported here (Table S2). [52] In the medium to high frequency region, small semicircle arc appears in HPC-5, HPC-10, and HPC-15 cases in both solutions, which corresponds to the presence of R ct at the electrode j electrolyte interface (insets of Figure 6(a) and Figure 6(b)). [53] HPC-10 clearly has the lowest R ct among the four HPCs samples in both 1 M H 2 SO 4 and 6 M KOH (Table S2), which correlates with its highest specific capacitance and performance retention.…”

Highly Stable Dispersion of Carbon Nanotubes in Deep Eutectic Solvent for the Preparation of CNT‐Embedded Carbon Xerogels for Supercapacitors

“…The specific capacitance of O‐D‐CNT@RFC, calculated at a current density of 0.5 A g −1 , is higher than that of GO‐embedded carbon xerogels synthesized from aqueous conditions reported by Gloria Ramos‐Fernández, where the polymerization of resorcinol and formaldehyde is carried out using a aqueous suspension of graphene oxide as reaction medium. After steam activation, the resultant activated GO‐embedded carbon xerogel delivers a specific capacitance of 160 F g −1 at a current density of 0.1 A g −1 . The capacitance of O‐D‐CNT@RFC is also superior to that of carbon aerogels prepared though supercritical drying followed by HNO 3 oxidation, which generates a RF‐based carbon aerogels with a specific capacitance of 124 F g −1 at a current density of 0.5 A g −1 .…”

“…The electrical conductivity of the RF based carbon aerogels plays a key role in their electrochemical performances, such as energy density, charge transfer resistance, cyclic stability, and energy efficiency . A few recent works even demonstrated that the electrical conductivity, rather than the surface area, is the determinant to the final supercapacitor performances of the RF carbon aerogels . Carbon nanotubes (CNT) possess an ordered hollow nanostructure exclusively composed of graphitic carbon sheets which endows the CNT with extremely high electrical conductivity.…”

“…[7] A few recent works even demonstrated that the electrical conductivity, rather than the surface area, is the determinant to the final supercapacitor performances of the RF carbon aerogels. [8,9] Carbon nanotubes (CNT) possess an ordered hollow nanostructure exclusively composed of graphitic carbon sheets which endows the CNT with extremely high electrical conductivity. Incorporation of such an ordered, high conductive carbon material into the RF carbon framework is an effective way to boost its electrical conductivity based on the principle that the conductive carbon creates a network that facilitates electron transportation within the porous RF carbon matrix.…”