Enhanced supercapacitance of activated vertical graphene nanosheets in hybrid electrolyte

Abstract

Supercapacitors are becoming the workhorse for emerging energy storage applications due to their higher power density and superior cycle life compared to conventional batteries. The performance of supercapacitors depends on the electrode material, type of electrolyte, and interaction between them. Owing to the beneficial interconnected porous structure with multiple conducting channels, vertical graphene nanosheets (VGN) have proved to be leading supercapacitor electrode materials. Herein, we demonstrate a novel approach based on the combination of surface activation and a new organo-aqueous hybrid electrolyte, tetraethylammonium tetrafluoroborate in H2SO4, to achieve significant enhancement in supercapacitor performance of VGN. As-synthesized VGN exhibits an excellent supercapacitance of 0.64 mF/cm2 in H2SO4. However, identification of a novel electrolyte for performance enhancement is the subject of current research. The present manuscript demonstrates the potential of the hybrid electrolyte in enhancing the areal capacitance (1.99 mF/cm2) with excellent retention (only 5.4% loss after 5000 cycles) and Coulombic efficiency (93.1%). In addition, a five-fold enhancement in the capacitance of VGNs (0.64 to 3.31 mF/cm2) with a reduced internal resistance is achieved by the combination of KOH activation and the hybrid electrolyte.

Oriented Graphenes from Plasma-Reformed Coconut Oil for Supercapacitor Electrodes

“…These values of electrical resistance in F-VGNs are comparable to other graphene-based electrodes prepared by conventional chemical or thermal methods. These conclusions are consistent with the results of previous studies on vertical graphene and similar structures [27,28].…”

Heteroatom‐Doped and Oxygen‐Functionalized Nanocarbons for High‐Performance Supercapacitors

“…[217] Oxygen plasma functionalization can make the surface near or completely hydrophilic, a higher amount of defects and hence higher ion diffusion rate at the electrode-electrolyte interface, excellent charge-transfer, reduced contact resistance and internal resistance ( Figure 15C,D). [10,163,211] It is also reported that the oxygen plasma activated biochar contains larger pore volumes with higher average pore size compared to that of chemically activated biochar. Not surprisingly, plasma-activated biochar exhibits around two times higher specific capacitance compared to that of chemically activated biochar although chemically activated biochar showed a higher BET surface area.…”

“…Most popular ways to simultaneously make the surface hydrophilic and introduce controlled O-functionalities in nanocarbon matrix are chemical activation or plasma treatment. [10,[212][213][214] It has been observed that KOH activation of the vertically graphenes assists in reducing its water contact angle by 30° along with pore formation, better graphitic quality and higher specific capacitance than that of the pristine material. [10] It is also possible to create mesoporous channels with micropores which significantly enhance the ion accessible surface area and ion diffusion onto the entire electrode surface.…”

“…[10,[212][213][214] It has been observed that KOH activation of the vertically graphenes assists in reducing its water contact angle by 30° along with pore formation, better graphitic quality and higher specific capacitance than that of the pristine material. [10] It is also possible to create mesoporous channels with micropores which significantly enhance the ion accessible surface area and ion diffusion onto the entire electrode surface. [215] The higher rate of wettability of pristine nanocarbons in KOH is ascribed to the higher specific capacitance compared to H 2 SO 4 and Na 2 SO 4 .…”

Mixed‐Dimensional In‐Plane Heterostructures from 1D Mo6Te6 and 2D MoTe2 Synthesized by Te‐Flux‐Controlled Chemical Vapor Deposition

“…The actual temperature distribution of the furnace heated at 450, 465, 500, 550 and 600 °C is shown in Figure S2 Figures S3 and S4, Supporting Information). These 1D Mo 6 Te 6 wires are not vertical nanostructures such as vertical nanowall or vertical nanoflakes, [31,32] but horizontal 1D nanostructures. Figure 2d shows a Raman spectrum of the 1D Mo 6 Te 6 wires taken under 532 nm laser excitation, in which two characteristic peaks at 155.2 and 245.5 cm -1 are observed.…”