Electrochemically Active Phosphotungstic Acid Assisted Prevention of Graphene Restacking for High‐Capacitance Supercapacitors

Abstract

Direct reduction of graphene oxide usually leads to the agglomeration of the as‐generated graphene sheets, thus suppressing the surface exposed for energy storage. Herein, graphene oxide was reduced by a one‐pot hydrothermal process in the presence of an electrochemically active phosphotungstic acid to produce three‐dimensional porous phosphotungstic acid/reduced graphene oxide composites. Phosphotungstic acid molecules were found to be uniformly anchored on the surface of reduced graphene oxide sheets through the electrostatic interaction to prevent the reduced graphene oxide sheets from restacking. Meanwhile, phosphotungstic acid has the capability of undergoing fast reversible multi‐electron redox reactions and hence providing the pseudocapacitance. As expected, phosphotungstic acid/reduced graphene oxide composites display the specific capacitance as high as 456.7 F g−1 at 5 mV s−1 and 363.8 F g−1 at 0.5 A g−1, which are much larger than those obtained in reduced graphene oxide (162.4 F g−1 at 5 mV s−1 and 190.6 F g−1 at 0.5 A g−1). The retention also maintains 82.9% of initial specific capacitance after 1000 charge/discharge cycles. Such excellent electrochemical performance comes from the three‐dimensional porous architecture and synergistic interaction between the pseudocapacitive phosphotungstic acid and electric double‐layer capacitive graphene.

Intercalation in Two‐Dimensional Transition Metal Carbides and Nitrides (MXenes) toward Electrochemical Capacitor and Beyond

“…[41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] Electrochemical double-layer capacitors (EDLCs) normally use carbon-based active materials, such as activated carbon, graphene, and carbon nanotubes, with high surface area. [3,66,67] However, carbon-based EDLCs always have limited charge storage capability. Also, considering their relatively low packing density, carbon-based ECs usually perform relatively low volumetric energy density.…”

Enhanced Electrocatalytic Activity of Cobalt-Doped Ceria Embedded on Nitrogen, Sulfur-Doped Reduced Graphene Oxide as an Electrocatalyst for Oxygen Reduction Reaction

“…Figure 2b shows the Raman spectra of GO, N, S-rGO and the Co-CeO 2 /N, S-rGO composite. All samples exhibit two characteristic peaks of the D band at 1350 cm −1 and the G band at 1579 cm −1 [50,51]. The D band is assigned to the sp 3 structural defect sites, and the G band is associated with the sp 2 -bonded graphitic carbon atom.…”

One-pot mechanochemical exfoliation of graphite andin situpolymerization of aniline for the production of graphene/polyaniline composites for high-performance supercapacitors

“…The CV curve of the graphene electrode shows a nearly rectangular shape in the potential window of À0.2 to 0.8 V, indicating a typical EDLC characteristic. 38,39 In comparison, two pairs of redox peaks (A1/C1 and A2/C2) appear in the CV curves of pure PANI and graphene/PANI composites, representing their pseudocapacitive characteristics. The A1/C1 peaks are attributed to the redox transitions of PANI between the leucoemeraldine and polaronic emeraldine, while the A2/C2 peaks are due to the faradaic transformations between the emeraldine and pernigraniline states.…”