High-Level Supercapacitive Performance of Chemically Reduced Graphene Oxide

Abstract

Commercial supercapacitors, mainly made of activated carbon, offers insufficient capacitance at high cost. Recently, graphene-based materials are emerging as smart alternatives. Reduction of graphene oxide (GO) is an elegant and important approach to produce reduced graphene oxide (rGO), because it holds the promise to closely resemble its physicochemical properties with pristine graphene. The conventional reducing agents such as sodium borohydride and hydrazine are strong reducing agents, and cannot be recycled. The fast reaction kinetics bring an imbalance in the desirable properties of rGO. Here, we present onepot chemical reduction of GO in aqueous medium by an unconventional mild reducing agent (FeCl2/HCl) where pure rGO is isolated and the reducing agent is recycled upon simple treatment of the filtrate with HCl. The fabricated all-solid-state supercapacitor of assynthesized rGO exhibited significantly higher specific capacitance (171 F/g at 1.1 A/g), remarkable cycling stability (>80% retention of capacitance beyond 100,000 continued cycles), and flexibility (>500 bending cycles), which is comparatively better than those of rGO derived from conventional reducing agents. Use of commercially available organic electrolyte further boosted the supercapacitor performance (282 F/g at 1.8 A/g) of rGO. 1

Exfoliated Mesoporous 2D Covalent Organic Frameworks for High‐Rate Electrochemical Double‐Layer Capacitors

“…Remarkably, the τ 0 value is about 121 ms for e‐JUC‐511 and 178 ms for e‐JUC‐512, which represents the fast discharging process. Significantly, those τ 0 values are much lower than those of reported activated carbon microcapacitor (700 ms) and chemically reduced graphene oxide capacitor (188 ms) . Meanwhile, e‐JUC‐510 capacitor cell exhibits capacitive response of 68 Hz with relatively high τ 0 value (464 ms) (Figure S52b, Supporting Information).…”

Noble‐free oxygen reduction reaction catalyst supported on Sengon wood ( Paraserianthes falcataria L. ) derived reduced graphene oxide for fuel cell application

“…Nonetheless, overall, compared with the RGO prepared from graphite, the RGO from Sengon wood was merely multilayer RGO, which has yet to be achieved as high quality graphene‐based material. The agglomeration on RGO layer was prompt by the incomplete mechanical exfoliation due to the re‐stacking of sp 3 bond on graphene lattice . Although the mechanism of the synthesis of RGO from biomass sources is still vague and requires more comprehensive and systematic study.…”

“…The agglomeration on RGO layer was prompt by the incomplete mechanical exfoliation due to the re-stacking of sp 3 bond on graphene lattice. 32,33 Although the mechanism of the synthesis of RGO from biomass sources is still vague and requires more comprehensive and systematic study. However, we postulate that the reduction process follows steps similar to those from graphite sources.…”

A Rechargeable Aqueous Sodium‐Ion Battery

“…[23,[27][28][29][30][31][32][33] Here we report an aqueous sodium ion battery with extended cyclability using hydrophobic few layer graphene (FLG) as sodium ion adsorption anode and metal hexacyanoferrate (MHF) as the insertion cathode in aquatic environment. Hydrophobic FLG was produced by the reduction of graphene oxide's (GO) hydrophilic functionalities using Fe powder over conventionally used chemical reducing agents such as hydrazine and NaBH 4 [34,35] which predominantly yielded incompletely reduced GO thereby affecting its electrical and electronic properties. [34][35][36] We show here that the mode of reduction and therefore the hydrophobicity of FLG noticeably affect metal ion adsorption and charge-discharge chemistry at the anode/ electrolyte interface.FLG formed by two types of reduction processes are compared here, one by the Fe powder reduction method and the other by the conventional borohydride reduction method (see experimental section for more details).…”

“…Hydrophobic FLG was produced by the reduction of graphene oxide's (GO) hydrophilic functionalities using Fe powder over conventionally used chemical reducing agents such as hydrazine and NaBH 4 [34,35] which predominantly yielded incompletely reduced GO thereby affecting its electrical and electronic properties. [34][35][36] We show here that the mode of reduction and therefore the hydrophobicity of FLG noticeably affect metal ion adsorption and charge-discharge chemistry at the anode/ electrolyte interface.FLG formed by two types of reduction processes are compared here, one by the Fe powder reduction method and the other by the conventional borohydride reduction method (see experimental section for more details). Few layers structure of graphene formed by the two reduction methods are evident in their atomic force microscopy images and the corresponding line profiles, Figures 1a and 1b, indicating that each flake approximately contains 3-4 graphene layers.The Raman spectra demonstrate a higher I D /I G ratio (intensity of defect band/intensity of graphitic band) for the FLG formed by borohydride reduction method compared to the corresponding FLG obtained by Fe powder reduction method, ( Figure S1), suggesting the presence of more hydrophilic functionalities in the former.…”