Partially Reduced Graphite Oxide as an Electrode Material for Electrochemical Double‐Layer Capacitors

Abstract

Partially reduced graphite oxide was prepared from graphite oxide by using synthetic graphite as precursor. The reduction of graphite oxide with a layer distance of 0.57 nm resulted in a reduction of the layer distance depending on the degree of reduction. Simultaneously the amount of oxygen functionalities in the graphite oxide was reduced, which was corroborated by elemental analysis and EDX. The electrochemical activation of the partially reduced graphite oxide was investigated for tetraethylammonium tetrafluoroborate in acetonitrile and in propylene carbonate. The activation potential depends significantly on the degree of reduction, that is, on the graphene‐layer distance and on the solvent used. The activation potential decreased with increasing layer distance for both positive and negative activation. The resulting capacitance after activation was found to be affected by the layer distance, the oxygen functionalities and the used electrolyte. For a layer distance of 0.43 nm and with acetonitrile as the solvent, a differential capacitance of 220 Fg−1 was achieved for the discharge of the positive electrode near the open‐circuit potential and 195 Fg−1 in a symmetric full‐cell assembly.

Dielectric relaxation characteristics of chemically reduced graphite oxide

“…For 17 "dehydrated" as well as reduced graphite oxide it is (001), corresponding to 6.2 Å, but it 18 gradually disappeared as we go from rGO1 to rGO8. In rGO3 and rGO8 a broad peak arose and 19 which also approached the position of the graphite (002) reflection, as previously observed [15]. 20 In rGO8 the interlayer distance was calculated to be 3.77 Å, a much smaller value that 21 approaches the spacing in natural graphite, namely 3.36 Å.…”

“…We shall refer to these three kinds of powders as 12 rGO1, rGO3 and rGO8 respectively. 15 X-ray diffraction was performed in a Philips X'pert Pro using Cu Kα 1 radiation (λ=1.5406 Å) 16 at 0.017° steps over the range of 2θ from 5° to 50°, with the sample heated to 70°C at 10°C/min, 17 under vacuum. The diffractogram thus obtained at 70°C was refreshed every 5 min until no 18 further change was discernible.…”

“…Hydrated GO becomes an ionic (and protonic) 13 conductor, with conductance increased by more than three orders of magnitude [7]. When single-14 layer water is intercalated into the interspace between two carbon backbones of GO, the 15 interlayer distance is about 9 ± 1 Å [33], permitting proton diffusion through the hydrogen 16 bonds network of water via the Grotthuss mechanism [12]. However, after our sample had been 17 dried under vaccum at elevated temperature, its interlayer distance shrinked to 6.2 Å.…”

Camphoric Carbon‐Grafted Ni/NiO Nanowire Electrodes for High‐Performance Energy‐Storage Systems

“…This decrease could be mainly attributed to the reduced NiO content, which decreased the number of redox sites available on the electrode. [13] The improvement in the electrochemical performance of NiO when grafted to the CDC surface can be attributed to the combined influence of different mechanisms, such as increased surface area (see Figure SI-B in the Supporting Information) and conductivity of the electrode overlay. This is predominated by the relative ability of electrons to jump the gap between closely spaced aggregates (electron tunneling), [45] and by graphitic conduction through aggregates in contact, as observed in other carbon composite systems.…”

“…Figure 1 compares the energy density and power density performances of some recent studies in which NiO has been used in combination with these nanostructured carbons as composite electrodes. [12][13][14][15][16][17][18][19][20][21][22][23] However, reports have shown that it is difficult to produce large-scale porous electrode areas when using graphene and CNTs. [24,25] Graphene sheets without proper surfactant tend to aggregate (causing reduction in the conductivity), which restricts the intervening pore volume for…”