Post-heating effects on the physical and electrochemical capacitive properties of reduced graphene oxide paper

Abstract

We report combined electrochemical double-layer capacitance (EDLC) and pseudocapacitance in reduced graphene oxide (rGO) thick film like paper due to annealing temperature variations. The influence of annealing temperature (from room temperature (RT) to 1000 C) on the structural, morphological, electrical, and electrochemical properties of rGO paper was evaluated. Upon increasing the annealing temperature, shifting of the dominant (002) X-ray diffraction (XRD) peak to a higher degree, volume expansion, and red-shifting of the G band in Raman spectra were observed. High-resolution transmission electron microscopy (HRTEM) images showed a reduction in the interlayer distance in rGO sheets from 0.369 to 0.349 nm as the annealing temperature increased from RT to 1000 C; these results were congruent with the XRD results. According to X-ray photoelectron spectroscopy (XPS), the presence of hydroxyl, carboxyl, and other oxygen-containing groups decreased in samples annealed at higher temperatures. The attached functional groups, the electrical conductivity, and the supercapacitance of rGO papers were found to be mutually interrelated and could be tuned by varying the annealing temperature. The rGO paper annealed at 200 C in a 1 M H 2 SO 4 electrolyte at a scan rate of 50 mV s À1 exhibited a maximum specific capacitance of 198 F g À1 .

Acoustotemplating: rapid synthesis of freestanding quasi-2D MOF/graphene oxide heterostructures for supercapacitor applications

“…These values place the acoustically-synthesized q-2D-MOF/rGO composite well within those reported in literature (Table 1), but with the added advantage of not requiring the use of conductive supports or additives to supplement the material's capacitive properties. Parenthetically, we note the capacitance value for rGO alone under similar electrochemical conditions to be 198 F g −1 at 50 mV s −1 , 103 therefore highlighting the synergistic advantage of both the q-2D-MOF and rGO constituents in the q-2D-MOF/rGO composite.…”

Holey Graphene Nanosheets with Surface Functional Groups as High‐Performance Supercapacitors in Ionic‐Liquid Electrolyte

“…[18][19][20][21] The reversible redox reactions between the surfaceg roups and H + (and OH À )i nt he electrolyte contribute extra pseudocapacitance [besides the electric double-layer capacitance (EDLC)o nt he carbon surface]. [18][19][20][21] The reversible redox reactions between the surfaceg roups and H + (and OH À )i nt he electrolyte contribute extra pseudocapacitance [besides the electric double-layer capacitance (EDLC)o nt he carbon surface].…”

“…In aqueous electrolytes, an appropriate number of oxygencontaining functional groups on GNSs was confirmed to be beneficial for increasing electrode capacitance. [18][19][20][21] The reversible redox reactions between the surfaceg roups and H + (and OH À )i nt he electrolyte contribute extra pseudocapacitance [besides the electric double-layer capacitance (EDLC)o nt he carbon surface]. [20] Whether as imilarp seudocapactive mechanism can occur in an on-aqueous electrolyte is not clear,b ecause neither H + nor OH À exists in the electrolyte.…”

Ultrafast Growth of Uniform Multi-Layer Graphene Films Directly on Silicon Dioxide Substrates

“…The I D /I G increased a little at first and then uniformly decreased down to 0.94 ± 0.11 (Figure 4a), reflecting the constantly improved crystallization of the graphene film as the growth duration increased. This could be attributed to the restoration of the sp 2 –hybrid structure in-plane during the high temperature annealing process, which was also used to restore the graphene oxide [32]. Nevertheless, the value of I D /I G was still larger than that measured in graphene grown with a long duration or on the metals.…”