Controllable synthesis of activated graphene and its application in supercapacitors

Abstract

Activated graphene has been considered as an ideal electrode material for supercapacitors. In order to reveal the relationship between activated graphene and its precursor and controllably synthesize activated graphene, the structural parameters of the precursor (reduced graphene oxide, RGO) such as crystallinity and attached oxygen-functional groups were controllably adjusted during the synthesis of activated graphene and the effects of the precursor structure on the microstructure of activated graphene were investigated. The activation results reveal that the structure of RGO obviously affects the porous structure of activated graphene. Specifically, the crystallinity and oxygen-functional groups play an important role in the porosity development of activated graphene. By combining the simplified Brodie method and the subsequent post-oxidation process, porous activated graphene with a specific surface area of as high as 2406 m 2 g À1 and high pore volume has been successfully prepared. The as-prepared activated graphene exhibits good capacitive characteristics and delivers high energy density (55.7 W h kg À1 ) when measured in a two-electrode cell with the EMIMBF 4 ionic liquid as the electrolyte. The results demonstrate that the obtained activated graphene can be considered as a candidate for advanced electrode materials for supercapacitors.

Facile Synthesis of Mesoporous Graphene Materials from Potassium Humate for Supercapacitor Electrodes

“…The CV curves of MG-X at the scan rate of 1 mV·s −1 (Figure 4(c)) exhibit a quasirectangular shape without visible distortion, revealing a near-ideal double-layer capacitive behavior. Furthermore, the relatively ideal rectangle shape of CV curves for MG-3 can be well maintained up to 20 mV·s −1 (Figure 4(d)), confirming the improved rate capability [36].…”

Sandwich-type ordered mesoporous carbon/graphene nanocomposites derived from ionic liquid

“…According to the XPS spectra of C1s, the most pronounced peak located at 285 eV is characteristic of a carbon lattice, and the remaining peaks in sequence are C-OH and C-N (286 eV), C=O (287 eV), COOH (289 eV), and carbonate (291 eV) [33][34][35]. Oxygen is commonly present in carbon because of its incorporation in the dangling bonds when the materials are exposed to air.…”

Facile Assembly of 3D Porous Reduced Graphene Oxide/Ultrathin MnO2 Nanosheets‐S Aerogels as Efficient Polysulfide Adsorption Sites for High‐Performance Lithium–Sulfur Batteries

“…Among these carbonaceous materials, graphene with a unique two‐dimensional plane has been confirmed as a stabilizing host for the sulfur because of its excellent electrical conductivity, mechanical strength and flexibility, and large specific surface area in the Li–S batteries. However, the inevitable trend to agglomerate owing to strong π–π stacking of graphene layers results in a significant compromise of many of the unique properties of graphene . Although previous studies on nonpolar carbon materials as hosts of sulfur cathodes have made significant achievements on cyclability and specific capacity, the specific capacity often decayed rapidly after long‐term cycling, which can be attributed to the weak interactions between polar polysulfides and these host materials and thus resulting in the loss of active materials in the form of polysulfides.…”

“…However,t he inevitable trend to agglomerateo wing to strong p-p stacking of graphene layers resultsi nasignificant compromise of many of the uniquep roperties of graphene. [28,29] Although previouss tudies on nonpolar carbon materials as hosts of sulfur cathodes have made significant achievements on cyclability and specific capacity,t he specific capacity often decayed rapidly after long-term cycling, which can be attributedt ot he weak interactions between polar polysulfides and these host materials and thus resulting in the loss of active materials in the form of polysulfides. Presently,i th as been discoveredt hat lithium polysulfides can be effective in binding to noncarbon polar materials through either interactions or chemical reactions in Li-S batteries, such as g-C 3 N 4 , [30] Co(OH) 2 , [31] V 2 O 5 , [32] TiO 2 , [33,34] Ti 4 O 7 , [35] TiN, [36] NiS 2 , [37] SnO 2 , [38] Si/SiO 2 , [39] and MnO 2 .…”