Carbothermic reduction in the chemistry of metal extraction (MO(s) + C(s) → M(s) + CO(g)) using carbon as a sacrificial agent has been used to smelt metals from diverse oxide ores since ancient times. Here, we paid attention to another aspect of the carbothermic reduction to prepare an activated carbon textile for high-rate-performance supercapacitors. On the basis of thermodynamic reducibility of metal oxides reported by Ellingham, we employed not carbon, but metal oxide as a sacrificial agent in order to prepare an activated carbon textile. We conformally coated ZnO on a bare cotton textile using atomic layer deposition, followed by pyrolysis at high temperature (C(s) + ZnO(s) → C'(s) + Zn(g) + CO(g)). We figured out that it leads to concurrent carbonization and activation in a chemical as well as mechanical way. Particularly, the combined effects of mechanical buckling and fracture that occurred between ZnO and cotton turned out to play an important role in carbonizing and activating the cotton textile, thereby significantly increasing surface area (nearly 10 times) compared with the cotton textile prepared without ZnO. The carbon textiles prepared by carbothermic reduction showed impressive combination properties of high power and energy densities (over 20-fold increase) together with high cyclic stability.

wileyonlinelibrary.commolecules, so GO is hydrophilic and can easily be dispersed in water. [ 2 ] The freestanding laminated GO membranes that are prepared from GO solutions can play an important role in many technological applications, including surface coatings, [ 3 ] ionic and molecular sieving, [4][5][6] hydrogen storage, [ 7,8 ] transparent and fl exible electronics, [9][10][11][12] composites, [ 13,14 ] micro-and nanoscale devices, [ 15 ] and biology and medicine. [ 16,17 ] GO papers require certain mechanical properties to provide adequate resistance to the mechanical loads and harsh environments that arise in commercial applications and must retain structural integrity over their lifetimes.Dikin et al. investigated the mechanical properties of GO papers with thicknesses varying from 2.5 to 25 µm with tensile testing. [ 2 ] Kang et al. used nano-indentation on a dynamic contact module system to measure the mechanical properties of 50-and 60-nm-thick GO fi lms. [ 18 ] Park et al. characterized the mechanical properties of one, two, and three overlapped layers of GO platelets using atomic force microscopy (AFM). [ 19 ] The Young's moduli measured with nanoresonators consisting of thin, stacked GO fi lms were found to surpass values obtained in previous measurements. [ 20 ] These results suggest that the mechanical properties of GO fi lms or papers, such as stiffness and fracture strength, might vary with thickness; however, no systematic study of this issue has been carried out to date.Graphene oxide (GO) papers are candidates for structural materials in modern technology due to their high specifi c strength and stiffness. The relationship between their mechanical properties and structure needs to be systematically investigated before they can be applied to the broad range fi elds where they have potential. Herein, the mechanical properties of GO papers with various thicknesses (0.5-100 µm) are investigated using bulge and tensile test methods; this includes the Young's modulus, fracture strength, fracture strain, and toughness. The Young's modulus, fracture strength, and toughness are found to decrease with increasing thickness, with the fi rst two exhibiting differences by a factor of four. In contrast, the fracture strain slightly increases with thickness. Transmission electron, scanning electron, and atomic force microscopy indicate that the mechanical properties vary with thickness due to variations in the inner structure and surface morphology, such as crack formation and surface roughness. Thicker GO papers are weaker because they contain more voids that are produced during the fabrication process. Surface wrinkles and residual stress are found to result in increased fracture strain. Determination of this structure-property relationship provide improved guidelines for the use of GO-based thin-fi lm materials in mechanical structures.

Transition metal oxides used as electrode materials for flexible supercapacitors have attracted huge attention due to their high specific capacitance and surface-to-volume ratio, specifically for cobalt oxide (Co3O4) nanoparticles.