Immobilization of Co–Al Layered Double Hydroxides on Graphene Oxide Nanosheets: Growth Mechanism and Supercapacitor Studies

Abstract

Layered double hydroxides (LDHs) are generally expressed as [M(2+)(1-x)M(3+)(x) (OH)(2)] [A(n-)(x/n)·mH(2)O], where M(2+) and M(3+) are divalent and trivalent metal cations respectively, and A is n-valent interlayer guest anion. Co-Al layered double hydroxides (LDHs) with different sizes have been grown on graphene oxide (GO) via in situ hydrothermal crystallization. In the synthesis procedure, the GO is partially reduced in company with the formation of Co-Al LDHs. The morphology and structure of LDHs/GO hybrids are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The growth mechanism of LDHs on GO nanosheets is discussed. Moreover, both LDHs and LDHs/graphene nanosheets (GNS) hybrids are further used as electrochemical supercapacitor materials and their performance is evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge measurements. It is shown that the specific capacitances of LDHs are significantly enhanced by the hybridization with GNS.

High performance asymmetric supercapacitor based on CoAl-LDH/GF and activated carbon from expanded graphite

“…As a result, the weak graphene peak was enshrouded by the stronger CoAl-LDH peaks. is associated with the metal-oxygen (M-O) stretching and bending modes 28,37 .…”

“…However, the poor electric conductivity of LDHs affects their charge transfer ability resulting in a poor charge and discharge capability that affects their electrochemical performance when used as electrode materials 28,35,36 . It has been established that modifying the LDH with carbon materials to prepare composites is one of the most effective strategies to increase the conductivity as well as the electrochemical properties of LDH 28,[37][38][39] stainless-steel autoclave and kept at a temperature of 120° C for 18 h. After cooling to room temperature, the pinkish product was repeatedly washed with deionized water and ethanol several times to remove any unreacted precursor and residual. Thereafter, drying was done at 60° C for 6 h to obtain the final product.…”

Direct synthesis of Co 2 Al(OH) 7−2x (CO 3 ) x · n H 2 O layered double hydroxide nanolayers by successive ionic layer deposition and their capacitive performance

“…On FTIR spectra (Fig. 4) of the films one can note that the valence band (3430 cm −1 ) and the deformation band (1640 cm −1 ) correspond to vibrations of O H bond, and the band with peaks at 1358 cm −1 and 777 cm −1 vibrations of C O in anion CO 3 2− [14], which may be attributed to the adsorbed CO 2 from the atmosphere. Other absorption bands in the region of 700-400 cm −1 may be assigned to the valence vibrations Co O in LDH [15].…”

“…Among LDHs the most promising for the creation of new supercapacitors are layers containing cations of Co 2+ , for example Co 2 Al(OH) 7 ·nH 2 O. Previously, the electrochemical properties of electrodes of this composition were examined for a sample obtained by precipitation [12], hydrothermal [13,14] and refluxing [15] methods. It was shown that the capacitance of supercapacitors based on these electrodes is in the range from 263 to 641 F/g at a current density of 1 A/g.…”

Novel route to synthesis of N-doped graphene/Cu–Ni oxide composite for high electrochemical performance

“…7), the intensities of sp 2 and sp 3 C-C bonds (284.4 eV) are obviously increased and the bonds associated with oxidized carbon (including C-N at 285.5 eV, C-O at 286.7 eV, C@O at 287.7 eV, and O-C@O at 288.9 eV) are decreased, indicating that GO has been deoxygenated to form NG in the composite (Fig. 7) [47,48].…”