Immobilization of Co-Al layered double hydroxides on graphene oxide nanosheets: growth mechanism and supercapacitor studies.

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.