Preparations And Electrochemical Properties Of Layered Double Hydroxide-based Nanocomposites Materials

Layered double hydroxides （LDHs）, been well known as hydrotalcite-likemultifunctional materials or anionic clays. This highly tunable interlayercomposition, combining with a wide possible choice of anionic moieties,allows a large variety of multifunctional LDH materials such as ionexchangers, catalysts or catalyst precursors, adsorbents for environmentalcontaminants, and carriers for the immobilization of biological materials forpotential applications. LDHs have aroused widely concern in the field ofelectrochemical and biological sensors because of the excellent chemical andphysical properties. The inherently weak conductivity of LDHs, however,unfavorably transfers electron, thereby limiting the applications inelectrochemical active materials. The paper focuses on the preparations andelectrochemical properties of LDH-based materials. One is NiAl-LDH/G nanocomposites, using a conventional coprecipitation process underlow-temperature conditions and subsequent reduction of the supportinggraphene oxide to prepare NiAl-LDH/G nanocomposites, further study onthe morphology and structure and properties in the detection of dopamineof the nanocomposites. The other material is CoO/CoFe₂O₄nanocompositeswhich is by thermal treatment of Co/Fe-LDH precursor has clearly obtainedgood dispersion that the resulting CoO matrix was able to be separatedefficiently and spatially by the coexisting CoFe₂O₄phase. The morphologyand structure of the nanocomposites as well as the cycling performance forlithium battery cathode material have also been studied. This results obtainedare presented below：（1） Using a conventional coprecipitation process under low-temperatureconditions and subsequent reduction of the supporting graphene oxide toprepare NiAl-LDH/G nanocomposites, the results of XRD and Ramanspectra provide convincing information that the NiAl-LDH and grapheneboth exist. Electrochemical tests showed that the NiAl-LDH/G modifiedelectrode exhibited highly enhanced electrochemical performance ofdopamine electrooxidation in comparison with the pristine NiAl-LDHmodified electrode.（2） Adjusting the proportion of the metal cation of the LDH to prepareCoFe-LDH precursors with different Co/Fe molar ratios （3:1and2:1）,further thermal treatment of Co/Fe-LDH precursor has clearly obtained good dispersion that the resulting CoO matrix was able to be separatedefficiently and spatially by the coexisting CoFe₂O₄phase, they are3CoO/CoFe₂O₄and5CoO/CoFe₂O₄nanocomposites, respectively. Thestructural, compositional, and textural features of the as-preparedCoO/CoFe₂O₄nanocomposites were detailed on the basis of transmissionelectron microscopy （TEM）, scanning electron microscope （SEM）, powderX-ray diffraction （XRD） and chemical analysis. The cyclingperformance for lithium battery cathode material was evaluated.Electrochemical tests show that the CoO/CoFe₂O₄nanocomposite exhibitsthe greatly enhanced cycle performance and rate capacibility comparedwith CoO, CoFe₂O₄, and the physically mixed CoO/CoFe₂O₄composite.3CoO/CoFe₂O₄nanocomposite exhibits the greatly enhanced cycleperformance and rate capacibility compared with5CoO/CoFe₂O₄. Ourapproach of enhancing performances could be extended to otherhigh-capacity lithium-storage hybrid materials on the basis of chemicaldesigning LDH-precursors.