Studies On The Fabrication And Electrochemical Performance Of Layered Double Hydroxides-based Materials

Transitional metal-based nanocomposite materials have been widelyused in electrochemical sensors, supercapacitors and secondary batteriesdue to their large proton diffusion coefficient, high electrocatalyticactivity and low toxicity. In this dissertation, a series of transitionalmetal-containing electroactive materials with0D,2D and3Dnanostructure have been synthesized based on layered double hydroxide(LDH) materials, and the relationship between the electrochemicalbehavior of the as-prepared species and their structure, morphology,host-guest interactions was investigated for the sake of exploring novelelectrocatalytic materials. Furthermore, enzyme-free electrodes modifiedby the above materials have been fabricated, which were demonstrated asexcellent sensors in electrochemical detection and measurement. Themainly results of this dissertation are summarized as below:1. Nickel nanoparticles with high dispersion on the surface of LDHshave been prepared by partial reduction of the NiAl/LDH precursor withsodium hypophosphite. TEM images reveal that the nickel nanoparticles are highly dispersed in the NiAl/LDH matrix with a size of⁶nm. Theresulting nanocomposite modified electrode displays significantelectrocatalytic performance for glucose with a linear response range (8×10^-52×10^-3M), high sensitivity (339.2μA/mM) and low detectionlimit (3.6μM). The enhaced electrocatalytic activity of the Ninanoparticles is mainly attributed to the the specific nanostructure whichsupplies abundant active species to participate in electrochemical reactionas well as facilitates the mass/electron transfer. This work provides afeasible method for the preparation of transitional metal nanoparticleswith high dispersion, which can be potentially used in electrocatalysisand sensors.2. A novel inorganic/organic composite multilayer film wasfabricated by layer-by-layer (LBL) assembly of naphthol green B (NGB)and LDHs nanoplatelets. The NGB molecules are immobilized in theinorganic matrix with high dispersion and uniform arrangement, whichbenefits the electron transfer between NGB and underlying electrode. Thefilm modified electrode displays a high electrocatalytic activity towardsascorbic acid in the range1.2⁵5.2μM with a detection limit of0.51μM (S/N=3), much lower than that of the organic/organic film modifiedelectrode and the ascorbate oxidase biosensor. Futhermore, in order toinvestigate the influence of organic species on the electrochemicalactivity for the LDH materials, ultrathin films containing exfoliated CoAl/LDHs nanosheets and negatively charged counterpart (NGB andPSS, respectively) were also fabricated by the LBL method. It was foundthat the LDHs/NGB modified electrode displays a marked electrocatalyticactivity towards H2O2, indicating that NGB serves as a kind of conductivesubstance facilitating charge transfer. This work demonstrates a feasibleapproach for the fabrication of inorganic/organic film materials withsuperior electrochemical properties, for the purpose of potentialapplications in electroanalysis and electrochemical sensors.3. The NiAl/LDHs microspheres with flowerlike hierarchical structurewere successfully synthesized via a facile hydrothermal method with theassistance of ionic liquid ([BMIM]BF4). The hierarchical NiAl/LDHsmodified electrode displays a couple of well-defined reversible redoxpeaks (Ep=67mV and Ia/Ic=0.91) and a fast direct electron transferrate constant (ks=3.32s1), owing to the high dispersion of active speciesas well as abundant mass transfer channels which facilitate themass/electron transfer. In addition, the modified electrode presents asignificant electrocatalytic performance towards the oxidation ofhydrazine with a linear response range (5.0×10^-61.0×10^-4M), highsensitivity (144μA/μM cm²), low detection limit (0.8μM) as well as fastresponse time (2s). The hierarchical NiAl/LDHs with largely enhancedelectrochemical behavior demonstrated in this work can be used inelectrochemical sensor and electroanalysis.