Preparation And Electrochemical Properties Of CeO₂-Ni（OH）₂Nanocomposites

In recent years, the synthesis and properties of nano materials became one of themost active research areas. Due to their large specific surface area and high surfaceactivity, nano materials have broad prospet of applications in electrochemical sensors,and many challenging problems such as specificity, stability and sensitivity in theelectrochemical analysis may be solved. Considering these characteristics of nanomaterials, nickel hydroxide and its composite with different morphologies wereprepared through hydrothermal method. Hydrogen peroxide non-enzyme sensors wereconstructed by assembling the obtained nano materials on the electrode surface. Thestability, electric catalytic activity and selectivity of the sensor were expected to beimproved to broaden its application in the field of electrochemical analysis. The mainpoints of the dissertation are as follows:(1) Self-assembly β-Ni(OH)2microspheres were synthesized via a simplehydrothermal method, with hexadecyl trimethyl ammonium bromide (CTAB) assurfactant and hexamethylenetetramine (HMT) as precipitant. The influence of theconcentration of HMT and NiSO4·6H2O on the morphology and crystal structure of theproduct was studied. The formation mechanism of nano Ni(OH)2structures wasdiscussed. The morphology and phase of the products were characterized by usingSEM, XRD, etc. The thermal decomposition behavior of nickel hydroxide productswas analyzed based on thermogravimetric and differential thermal analysis. Theas-prepared Ni(OH)2was modified on the electrode surface, and the sensingperformance for H2O2and electric catalytic mechanism were investigated throughcyclic voltammetry (CV) and i-t curve measurement. The sensitivity, detection limitand stability of the modified electrode were evaluated.(2) Three-dimensional hierarchical architectures of CeO2-Ni(OH)2compositeswere synthesized adding ammonium cerium nitrate ((NH4)2Ce(NO3)6) in a previous reaction system. The influence of reaction time and surfactant types on themorphologies and microstructures of the composites was investigated. TheCeO2–Ni(OH)2composites were modified onto a glassy carbon electrode (GCE) toprepare CeO2–Ni(OH)2/GCE to fabricate an nonenzymatic H2O2sensor. The electrochemical behavior of CeO2-Ni(OH)2/GCE sensor on hydrogen peroxide wasevaluated by cyclic voltammetry (CV) and amperometric (i-t). And electrochemicalperformance and catalytic effect of the sensor were affected by hydrothermal time. Theresult showed hydrothermal reaction6h exhibited obviously electric catalyticoxidation of H2O2, and the sensitivity and detection limit of the material were superiorto some materials of previous literature reported. This suggests that CeO2-Ni(OH)2materials in terms of detection of hydrogen peroxide, which has a good applicationprospect.(3) Plate-like CeO2-Ni(OH)2nano composites were synthesized by hydrothermalmethod with acetyl acetone as the modifier, NaOH as precipitant. The morphology,phase and crystallinity of as-prepared samples were characterized by using SEM, XRD.The hydrogen peroxide nonenzyme sensor was fabricated by modifying theCeO2-Ni(OH)2nanoplates on the surface of glassy carbon electrode. Electricalconductivity of the sensor was tested by electrochemical impedance spectroscopy(EIS). The working potential in amperometric detection of H2O2was optimized. Themodified electrode was used for the determination of hydrogen peroxide exhibitinggood stability. The sensor shows advantages of rapid response and good stability,simple and cheap, and easy to store.