Preparation Of Transition Metal Oxide/Noble Metal Electrode Materials And Their Electroanalytical Application

Transition metal oxide/precious metal functional materials exhibit excellent electrical conductivity,photochemical properties and good gas sensitivity.It will broaden the application of the modified electrodes as a new type of environment-friendly and highly efficient conductive materials.Thus,it is of great interests for the development of electrochemical studies.In this thesis,three types of metal oxide/precious metal electrode materials were prepared based on reduced graphene oxide（RGO）as the support,including RGO/Au@CeO₂,NiO/Ag/RGO and amorphous PtNiP ternary alloy.Their composition,structure and morphology were characterized.The electrochemical performances of the materials were investigated systematically by electrochemical methods and differential pulse voltammetry.Importantly,the electrode materials were successfully developed as electrochemical sensors with high sensitivity and selectivity and as a high-performance catalyst for methanol oxidation.The main contents are as follows:1.Amperometric sensing of hydrazine in environmental and biological samples by using CeO₂-encapsulated gold nanoparticles on reduced graphene oxide.CeO₂-encapsulated gold nanoparticles（AuNPs）were anchored to reduced graphene oxide（RGO/Au@CeO₂）by an interfacial auto-redox reaction in a solution containing tetrachloroauric acid and Ce（III）ion on a solid RGO support.The resulting material was modified on a glassy carbon electrode（GCE）as an electrochemical hydrazine sensor.The electrocatalytic activity of the modified GCE towards hydrazine oxidation was significantly enhanced,as compared to RGO/CeO₂,or CeO₂-encapsulated AuNPs,and surface-loading AuNPs on CeO₂-modified with RGO.This enhancement can be attributed to the excellent conductivity of RGO and the strong interaction between the reversible Ce⁴⁺/Ce³⁺and Au^δ+/Au⁰ redox systems.The sensor had a wide linear range（that extends from 10 nM to 3 mM）,a low detection limit（3.0 nM）,good selectivity and good stability for hydrazine detection.It was successfully employed for the monitoring of hydrazine in spiked environmental water samples and in-vitro tracking of hydrazine in cells with respect to its potential cytotoxicity.2.A sensitive electrochemical sensor based on NiO/Ag/RGO for the determination of Sunset Yellow in soft drink.NiO/Ag/reduced graphene oxide（RGO）materials were synthesized by a hydrothermal process.The nanocomposites were characterized by Raman spectroscopy,X-ray diffraction and transmission electron microscopy.After being modified on glassy carbon electrode（GCE）,the NiO/Ag/RGO nanocomposites were used for electrochemical detection of sunset yellow（SY）,an azo synthetic colorant.Due to the synergistic effect of Ag and NiO,the electrochemical sensor showed superior catalytic performance towards the electro-oxidation of sunset yellow,including rapid response,good specificity,a broad linear range and a low detedtion limit of 13 nM.In addition,this sensor was successfully employed for the analysis of SY in soft drink with good recoveries.3.Exploring the role of nickel in the formation of amorphous Pt-based metallic alloys for methanol electro-oxidation with significant.AmorphousPtNiPternarynanoparticlesweresuccessfullysynthesizedviaa hypophospite-assisted reduction process.Due to the difficulty of P doping into pure Pt,it was found that adding a small quantity of nickel salt in the Pt-P synthetic solution could promote the P content by the formation of NiP matrixes.And thus ternary PtNiP nanoparticles with amorphous structure were obtained.Notably,the ternary amorphous PtNiP nanoparticles showed high electrochemical activity and long-term stability for methanol oxidation,which was explored by XPS analysis.