Investigation On H₂O₂ Electrochemical Sensing Method Based On Zero Current Potential Signals

Zero current potentiometry is a new electrochemical method for the determination of the electrode solution interfaces in recent years,it can be applied to measure the interfacial potential of various electrochemical sensor.Compared to the ordinary electrochemical sensing method,it has unique advantage.In this thesis,three types of electrochemical sensor were fabricated based on three types of layered or core-shell materials and their composites with metal nanoparticles,and to establish a new method of H2O2 electrochemical sensing based on zero current potential signals.These studies provide the reference for improving the performance of electrochemical sensor and enrich the electrochemical research content to some extent.The thesis was divided into two chapters and the author's main contributions were as follows:1.Ag@C@Ag composite was prepared by using hydrothermal and chemical reduction,and the Ag@C@Ag composite was used to construct electrochemical sensor.The morphology,composition and structure of the sensing interface materials were studied and the relationship between the sensing interface materials and the response performance to zero current potential signals of H2O2.The results of the study which by using scanning electron microscope(SEM),X-ray spectrometer(EDS)and X-ray powder diffraction(XRD)show that the composite is composed of elements such as Ag,C,and Ag@C is core-shell shape.The diameter of C shell is about 800 nn,Ag core is about 100 nm.And then further reduction of AgNPs evenly distributed in the C shell surface,particle size of about 25 nm.The electrochemical results have shown that AgNPs on the surface of Ag@C@Ag had an obvious electrochemical reduction effect to H2O2.The method of H2O2 electrochemical sensing based on zero current potential signals is applied to detect H2O2,and the linear range is from 0.2 pmol/L to 0.01 mmol/L,with a detection limit of 0.07?mol/L and a sensitivity of 290 ?V·(mmol·L-1)·cm-2.Compared to the ordinary electrochemical sensing method,the detection limit of the new method reduces two orders of magnitude.2.The uniform size Ag@SiO2@Ag nanocomposite was successfully synthesized by a simple one-step method,and the Ag@SiO2@Ag nanocomposite was used to construct electrochemical sensor.The morphology,composition and structure of the sensing interface materials were studied and the relationship between the sensing interface materials and the response performance to zero current potential signals of H2O2.The results of the study which by using transmission electron microscope(TEM),X-ray spectrometer(EDS)and X-ray powder diffraction(XRD)show that the composite is composed of elements such as Ag,Si,O,and Ag@SiO2@Ag nanocomposite is the evenly core-shell shape.The diameter of AgNPs on the surface of SiO2 is about 2.6 nm,and the diameter of Ag core and silica shell is 26 nm and 100 nm respectively.The electrochemical results have shown that AgNPs on the surface of Ag@SiO2@Ag had an obvious electrochemical reduction effect to H2O2.The method of H2O2 electrochemical sensing based on zero current potential signals is applied to detect H2O2,and the linear range is from 0.002 ?mol/L to 10 ?mol/L,with a detection limit and a sensitivity of 0.0007?mol/L and 103.3 ?V·(mmol·L-1)·cm-2.Compared to the ordinary electrochemical sensing method,the detection limit of the new method reduces four orders of magnitude and the sensitivity improves an order of magnitude.3.The layered NNH nickel base material was prepared by using hydrothermal,and the AgNPs were synthesized on the surface of NNH,and the layered Ag-NNH composites were used to construct electrochemical sensor.The morphology,composition and structure of the sensing interface materials were studied and the relationship between the sensing interface materials and the response performance to zero current potential signals of H2O2.The results of the study which by using field emission electron microscope(FESEM),transmission electron microscope(TEM)show that the composite is composed of elements such as Ni,Ag,O,and the synthetic NNH is a uniform thickness of layered material.The thickness is about 60 nm,and AgNPs evenly dispersed in the NNH layer surface,and particle size contains two kinds of size,namely,15 nm and 23 nm.The electrochemical results have shown that AgNPs on the surface of Ag-NNH had an obvious electrochemical reduction effect to H2O2.The method of H2O2 electrochemical sensing based on zero current potential signals is applied to detect H2O2,and the linear range is from 0.001?mol/L to 1 mmol/L,with a detection limit and a sensitivity of 0.0003?mol/L and 33.7?V·(mmol·L-1)· cm-2.Compared to the ordinary electrochemical sensing method,the detection limit reduces four orders of magnitude.Compared with the similar methods,the new method has wider linear range and higher sensitivity.