Study On Transient Process Of Electrochemical Double Layer On Single Particles

The electrochemical double layer exists at almost all the electrochemical interfaces.Therefore,to explore the nature of electrochemical double layer is an important mission of the modern electrochemistry.Known of the dynamic formation process of electrochemical double layer,especially on nanoparticles,will help to understand electrochemical reactions in microcosmic system.That it would promote the technological advance of electrocatalysis,electrochemical energy storage and electrochemical corrosion etc.However,the real dynamic formation process of electrochemical double layer is still unclear untill now,which is limited by the backward detection technology.Because the formation of electrochemical double layer is very complex and that is difficult to detect lying on the traditional probing technique.Here a new transient electrochemical research method was proposed based on the unique plasmon resonance properties of noble metal nanomaterials,and we used it to explore the dynamic process of electrochemical double layer on a single Au nanoparticle.The main research contents are as follows:(1)A transient photoelectrochemical microscope system was designed and built.We successfully observed the formation of electrochemical double layer on a 80 nm Au nanoparticle utlizing the home-built system.As known,the formation process of the electrochemical double layer formed by two parts,the process of electron injection and mass transport.And both of them could influence the intensity of scattered light signal on the gold nanoparticles.Therefore,the optical system of transient photoelectrochemical microscope could be used to monitor the formation of the electrochemical double layer on the Au nanoparticles by detecting the changes of scattered light signal.And we collected the current signal to monitor the electron injection process at the same time.The data indicated that time constant of the formation of the electrochemical double layer is significantly different from that of nonFaradaic current.Therefore,the traditional simple capacitor charging model could not be used to represent the real formation of the electrochemical double layer,especially in microcosmic system.(2)We have observed the transient processes of electrochemical double layer on Au nanoparticles under different solution conditions,and explored the influence factors of transient formation of electrochemical double layer in microcosmic system.When the viscosity of the solution increases,the migration rate of ions becomes slower.Under the condition that the time of electron injection is constant,the structure of the electric double layer need a longer time to stable.At this time,the mass transport plays a great role on the formation process of the electrochemical double layer.When the ions concentration of the solution becomes small,the time of electron injection have stretched.The time required for the electrochemical double layer to reach a steady state is also increases while the ions motion rate does not change.When the concentration of the solution is reduced to a certain extent,the charging process can represent the formation process of the electrochemical double layer,and the electron injection and mass transport are gradually unified.Finally,a theoretical model of the formation of electrochemical double layer on the nanoelectrode was carried out in combination with the classical law,which is helpful to understand the charge and discharge behavior of the microelectrochemical system under transient conditions.