Spatio-temporally Resolved Investigation Of Electrochemical Interface And Process By Oblique-incidence Reflectivity Difference Technology

Oblique-incidence reflectivity difference（OIRD）technology is a new method developed in the past two decades to detect surface/interface changes online in real time,unlabeled,non-destructive and based on the changes of s and p components in reflected light.OIRD technology was originally used for in-situ real-time detection of solid/gas interface processes such as atomic/molecular adsorption/desorption and diffusion on metal surfaces and oxide film epitaxial growth.Recently,OIRD technology has been transplanted to solid/liquid interface analysis for real-time label-free study of biomolecule binding/dissociation processes,and detection of biochips.However,the wider solid/liquid interface detection of this technology still needs to be further expanded.Exploring the relevant information of the electrochemical table interface is of great significance for the research of surface electrochemistry,energy storage,solar energy collection and bioelectrochemistry.However,conventional electrochemical methods have been unable to meet the growing research requirements in terms of detection sensitivity,temporal resolution,and spatial resolution.Therefore,based on the previous achievements of OIRD technology in the study of solid/gas and solid/liquid interface processes,as well as its unique non-contact,non-damage,and spatio-temporal resolution and many other advantages,it is reasonable to believe that this technology is used at the electrochemical interface and process detection has huge potential.Therefore,this paper focuses on the application of OIRD technology in the electrochemical interface/process,and explores the space-time detection of the surface potential of the transparent electrode and the de-intercalation process of alkali metal ions,respectively.The main research contents of this dissertation are as follows:（1）For the first time,the OIRD technology was successfully used to detect the potential of a transparent electrode（ITO,FTO or single-layer graphene,etc.）.The research results show that OIRD can monitor the electrode potential change of the transparent electrode in real time,and the response signal strength is linearly related to the potential.Further research shows that the sensitivity of the OIRD signal to potential changes is closely related to the thickness and properties of the electrode conductive layer,but not to the ionic strength of the solution phase and Faraday current density.In scanning mode,OIRD can image the potential distribution across the transparent electrode.Theoretical analysis further shows that its physical origin is that the change in electrode potential causes the change in electron density in the transparent conductive layer to cause the change in dielectric constant,which in turn causes a sensitive OIRD signal for the dielectric constant.This method provides important information on the interface potential with spatiotemporal resolution,and has certain potential in the interface process and physical information of the nondestructive detection table,providing a useful tool for studying various electrochemical processes.（2）The bimetallic Prussian blue analogue has the ability to store lithium and sodium ions,and is a potential anode material for secondary battery electrodes.Using OIRD technology,this thesis conducted an in-situ study on the insertion and extraction of sodium ions in Prussian blue analogues.First,three Prussian blue analogues Nax My Fe（CN）₆（M=Co,Ni,Cu）were synthesized by chemical precipitation method,and they were loaded on the surface of the transparent electrode by screen printing,and the active material loading thickness on OIRD was discussed.The influence of the signal.The results show that at the optimal thickness,OIRD technology can monitor this electrochemical process in real time.With the insertion and extraction of sodium ions,OIRD exhibits reversible signal fluctuations.Theoretical analysis shows that the origin of the OIRD signal is due to the change in the dielectric constant of the electrode material due to the entry and exit of ions.Further using the high spatial resolution of OIRD,two-dimensional imaging of the desorption behavior of sodium ions in Prussian blue analogues with different proportions or different transition metals proves that the optical technology of OIRD can detect the difference in desorption of sodium ions.As an advantageous tool for high-throughput screening of electrode active materials and study of electrode material cycling performance,this method has broad development prospects.In summary,this paper focuses on the application of OIRD technology in the electrochemical interface/process detection,respectively showing the interface potential monitoring and distribution imaging on the transparent electrode/solution interface,and the similarity of sodium ions in different transition metals Prussian blue In-situ real-time monitoring and two-dimensional imaging of de-embedding behavior in physical materials.It is preliminary proved that OIRD has great potential in chemical interface/process detection,and is expected to provide a powerful tool for electrochemical related research.