Preparation And Application Of All Solid-state Reference Electrodes For Ocean Electrochemical Sensors

In-situ chemical analysis in marine science requires the development of various electrochemical sensors,and the key component is the reference electrode.To this end,we developed Ag/AgCl reference electrodes with Nafion membrane packaging,LLTO solid electrolyte by solid-phase synthesis,NLTO all-solid-state reference electrodes,and researched the structure and performance of these reference electrodes.The main research contents are as follows:（1）The Ag/AgCl electrode was prepared by the electrophoretic deposition method,and was encapsulated with Nafion film to be the reference electrode.Added AgCl to keep AgCl ionization balance.After a series of tests,it can be obtained that the Ag/AgCl reference electrode encapsulated with Nafion membrane can maintain a stable potential for buffer solutions under different pH conditions.Due to the softness of the Nafion membrane,the electrode structure is stable under simulated high pressure conditions in the deep sea,which solves the fragile problem of commercial Ag/AgCl reference electrodes.（2）The solid phase diffusion reaction is used to prepare pure phase lithium lanthanum titanate powders.After being ground,a well-dispersed lithium lanthanum titanate powders were obtained.Then high-density LLTO ceramics can be obtained after sintering.The obtained LLTO ceramics with high conductivity were used to prepare a new LLTO all-solid-state reference electrode,and its performance was verified.After a series of tests,it can be found that the reference electrode can maintain a stable potential for buffer solutions under different pH conditions.After being combined with the Ir/IrO₂ electrode,all-solid-state pH sensor was obtained.Moreover,the reference electrode has stable electrochemical performance and can be used in other electrochemical sensors.We tested the stability of the reference electrode in a high temperature,high pressure,and high sulfur environment,and it is expected to be used in deep-sea equipment.（3）lanthanum sodium titanate powders were prepared by the solid phase diffusion reaction,and after high temperature sintering to obtain a densified ceramic,which is designed as an all-solid-state reference electrode.Combination of NLTO reference electrode and Ir/IrO₂ working electrode to obtain the all-solid-state pH sensor,and the performance of the sensor was preliminarily explored.Although it can perform measurements in high temperature and high pressure environments,due to the large resistance of NLTO,the all-solid-state pH sensor is less sensitive to seawater.