The Study Of All-Solid-State Sensor Based On NASICON All-Solid-State Reference Electrode

The ocean contains rich resources of minerals,medicine,food and aquatic products,providing an important material basis and energy guarantee for human survival and development.Marine economy and Marine scientific research have become the key factors and core themes for the well-being of Chinese people and the national economy to take off again.The deep-sea mineral resources are rich and have potential exploitation and application prospect.However,the deep-sea environment is complicated,so the preparation of deep-sea in-situ electrochemical sensor which can be tested at high temperature and high pressure（400℃,40MPa）for a long time and has stable chemical properties is the key and difficult point of deep-sea resource exploration.Reference electrode,as an important component of in-situ deep-sea electrochemical sensor,plays a fundamental and decisive role in sensor measurement.Compared with the traditional liquid reference electrode,the all-solid-state reference electrode has the advantages of high temperature and pressure resistance,high stability,etc.Therefore,the development of in-situ electrochemical sensors based on the all-solid-state reference electrode has become a research focus of many scientists.According to the research progress and status quo of in-situ all-solid-state sensors,the research content of this paper is carried out from the following aspects:（1）Synthesis of NASICON all-solid electrolytes:Firstly,a variety of NASICON powders(Na₃Zr₂Si₂PO₁₂,NZSP;Na₄Zr₂Si₃O₁₂,NZS;Na₃V₂（PO₄）₃,NVP),and ball-milling,sand-milling and other processes were used to treat the powder,to solve the agglomeration problem of high temperature calcined powder.After that,the synthesized electrolytes were prepared into ceramic sheets,and the morphology,density,microstructure and electrical properties of the solid electrolytes were analyzed.The structure and properties of NASICON all-solid electrolyte were investigated by hydrothermal treatment（100℃,2h）and supercritical treatment（400℃,40MPa,3h）.（2）Using NVP as electrode material and NASICON solid electrolyte as substrate,a new type of NVP@NASICON all-solid reference electrode was designed and prepared,and its electrochemical performance before and after supercritical treatment was characterized.In the electrochemical system,the stability of NVP@NASICON all-solid reference electrode before and after supercritical under different pH conditions,cyclic voltammetry reversibility,stability under different ion interference were investigated.The results above confirm the feasibility and reliability of the reference electrode.The effect of NVP REDOX reaction as a mechanism of sodium ion removal/embedding on the performance of solid-state reference electrode was analyzed by comparing with Ag@NASICON.（3）Design and preparation of all-solid state electrochemical deep-sea sensor based on NVP@NASICON:The Ir/IrO₂ working electrode was paired with NVP@NASICON all-solid-state reference electrode to obtain an all-solid-state pH potential sensor.The long-term stability,response rate and sensitivity of the sensor in different pH solutions were tested in sequence in buffer solution and simulated seawater.It was confirmed that the response of the sensor was linearly correlated with pH,and the Nernst equation was combined.The self-made Au-Hg PEEK tube working electrode was paired with NVP@NASICON all-solid state reference electrode to obtain an all-solid state multi-ion electrochemical sensor,and the contents of Cu²⁺,Fe²⁺and S^2-of different concentration gradient were measured.NVP@NASICON The all-solid-state electrochemical deep-sea sensor tested Cu²⁺,Fe²⁺,S^2-has wide detection range and sensitive response,and the peak current is linearly correlated with ion concentration.The above new all-solid-state sensor composed of NVP@NASICON all-solid-state reference electrode has good electrochemical performance and stability,and has a potential application prospect in deep-sea substance detection.