All-solid-state Sensor Based On All-solid-state Zr Doped LLTO Reference Electrode

In the 21st century,the contradiction between the supply and demand of mineral resources is more outstanding.The polymetallic sulfide deposits formed by seabed hydrothermal fluids are rich in copper,zinc,gold,silver and other useful elements,about 6×10~8t,which is an important strategic key mineral resources.Chairman Xi Jinping pointed out:"In the 21st century,human beings have entered a period of large-scale development and utilization of the ocean."However,deep-sea hydrothermal fluids are a special environment of darkness,high pressure,high temperature,high salinity,low p H,and low Eh.Therefore,it is an urgent problem to develop an in-situ all-solid-state sensor suitable for the deep-sea environment.In any electrochemical system,the reference electrode is a very critical component.However,many traditional reference electrodes have problems,such as high temperature,high pressure resistance,easy clogging,brittleness,and poor chemical stability.Therefore,the solid reference electrode is the key to the design and development of all solid-state sensors.Based on the current research status of marine all-solid-state sensors,the main research contents of this topic are as follows:（1）Zirconium-doped perovskite（Zr-LLTO）fast ion conductors were synthesized by high-temperature solid-phase method and sand milling.The structure and properties of fast ion conductors were characterized by SEM,XRD,complex impedance spectroscopy,etc.The results show that the as-prepared fast ionic conductor has a dense structure and high total ionic conductivity at room temperature.The fast ionic conductor was fabricated as an all-solid-state reference electrode,and cyclic voltammetry was performed by an electrochemical system as well as potentiometric measurements in different p H buffer solutions.The results show that this reference electrode has good stability and reversible and repeatable electrode reactions.In order to further explore the effect of supercritical environment on the electrode performance,this all-solid-state reference electrode was treated at 400°C and 35 MPa for 3 h.It was found that its electrical conductivity,stability,reversibility and repeatability were further improved due to the optimized structure.（2）Based on slow hydrolysis of CH₃CSNH₂（TAA）,the Ag/Ag₂S electrode was directly sulfurized in a 0.5 mol/L CH₃CSNH₂ solution at 100°C.The electrode structure was characterized by SEM,EDS,etc.It was found that the extent of sulfidation of the electrode was high,and the film and the substrate joined close.After being tested in different concentrations of sulfur ion solution by electrochemical system,this electrode showed quick potential response with high sensitivity and wide detection range.In order to further explore the effect of supercritical environment on the electrode,supercritical treatment was also carried out.It was found that the structure on the surface film of this electrode,its chemical properties and electrochemical properties hardly changed.According to the experimental results,this electrode can be used for the detection of sulfide ions in harsh environments such as deep sea.（3）An all-solid-state sensor for sulfide ions was assembled based on Zr-LLTO reference electrode with supercritical treatment and gold amalgam microelectrode or Ag/Ag₂S electrode;An all-solid-state p H sensor was designed from Zr-LLTO reference electrode paired with Ir/Ir O₂ p H electrode.The results show that as-obtained Zr-LLTO reference electrode after supercritical treatment is more suitable for the detection of high-concentration sulfur ion solution than the commercial silver/silver chloride electrode.The as-produced all-solid-state sensor for sulfide ions has high sensitivity,good stability and wide detection range.The as-prepared all-solid-state p H sensor responds quickly in buffer solutions of different p H,and display stable potential and similar sensitivity to the theoretical value.The all-solid-state sensors based on the Zr-LLTO solid-state reference electrode and different working electrodes have good application prospects in harsh environments such as deep sea.