All-solid-state reference electrode based on a solid-state electrolyte of high densified Lithium lanthanum titanium oxide (LLTO)

Using powders treated by sand milling as starting materials, high densified lithium lanthanum titanium oxide (LLTO) ceramics with high conductivity were prepared. A novel all-solid-state reference electrode was fabricated using the as-prepared LLTO ceramics for electrochemical measurements in marine environments that require robustness, no clogging, and resistance to high salinity and high temperatures and pressures. This reference electrode functioned without any filling solution and any porous junction between it and the analyte. The characteristics, stability, and impedance of the all-solid-state reference electrode were examined in different pH buffer aqueous solutions; its I–V curves were recorded during cyclic voltammetric experiments, which were then compared with those obtained for a classic Ag/AgCl reference electrode. The fabricated reference electrode was connected to an Ir/IrO₂ working electrode to prepare an all-solid-state pH sensor for measuring the pH of simulated seawater and for capturing variations in the behavior of the reference electrode on addition of acidic or alkaline solutions. This all-solid-state potentiometric sensor can be used in association with other sensing electrodes and in harsh environments, such as at great ocean depths and in high temperature and pressure environments.