New concept of an all-solid-state reference electrode using a film of lithium lanthanum titanium oxide (LLTO)

A new type of all-solid-state reference electrode based on thick films of lithium lanthanum titanium oxide (LLTO) was developed for electrochemical measurements in harsh environments where robustness, no clogging and resistance to high temperatures and high pressures are required. These reference electrodes do not need any filling solution and any porous junction between them and the analyte. The characteristics, namely stability and impedance of the all-solid-state reference electrode, are studied in different pH buffer aqueous solutions. This reference electrode is then used during cyclic voltammetric experiments in different aqueous media. The recorded voltammograms are compared to those obtained with a classical liquid reference electrode, i.e. a saturated calomel electrode. Finally, this reference electrode is associated to an antimony pH indicating electrode to prepare an all-solid-state pH sensor able to measure the pH of muds and to follow its variations during addition of acid or alkaline solutions. This all-solid-state potentiometric sensor can then be used in oil or geothermic drilling muds in order to prevent hydrogen sulphide evolution when sulphide ions are present in the muds.

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► Solid state reference electrode using a thick film of ion-conductive lithium oxide.
► Low impedance reference electrode requiring no maintenance.
► No electrode clogging observed in oil drilling mud.
► No sensitivity to redox potentials.