An electrochemical sulfur sensor based on ZrO2(MgO) as solid electrolyte and ZrS2 + MgS as auxiliary electrode

A sulfur sensor Mo|Mo, Mo2S3|ZrS2 + MgS|ZrO2(MgO)|ZrS2 + MgS|[S]Fe|Mo was developed and tested in carbon-saturated liquid iron. The auxiliary electrode was ZrS2 + MgS, which was formed on the surface of ZrO2(MgO) electrolyte by: ZrO2(MgO)(s) + 3H2S(g) = ZrS2(s) + MgS(s) + 3H2O(g). The results indicate that the auxiliary electrode is dense, and has a good adhesion to the solid electrolyte. ZrS2 and MgS are stable in the carbon-saturated liquid iron where the aO < 1.25 × 10−7 at 1550 K and aO < 2.10 × 10−7 at 1600 K. The variations of the EMF versus [wt% S] can be obtained as follows:E=−65.48 ln[wt%   S]+134.42 (1550 K)E=−65.48 ln[wt%   S]+134.42 (1550 K)E=−81.18 ln[wt%   S]+111.66 (1600 K)E=−81.18 ln[wt%   S]+111.66 (1600 K)