ELECTROCHEMICAL-BEHAVIOR OF GRAPHITE AND NI-CR ELECTRODES IN SODIUM POLYSULFIDE IN THE ABSENCE AND PRESENCE OF HYDROGEN-SULFIDE

The electrochemical behavior of graphite and Ni-Cr electrodes in sodium tetrasulfide melt has been investigated using voltammetric, chronoamperometric, and chronopotentiometric techniques in the presence and absence of hydrogen sulfide. Two continuous phases, namely, Na2S2 and Na2S, are apparently formed at different potentials during the cathodic polarization. The blocking effect by these layers was much less significant on the Ni-Cr electrode than on graphite. The presence of H2S did not appear to influence the electrode reactions, but it significantly reduced the rate of formation of the continuous phases (Na2S2 or Na2S) during cathodic polarization. A small amount of hydrogen gas was formed, possibly by chemical reactions between polysulfides and hydrogen sulfide. © 1990, The Electrochemical Society, Inc. All rights reserved.