The sluggish kinetics of cyclic polysulfide electrochemistry, where sulfur species typically range from S-2(2-) to S-6(2-), presents a challenge in several common electrochemical systems. Recently, transition metal dichalcogenides such as WS2 and MoS2 have been proposed for catalysis of polysulfide oxidation-reduction. Here electrodeposited WS2, MoS2, and Cu-doped MoS2 thin films are tested for 24 h cycling in an electrolyte containing 1.8 M Na2Sx + 1.0 M NaOH. Although their initial catalytic activity is high, electrodeposited WS2 films delaminated after similar to 4 h. The initial catalytic activity of MoS2 films is also high, but MoS2 gradually transforms to Mo2S3 during 24 h of polysulfide oxidation-reduction cycling, as shown by X-ray diffraction (XRD), cross-sectional scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The best results were obtained for Cu-doped MoS2, which exhibited both high catalytic activity and stable polarization curves during 24 h of potential cycling. To the best of the authors' knowledge, this is the first report of MoS2 stabilization during cyclic polysulfide electrochemistry through incorporation of a metal dopant into MoS2. (C) 2019 The Electrochemical Society.