Supporting Information: Fig S1. FESEM images of annealed samples on FTO (a) Pt, (b) Co 8.4 S 8 , (c) Cu 1.8 S and (d) Ni 3 S 2 . Cyclic voltammetry in polysulfide electrolyte: To investigate the catalytic activities of the counter electrodes prepared, cyclic voltammetry (CV) (Solartron-analytical, 1470E) was performed in a three electrode system (Pt mesh , Ag/AgCl as counter and reference electrode respectively) with 1 M Na 2 S, 1 M S, and 0.1 M NaOH, at a scan rate of 100 mVs -1 , Fig S2. The

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... est potentials of all the electrodes when immersed in the electrolyte were found to be ≈ -0.7 V which is equal to the values reported for E redox,PS . (1) The value of E redox,PS is in good agreement with Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is