Energy storage addresses the problem of sustainability for renewable but intermittent energy sources like solar, wave and wind power. Electrochemical supercapacitors represent a new technology that helps meet the demands for high power and energy density for the optimal storage of renewable but intermittent energy sources. For inclusion in supercapacitors, transition metal oxide and sulfide electrodes such as RuO₂, IrO₂, TiS₂, and MoS₂ exhibit rapid faradaic electron–transfer reactions combined with low resistance.

The pseudocapacitance of RuO₂ is about 720 F/g and is 100 times greater than the double-layer capacitance of activated carbon electrodes. However syntheses of these oxide and sulfide electrode materials can be expensive and are not presently in commercial use. We report cathodic electrodeposition of molybdenum disulfide onto glassy carbon electrodes from electrolytes containing 10 mM (NH₄)₂MoS₄ and 0.2 M KCl. Four minutes of electrodeposition yields compact 1 µm thick MoS₂ film deposit, as confirmed by SEM/EDX analysis, whereas longer deposition times yields much thicker MoS₂ film but with nanoscale cracks.

The film capacitance is studied as a function of bulk film thickness and crystallinity. X-ray diffraction analysis demonstrates crystallization of MoS₂ after annealing in Ar at 600°C for 1 hr. The electrochemical performance of both amorphous and crystalline MoS₂ films is studied in 1 M TEA-BF₄ in acetonitrile by electrochemical impedance spectroscopy, cyclic voltammetry and chronocoulometry. The films demonstrate stable pseudocapacitive behavior; for both the amorphous and annealed films, with specific capacitances of 40 F/g and 300 F/g, respectively. Studies as a function of MoS₂ thickness demonstrate that the capacitance eventually plateaus’, suggesting that only the near-surface region is available for charge storage. Results will also be presented for electrochemical impedance spectroscopy and atomic force microscopy of these films before and after capacitance cycling.