Electrochemical double-layer capacitance of MoS2 nanowall films

Edge-oriented MoS2 films synthesized by single source precursor chemical vapor deposition exhibit a high density of nanowalls, which can potentially exhibit excellent electrochemical charge storage properties. The electrochemical double- layer capacitance of layered, nanowalled MoS2 film has been investigated in this work using electrochemical impedance spectroscopy. We show that edge-oriented MoS2 thin films can behave as a supercapacitor at alternating current frequencies up to 100 Hz. The supercapacitor performance is comparable to that of carbon nanotube array electrodes. In addition to double- layer capacitance, diffusion of the ions into the films at slow scan rates gives rise to faradaic capacitance, which enhances the capacitance significantly. The real and imaginary part of the capacitance of the MoS2 films was analyzed as a function of frequency, in order to obtain information on the relaxation time constant and frequency dependence of the supercapacitor properties.