Free-standing hydrophilic carbon nanotube films supported edge exposed MoS2 nanoflakes for flexible supercapacitor application

P. Tiwari
IIT Roorkee,
India

Keywords: microsupercapacitors, layered materials, on-chip devices

Summary:

Recently, two-dimensional layered structures, specially MoS2 has come out as the most investigated electrode material for batteries and supercapacitors, possessing well preserved in-plane covalent bonding, leading to extraordinary mechanical elasticity within the layers as well as outstanding firmness along the c-axis. The present work is aimed to fabricate vertically aligned edge exposed molybdenum disulfide nanoflakes on the surface of the self-standing hydrophilic carbon nanotubes, using a two-step process involving a chemical route and magnetron sputtering techniques for flexible supercapacitor application. These hybrid heterostructures have been characterized using XRD, FESEM, TEM, XPS and cyclic voltammetry. The three electrode measurements revealed very high areal capacitance of 0.2 F/cm2 at a scan rate of 10 mV/sec in 1M Na2SO4 system. The electrode was then tested for 3000 cycles (50 mV/sec), in which the system displayed extraordinary capacitance retention of 99.2%. Next, we constructed a symmetric supercapacitor device using MoS2-CNT hybrid heterostructures and found enhanced electrochemical performance with energy density of the order of 400 μW h/cm2. Also, the bending measurements revealed that the device capacitance as well as the charging-discharging rates had no major influence, indicative of robustness of our device. The inherit hydrophilicity and controlled chirality of carbon nanotubes makes them an ideal candidate for electrode material. Moreover, their self-standing nature allows them to function both as the active material, as well as highly conductive current collector. Coherent and efficient design of structurally stable electrodes is very significant, when aimed at high-performance flexible electrochemical energy storage devices.