Transparent 1T-MoS2 nanofilm robustly anchored on substrate by layer-by-layer self-assembly and its ultra-high cycling stability as supercapacitors

Two-dimensional MoS₂ materials have attracted more and more interest and been applied to the field of energy storage because of its unique physical, optical, electronic and electrochemical properties. However, there are no reports on high-stable transparent MoS₂ nanofilms as supercapacitors electrode. Here, we describe a transparent 1T-MoS₂ nanofilm electrode with super-long stability anchored on the indium tin oxide (ITO) glass by a simple alternate layer-by-layer (LBL) self-assembly of a highly charged cationic poly(diallyldimethylammonium chloride) (PDDA) and negative single-/few-layer 1T MoS₂ nanosheets. The ITO/(PDDA/MoS₂)₂₀ electrode shows a transmittance of 51.6% at 550 nm and obviously exhibits excellent transparency by naked eye observation. Ultrasonic damage test validates that the (PDDA/MoS₂)₂₀ film with the average thickness about 50 nm is robustly anchored on ITO substrate. Additionally, the electrochemical results indicate that the ITO/(PDDA/MoS₂)₂₀ film shows areal capacitance of 1.1 mF cm^-2 and volumetric capacitance of 220 F cm^-3 at 0.04 mA cm^-2, 130.6% retention of the original capacitance value after 5000 cycles. Further experiments indicate that the formation of transparent (PDDA/MoS₂) _x nanofilm by LBL self-assembly can be extended to other substrates, e.g., slide glass and flexible polyethylene terephthalate (PET). Thus, the easily available (PDDA/MoS₂) _x nanofilm electrode has great potential for application in transparent and/or flexible optoelectronic and electronics devices.