Layer-by-layer nanostructured supercapacitor electrodes consisting of ZnO nanoparticles and multi-walled carbon nanotubes

The study of nanostructures combining carbon and metal oxide materials in a synergistic way is propitious to achieve new nanocomposites with enhanced capacitive electrochemical properties for energy storage applications such as supercapacitors. Here, we investigate the electrochemical properties of electrodes containing nanostructured films made from layer-by-layer (LbL) multilayers consisting of ZnO nanoparticles (ZnONPs) complexed with polyallylamine hydrochloride (PAH) and multi-walled carbon nanotubes (MWNTs) for supercapacitor applications. The surface of PAH–ZnO/MWNT LbL films was analyzed by atomic force microscopy (AFM), which displayed a nanofilm with high superficial area and porosity due to the high interconnection of MWNTs and ZnONPs in the film's multilayers. Cyclic voltammetry and galvanostatic charge–discharge measurements were used to evaluate the electrochemical properties of the films. A high observed areal capacitance of ca. 1000 μF/cm² was achieved for a 10-bilayer LbL film at a current density of 1.0 × 10⁻⁵ A/cm². Furthermore, the PAH–ZnO/MWNT LbL film exhibited a high cycling stability with a capacitive retention of 96% over 1000 cycles. These results demonstrate that the nanostructured PAH–ZnO/MWNT LbL film may be explored as supercapacitors electrodes for energy storage applications.