Liquid and solid states on-chip micro-supercapacitors using silicon nanowire-graphene nanowall-pani electrode based on microfabrication technology

Liquid and solid states on-chip micro-supercapacitors based on polyaniline (PANI) coated on graphene nanowalls which grown on silicon nanowires were reported in this work. Novel micro-fabrication technologies were investigated to create three dimension (3D) hierarchical electrodes. High aspect ratio silicon nanowires were produced by metal-assisted chemical etching (MACE). 3D hierarchical graphene nanowalls were grown on silicon nanowire surface by a microwave plasma-enhanced chemical vapor deposition (PECVD). Graphene nanowalls were subsequently coated by conductive PANI. Both of liquid and solid state micro-supercapacitors were successfully fabricated with symmetric face to face high density nanowire arrays separated by liquid and gel electrolytes, respectively. The areal energy and power density of the liquid-state on-chip micro-supercapacitor are 11.7 μWh/cm² and 0.42 mW/cm², respectively, while those of the solid-state on-chip micro-supercapacitor are 10.8 μWh/cm² and 0.78 mW/cm².