Well-Aligned Cone-Shaped Nanostructure of Polypyrrole/RuO₂ and Its Electrochemical Supercapacitor

Abstract

A new well-aligned cone-shaped nanostructure of polypyrrole (WACNP) has been successfully grown on Au substrate by using a simple, one-step, reliable, and template-free anodic deposition method. The formation mechanism of WACNP is proposed, in which the hydrogen bonding introduced from phosphate buffer solution (PBS) promotes the formation of a well-aligned nanostructure of polypyrrole (PPy), while the steric hindrance effect arisen from high concentration of pyrrole (Py) boosts its vertical alignment and further forms a cone-shaped nanostructure. The 3D, arrayed, nanotubular architecture coated with an ultrathin layer of RuO 2 by the magnetron sputtering deposition method was tailored to construct a supercapacitor. The unique structure and design not only reduces the diffusion resistance of electrolytes in the electrode material but also enhances its electrochemical performance. The modification of RuO 2 on WACNP results in a capacitance higher than that of WACNP by three times. The specific capacitance of RuO 2 /WACNP is 15.1 mF cm −2 (∼302 F g −1 ) measured by the charge−discharge method with an applied current density of 0.5 mA cm −2 over a potential range of −0.2 to 0.7 V, and is greater than that of commercial carbon materials by 2−3 orders of magnitude. The high capacitance and good stability of the RuO 2 /WACNP electrode is very promising for applications in microsupercapacitor devices.