Fabrication and charge storage capacitance of PPY/TiO<sub>2</sub>/PPY jacket nanotube array
Yibing Xie
Abstract
Abstract A PPY/TiO 2 /PPY jacket nanotube array was fabricated by coating PPY layer on the external and internal surface of a tube wall-separated TiO 2 nanotube array. It shows coaxial triple-walled nanotube structure with two PPY nanotube layers sandwiching one TiO 2 nanotube layer. PPY/TiO 2 /PPY reveals much higher current response than TiO 2 . The theoretical calculation indicates PPY/TiO 2 /PPY reveals higher density of states and lower band gap, accordingly presenting higher conductivity and electroactivity, which is consistent with the experimental result of a higher current response. The electroactivity is highly enhanced in H 2 SO 4 rather than Na 2 SO 4 electrolyte due to feasible pronation process of PPY in an acidic solution. PPY/TiO 2 /PPY could conduct the redox reaction in H 2 SO 4 electrolyte which involves the reversible protonation/deprotonation and HSO 4 − doping/dedoping process and accordingly contributes to Faradaic pseudocapacitance. The specific capacitance is highly enhanced from 1.7 mF cm −2 of TiO 2 to 123.4 mF cm −2 of PPY/TiO 2 /PPY at 0.1 mA cm −2 in H 2 SO 4 electrolyte. The capacitance also declines from 123.4 to 31.7 mF cm −2 when the current density increases from 0.1 to 1 mA cm −2 , presenting the rate capacitance retention of 26.7% due to the semiconductivity of TiO 2 . A PPY/TiO 2 /PPY jacket nanotube with high charge storage capacitance is regarded as a promising supercapacitor electrode material.