TiO2 Nanowire Arrays on Titanium Substrate as a Novel Binder-free Negative Electrode for Asymmetric Supercapacitor

To enhance the energy density, a novel asymmetric supercapacitor with a high cell voltage of 2.3 V is firstly assembled with a binder-free TiO2 nanowire arrays (NWAs) electrode as the negative electrode and a home-made porous carbon electrode as the positive electrode. The binder-free TiO2 NWAs electrode anchored on the titanium substrate is prepared via a two step method combining a chemical oxidation (with melamine as soft-template) process with a pyrolysis process. The TiO2 NWAs precursor is obtained via the dissolution of titanium to titania sol and the recrystallization to titania nanowire arrays gel assisted by the melamine. Due to the good electrochenlical stability and the high over-potential for hydrogen evolution, the TiO2 NWAs electrode exhibits ultra-negative potential range in the aqueous electrolyte (0-1.4 V (vs.SCE)), making it ideal for the negative electrode of asymmetric supercapacitor. The as-assembled HMPC/iTiO(2)-NWAs asymmetric supercapacitor exhibits ultrahigh cell voltage (2.3 V) and high volumtric energy density (6.27 mWh cm(-3)). Only one single cell of the asymmetric supercapacitor can light a red light emitting diode (LED) indicator for 10 min, implying its promising practical application. (C) 2017 Elsevier Ltd. All rights reserved.