Polyaniline/reduced graphene oxide nanosheets on TiO2 nanotube arrays as a high-performance supercapacitor electrode: Understanding the origin of high rate capability

As charge storage occurs both on the surface and in the bulk of material, the dynamics of charge storage is a key issue in the practice of energy storage. Although the energy storage can be increased in the bulk of the material, it often suffers from a quite slow kinetics, which seriously hinders the rate capability. Keeping high surface-induced capacitive contribution is proposed to address this issue. Herein, a porous scaffold, TiO2 nanotube arrays grown in a Ti foil (TiO2 NTs/Ti) is selected as the current collector for electrodeposition of porous polyaniline/reduced graphene oxide (PANI/rGO) hybrid film. The capacitive contribution of PANI/rGO@TiO2 /Ti is quantitatively evaluated, showing a high surface-induced capacitive contribution up to 58% at high rates (>25 mV s(-1)) and large electron transfer coefficient of 2. As a result, the electrode not only shows an ultrahigh specific capacity of 908 C g(-1) at 1 mV s(-1), but also delivers an outstanding rate capacity of 310 C g(-1) at 500 mV s(-1). PANI/rGO@TiO2/Ti also shows excellent cycling stability with 80% capacity retention after 10,000 cycles at a high current density of 25 A g(-1). (C) 2020 Elsevier Ltd. All rights reserved.