Surface-Charge Regulated TiO2 Nanotube Arrays as Scaffold for Constructing Binder-Free High-Performance Supercapacitor

Abstract

Abstract Although TiO2 with outstanding photocatalytic activity has wide applications as a photo-to-electricity conversion material, the electrochemical energy storage of TiO2-based electrodes is commonly restricted by inherent limitations such as intrinsic low theoretical specific capacitance and poor electroconductivity. In this study, we introduce highly uniformed spaced TiO2 nanotube arrays (NTA) as a robust ultrathin scaffold and current collector in a potassium ion electrochemical storage capacitor. By integrating a simple surface-charge regulation with successive ionic adsorption technique, we construct both the cathodic and anodic electroactive materials on a TiO2 NTA based ~5\xa0μm film. Hierarchical MnO2 nanosheets modified TiO2 NTA cathode exhibited a high volumetric capacitance of 1051 F cm−3, and the Fe2O3 nanospindles anchored TiO2 NTA anode exhibited a volumetric capacitance of 608.2 F cm−3. Based on the as-prepared cathode and anode, the assembled asymmetric supercapacitor with a thickness of only 0.4\xa0mm exhibits a high energy density of 2.67 mWh cm−3 in K2SO4 electrolyte with 91.7% capacitance retention after 5000 cycles. The deformable Ti-substrate, excellent stability, good biocompatibility, and satisfactory capacitance in a neutral aqueous system enable the as-proposed supercapacitor a promising energy-storage system, thus expanding the application potentials of TiO2 photocatalysis based energy conversion devices.