Hierarchically Porous 3D Freestanding Holey-MXene Framework via Mild Oxidation of Self-Assembled MXene Hydrogel for Ultrafast Pseudocapacitive Energy Storage
Anirban Sikdar, Frédéric Héraly, Hao Zhang, Stephen A. Hall, Kanglei Pang, Miao Zhang, Jiayin Yuan
Abstract
High Resolution Image Download MS PowerPoint Slide The true promise of MXene as a practical supercapacitor electrode hinges on the simultaneous advancement of its three-dimensional (3D) assembly and the engineering of its nanoscopic architecture, two critical factors for facilitating mass transport and enhancing an electrode’s charge-storage performance. Herein, we present a straightforward strategy to engineer robust 3D freestanding MXene (Ti 3 C 2 T x ) hydrogels with hierarchically porous structures. The tetraamminezinc(II) complex cation ([Zn(NH 3 ) 4 ] 2+ ) is selected to electrostatically assemble colloidal MXene nanosheets into a 3D interconnected hydrogel framework, followed by a mild oxidative acid-etching process to create nanoholes on the MXene surface. These hierarchically porous, conductive holey-MXene frameworks facilitate 3D transport of both electrons and electrolyte ions to deliver an excellent specific capacitance of 359.2 F g –1 at 10 mV s –1 and superb capacitance retention of 79% at 5000 mV s –1, representing a 42.2% and 15.3% improvement over pristine MXene hydrogel, respectively. Even at a commercial-standard mass loading of 10.1 mg cm –2, it maintains an impressive capacitance retention of 52% at 1000 mV s –1 . This rational design of an electrode by engineering nanoholes on MXene nanosheets within a 3D porous framework dictates a significant step forward toward the practical use of MXene and other 2D materials in electrochemical energy storage systems.