Bimetallic Co–W–S Chalcogenides Confined in N,S-Codoped Porous Carbon Matrix Derived from Metal–Organic Frameworks for Highly Stable Electrochemical Supercapacitors

Abstract

Transition-metal dichalcogenides are gaining much interest in the energy storage sector due to the two-dimensional (2D) nature and conductivity of the materials. However, single transition-metal dichalcogenides are not stable, preventing their practical use in real devices. Herein, we demonstrate the synthesis of binary metal dichalcogenides (Co–W–S) via carbonization of zeolitic imidazolate framework (ZIF-67), a subclass of metal–organic frameworks, encapsulated with phosphotungstic acid (PTA@ZIF-67). The morphology and surface functional groups of the as-synthesized Co–W–S composite are characterized via field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the crystal structure and elemental composition of the fabricated Co–W–S composite are elucidated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. Upon testing its electrochemical performance as a supercapacitor electrode, the fabricated Co–W–S@N,S-codoped porous carbon (N,S-PC) shows exceptional specific capacitance (1929 F g–1 at 5 mV s–1). Furthermore, the constructed asymmetric supercapacitor device using Co–W–S@N,S-PC and activated carbon as positive and negative poles, respectively, displays superior energy density and power density of 32.9 Wh kg–1 and 700.2 W kg–1, respectively, with high Columbic efficiency over 10 000 charge/discharge cycles at 10 A g–1.