Enhanced Electrochemical Performance of Metallic CoS-Based Supercapacitor by Cathodic Exfoliation

Abstract

Two-dimensional nanomaterials hold great promise as electrode materials for the construction of excellent electrochemical energy storage and transformation apparatuses. In the study, metallic layered cobalt sulfide was, firstly, applied to the area of energy storage as a supercapacitor electrode. By a facile and scalable method for cathodic electrochemical exfoliation, metallic layered cobalt sulfide bulk can be exfoliated into high-quality and few-layered nanosheets with size distributions in the micrometer scale range and thickness in the order of several nanometers. With a two-dimensional thin sheet structure of metallic cobalt sulfide nanosheets, not only was a larger active surface area created, but also, the insertion/extraction of ions in the procedure of charge and discharge were enhanced. The exfoliated cobalt sulfide was applied as a supercapacitor electrode with obvious improvement compared with the original sample, and the specific capacitance increased from 307 F∙g−1 to 450 F∙g−1 at the current density of 1 A∙g−1. The capacitance retention rate of exfoliated cobalt sulfide enlarged to 84.7% from the original 81.9% of unexfoliated samples while the current density multiplied by 5 times. Moreover, a button-type asymmetric supercapacitor assembled using exfoliated cobalt sulfide as the positive electrode exhibits a maximum specific energy of 9.4 Wh∙kg−1 at the specific power of 1520 W∙kg−1.

Modifying Electronic Structure of Cation‐Exchanged Bimetallic Sulfide/Metal Oxide Heterostructure through In Situ Inclusion of Silver (Ag) Nanoparticles for Extrinsic Pseudocapacitor

“…[ 46 ] Besides, in the CV curves of the Ag‐Co 9‐x Fe x S 8 @α‐Fe x O y electrode, the pairs of oxidation (Ox‐1 and Ox‐2) and reduction (Red‐1 and Red‐2) peaks appeared correspondingly at ≈0.05 and ≈0.35 V (vs Hg/HgO), which correspond to the Faradic reversible redox processes of Co 2+ /Co 3+ and Fe 2+ /Fe 3+ occurring as a result of the interaction of OH − ions from the KOH electrolyte with Co 9‐x Fe x S 8 and α‐Fe x O y (Equations (1)–(4)). [ 22a,47 ] Additionally, the electrochemical interaction between Ag and Ag 2 O (Equation (6)) also contributes to charge storage with the appearance of redox peaks at similar potentials in the Ag‐Co 9‐x Fe x S 8 @α‐Fe x O y electrode. [ 48 ] The integral area under the CV curve of the Ag‐Co 9‐x Fe x S 8 @α‐Fe x O y electrode was significantly higher than that of the pristine α‐Fe x O y electrode, and the CV curve of the CF substrate with a negligible integral area under the curve confirmed the negligible charge storage contribution made by the CF substrate to the main electrode.…”

Enhanced synergistic redox activity of SrCoS/PANI for hybrid energy storage and oxygen evolution reaction

“…The 2D thin sheet structure of metallic CoS nanosheets improved the insertion/extraction of ions during charge and discharge. Button-type asymmetric SC with exfoliated CoS positive electrodes have a maximum E d of 9.4 Wh kg −1 at 1520 W kg −1 [25]. At room temperature, a simple biomembrane support system synthesized CoS nanoflakes with a porous structure.…”