Interface-Engineered MoSe 2 -Co 9 S 8 Nanoheterostructures with Enhanced Charge Storage Performance for Supercapacitor Application.

Cobalt-based chalcogenides have emerged as fascinating materials for supercapacitor applications owing to the presence of various mixed valance oxidation states in their structure along with rich electrochemical properties. However, their limited stability and cyclic performance hinder their viability for practical use in supercapacitors. Herein, a facile hot injection colloidal route is demonstrated to design MoSe ₂ -Co ₉ S ₈ nanoheterostructures (NHSs), which entails the epitaxial growth of Co ₉ S ₈ nanoparticles (NPs) over the basal planes of ultrathin MoSe ₂ nanosheets (NSs). The interfacial engineering of the basal planes of MoSe ₂ NSs with Co ₉ S ₈ NPs regulates the electronic properties and defects at the interfaces and increases the overall specific surface area and conductivity. As a result, MoSe ₂ -Co ₉ S ₈ NHSs electrode unveils a substantially higher specific capacitance of 910.5 F g ^-1 at 1 A g ^-1 current density surpassing their individual counterparts. In addition, it demonstrates worthy solidity, retaining ≈90% of its capacitance and coulombic efficiency of 93.3% after 10,000 charge-discharge cycles at a high charge-discharge current density of 15 A g ^-1 . As a proof-of-concept, coin cells are fabricated using MoSe ₂ -Co ₉ S ₈ NHSs which show 93% Coulomb efficiency and 86% capacitance retention. This study would pave the way for designing transition metal dichalcogenides (TMDs) - derived NHSs with superior capacitive properties.
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