Interface-Engineered MoSe₂-Co₉S₈ Nanoheterostructures with Enhanced Charge Storage Performance for Supercapacitor...

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 MoSe₂-Co₉S₈ nanoheterostructures (NHSs), which entails the epitaxial growth of Co₉S₈ nanoparticles (NPs) over the basal planes of ultrathin MoSe₂ nanosheets (NSs). The interfacial engineering of the basal planes of MoSe₂ NSs with Co₉S₈ NPs regulates the electronic properties and defects at the interfaces and increases the overall specific surface area and conductivity. As a result, MoSe₂-Co₉S₈ NHSs electrode unveils a substantially higher specific capacitance of 910.5 F g^-1 at 1 A g^-1current 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 MoSe₂-Co₉S₈ 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.