Design and construction of hollow metal sulfide/selenide core–shell heterostructure arrays for hybrid supercapacitor

Transition metal sulfides and selenides are common electrode materials in supercapacitors. However, the slow redox kinetics and structural collapse during charge-discharge cycles of single-component materials have impeded their electrochemical performance. In this study, hollow Co₉S₈ nanotubes were synthesized through a rational morphology design approach. Subsequently, NiSe₂ or Co_0.85Se was electrodeposited onto the Co₉S₈ nanotubes, yielding two core-shell heterostructure arrays, namely, NiSe₂@Co₉S₈ and Co_0.85Se@Co₉S₈. By fully leveraging the advantages and synergistic effects of these dual-phase heterostructures, the NiSe₂@Co₉S₈ and Co_0.85Se@Co₉S₈ configurations demonstrated outstanding areal capacitances of 12.54 F cm^-2 and 9.61 F cm^-2, respectively, at 2 mA cm^-2. When integrated with activated carbon in hybrid supercapacitors, the NiSe₂@Co₉S₈//AC and Co_0.85Se@Co₉S₈//AC devices exhibited excellent energy storage performance, with energy densities of 0.959 mW h at 1.681 mW and 0.745 mW h at 1.569 mW, respectively. Additionally, these hybrid supercapacitors demonstrated remarkable cycling stability, with capacitance retention of 87.5% and 89.5% after 5000 cycles for NiSe₂@Co₉S₈//AC and Co_0.85Se@Co₉S₈//AC, respectively. This study provides a novel approach to the synthesis of multiphase core-shell heterostructures based on metal sulfides and selenides, opening new avenues for future research.