Bath temperature controlled phase stability of hierarchical nanoflakes CoS2 thin films for supercapacitor application

Abstract

In the present study, CoS₂ thin-film electrodes are synthesized at different bath temperatures using a simple chemical bath deposition (CBD) method. The bath temperature controls the phase stability of the CoS₂ thin film along the in-plane direction up to 353 K. However, at 363 K, an oxide phase is included in the film. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies showed enhanced crystallinity of CoS₂ as the bath temperature increased and evolution in surface morphology from immature nanoflakes to well-grown aligned mature nanoflakes. A specific capacitance of 800 F g⁻¹ is obtained from cyclic voltammetry measurements by utilizing the 83.6 m² g⁻¹ surface area of CoS₂ nanoflakes synthesized at 353 K. The hierarchical distribution of pores gives rise to a high specific energy and specific power of 40.74 W h kg⁻¹ and 3333 W kg⁻¹, respectively, as a result of utilization of the high electrochemically active surface area. Furthermore, good long-term cycling stability of CoS₂ nanoflakes has been observed in a 2 M KOH electrolyte. A low impedance value suggests that the CoS₂ nanoflake electrode prepared by a facile CBD method is a potential candidate for supercapacitor application.