Core-double shell ZnO/ZnS@Co3O4 heterostructure as high performance pseudocapacitor

Abstract

In recent times, a great deal of attention has been paid to the balanced design and fabrication of core–shell heterostructures for enhanced pseudocapacitor (SC) performance. In this paper, we report the synthesis of ZnO@Co₃O₄ based core–shell heterostructures with controllable shell thickness for the first time by a simple low-temperature solution-based method and their detailed electrode performance as SC wherein a highly enhanced pseudocapacitance of 296 C g⁻¹ at a current density of 0.5 A g⁻¹ has been observed. Further, modifying the surface of ZnO by its sulfur analogue (i.e., by creating a ZnO/ZnS heterostructure), an improved capacitance of 317 C g⁻¹ at a current density of 0.5 A g⁻¹ for ZnO/ZnS@Co₃O₄ has been obtained along with a better rate performance. This is attributed to an efficient charge transfer from ZnS to ZnO. Impressively, the core-double shell heterostructure exhibits high energy density of 36 Wh kg⁻¹ at a power density of 204.3 W kg⁻¹. Even at a very high power density of 10.9 kW kg⁻¹, it shows an energy density of 14.7 Wh kg⁻¹. To the best of our knowledge, this is the first study of the electrochemical properties of ZnO/ZnS@Co₃O₄ heterostructure.