Interfacial charge engineering of Cu-BTC derived octahedron-like CuS–C@SnO2 p-n heterojunction for boosting energy storage performance

Constructing unique interfaces is a reliable strategy for improving charge transfer kinetics of electrode materials and thus enhances their energy storage. Therefore, in this work, by using an ortho-octahedral Cu-BTC (Tricopper; benzene-1,3,5-tricarboxylate) to derive CuS and further anchoring SnO₂ nanoparticles on its surface, a CuS–C@SnO₂ p-n heterojunction with an octahedron-like structure is constructed. Benefiting from the joint influence of the novel structure and built-in electric field produced by the CuS–C@SnO₂ p-n heterojunction, the CuS–C@SnO₂ electrode shows a specific capacitance of 589.25 F g⁻¹ at 1 A g⁻¹ and an excellent rate capacity of 81.4% at 10 A g⁻¹. Particularly, the packaged CuS–C@SnO₂//AC asymmetric supercapacitor (ASC) represents a high energy density of 50.79 Wh kg⁻¹ at a power density of 800.01 W kg⁻¹ and an outstanding capacitance retention of 86.7% after 10000 cycles. In addition, by using density functional theory (DFT) calculations, we further confirm that CuS–C@SnO₂ p-n heterojunction has a satisfactory adsorption capacity for OH⁻ and an accelerated transfer for free electrons by the electron rearrangements at the interface, which are beneficial for CuS–C@SnO₂ to enhance its storage capacity. This work provides an effective strategy for designing efficient energy storage devices.