Engineering novel sea urchin-like bimetallic cu co selenide nanostructures for high-performance asymmetric supercapacitors

Transition metal selenides are popular due to their abundant resources, low cost and high theoretical capacitance. In this study, the bimetallic Cu Co selenides (CuCoSe) heterostructures with sea urchin-like morphology are prepared as self-supporting electrodes for supercapacitors by a simple two-step hydrothermal method. The CuCoSe with a 1:2:1 elemental ratio exhibits optimal electrochemical performance, attributed to the synergistic effect of the dual metals and its optimized morphology. The sea urchin-like structure of the precursor is preserved after selenization. As a result, the sea urchin-like CuCoSe heterostructures show a high specific capacitance of 5.449 F cm −2 at 5 mA cm −2 , and achieve 80.46 % capacitance retention with 96.25 % Coulombic efficiency after 6000 cycles. The developed CuCoSe/AC asymmetric supercapacitor achieves the energy density 0.39 mW h cm −2 (21.53 Wh kg −1 ) at 3.03 mW cm −2 (168.29 W kg −1 ). A capacitance retention of 87.84 % is maintained after 6000 cycles at 30 mA cm −2 . Density Functional Theory (DFT) demonstrates the direction of charge transfer, and the heterojunction is able to enhance the conductivity and affinity for OH − . This study proposes an effective approach for designing transition metal selenide heterostructures with distinctive morphological features to enhance energy storage capabilities.