Bimetallic CoSe/FeSe hollow nanocuboids assembled by nanoparticles as a positive electrode material for a high-performance hybrid supercapacitor.

Design and fabrication of impressive and novel electrode materials for energy storage devices, especially supercapacitors, are of great importance. Herein, bimetallic CoSe/FeSe hollow nanocuboid nanostructures derived from Co/Fe-Prussian Blue analogues (denoted as CoSe/FeSe HNCs) are successfully designed and fabricated as a remarkable positive electrode material for high-performance supercapacitors. The bimetallic CoSe/FeSe HNC nanostructures can have increased active sites and short electron-ion diffusion pathways. Bimetallic CoSe/FeSe HNCs@NiF as a positive electrode showed efficient supercapacitive properties with a great specific capacity of 332.75 mA h g (1197.90 C g) at 1 A g, retaining 80.61% of its initial capacity at 20 A g, considerable longevity (91.47% of its initial capacity after 10 000 cycles) and an excellent coulombic efficiency of 98.49%. Also, the designed and fabricated CoSe/FeSe HNCs@NiF||AC@NiF hybrid supercapacitor device using bimetallic CoSe/FeSe HNCs@NiF (positive electrode) and activated carbon@NiF (AC, negative electrode) exhibited an efficient energy density of 63.62 W h kg and a superior durability of 91.14% after 10 000 cycles.