Supercapacitor performance of MOF-derived double-shell hollow Ni-Fe-Mn-Se nanocubes

In this study, Ni-Fe-Mn-Se nano boxes with a double-layer hollow structure were synthesized by a static self-assembly and hydrothermal method. To generate a stable structure, NiFe Prussian blue analogue (NiFe-PBA) was used as the substrate material. Moreover, a layer of polydopamine (PDA) was applied onto the surface of the PBA as a “connecting link” to protect the PBA core from collapsing internally and anchor metal ions, enabling the external in-situ growth of NiMn-LDH. A comparison was made between the morphology and properties of nano boxes that were etched using varying concentrations of selenium acid. It was observed that the combination of multi-metallic elements with Se effectively modified the electronic structure of the material, improving its electrical conductivity. The synthesized electrode material, Ni-Fe-Mn-Se, exhibited a high specific capacitance of 1433 F g−1 at 1 A g−1. Moreover, an asymmetric supercapacitor made of a Ni-Fe-Mn-Se cathode, Ni-Fe-Mn-Se//AC, demonstrated outstanding cycling stability (85 % capacitance retention after 8000 cycles) and a maximum energy density of 66.8 Wh kg−1 at a power density of 791 W kg−1. Thus, the electrode material synthesized in this study, Ni-Fe-Mn-Se, exhibits great promise for use in energy storage applications. •Synthesis of double-layer hollow Ni-Fe-Mn-Se nanoboxes•Electronic-structure modulation by synergy of multi-metallic elements with Se•Ni-Fe-Mn-Se exhibits high potential for energy storage applications.