NiSe₂/Ni(OH)₂ Heterojunction Composite through Epitaxial-like Strategy as High-Rate Battery-Type Electrode Material

Constructing heterojunction is a promising way to improve the charge transfer efficiency and can thus promote the electrochemical properties. Herein, a facile and effective epitaxial-like growth strategy is applied to NiSe₂ nano-octahedra to fabricate the NiSe₂-(100)/Ni(OH)₂-(110) heterojunction. The heterojunction composite and Ni(OH)₂ (performing high electrochemical activity) is ideal high-rate battery-type supercapacitor electrode. The NiSe₂/Ni(OH)₂ electrode exhibits a high specific capacity of 909 C g^-1 at 1 A g^-1 and 597 C g^-1 at 20 A g^-1. The assembled asymmetric supercapacitor composed of the NiSe₂/Ni(OH)₂ cathode and p-phenylenediamine-functional reduced graphene oxide anode achieves an ultrahigh specific capacity of 303 C g^-1 at 1 A g^-1 and a superior energy density of 76.1 Wh kg^-1 at 906 W kg^-1, as well as an outstanding cycling stability of 82% retention for 8000 cycles at 10 A g^-1. To the best of our knowledge, this is the first example of NiSe₂/Ni(OH)₂ heterojunction exhibiting such remarkable supercapacitor performance. This work not only provides a promising candidate for next-generation energy storage device but also offers a possible universal strategy to fabricate metal selenides/metal hydroxides heterojunctions.