NiSe/Ni(OH) 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 NiSe nano-octahedra to fabricate the NiSe-(100)/Ni(OH)-(110) heterojunction. The heterojunction composite and Ni(OH) (performing high electrochemical activity) is ideal high-rate battery-type supercapacitor electrode. The NiSe/Ni(OH) electrode exhibits a high specific capacity of 909 C g at 1 A g and 597 C g at 20 A g. The assembled asymmetric supercapacitor composed of the NiSe/Ni(OH) cathode and p-phenylenediamine-functional reduced graphene oxide anode achieves an ultrahigh specific capacity of 303 C g at 1 A g and a superior energy density of 76.1 Wh kg at 906 W kg, as well as an outstanding cycling stability of 82% retention for 8000 cycles at 10 A g. To the best of our knowledge, this is the first example of NiSe/Ni(OH) 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.