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.