Hierarchical Nickel–Cobalt Phosphide/Phosphate/Carbon\nNanosheets for High-Performance Supercapacitors

Abstract

Transition-metal\nphosphates/phosphides, as an emerging kind of prominent electroactive\nmaterial, have drawn extensive attention in the fields of energy conversion\nand storage owing to their high electrical conductivity and metal-like\nproperties. Herein, we report the preparation of hierarchical Ni–Co–P/PO_<i>x</i>/C nanosheets in a controllable manner using\nnickel–cobalt metal–organic framework (NiCo-MOF) as\nthe precursor, followed by a low-temperature phosphating method. Electrochemical\nstudies show that the Ni–Co–P/PO_<i>x</i>/C nanosheets exhibit good reversible capacity and excellent\nrate capability and possess capacities of 583 and 365.7 C g^–1 at 1 and 30 A g^–1, respectively. Furthermore,\na two-electrode device assembled by Ni–Co–P/PO_<i>x</i>/C and reduced graphene oxide shows a peak energy\ndensity of 37.59 Wh kg^–1 at a power density of 800\nW kg^–1 and a stable capacitive performance. These\nresults indicate that the obtained bimetallic Ni–Co–P/C\nis a promising anode material for capacitive energy storage devices.