Three-dimensional branched single-crystal β-Co(OH)2 nanowire array and its application for supercapacitor with excellent electrochemical property

Abstract We have for the first time fabricated a unique three-dimensional branched single-crystal β-Co(OH)2 nanowire array supported on Ni foam. This structure is formed by the splitting crystal growth effect combined with the specific topological structure of β-Co(OH)2. A branched Co3O4@MnO2 core–shell nanowire array is prepared for use as supercapacitor electrode. At a current density of 10 mA cm−2, the branched Co3O4@MnO2 core–shell nanowire array exhibits 0.99 F cm−2 of areal capacitance, which is 69.3% of the capacitance (1.43 F cm−2) measured at 1 mA cm−2. In addition, the branched core–shell hybrid can still retain 93.6% of the initial capacitance after 5000 cycles. Such excellent electrochemical performance of the branched Co3O4@MnO2 core–shell nanowire array is attributed to the unique configuration and the strong synergistic effect from the porous Co3O4 nanowire core and the ultrathin MnO2 shell.