A general synthetic strategy for converting metal−organic frameworks to hydroxides as advanced electrodes for supercapacitors by magnetic field assistance

Abstract

Herein, a general magnetic field-assisted strategy of transforming Ni/Co-MOF into porous layered Ni/Co hydroxide has been formulated to enhance the charge storage performance of the material. In the process of alkaline hydrolysis assisted by magnetic field, the magnetic dipoles of Ni/Co-containing magnetic materials are modulated in the same direction as the magnetic field, accelerating the nucleation rate of Ni/Co hydroxide nanosheets, regulating the migration behavior of ions, and thus optimizing the conductivity and morphology of electrode materials. Consequently, the hydroxide of Ni0.5Co0.5(OH)2-3c derived from the alkaline hydrolysis of Ni/Co-MOF with magnetic field assistance provides a much better specific capacity of 1367 C g−1 at 1 A g−1 than that without magnetic field assistance (1007 C g−1). Furthermore, the hybrid supercapacitor composed of Ni0.5Co0.5(OH)2-3c and active carbon (AC) exhibited an energy density of 35.5 Wh kg−1 at the power density of 806.8 W kg−1 and possesses the remarkable cycling stability with the capacity retention of 86.5% after 20,000 cycles.