Micrometer long bimetallic Nickel-cobalt schiff base MOF as supercapacitor electrodes

Abstract

Nickel and Nickel-cobalt [Ni1/3Co2/3(HL)2].3H2O Schiff base complexes were synthesized from 2-(methoxycarbonyl-hydrazono)-pentanedioic acid, H2L ligand with metal salts. The structural analysis reveals that the prepared samples were endowed with well crystalline nature. The electrodes of Nickel-cobalt Schiff base complex (Ni-Co) exhibits Faradaic peaks indicating the diffusion controlled charge transfer mechanism. As a supercapacitor electrode, the Ni-Co exhibits higher specific capacitance of 683 F g−1 at a current rate of 1 A g−1, which is higher than the Nickel complex. Further the bimetallic material possesses better cyclic stability and very less charge – transfer resistance. An asymmetric device was fabricated using Ni-Co complex as the positive electrode material and activated carbon as the negative electrode. The as fabricated device displays a specific capacitance of 239 F g−1 with energy density of 69 Wh kg−1 and power density of 1385 W kg−1. This device demonstrated preservation of 91 % of initial capacitance after 2000 cycles. These attractive features demonstrate Ni-Co complex is a better candidate for supercapacitor electrode applications.