Affordable Two-Dimensional\nLayered Cd(II) Coordination\nPolymer: High-Performance Pseudocapacitor Electrode Behavior

In recent years, pseudocapacitive materials have been\ninvestigated\nrigorously as they provide a unique pathway for realizing high-energy\nand high-power densities. However, innovative approaches involving\nrational design and synthesis of new materials are still vital to\naddress concerns such as degradation, low conductivity, low cycling\nperformance, high resistance, production cost, etc. Working in this\ndirection, we report the cost-effective synthesis, characterization,\nand excellent pseudocapacitive behavior of a Cd(II)-based coordination\npolymer (COP) abbreviated as Cd(DAB). It has been realized in quantitative\nyield through a facile one-pot reaction occurring among the N4-ligand,\n3,3′-diaminobenzidine (DAB), and Cd(II) ions, derived from\nCd(OAc)<sub>2</sub>·2H<sub>2</sub>O, at room temperature. The\nproposed structure of the COP was ascertained by subjecting it to\nvarious standard spectroscopic and electron microscopic studies; these\ntechniques reveal the self-assembly of indefinitely long coordination\nstrands into a two-dimensional (2D) layered structure. The electrochemical\nperformance of Cd(DAB) was evaluated as an electrode material for\nsupercapacitors. Owing to its high conductivity, it portrayed remarkable\nenergy storage (pseudocapacitor) behavior; it exhibited a high specific\ncapacitance of 1341.6 F g<sup>–1</sup> and a long cycle life\nwith 81% retention over 10,000 cycles at 20 A g<sup>–1</sup>. Additionally, an asymmetrical supercapacitor device was fabricated,\nwhich exhibited a specific capacitance of 428.5 F g<sup>–1</sup> at a current density of 1 A g<sup>–1</sup>.