An asymmetric supercapacitor with an interpenetrating crystalline Fe-MOF as the positive electrode and its congenetic derivative as the negative electrode

Abstract

Herein, a novel Fe-based MOF Fe(TATB)(Tipa)(H₂O) (FeSC) with 3D interpenetrated topology has been successfully prepared through the reaction of a tribasic aromatic carboxylic acid 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tribenzoic acid (H₃TATB), Fe(SO₄)₂·7H₂O, and a flexible nitrogen-containing pro-ligand tris(4-(1H-imidazol-l-yl)phenyl)amine (Tipa) under hydrothermal conditions. After high-temperature annealing of FeSC, another three-component composite Fe₂O₃/Fe₃N/Fe₃C (denoted as FeSC^#) is obtained. The physicochemical properties of both congenetic materials are explored through X-ray single-crystal diffraction, PXRD, FTIR, XPS, TGA, and SEM. Moreover, cyclic voltammetry, constant current charge–discharge, and electrochemical impedance spectroscopy techniques were applied to conduct electrochemical studies on the two electrode materials in alkaline electrolytes. Crystalline FeSC and annealed FeSC^# showed high specific capacities of 409.2 and 415.2 C g⁻¹ at a current density of 1 A g⁻¹, respectively. Furthermore, FeSC and FeSC^# have been employed as positive and negative electrode materials to assemble an asymmetric supercapacitor (namely Fe-ASC), where this device displays excellent characteristics of high capacitance and low impedance, providing an energy density of 49.85 W h kg⁻¹ with 90.6% capacitance retention after 6000 charge–discharge cycles. These results suggest that the crystalline FeSC and the corresponding three-component congenetic composite FeSC^# are promising electrode materials to construct full energy-storage cells.