Synthesis of copper/chromium metal organic frameworks - Derivatives as an advanced electrode material for high-performance supercapacitors

Abstract

Highly optimized copper chromium mixed oxides, derived from mixed cupper/chromium metal organic frameworks (Cu/Cr-MOF), have been successfully synthesized by calcination of parent chromium metal organic frameworks (Cr-MIL-101), cupper metal organic frameworks (Cu-BDC), and mixed Cu/Cr-MOFs in air. The as-synthesized MOF derivatives (CuxCr(1-x)-MOF-D) were characterized using nitrogen adsorption desorption isotherms (BET), SEM, EDX, TEM, XRD, XPS, SEM-elemental mapping, FT-IR, DSC and TGA analysis. XRD displayed that only one crystalline phase resulted for copper and chromium which is CuO and Cr2O3, respectively. The prepared MOF derivatives (MOF-D) displayed a regular octahedral morphology in case of Cr-MOF-D, which is changed to distorted octahedral structure after the addition of copper in the same frameworks, as confirmed by TEM and SEM techniques. Cu/Cr-MOF-D displayed exceptional electrochemical behavior for Cu0.50Cr0.50-MOF-D electrode with specific capacitance of 535.1 F. g−1 at 0.7 A. g−1 within potential window (ΔV) of 1.04 V. Also, it generated high power and energy density of 2600 W kg−1 and 36.7 W h kg−1, respectively. Cu0.50Cr0.50-MOF-D electrode has excellent cycling stability, that retained 90.3% of its initial specific capacitance even after 5000 cycles compared to the capacitance retention of Cu-MOF-D and Cr-MOF-D electrodes that reached 70.26% and 69.17%, respectively.