CdSe-nanoparticles-regulated synthesis of ZnCo-MOFs derived conductive porous carbon nanoflakes on carbon cloth for flexible sodium-ion supercapacitors

Abstract

Porous carbon derived from metal-organic frameworks (MOFs) represents a novel class of carbonaceous materials with unique structural characteristics, conductivity, and chemical stability, rendering them suitable for electrodes in supercapacitors. Herein, a three-dimensional structure of conductive porous carbon nanoflakes (CPCN) is synthesized based on MOFs composed of organic ligands containing zinc and cobalt. Nanoscale CdSe particles serving as energy-storage materials are incorporated into CPCN (CdSe/CPCN@CC) to form the flexible electrode for sodium-ion supercapacitors. The electrochemical properties of CdSe/CC, CdSe/ZnCo-MOF@CC, Cd/CPCN@CC, and CdSe/CPCN@CC are studied in 1 M Na2SO4. The CdSe/CPCN@CC electrode shows an impressive specific capacitance of 893.52 F g-1 at a current density of 0.125 mA cm-2 and excellent cycling stability with 80.68% retention after 10,000 cycles in 1.0 M Na2SO4. The asymmetric supercapacitor constructed with CdSe/CPCN@CC and 1 M NaPF6 electrolyte shows a capacitance of 97.8 F g-1, an energy density of 139.10 Wh kg-1, and a power density of 589.82 W kg-1 at a current density of 1 mA cm-2. In addition, the capacitance retention is 88.45% after 10,000 cycles. The electrochemical properties of CdSe/CPCN@CC are improved due to the incorporation of more active materials as well as the synergistic effects of the CdSe nanoparticles and CPCN. Density-functional theory (DFT) calculations reveal a sodium ion adsorption energy of -1.0692 eV and large DOS near the Fermi level. More importantly, in spite of severe mechanical bending, the device continues to power an LED array boding well for flexible and wearable applications.