Optimization of a Conductive Polymer Layer on MOF-Derived Carbon Materials for High-Performance Supercapacitor Electrodes

Abstract

In this study, we report the preparation of a highly conductive metal−organic framework-derived carbon nanocomposite material with excellent electrochemical activity through a simple surface coating of carbonized-ZIF-8 (C-ZIF-8) with poly(3,4-ethylenedioxythiophene)−poly(styrenesulfonate) (PEDOT−PSS). X-ray diffraction results indicate the successful transformation of crystalline ZIF-8 to amorphous carbon (C-ZIF-8) during carbonization at 850 °C. As-prepared C-ZIF-8 and C-ZIF-8/PEDOT−PSS nanocomposites with different weight ratios of 2:1, 8:1, and 14:1 (C-ZIF-8:PEDOT−PSS) were found to have specific surface areas of 920, 450, 740, and 810 m 2 g −1 , respectively. Importantly, the increase in the ratio of PEDOT−PSS (to 2:1) reveals that the PEDOT−PSS seems to block the micro-and mesopores of C-ZIF-8 due to the high density of the PEDOT−PSS coating. In cyclic voltammetry results, the specific capacitances of C-ZIF-8 and C-ZIF-8/PEDOT−PSS (14:1, 8:1, 2:1) at a scan rate of 5 mV S −1 were 44.1, 114.2, 149.4, and 110.3 F g −1 , respectively. The C-ZIF-8/PEDOT−PSS nanocomposite exhibited a 4-fold increase in specific capacitance (77 F g −1 ) compared to that of pristine C-ZIF-8 (18.4 F g −1 ) at a current density of 0.5 A g −1 by galvanostatic charge−discharge. The retention of specific capacitance is maintained over 86% subsequent to 1100 cycles at 2 A g −1 by cyclic stability tests. Furthermore, the specific capacitances of C-ZIF-8/PEDOT−PSS coated on a bendable carbon cloth in its initial state and after the bending cycle test were 208.2 and 186.8 F g −1 , respectively. This indicates that it maintained approximately 90% of its specific capacitance after 1000 bending cycles. Our experiments demonstrate that the C-ZIF-8/PEDOT−PSS nanocomposite exhibits a continuous conductive pathway and electrochemical activity due to PEDOT−PSS along with high porosity, a high specific surface area, abundant electroactive sites, and faster ion diffusion kinetics due to C-ZIF-8.

Metal‐Organic Frameworks‐Derived Nanocarbon Materials and Nanometal Oxides for Photocatalytic Applications

“…After derivation, this type of MOFs can well preserve the original morphology without collapse, thereby obtaining the expected MOFs-derived nanomaterials. [51] External-template MOFs can be prepared by mechanical mixing or in-situ growth methods of MOFs, leading to the derivation of nanomaterials from MOFs. Moreover, adjusting the pyrolysis conditions (such as temperature, calcination time, heating rate, and gas atmosphere) can optimize the characteristics of the derived nanomaterials.…”