Metal-organic frameworks (MOFs) can serve as high-surface-area templates to generate hierarchically ordered nanoporous carbon electrodes for high-performance supercapacitor devices. Here we describe a simple chemical approach to synthesize dense three-dimensional (3D) arrays of core-shell ZnO@ZIF-8 and Co(CO3)0.5(OH)·0.11H2O@ZIF-67 nanowires on a conductive carbon cloth. Annealing the core-shell structures at high temperatures converted the MOF shell into a composite of nanoporous carbon (NC) mixed with conductive metal oxides. The conformal nature of the MOF-coating process generates a NC film with continuous conductive paths from the outer surfaces of the nanowires down to the flexible carbon electrode. Carbonization of ZIF-67 transforms the material into conductive sp2 type carbon mixed with Co3O4 nanostructures. Because Co3O4 is a faradic metal oxide with a high theoretical capacitance, these Co3O4/NC hybrid heterostructure arrays are a promising candidate material for use in an electrochemical supercapacitor device. The Co3O4/NC hybrid electrodes had good performance and exhibited a high areal capacitance of 1.22 F·cm-2 at 0.5 mA·cm-2. Conformal deposition of MOFs via the chemical vapor method offers a promising new platform to design conductive, ultrahigh surface area electrodes that preserve the 3D morphology for applications in supercapacitors and electrocatalysis.
Bibliographical noteFunding Information:
This work was supported by an Australian Research Council (ARC) Future Fellow (Grant No. FT150100479), JSPS KAKENHI (Grant Numbers 17H05393 and 17K19044), and the research funds by Qingdao University of Science and Technology and the Suzuken Memorial Foundation. The authors thank New Innovative Technology (NIT) for helpful suggestions and discussions on materials fabrication.
© Copyright 2018 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry