Bursting and transforming MOF into n-type ZnO and p-type NiO based heterostructure for supercapacitive energy storage

Abstract

Metal-organic frameworks (MOFs) have been considered as great contender and promising electrode materials for supercapacitors. However, their low capacity, aggregation, and poor porosity have necessitated the exploration of new approaches to enhance the performance of these active materials. In this study, sphere-like MOF were in-situ grown and it subsequently burst, transformed into a desired metal oxide heterostructure comprising n-type ZnO and p-type NiO (ZnO/NiO-350). The resulting optimized flower-like structure, composed of interlaced nanoflakes derived from MOFs, greatly improved the active sites, porosity, and functionality of the electrode materials. The ZnO/NiO-350 electrode exhibited superior electrochemical activities for supercapacitors, compared to the parent MOF, bare n-type, and p-type counterparts. The specific capacitance can reach to 543 ​F ​g⁻¹ at a current density of 1 ​A ​g⁻¹. Theoretical modeling and simulations were employed to gain insights into the atomic-scale properties of the materials. Furthermore, an assembled hybrid device using active carbon and ZnO/NiO-350 as electrodes demonstrated excellent energy density of 44 ​Wh kg⁻¹ at a power density of 1.6 Kw kg⁻¹. After 5000 cycles at 10 ​A ​g⁻¹, the cycling stability remained excellent 80 % of the initial capacitance. Overall, such evaluation of unique electrode with superior properties may be useful for the next generation supercapacitor electrode.