Diffusion control and surface control mechanism in hierarchical nanostructured porous zinc‐based MOF material for supercapattery

In this paper, we are reporting the zinc-based metal-organic framework nanomaterials for their application as a supercapattery device. The facile hydrothermal technique had been utilized to synthesize the MOF material. The surface morphology, crystallinity, and porosity were investigated with X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller, and energy dispersive X-ray analysis. To study the ability of the synthesized material for the storage of charges, electrochemical characterizations such as cyclic voltammetry (CV), galvanostatic charge (GCD), and electrochemical impedance spectroscopy (EIS) were performed in 1.0 M potassium hydroxide electrolyte. The specific capacity has been calculated from GCD curves and the material delivers 200 C/g at a current density of 0.7 A/g. This material revealed excellent performance in three-electrode assembly and therefore coupled with activated carbon (Zn-MOF//AC) to analyze the real energy and power density. This asymmetric assembly (supercapattery) had been tested with CV, GCD, and EIS. From all these characterizations, it was founded that the device was able to store charges of 172 C/g along with the excellent energy density and power density of 38.05 Wh/kg and 240 W/kg, respectively. The supercapattery revealed exceptional cyclic stability of 93.6% even after 2500 GCD cycles along with 100% of columbic efficiency. Furthermore, the diffusion-controlled and surface-controlled contributions were investigated for the assembled supercapattery, and it is found that the device stores energy through both the contributions. The maximum diffusive contribution by the device was 70.13% at the scan rate of 10 mV/s, which reaches to 42.75% at 100 mV/s scan rate. Likewise, the surface control contribution of the device was 29.86% at 10 mV/s, which rises up to 57.24% at 100 mV/s scan rate. These variations are attributed to the scan rates, which allow the ions to interact fast/slow with electrodes. Our analysis indicates that the synthesized material can be utilized as an interesting high-performance electrode material for supercapattery devices.