Fine-tuning interconnected leaf-like architecture of Co-MOFs by varying linker concentrations for solid-state supercapacitors

Abstract

Metal Organic Frameworks (MOFs) have risen as potential contenders for applications in supercapacitors (SCs) owing to their tunable porosity and surface chemistry. In this article, we synthesized Co-MOFs electrodes via Reaction Diffusion Framework approach, employing different linker concentrations, namely 0.7 M (CMA), 0.8 M (CMB), 0.9 M (CMC), and 1 M (CMD). The primary focus of this article lies in fine-tuning the concentration of the linker to optimize the synthesis of Co-MOFs, along with investigating how this optimization enhances their performance in an electrochemical study. Structural, morphological, and compositional studies have been conducted on Co-MOFs electrodes. Morphological studies unveiled CMB electrode exhibited a high interconnected leaf-like structure which enables high structural stability, low resistance, quick ion diffusion, and efficient charge-transfer in SCs than other electrodes. While the X-ray Photoelectron Spectroscopy analysis confirmed that the Co 2p exhibited an oxidation state of + 2. The electrochemical results demonstrated a direct correlation between linker concentration and the resultant leaf-like architecture. Specifically, the CMB exhibited high SCs performance, including a specific capacity (Csp) of 66 mAh/g and a specific capacitance (Cs) of 597 F/g at 5 mV/s, maintaining an impressive cyclic stability of 80 % over 3000th cycles at 100 mV/s. Additionally, it achieved a good energy density (Ed) of 11.14 Wh/kg and power density (Pd) of 4000 W/kg at 4 mA/cm². Furthermore, the solid-state device was fabricated and evaluated for its practical application in SCs. This device achieved higher Cs of 49 F/g at 10 mV/s, along with an 82 % retention rate over 2000 cycles at 15 mA. Moreover, this device attained a good Ed of 3.56 Wh/kg and Pd of 2266 W/kg at 4 mA. These findings manifested the significance of tailoring the morphology of Co-MOFs through optimal linker concentration for achieving high-performance solid-state SCs.