Exploring the role of metal concentrations on the chemically synthesized Ni-MOFs nanostructures for asymmetric supercapacitor

Abstract

The tunable porosity and surface chemistry of metal-organic frameworks (MOFs) have made such attractive candidates for application in supercapacitors (SCs). In this article, Ni-MOFs are synthesized via the solvothermal method, employing different metal concentrations, including 1M (NM-1), 2 M (NM-2), 3 M (NM-3), and 4 M (NM-4) respectively. This article primarily focuses on the impact of different metal concentrations of Ni-MOFs on examining structural, morphological, compositional, and electrochemical performance. The structural analysis of the NM-2, NM-3, and NM-4 samples confirms the formation of Layer Double Hydroxides (LDH). The electrochemical performance is facilitated by the availability of active sites with large surface areas and favorable pore sizes that are provided by the sheet-like structure (Ni (OH)2-LDH), as revealed by morphological examination. Furthermore, supercapacitive properties in an aqueous electrolyte have been used to analyze the electrochemical characteristics of the Ni-MOF electrodes. Maximum specific capacitance (Cs) of 1668 F g−1 and specific capacity (Csp) of 294 mAh g−1 at 10 A g−1 were achieved by the NM-3 electrode. It also demonstrated a high energy density (ED) of 37.07 Wh kg−1, power density (PD) of 434 W kg−1, and remarkable retentivity of 79 % after 10,000th cycles at 100 mV s−1. From the perspective of industrial production, an asymmetric NM-3//activated carbon (AC) device was fabricated. It exhibits improved PD of 193 W kg−1 with ED of 7.32 Wh kg−1 at 3 A g−1 and an elevated Cs of 180 F g−1 at 5 mV s−1, along with a notable retention rate of 86 % even after 5000th cycles at 100 mV s−1. This study demonstrates the great potential of NM-3/LDH composites for the development of superior-performance SC applications.