Carbon Nanotubes Decorated Bimetallic Metal–Organic Framework Nanocomposite for High-Performance Symmetric Supercapacitor Device and Their Charge Storage Mechanism

Metal–organic frameworks (MOFs) have garnered significant interest due to their diverse properties, indicating their potential as energy storage applications. Integrating carbon compounds can further enhance their electrochemical activity. In this study, we present a novel method for synthesizing bimetallic nickel- and yttrium-based metal–organic frameworks (NiY-MOFs) anchored with varying weight percentages of carbon nanotubes (CNTs): 5% CNT with NiY-MOF (C1@NiY-MOF), 10% CNT with NiY-MOF (C3@NiY-MOF), and 15% CNT with NiY-MOF (C5@NiY-MOF). The focus was on optimizing the CNT concentration in bimetallic NiY-MOF for high-performance supercapacitors. The optimal concentration of CNT in NiY-MOF was identified as 10% (C3@NiY-MOF), which was subsequently used to fabricate symmetric supercapacitor devices. The findings indicate that the C3@NiY-MOF (209.61 F/g) Y-MOF (245.03F/g), NiY-MOF (353.32 F/g), C1@NiY-MOF (570.61 F/g), and C5@NiY-MOF (713.26 F/g) all samples were measured at a current density 2 A/g. Additionally, the C3@NiY-MOF electrodes retained 89% of their capacitance after 10,000 cycles. The capacitive and diffusive contributions of the C3@NiY-MOF electrode were examined using regression parameters obtained from Dunn and Trasatti’s models. Moreover, practical applicability was illustrated by incorporating the optimized electrode C3@NiY-MOF onto carbon cloth and constructing a symmetric supercapacitor device with a poly(vinyl alcohol)-KOH gel serving as the electrolyte and electrode separator. The device demonstrated a specific capacitance of 297.82 F/g at a current density of 1 A/g and a maximum energy density of 57.90 Wh/kg at a power density of 500 W/kg.