Ligand-Controlled Growth of Different Morphological Bimetallic Metal-Organic Frameworks for Enhanced Charge-Storage Performance and Quasi-Solid-State Hybrid Supercapacitors

by Selleckchem | May 06 2023

The present research work facilitates a ligand-mediated effective strategy to achieve different morphological surface structures of bimetallic (Ni and Co) metal-organic frameworks (MOFs) by utilizing different types of organic ligands like terephthalic acid (BDC), 2-methylimidazole (2-Melm), and trimesic acid (BTC). Different morphological structures, rectangular-like nanosheets, petal-like nanosheets, and nanosheet-assembled flower-like spheres (NSFS) of NiCo MOFs, are confirmed from the structural characterization for ligands BDC, 2-Melm, and BTC, respectively. The basic characterization studies like scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Brunauer-Emmett-Teller revealed that the NiCo MOF prepared by using trimesic acid as the ligand (NiCo MOF_BTC) with a long organic linker exhibits a three-dimensional architecture of NSFS that possesses higher surface area and pore dimensions, which enables better ion kinetics. Also, the NiCo MOF_BTC delivered the highest capacity of 1471.4 C g-1 (and 408 mA h g-1) at 1 A g-1 current density, compared to the other prepared NiCo MOFs and already reported different NiCo MOF structures. High interaction of trimesic acid with the metal ions confirmed from ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy leads to a NSFS structure of NiCo MOF_BTC. For practical application, an asymmetric supercapacitor device (NiCo MOF_BTC//AC) is fabricated by taking NiCo MOF_BTC and activated carbon as the positive and negative electrode, respectively, where the PVA + KOH gel electrolyte serves as a separator as well as an electrolyte. The device delivered an outstanding energy density of 78.1 Wh kg-1 at a power density of 750 W kg-1 in an operating potential window of 1.5 V. In addition, it displays a long cycle life of 5000 cycles with only 12% decay of the initial specific capacitance. Therefore, these findings manifest the morphology control of MOFs by using different ligands and the mechanism behind the different morphologies that will provide an effective way to synthesize differently structured MOF materials for future energy-storage applications.

Comments：

This research work demonstrates a novel ligand-mediated strategy to obtain various morphological surface structures of bimetallic (Ni and Co) metal-organic frameworks (MOFs) using different organic ligands, namely terephthalic acid (BDC), 2-methylimidazole (2-Melm), and trimesic acid (BTC). The study confirms the existence of different morphologies, such as rectangular-like nanosheets, petal-like nanosheets, and nanosheet-assembled flower-like spheres (NSFS) of NiCo MOFs, for ligands BDC, 2-Melm, and BTC, respectively.

Through various characterization techniques, including scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Brunauer-Emmett-Teller analysis, the study shows that the NiCo MOF prepared with trimesic acid as the ligand (NiCo MOF_BTC) possesses a three-dimensional architecture of NSFS, which has higher surface area and pore dimensions, resulting in better ion kinetics. Furthermore, the study reveals that NiCo MOF_BTC has a higher capacity of 1471.4 C g-1 (and 408 mA h g-1) at 1 A g-1 current density than other prepared NiCo MOFs and previously reported NiCo MOF structures.

The study explains the higher interaction of trimesic acid with the metal ions, as confirmed by ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy, which leads to the formation of NSFS in NiCo MOF_BTC. The study further demonstrates the practical application of NiCo MOF_BTC by fabricating an asymmetric supercapacitor device (NiCo MOF_BTC//AC), using activated carbon as the negative electrode and PVA + KOH gel electrolyte as the separator and electrolyte. The device delivered an excellent energy density of 78.1 Wh kg-1 at a power density of 750 W kg-1 in an operating potential window of 1.5 V, with a long cycle life of 5000 cycles and only 12% decay of the initial specific capacitance.

Overall, this research work highlights the ability to control the morphology of MOFs by utilizing different ligands and the underlying mechanism behind different morphologies, which can provide a new approach to synthesize MOF materials with varied structures for future energy storage applications.