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

Abstract

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.

Experimental and Theoretical Insights of Anion Regulation in MOF-Derived Ni–Co-Based Nanosheets for Supercapacitors and Anion Exchange Membrane Water Electrolyzers

“…These three survey spectra showed the presence of (Ni, Co, and Se), (Ni, Co, and S), and (Ni, Co, and P), respectively. The high-resolution (H-R) Ni 2p spectrum (Figure a) analysis of Ni–Co–Se NAs showed two prominent peaks at ∼873.48 and 855.81 eV ascribed to Ni 2p 1/2 and Ni 2p 3/2 energy levels, respectively, indicating a spin-energy separation value of 17.7 eV. , According to the literature report, this spectral analysis confirms the existence of the Ni 2+ state. ,,− Besides, two intense satellite peaks were also located at 879.8 and 861.6 eV in the Ni 2p spectrum. The H-R curve-fitted Co 2p H-R spectra showed two clear spin–orbit doublets and two obvious shake-up satellite peaks.…”

Nickel Metal–Organic Frameworks of Amino Acid Tyrosine-Functionalized Naphthalenediimide for Pseudocapacitor Applications

“…It was reported that at a higher potential window, acidic electrolyte is unstable. Therefore, 0–1.4 V window is picked out for the SSC device to exclude the polarization phenomenon and evolution of oxygen at the higher applied potential window . Furthermore, the electrochemical performance of the as-fabricated Ni-Tyr-NDI-MOF/GF//Ni-Tyr-NDI-MOF/GF SSC cell was evaluated by means of CV, GCD, cyclic stability, and EIS measurements.…”

Metal Ion‐controlled Growth of Different Metal‐Organic Framework Micro/nanostructures for Enhanced Supercapacitor Performance

“…[12][13][14][15] However, bulk pristine MOFs often suffer from poor electroactivity, electrical conductivity and stability, which dramatically restrict their direct application for energy storage. Various strategies, such as alloying metal nodes, [16][17][18] carbonization, [19,20] constructing tailored micro/nanostructures, [21][22][23] and introducing highly electrical conductive materials, [24] have been adopted to enhance the energy storage capability of MOFs. Among them, alloying metal nodes not only allow rapid and rich redox reactions but also improve electrochemical conductivity, [16][17][18] thereby improving the electrochemical kinetic performance.…”

“…Various strategies, such as alloying metal nodes, [16][17][18] carbonization, [19,20] constructing tailored micro/nanostructures, [21][22][23] and introducing highly electrical conductive materials, [24] have been adopted to enhance the energy storage capability of MOFs. Among them, alloying metal nodes not only allow rapid and rich redox reactions but also improve electrochemical conductivity, [16][17][18] thereby improving the electrochemical kinetic performance. Especially, the alloying metal nodes of Co and Ni show unique chemical activity due to the change in band energy by the coupling Co 2 + with unpaired electrons and Ni 2 + with filled π-symmetry (t 2g ) d-orbitals.…”

“…Especially, the alloying metal nodes of Co and Ni show unique chemical activity due to the change in band energy by the coupling Co 2 + with unpaired electrons and Ni 2 + with filled π-symmetry (t 2g ) d-orbitals. [17] Constructing tailored micro/nanostructures can not only in-crease the electroactive specific surface area to improve the charge/discharge efficiency but also shorten the electron transport pathways to reduce equivalent serial resistance. [21][22][23] Therefore, the tailored design of MOFs with alloying metal nodes and unique microstructures will achieve potential supercapacitor performance gains.…”