Highly Interconnected Nanorods and Nanosheets Based on a Hierarchically Layered Metal–Organic Framework for a Flexible, High-Performance Energy Storage Device

Abstract

The pseudocapacitors based on metal−organic frameworks (MOFs) are one of the state-of-the-art candidates to improve the future energy storage systems because of their high porosity, diverse functional groups, and potential as the template. In this study, the direct growth of a urea-assisted hierarchically layered cobalt-based MOF (u-hl-MOF) on Ni foam and direct growth of nanorods and nanosheets on the surface of the u-hl-MOF via the MOF-mediated approach without the addition of a cobalt precursor are reported. After the annealing process with sulfur powder under an Ar flow is complete, only the surface of the u-hl-MOF is converted into cobalt sulfide@carbon (Co 1−x S@C), whereas the bulk internal u-hl-MOF remains without any degradation. Therefore, a core−shell structure of u-hl-MOF@Co 1−x S@ C (u-hl-MSC) is formed, which exhibits a high areal specific capacitance of 13.1 F cm −2 with a three-electrode system. A solid-state flexible asymmetric supercapacitor (ASC) is also assembled using poly(vinyl alcohol)/KOH, u-hl-MSC, and activated carbon/Super P as the electrolyte, cathode, and anode materials, respectively. This solid capacitor exhibits one of the highest areal capacitance of 1.35 F cm −2 and an energy density of 270 mW h cm −2 with a high power density of 0.6 W cm −2 among all the MOF-or sulfide-based ASCs.

Sustainable Liquid-Phase Exfoliation of Layered Materials with Nontoxic Polarclean Solvent

“…The advent of two-dimensional (2D) materials had a ground-breaking impact on science and technology, − due to their peculiar properties with high application capabilities in different fields, such as energy storage, − catalysis, − optoelectronic devices, − and gas sensing. − A key point for the technological exploitation of 2D materials is represented by their large-scale production, which still remains challenging. − Actually, since the isolation of graphene, , fundamental studies on 2D materials were carried out mostly on micrometric flakes mechanically exfoliated from parental bulk crystals (top-down approach) or on ultrathin layers grown by chemical vapor deposition , (bottom-up approach). While mechanical exfoliation suffers from nonscalable processes with scarce reproducibility, chemical vapor deposition requires specific substrates enabling epitaxial growth, − with subsequent problems related to the etching of 2D sheets from the substrate resulting in flakes with degraded crystalline quality with a high amount of defects and metallic impurities and/or polymer residuals from the transfer process altering the physicochemical properties of transferred flakes of 2D materials .…”

Sensitive and Homogeneous Surface‐Enhanced Raman Scattering Detection Using Heterometallic Interfaces on Metal–Organic Framework‐Derived Structure

“…Among MOFs, zeolitic imidazole framework‐67 (ZIF‐67), composed of Co 2+ metal ions and imidazolate ligands, [ 22–24 ] has been broadly used for gas separation, [ 25,26 ] optical fiber, [ 27 ] drug delivery, [ 28,29 ] and electrochemical catalysis. [ 30–32 ] Moreover, MOFs can allow enhanced physical and chemical properties to be achieved via postmodification processes, such as carbonization and oxidation. For example, the ZIF‐67‐derived cobalt oxide (Co 3 O 4 ) (ZIF‐67‐CO) structure was utilized to enhance the electrical and catalytic properties of electrochemical devices.…”

Discovery of High‐Performing Metal–Organic Frameworks for On‐Board Methane Storage and Delivery via LNG–ANG Coupling: High‐Throughput Screening, Machine Learning, and Experimental Validation

“…[ 6 ] MOFs have been employed for various applications including gas storage and separation, catalysis, and energy applications. [ 7 ] However, the number of porous MOFs synthesized to date exceeds 14 000 [ 8 ] ; thus, it is difficult to assess the properties of these materials via synthetic approaches alone.…”