Takovite-derived 2-D Ni/Al double hydroxide monolayer and graphene hybrid electrodes for electrochemical energy storage applications with high volumetric capacitance

Ternary NiCeCo-Layered Double Hydroxides Grown on CuBr2@ZIF-67 Nanowire Arrays for High-Performance Supercapacitors

Ternary layered double-hydroxide-based active compounds are regarded as ideal electrode materials for supercapacitors because of their unique structural characteristics and excellent electrochemical properties. Herein, an NiCeCo-layered double hydroxide with a core-shell structure grown on copper bromide nanowire arrays (CuBr₂@NCC-LDH/CF) has been synthesized through a hydrothermal strategy and calcination process and utilized to fabricate a binder-free electrode. Due to the unique top-tangled structure and the complex assembly of different active components, the prepared hierarchical CuBr₂@NCC-LDH/CF binder-free electrode exhibits an outstanding electrochemical performance, including a remarkable areal capacitance of 5460 mF cm^-2 at 2 mA cm^-2 and a capacitance retention of 88% at 50 mA cm^-2 as well as a low internal resistance of 0.163 Ω. Moreover, an all-solid-state asymmetric supercapacitor (ASC) installed with CuBr₂@NCC-LDH/CF and activated carbon electrodes shows a high energy density of 118 Wh kg^-1 at a power density of 1013 W kg^-1. Three assembled ASCs connected in series can operate a multifunctional display for over three and a half hours. Therefore, this innovative work provides new inspiration for the preparation of electrode materials for supercapacitors.

Ni-Al layered double hydroxides modified sponge skeleton with polydopamine coating for enhanced U(VI) extraction from aqueous solution

Uranium (VI) (U(VI)) is a major fuel for nuclear power, and the mass of it in seawater is about 4.5 billion tons. However, many current U(VI) adsorbents exist in the form of powder, which hinders the smooth recovery of U(VI) from aqueous solutions and its application in actual environments. Herein, the MP@LDH as an easy-to-recover and 3D macroscopic adsorbent for U(VI) extraction from aqueous solution was successfully prepared. The adsorbent was obtained via anchoring of LDH on the surface of melamine sponge (MS) coated with polydopamine (PDA). The maximum experimental adsorption capacity of MP@LDH sponge for U(VI) was as high as 559.8 mg g^-1 (at pH = 8.0, T = 298 K). In the competitive sorption experiments against the competitions of Ba(II), Sr(II), Zn(II) and others ions, MP@LDH still exhibited a particularly excellent selectivity for U(VI) (almost 90% removal rate). Furthermore, the removal rate of MP@LDH towards U(VI) reached 88.18% under simulated seawater (C₀ = 3.47 μg L^-1). We believe that the MP@LDH with easy retrieval, excellent selectivity and uptake amount provides a convenient way for U(VI) extraction from seawater.

Recent Progress in Two-Dimensional Layered Double Hydroxides and Their Derivatives for Supercapacitors

High-performance supercapacitors have attracted great attention due to their high power, fast charging/discharging, long lifetime, and high safety. However, the generally low energy density and overall device performance of supercapacitors limit their applications. In recent years, the design of rational electrode materials has proven to be an effective pathway to improve the capacitive performances of supercapacitors. Layered double hydroxides (LDHs), have shown great potential in new-generation supercapacitors, due to their unique two-dimensional layered structures with a high surface area and tunable composition of the host layers and intercalation species. Herein, recent progress in LDH-based, LDH-derived, and composite-type electrode materials targeted for applications in supercapacitors, by tuning the chemical/metal composition, growth morphology, architectures, and device integration, is reviewed. The complicated relationships between the composition, morphology, structure, and capacitive performance are presented. A brief projection is given for the challenges and perspectives of LDHs for energy research.

Mechanically stable ternary heterogeneous electrodes for energy storage and conversion

Recently, solid asymmetric supercapacitor (ASC) has been deemed as an emerging portable power storage or backup device for harvesting natural resources. Here we rationally engineered a hierarchical, mechanically stable heterostructured FeCo@NiCo layered double hydroxide (LDH) with superior capacitive performance by a simple two-step electrodeposition route for energy storage and conversion. In situ scanning electron microscope (SEM) nanoindentation and electrochemical tests demonstrated the mechanical robustness and good conductivity of FeCo-LDH. This serves as a reliable backbone for supporting the NiCo-LDH nanosheets. When employed as the positive electrode in the solid ASC, the assembly presents high energy density of 36.6 W h kg^-1 at a corresponding power density of 783 W kg^-1 and durable cycling stability (87.3% after 5000 cycles) as well as robust mechanical stability without obvious capacitance fading when subjected to bending deformation. To demonstrate its promising capability for practical energy storage applications, the ASC has been employed as a portable energy source to power a commercially available digital watch, mini motor car, or household lamp bulb as well as an energy storage reservoir, coupled with a wind energy harvester to power patterned light-emitting diodes (LEDs).