Rational Construction of Core‐Shell Ni−Mn−Co−S@Co(OH) 2 Nanoarrays toward High‐Performance Hybrid Supercapacitors

Enhancing the electrochemical performance of supercapacitor electrodes using as-synthesized CuO and MOF-derived CuO nanostructures

Metal organic frameworks (MOF's) have gained considerable attention in the field of energy storage and supercapacitors applications. Herein, we synthesized copper oxide (CuO) through the precipitation method and concurrently derived from the solvothermal prepared copper-benzene dicarboxylate (Cu-BDC) by calcination. The integration of MOF-derived nanostructures with traditional CuO to form a hybrid electrode material, has not been extensively explored. The synthesized materials were characterized using x-ray Diffractometry, FTIR, XPS, Brunauer, Emmett, and Teller and morphological analysis was conducted using scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) affirming the composite's nature. Electrochemical impedance spectroscopy, galvanostatic charge-discharge, and cyclic voltammetry were used to evaluate the electrochemical properties of electrode material. With a specific capacitance of 691 Fg-1for CuO obtained from Cu-BDC (benzene dicarboxylic acid) and 236 Fg-1for CuO via the precipitation method, measured at a scan rate of 5 m Vs-1in 6 M KOH was found to be the optimal performance solution for the electrode material. The mesoporous structures are crucial for their absorption ability and improved ion transport, resulting in optimized electrochemical performance. Finally, we demonstrate significant improvements in specific capacitance and cycling stability compared to pure CuO-based electrodes, highlighting the potential of this composite structure for advanced supercapacitor applications.

Investigating the Potential Use of Ni-Mn-Co (NMC) Battery Materials as Electrocatalysts for Electrochemical Water Splitting

The imminent generation of significant amounts of Li ion battery waste is of concern due to potential detrimental environmental impacts. However, this also poses an opportunity to recycle valuable battery materials for later use. One underexplored area is using commonly employed cathode materials such as nickel, manganese cobalt (NMC) oxide as an electrocatalyst for water splitting reactions. In this work we explore the possibility of using NMC materials of different metallic ratios (NMC 622 and 811) as oxygen evolution and hydrogen evolution catalysts under alkaline conditions. We show that both materials are excellent oxygen evolution reaction (OER) electrocatalysts but perform poorly for the hydrogen evolution reaction. NMC 622 demonstrates the better OER activity with an overpotential of only 280 mV to pass 100 mA cm-2 and a low tafel slope of 42 mV dec-1. The material can also pass high current densities of 150 mA cm-2 for 24 h while also being tolerant to extensive potential cycling indicating suitability for direct integration with renewable energy inputs. This work demonstrates that NMC cathode materials if recovered from Li ion batteries are suitable OER electrocatalysts.

Electrode Materials, Structural Design, and Storage Mechanisms in Hybrid Supercapacitors

Currently, energy storage systems are of great importance in daily life due to our dependence on portable electronic devices and hybrid electric vehicles. Among these energy storage systems, hybrid supercapacitor devices, constructed from a battery-type positive electrode and a capacitor-type negative electrode, have attracted widespread interest due to their potential applications. In general, they have a high energy density, a long cycling life, high safety, and environmental friendliness. This review first addresses the recent developments in state-of-the-art electrode materials, the structural design of electrodes, and the optimization of electrode performance. Then we summarize the possible classification of hybrid supercapacitor devices, and their potential applications. Finally, the fundamental theoretical aspects, charge-storage mechanism, and future developing trends are discussed. This review is intended to provide future research directions for the next generation of high-performance energy storage devices.

Controllable synthesis of ZIF-derived NixCo3-xO4 nanotube array hierarchical structures based on self-assembly for high-performance hybrid alkaline batteries

In this study, a novel NixCo3-xO4 nanotube array hierarchical structure derived from zeolitic imidazolate frameworks (ZIFs) is grown on Ni foam (NixCo3-xO4 NAHS/Ni foam) using the template-assisted and self-assembly approach for a high-performance hybrid energy storage device in alkaline solution. The material characteristics of the resultant samples were characterized by XPS, XRD, ICP, SEM, TEM and BET. Due to the unique hollow structure with a large specific surface area and the exposure of large active sites originating from ZIFs, the optimal NixCo3-xO4 NAHS/Ni foam exhibits substantially enhanced electrochemical properties. The NixCo3-xO4 NAHS/Ni foam directly acts as an electrode, which provides an excellent specific capacity of 290.48 mA h g-1 at 1 A g-1. Subsequently, the corresponding hybrid alkaline batteries that consist of NixCo3-xO4 NAHS/Ni foam and carbon materials display a highly satisfactory specific capacity of 54.94 mA h g-1 at 1 A g-1, a satisfactory long-term stability of 85.47% after 2000 cycles, a maximum energy density of 43.95 W h kg-1 and a power density of 8000 W kg-1. This work combines the design of the electronic structure with the optimization of composition, and provides a reference for the application of hybrid rechargeable alkaline batteries (RABs).

Metal-organic-framework derived hollow manganese nickel selenide spheres confined with nanosheets on nickel foam for hybrid supercapacitors

Metal-organic framework (MOF) derived nanoarchitectures have special features, such as high surface area (SA), abundant active sites, exclusive porous networks, and remarkable supercapacitive performance when compared to traditional nanoarchitectures. Herein, we propose a viable strategy for the synthesis of hollow manganese nickel selenide spheres comprising nanosheets supported on the nickel foam (denoted as MNSe@NF) from the MOF. The MNSe nanostructures can demonstrate enriched active sites, and shorten the ion-electron diffusion pathways. When the MNSe@NF electrode is used as a cathode electrode for a hybrid supercapacitor, the electrode reflected impressive supercapacitive properties with a high capacity of 325.6 mA h g-1 (1172.16 C g-1) at 2 A g-1, an exceptional rate performance of 86.6% at 60 A g-1, and remarkable longevity (3.2% capacity decline after 15 000 cycles). Also, the assembled MNSe@NF∥AC@NF hybrid supercapacitors employing activated carbon on the nickel foam (AC@NF, anode electrode) and MNSe@NF (cathode electrode) revealed an impressive energy density of 66.1 W h kg-1 at 858.45 W kg-1 and an excellent durability of 94.1% after 15 000 cycles.