Nanosized CoO Loaded on Copper Foam for High-Performance, Binder-Free Lithium-Ion Batteries

Enhanced hydrogen evolution reaction via regulating the adsorbability between 2D CoO nanosheets and CC substrate

In recent years, bifunctional electrocatalysts, nanomaterials directly grown on the substrate for application towards the hydrogen evolution reaction (HER), have become of interest for sustainable and clean energy technologies. However, the influence of interfacial interactions between the electrode materials and substrate on device performance remains unclear and is rarely investigated. Herein, we report two-dimensional (2D) CoO nanosheets grown on carbon cloth (CC) (2D CoO/CC) to construct a hybrid electrocatalyst with a seamlessly conductive network. By a series of structure analyses, we recommend that the CoO nanosheets and CC are connected via adsorption. The 2D CoO/CC nanosheets show superior HER performance to the commercial Pt/C and CoO(aq.)/CC nanosheets, including onset potentials of 2 mV, low overpotential of 22 mV at 10 mA cm-2 and Tafel slope of 37 mV dec-1. The results of density functional theory (DFT) calculations reveal that the adsorbability plays an important role in determining the performance of the electrocatalysts for the HER. This work provides a new insight into the interfacial interactions between the electrode material and the substrate in electrochemical devices, and paves the way for the rational design and construction of high-performance electrochemical devices for practical energy applications.

Cobalt Oxide Arrays Anchored to Copper Foam as Efficient Binder-free Anode for Lithium Ion Batteries

The development of lithium-ion batteries with simplified assembling steps and fast charge capability is crucial for current battery applications. In this study, we propose a simple in-situ strategy for the construction of high-dispersive cobalt oxide (CoO) nanoneedle arrays, which grow vertically on a copper foam substrate. It is demonstrated that this nanoneedle CoO electrodes provide abundant electrochemical surface area. The resulting CoO arrays directly act as binder-free anodes in lithium-ion batteries with the copper foam functioning as the current collector. The highly-dispersed feature of the nanoneedle arrays enhances the effectiveness of active materials, leading to outstanding rate capability and superior long-term cycling stability. These impressive electrochemical properties are attributed to the highly-dispersed self-standing nanoarrays, the advantages of binder-free constituent, and the high exposed surface area of the copper foam substrate compared to copper foil, which enrich active surface area and facilitate charge transfer. The proposed approach to prepare binder-free lithium-ion battery anodes streamlines the electrode fabrication steps and holds significant promise for the future development of the battery industry.

Synthesis of CNT@CoS/NiCo Layered Double Hydroxides with Hollow Nanocages to Enhance Supercapacitors Performance

One of the key factors to improve electrochemical properties is to find exceptional electrode materials. In this work, the nickel-cobalt layered double hydroxide (CNT@CoS/NiCo-LDH) with the structure of a hollow nanocage was prepared by etching CNT@CoS with zeolitic imidazolate framework-67 (ZIF-67) as a template. The results show that the addition of nickel has a great influence on the structure, morphology and chemical properties of materials. The prepared material CNT@CoS/NiCo-LDH-100 (C@CS/NCL-100) inherited the rhombic dodecahedral shape of ZIF-67 well and the CNTs were evenly interspersed among the rhombic dodecahedrons. The presence of CNTs improved the conductivity and surface area of the samples. The C@CS/NCL-100 demonstrates a high specific capacitance of 2794.6 F·g^-1 at 1 A·g^-1. Furthermore, as an assemble device, the device of C@CS/NCL-100 as a positive electrode exhibits a relatively high-energy density of 35.64 Wh·kg^-1 at a power density of 750 W·kg^-1 Further, even at the high-power density of 3750 W·kg^-1, the energy density can still retain 26.38 Wh·kg^-1. Hence, the superior performance of C@CS/NCL-100 can be ascribed to the synergy among CNTs, CoS and NiCo LDH, as well as the excellent three-dimensional structure obtained by used ZIF-67 as a template.