Effective NaBH4-exfoliated ultrathin multilayer Co(OH)2 nanosheets arrays and sulfidation for energy storage

3D hierarchical self-supported NiO/Co3O4@C/CoS2 nanocomposites as electrode materials for high-performance supercapacitors

Multi-dimensional nanomaterials have drawn great interest for application in supercapacitors due to their large accessible surface area. However, the achievements of superior rate capability and cycle stability are hindered by their intrinsic poor electronic/ionic conductivity and the erratic structure. Herein, we develop a three-dimensional hierarchical self-supported NiO/Co₃O₄@C/CoS₂ hybrid electrode, in which NiO/Co₃O₄ nanosheets are in situ grown on a nickel foam substrate and combined with CoS₂ nanospheres through a carbon medium. The hybrid electrode has a high specific capacity of ∼1025 C g^-1 at 1 A g^-1 with a superior rate performance of ∼74% capacity retention even at a current density of 30 A g^-1. Moreover, the assembled NiO/Co₃O₄@C/CoS₂//AC hybrid supercapacitor achieves excellent performance with a maximum voltage of 1.64 V and a high energy density of 62.83 W h kg^-1 at a power density of 824.99 W kg^-1 and excellent cycle stability performance with a capacity retention of ∼92% after 5000 cycles. The high electrochemical performance of the hybrid supercapacitor is mainly attributed to the porous structure of the NiO/Co₃O₄@C nanosheets and CoS₂ nanospheres and intimate integration of active species. The rational strategy for the combination of various earth-abundant nanomaterials paves a new way for energy storage materials.

Ti-Mesh supported porous CoS2 nanosheet self-interconnected networks with high oxidation states for efficient hydrogen production via urea electrolysis

The urea oxidation reaction (UOR) is an ideal alternative to the oxygen evolution reaction (OER) towards energy efficient hydrogen production. However developing Earth-abundant electrocatalysts for urea oxidation and hydrogen generation still remains a big challenge. Herein, porous CoS2 nanosheet self-interconnected networks with high oxidation states located on a Ti-mesh (P-CoS2/Ti) are synthesized and can act as a high activity catalyst for both the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). In this literature, we report a very interesting phenomenon that cobalt hydroxide with different chemical compositions and crystal structures can be synthesized by adjusting the concentration of NaOH during the etching process. Moreover, porous CoS2 nanosheets with different crystallite sizes can be synthesized by adjusting the sulfuration temperature. P-CoS2/Ti presents outstanding catalytic performance with an overpotential of 91 mV to deliver a current density of 10 mA cm-2 for the HER, and it gives an anode potential of 1.243 V vs. RHE at 10 mA cm-2 for the UOR. A two-electrode electrolyser is used to validate the catalyst performance, and the P-CoS2/Ti||P-CoS2/Ti electrode is capable of producing a current density of 10 mA cm-2 at a cell potential of only 1.375 V, demonstrating its potential feasibility in the practical application of efficient hydrogen production.

In situ Growth of Cu2O/CuO Nanosheets on Cu Coating Carbon Cloths as a Binder-Free Electrode for Asymmetric Supercapacitors

Cu₂O/CuO nanosheets in-situ grown on Cu-Carbon cloths (Cu-CCs), namely Cu₂O/CuO@Cu-CCs, are constructed by a simple strategy with electroless copper plating, chemical etching, and thermal dehydration. The as-prepared material is directly used as binder-free electrodes for supercapacitors (SCs). CCs coated with Cu, as the current collector, can effectively promote the charge collection and electron transfer, while the hierarchical Cu₂O/CuO nanosheets provide massive active sites for fast faradic reactions. The composite electrode exhibits high specific capacitance [1.71 F cm⁻², equivalent to 835.2 F g⁻¹, at the current density of 10 mA cm⁻² (3.57 A g⁻¹)]. The asymmetric supercapacitor device using Cu₂O/CuO@Cu-CCs as the positive electrode and activated carbon as the negative electrode, achieves a superior energy density up to 60.26 Wh kg⁻¹ at a power density of 299.73 W kg⁻¹ and an excellent long-term cycling stability (9.65% loss of its initial capacitance after 5,000 cycles). The excellent electrochemical performance is mainly ascribed to the unique hierarchical structure of Cu₂O/CuO@Cu-CCs, making it attractive as a potential electrode material for high performance SCs.

Urchin-Like Ni2/3Co1/3(CO3)1/2(OH)·0.11H2O for High-Performance Supercapacitors

Here, we report our finding in the fabrication of novel porous urchin-like Ni_2/3Co_1/3(CO₃)_1/2(OH)·0. 11H₂O (denoted as NC) nanomaterial composed of numerous nanoneedles through an one-step hydrothermal method, which deliveres a high specific capacity of 318 C g⁻¹ at a current density of 1 A g⁻¹. Moreover, an architectural composite electrode consisting of the porous NC nanoneedles wrapped by reduced graphene oxide (rGO) nanosheets exhibits large specific capacity (431 C g⁻¹ at 1 A g⁻¹), high rate capability and long cycling life (94% capacity retention after 5,000 cycles at 20 A g⁻¹). The presence of rGO in the composite electrode greatly improves the electronic conductivity, providing efficient current collection for fast energy storage.