Houzhao Wan

NiCo2S4 porous nanotubes synthesis via sacrificial templates: high-performance electrode materials of supercapacitors

NiCo2S4 porous nanotubes are synthesised by a sacrificial template method based on the Kirkendall effect. The as-prepared NiCo2S4 nanotube electrode shows a specific capacitance of 1093 F g−1 at a current density of 0.2 A g−1 (933 F g−1 at 1 A g−1).

Hierarchical Configuration of NiCo2S4 Nanotube@Ni–Mn Layered Double Hydroxide Arrays/Three-Dimensional Graphene Sponge as Electrode Materials for High-Capacitance Supercapacitors

Three dimensional (3D) hierarchical network configurations are composed of NiCo2S4 nanotube @Ni-Mn layered double hydroxide (LDH) arrays in situ grown on graphene sponge. The 3D graphene sponge with robust hierarchical porosity suitable for as a basal growth has been obtained from a colloidal dispersion of graphene oxide using a simple directional freeze-drying technique. The high conductive NiCo2S4 nanotube arrays grown on 3D graphene shows excellent pseudocapacity and good conductive support for high-performance Ni-Mn LDH. The 3D NiCo2S4@Ni-Mn LDH/GS shows a high specific capacitance (Csp) 1740 mF cm(-2) at 1 mA cm(-2), even at 10 mA cm(-2), 1267.9 mF cm(-2) maintained. This high-performance composite electrode proposes a new and feasible general pathway as 3D electrode configuration for energy storage devices.

Different charge-storage mechanisms in disulfide vanadium and vanadium carbide monolayer

Two-dimensional (2D) transition-metal (TM) compound nanomaterials, due to their high-surface-area and large potential charge capability of TM atoms, have been widely investigated as electrochemical capacitors. However, the understanding of charge-storage mechanisms of 2D transition-metal compounds as electrode materials is still limited. In this study, using density functional theory computations, we systematically investigate the electrochemical properties of monolayer VS2 and V2C. Their electronic structures show a significant electron storage capability of around 0.25 V, referenced to the standard hydrogen electrode, and indicate redox pseudocapacitance characteristics as cathodes. The different charge densities visually confirm that excess electrons tend to localize in the vanadium atoms nearby contact-adsorbed Li ions, corresponding to the redox of vanadium atoms. In contrast, only the electric double layer acts as a charge-storage mechanism in the V2C monolayer. However, the O saturation would induce redox pseudocapacitance in the V2C monolayer. Furthermore, the calculated metallic behavior and low Li ion diffusion barriers substantiate that V2C and VS2 monolayers would manifest low resistance in the charging process. Our findings provide insights for the different charge-storage mechanism of VS2 and V2C monolayers.

Mutually beneficial Co3O4@MoS2 heterostructures as a highly efficient bifunctional catalyst for electrochemical overall water splitting

Designing low-cost and highly efficient bifunctional electrocatalysts for compatible integration with the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) for overall water splitting is critical but challenging. Herein, mutually beneficial Co3O4@MoS2 heterostructures were adopted to efficiently balance both HER and OER performance by improving the sluggish kinetics. These heterostructures synergistically favoured the reduction of the energy barrier of the initial water dissociation step and optimization of the subsequent H adsorption/desorption for MoS2 in alkaline HER. Moreover, the adsorption of oxygen intermediates was enhanced for Co3O4 in the OER process. As a result, the Co3O4@MoS2 heterostructures showed excellent overall water splitting performance with a low overpotential and Tafel slope.