Abstract
Three-dimensional (3D) graphene composites have drawn increasing attention in energy storage/conversion applications due to their unique structures and properties. Herein, we synthesized 3D honeycomb-like Ni3S2@graphene oxide composite (3D honeycomb-like Ni3S2@GO) by a one-pot hydrothermal method. We found that positive charges of Ni2+ and negative charges of NO3− in Ni(NO3)2 induced a transformation of graphene oxide with smooth surface into graphene oxide with wrinkled surface (w-GO). The w-GO in the mixing solution of Ni(NO3)2/thioacetamide/H2O evolved into 3D honeycomb-like Ni3S2@GO in solvothermal process. The GO effectively inhibited the aggregation of Ni3S2 nanoparticles. Photoelectrochemical cells based on 3D Ni3S2@GO synthesized at 60 mM l−1 Ni(NO3)2 exhibited the best energy conversion efficiency. 3D Ni3S2@GO had smaller charge transfer resistance and larger exchange current density than pure Ni3S2 for iodine reduction reaction. The cyclic stability of 3D honeycomb-like Ni3S2@GO was good in the iodine electrolyte. Results are of great interest for fundamental research and practical applications of 3D GO and its composites in solar water-splitting, artificial photoelectrochemical cells, electrocatalysts and Li-S or Na-S batteries.
Highlights
Graphene is composed of SP2 hybrid C atoms
The graphene oxides with wrinkled surface were named wrinkled surface of GO (w-GO)
scanning electron microscopy (SEM) of w-GO is shown in electronic supplementary material, figure S1. w-GO has two advantages: on the one hand, it can keep the 2D structure of graphene; on the other hand, the wrinkles on the surface can increase the physical and chemical properties in graphene devices
Summary
Graphene is composed of SP2 hybrid C atoms. The thickness of two-dimensional (2D) monolayer graphene is 3.35 Å. The electrons in big π bonds can move freely, which gives good conductivity to graphene. The unique monolayer graphene has a large theoretical specific surface area of about 2630 m2 g−1. It has high conductivity, high electron mobility (15 000 cm V−1 s−1) [1], and thermal conductivity, quantum Holzer effect, quantum tunnelling effect [2], super mechanical properties [3], and so on. Three-dimensional (3D) graphene composites have drawn increasing attention in energy storage/conversion applications due to their unique structures and properties [4,5,6,7,8,9]. The structures of TMC/graphene composite material have four categories: 0D/2D (zero-dimensional TMC/two-dimensional graphene), 1D/2D (one-dimensional TMC/two-dimensional graphene), 2D/2D (two-dimensional TMC/twodimensional graphene) and 3D (TMC/three-dimensional graphene)
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