From two-dimensional graphene oxide to three-dimensional honeycomb-like Ni(3)S(2)@graphene oxide composite: insight into structure and electrocatalytic properties

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 Ni(3)S(2)@graphene oxide composite (3D honeycomb-like Ni(3)S(2)@GO) by a one-pot hydrothermal method. We found that positive charges of Ni(2+) and negative charges of NO(3)(−) in Ni(NO(3))(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(NO(3))(2)/thioacetamide/H(2)O evolved into 3D honeycomb-like Ni(3)S(2)@GO in solvothermal process. The GO effectively inhibited the aggregation of Ni(3)S(2) nanoparticles. Photoelectrochemical cells based on 3D Ni(3)S(2)@GO synthesized at 60 mM l(−1) Ni(NO(3))(2) exhibited the best energy conversion efficiency. 3D Ni(3)S(2)@GO had smaller charge transfer resistance and larger exchange current density than pure Ni(3)S(2) for iodine reduction reaction. The cyclic stability of 3D honeycomb-like Ni(3)S(2)@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.