Self-templated Synthesis of Nickel Silicate Hydroxide/Reduced Graphene Oxide Composite Hollow Microspheres as Highly Stable Supercapacitor Electrode Material.

Nickel silicate hydroxide/reduced graphene oxide (NiSiO(OH)/RGO) composite hollow microspheres were one-pot hydrothermally synthesized by employing graphene oxide (GO)-wrapped SiO microspheres as the template and silicon source, which were prepared through sonication-assisted interfacial self-assembly of tiny GO sheets on positively charged SiO substrate microspheres. The composition, morphology, structure, and phase of NiSiO(OH)/RGO microspheres as well as their electrochemical properties were carefully studied. It was found that NiSiO(OH)/RGO microspheres featured distinct hierarchical porous morphology with hollow architecture and a large specific surface area as high as 67.6 m g. When utilized as a supercapacitor electrode material, NiSiO(OH)/RGO hollow microspheres released a maximum specific capacitance of 178.9 F g at the current density of 1 A g, which was much higher than that of the contrastive bare NiSiO(OH) hollow microspheres and bare RGO material developed in this work, displaying enhanced supercapacitive behavior. Impressively, the NiSiO(OH)/RGO microsphere electrode exhibited outstanding rate capability and long-term cycling stability and durability with 97.6% retention of the initial capacitance after continuous charging/discharging for up to 5000 cycles at the current density of 6 A g, which is superior or comparable to that of most of other reported nickel-based electrode materials, hence showing promising application potential in the energy storage area.