NiO–TiO2 p–n heterostructured nanocables bridged by zero-bandgap rGO for highly efficient photocatalytic water splitting

Abstract

The construction of p–n junctions with built-in electric field effect between two photocatalytic semiconductors is an efficient strategy to separate photogenerated carriers and enhances photocatalytic activity. However the effect is limited because the built-in electric field can be saturated because of the charge accumulation during the photocatalysis process. In this work, we demonstrate that inserting a layer of zero-bandgap graphene at the interface between p-type NiO and n-type TiO2 can further enhance the separation of photogenerated carriers by building double-shelled NiO/rGO/TiO2 heterostructured coaxial nanocables This double-shell nanostructure is proved possessing a remarkably high photocatalytic activity through water splitting experiments and photoelectrochemical measurements. The main mechanism for enhancement of photocatalytic activity is that zero-bandgap rGO can increased the barrier height by lowering the Fermi level of the NiO nanofiber core and increasing the Fermi level of the TiO2 nanowire shell, and enhance the strength of built-in electron field. Furthermore, the design of NiO/rGO/TiO2 heterostructured coaxial nanocables can ensure that the UV light can be absorbed by the TiO2 at the outer shell, whereas visible light can reach the NiO inner core, thus leading to an efficient use of the white light spectrum. This heterostructured coaxial nanocable is a promising candidate for applications in environmental and energy fields because of its facile and easily scalable synthesis combined to its superior broad-spectrum photocatalytic activity.