Effective photocatalytic dechlorination of 2,4-dichlorophenol by a novel graphene encapsulated ZnO/Co3O4 core–shell hybrid under visible light

Abstract

In the present work, a graphene encapsulated ZnO/Co₃O₄ (GE/ZnO/Co₃O₄) core–shell hybrid is fabricated through a facile self-assembly approach, where the mutual electrostatic interaction force drives the ZnO/Co₃O₄ heteronanostructures to be fully wrapped with flexible ultrathin graphene shells. The as-prepared GE/ZnO/Co₃O₄ core–shell hybrid is characterized and exhibits excellent visible light photocatalytic ability toward dechlorination of 2,4-dichlorophenol (2,4-DCP) in the aqueous phase. It is worth noting that 2,4-DCP is almost completely mineralized into CO₂ and H₂O by the GE/ZnO/Co₃O₄ after 5 h of a photocatalytic reaction. This type of higher dechlorination and mineralization efficiency of 2,4-DCP is not generally observed, and is found to be higher than some previous studies. The dechlorination of 2,4-DCP has been achieved under different parametric conditions. The unique architecture of the GE/ZnO/Co₃O₄ core–shell hybrid also provides high stability and recyclability towards degradation of 2,4-DCP. The higher photocatalytic activity of the hybrid can be ascribed to the synergistic effect of ZnO, Co₃O₄ and graphene, and also by an increase in the contact surface between the metal oxide core and the graphene shell, which acts as a continuous path for rapid electron transport to offer a greater number of reactive species.