High-density three-dimension graphene macroscopic objects for high-capacity removal of heavy metal ions

Abstract

The chemical vapor deposition (CVD) fabrication of high-density three-dimension graphene macroscopic objects (3D-GMOs) with a relatively low porosity has not yet been realized, although they are desirable for applications in which high mechanical and electrical properties are required. Here, we explore a method to rapidly prepare the high-density 3D-GMOs using nickel chloride hexahydrate (NiCl2·6H2O) as a catalyst precursor by CVD process at atmospheric pressure. Further, the free-standing 3D-GMOs are employed as electrolytic electrodes to remove various heavy metal ions. The robust 3D structure, high conductivity (∼12 S/cm) and large specific surface area (∼560 m2/g) enable ultra-high electrical adsorption capacities (Cd2+ ∼ 434 mg/g, Pb2+ ∼ 882 mg/g, Ni2+ ∼ 1,683 mg/g, Cu2+ ∼ 3,820 mg/g) from aqueous solutions and fast desorption. The current work has significance in the studies of both the fabrication of high-density 3D-GMOs and the removal of heavy metal ions.