A comprehensive review on the environmental applications of graphene–carbon nanotube hybrids: recent progress, challenges and prospects

Abstract

Environmental pollution by water-soluble pollutants, heavy metal ions and harmful greenhouse gases is triggering significant concern worldwide and is affecting the stability of the environment. Hence, it is indispensable to develop novel materials to mitigate environmental pollution. Graphene/carbon nanotube hybrid materials exhibit exceptional potential for environmental applications including sensing and monitoring of contaminants and their remediation. These 3D network materials possess a larger surface area, enhanced electrical conductivity, thermal conductivity, porosity, minimal agglomeration and higher mechanical strength compared to their building blocks, i.e., 1D carbon nanotubes (CNTs) and 2D graphene. Moreover, the porosity and extremely interconnected structures of these hybrid materials yield an accessible interior surface area, efficient mass transport, etc. These outstanding properties combined with the hydrophobicity, stability and conductivity of these materials provide a general platform for the detection and disposal of various pollutants. This review presents the promising environmental applications of 3D graphene/CNT hybrid materials with special focus on the synergistic effects arising from the combination of graphene and CNT. Most of the relevant literature related to the removal of oils and organic solvents, adsorption of dyes, removal of heavy metal ions, gas sensors and the catalytic conversion of pollutants is reviewed to shed light on the current challenges and upcoming opportunities.