Sunlight-assisted tailoring of surface nanostructures on single-layer graphene nanosheets for highly efficient cation capture and high-flux desalination

Abstract

Highly efficient approaches using nanomaterials for ion capture and desalination have been widely explored to address fresh water scarcity worldwide; however, the complex preparation process and the large-scale and high-density perforation of porous graphene layers remain technical challenges. Herein, we found that sunlight-assisted tailoring of surface nanostructures involving controllable morphological and structural alterations of graphene unequivocally improved the ion adsorption and ion filtration performance. Notably, the interlayer spacing of single-layer graphene could be sufficiently tuned via lighting control to promote selective interactions between ions and nanosheets. After 7 d simulated sunlight treatment, the transformed SLG (SLG-S7) exhibited 86.1%, 77.3% and 46.1% increases of adsorption capacity for Na+, Pb2+ and Fe3+ in the complex ion system, respectively. Notably, the adsorption capacity of SLG-S7 for single Pb2+ was even 2.3-fold greater than that of pristine SLG. Further, the layer-stacked SLG-S7 membrane achieved super water fluxes (167.1 L m−2 h−1 bar−1) and a high separation performance without sacrificing salt ion rejection, which was attributed to the sunlight-induced larger water transport channels and defect-free nanosheets in the membrane. This work provides new insight for the design of novel graphene-based nanostructures to address the increasingly serious water contamination issue and the scarcity of fresh water.