The influence of mechanochemical treatment in hexane on dispersibility and floatability of graphite flakes with enhanced water evaporation performance

The dispersibility and floatability of graphitic carbon materials in water are two contradictory properties with significant importance in a wide variety of applications. Here, we investigate the effect of ball-milling (BM) in the presence of NaCl and n-hexane on the dispersibility and floatability of graphite flakes in water. The exfoliated carbons are characterized by different techniques including the ultraviolet-visible (UV-Vis) absorption and Fourier-transform infrared spectroscopy (FTIR), as well as Raman and X-ray diffraction (XRD) analysis. The increase in the defect density of carbons caused by the BM process, and the presence of n-hexane influence the behavior of exfoliated flakes in water. While the BM at shorter time periods enhances the dispersion performance, the ball-milled graphite is found to be readily floatable on the surface of water at longer BM durations in the presence of sufficiently high amounts of n-hexane used during the BM process. The mechanochemical mechanism involved in enhancing the dispersibility and floatability of graphitic carbon materials is discussed. Furthermore, the enhanced water evaporation performance of the water-floatable carbon prepared by the mechanochemical approach is demonstrated. This article suggests a facile and potentially scalable approach for the preparation of floatable graphene flakes with enhanced performance as free-standing media for light-induced water evaporation applications.