Distinctive evaporation characteristics of water and ethanol on graphene nanostructured surfaces.

• Permeation rate of ethanol through GNPs coating is much higher than that of water. • Distinctive evaporation characteristics of water and ethanol manifest on GNPs coating. • Ultrafast water permeation into GNPs nanostructures leads to filmwise evaporation. • Ethanol is retained in the GNPs nanostructures and no evaporation occurs. The mass transport of water and ethanol molecules through the oxygen-functionalized graphene nanostructures, particularly at a high temperature, is not well understood. Here, the evaporation characteristics of water and ethanol droplets on graphene nanoplatelets (GNPs) coating are experimentally investigated and compared. The ultrafast water permeation property of GNPs coatings has shown promising applications in enhancing the phase-change heat transfer attributed to the formation of ultrathin film of water, leading to the filmwise evaporation. Interestingly, the permeation rate of ethanol (and other short-chain alcohols) through the GNPs coatings is much higher than that of water, justified by our experiments and molecular dynamics simulations. However, the results of evaporation of ethanol from the GNPs at a high temperature are counterintuitive where ethanol is retained in the GNPs nanostructures and no evaporation occurs. These results are evidenced by the evaporation heat transfer experiments and thermal gravimetric analysis. Spectroscopic analyses are conducted to scrutinize the underlying mechanisms of sorption and desorption of water and ethanol through the GNPs nanostructures. It is found that ethanol absorbs the applied heat energy as the activation energy to form the molecular bonds between the ethanol molecules and the oxygenated functional groups of GNPs. The present study provides new insights into the sorption and desorption processes of water and ethanol through the GNPs nanostructures, which is beneficial to the phase-change heat transfer applications with graphene-based materials. [ABSTRACT FROM AUTHOR]