Edge-enhanced ultrafast water evaporation from graphene nanopores

Graphene nanoporous membranes are the ultimate ultrathin nanoporous membranes and have enormous potential applications due to efficient heat and mass transfer that is limited only by interfacial evaporation kinetics. Developing such membranes requires fundamental understanding of evaporation at the single-pore level, which has remained largely unexplored. Herein, we report the experimental study of kinetically limited evaporation from single/multiple circular graphene nanopores with diameters from 24 to 347 nm. We show that, despite a wide variation, the evaporation flux increases as nanopore diameter decreases and that the maximum evaporation flux exceeds the upper kinetic limit predicted by the classical Hertz-Knudsen relation for nanopores with diameters below 60 nm. We associate the enhancement with edge-facilitated evaporation and minimum contaminant accumulation at the liquid-vapor interface. We further find that such enhanced ultrafast evaporation exhibits a temperature-insensitive but diameter-dependent manner. Our work provides new insights into nanoscale evaporation and will shed light on developing 2D nanomaterials-based membrane evaporators.