Ultra-fast Vapor Generation by a Graphene Nano-ratchet

Vapor generation is of prime importance for a broad range of applications: domestic water heating, desalination and wastewater treatment, etc. However, the slow and low efficiency evaporation limits their development. In this paper, we proposed a nano-ratchet, multilayer graphene with cone-shaped nanopores (MGCN), to accelerate the vapor generation. By performing molecular dynamics simulations, we found that the air molecules spontaneously transport across MGCN and form a remarkable pressure difference, 21kPa, between the two sides of MGCN. Besides, we studied the dependence of pressure difference on the ambient temperature and the geometry of MGCN in detail. By further analysis of the diffusive transport, we identified that the pressure difference relates to the competition between ratchet transport and Knudsen diffusion. The significant pressure difference could lead to 15 times enhancement of vapor generation at least, which shows the wide applications of this nano-ratchet.