Holey graphene oxide membranes containing both nanopores and nanochannels for highly efficient harvesting of water evaporation energy

Abstract

The conversion of the electrokinetic energy arising from evaporation-induced water flow through nanoporous materials has great potential for renewable energy production. In this study, we prepare a nanocapillary membrane containing both nanopores and nanochannels based on an assembly of holey graphene oxide (HGO) nanosheets, which enables water molecules to permeate and simultaneously evaporate from the nanostructure. In particular, we find that the performance of our HGO membrane-based water evaporation-induced energy harvester (WEEH) can be significantly improved by ensuring (1) a high capillary flow of water through low-friction nanochannels and (2) a high rate of evaporation, which is achieved by the presence of large nanoscale pores with a broad size distribution. Our WEEH yields a maximum voltage of 0.44 V, current of 200 nA, and output energy density of 2.2 μWh cm−2. Furthermore, the use of multiple WEEHs allows for the generation of sufficient energy to charge a 1-F supercapacitor and power a light-emitting diode (2 V × 20 mA). Thus, our proposed nanocapillary, thin-membrane-based WEEH has great practical potential for energy generation, as well as other membrane-based technologies such as water purification.