Ion transport through graphene oxide fibers as promising candidate for blue energy harvesting

Abstract

Nanostructured graphene based membranes demonstrated excellent capabilities in various applications in nanofiltration and energy conversion due to unique atomically smooth surfaces and adjustable pore size or interlayers spacing at Angstrom scales. There are some reports on the osmotic power generation using physical confinements and electrostatic interactions between ions and GO membranes. However, the results indicated insufficient power densities (˂1 W/m2) can be achieved because of swelling of interlayer spacing of the GO membranes upon exposure to aqueous solutions which results in reducing the influence of confinement on ionic motilities. Here, the GO fibers is presented as one dimensional macrostructures including abundant aligned 2D nanochannels to produce electricity from salt concentration gradient. We used the GO fibers intercalated via cations to control the interlayer’s spacing depending on the cation’s hydrated size and consequently enhancing a stable confinement on ionic transport. Remarkable surface charge on nanochannel walls as well as cation pining of interlayer distances, provide a high mobility discrimination and the osmotic power density can reach to a value of 38 W/m2. This study introduces the GO fibers as new scalable structures for nanofluidics systems which could find range of applications in energy harvesting and molecular sieving.