Improving the efficiency of electrokinetic conversion in nanofluidics with graphene-engineered surface

Abstract

Nanofluidic electrokinetic systems have attracted increasing interest in view of their potential in miniaturized electricity generation and mass transport, but suffer from low efficiency. In this work, we propose a novel approach to boost the energy efficiency of electrokinetic devices by simply engineering the solid–liquid interface with single-layer graphene. Through molecular dynamics simulation and theoretical analysis, we demonstrate that the graphene engineered interface allows for strong slip flow, which commonly exists on hydrophobic surfaces, and high surface charge, which only exists on hydrophilic surfaces. The flow boundary and surface electrical charge are decoupled on such a uniquely heterogeneous surface. Owing to the decoupling, we demonstrate that the energy efficiency of a streaming generator can be enhanced by a factor of 20–100 at different charge densities, which suggests a general and effective strategy to promote the efficiency of a series of electrokinetic devices, such as nanofluidic generators and osmotic pumps.