Nanoelectrochemistry Concepts in Desalination Energy Harvesting and Analysis

Abstract

This talk will provide an overview of the research in GWang’s group at Georgia State centered around the electrochemical processes at the nanometer scale. Three examples will be discussed in two research topics. The first is the development of new analytical method/toolbox for actively controlled nucleation and crystal growth. By controlling charge transport through a single nanopore, a single crystal is synthesized while the whole process is monitored by combined electroanalytical and optical methods. In the second topic, ion transport through a single asymmetric nanopipette is studied by experiments and simulation. The solution-substrate interface confined inside the conical nanopore is viewed as structurally-defined unit elements in ensemble porous membrane/electrode/materials. The surface electric field direction is separated from the through-transport ion flux which affects both the structure and dynamics of the electrical double layer (EDL). Selective and efficient transport of ions is the fundamental process in 1. the desalination with energy input; and a retrospective process of 2. energy harvesting from salinity when fresh and brackish/sea water mix. Novel time-dependent current-potential features are captured in electrochemical experiments due to the polarization of the nanoscale EDL or selective transport of ions. Characteristic signatures include a non-zero cross point in I-V curves separating pinched hysteresis loops. Finite element simulations by solving the Poisson, Nernst-Planck and Navier-Stokes equations reveal the respective transport of cations and anions driven by migration, diffusion and electroosmotic flow. The transport selectivity and efficiency under time- and space- confined conditions provide fundamental insights to better transport related applications such as desalination separation and energy harvesting from salinity gradients. Financial supports from NSF (CHE-1610616) and DOE (DE-SC0019043) are acknowledged.