Energy harvesting from salinity gradient by reverse electrodialysis with anodic alumina nanopores

Abstract

Power generation by reverse electrodialysis from anodic alumina nanopores is experimentally investigated by placing an alumina nanopore array with a nominal pore radius of 10 nm between two sodium chloride solutions with various combinations of concentrations. Both bare and silica-coated alumina nanopore arrays are used in the present study. The current–potential characteristics are measured for various electrolyte concentration levels, and the transference number and the electrical conductance of the nanopore arrays are obtained from these characteristics. The transference numbers of the bare and silica-coated alumina nanopore arrays are 0.30 and 0.72, respectively; these values are nearly independent of the concentration of the sodium chloride solutions when it is less than 200 mM. Therefore, the bare and silica-coated alumina arrays can be used as anion selective and cation selective membranes, respectively, for micro batteries and micro power generators. Finally, power generation by reverse electrodialysis using an alumina nanopore array is presented. The highest power generation measured is 542 nW, which is several orders of magnitude higher than those measured in previous studies based on nanofluidic channels or nanopores.