Effect of ionic mobility of working electrolyte on electrokinetic energy conversion in sub-micron channels

In this study, the effect of the ionic mobility of a working electrolyte on the efficiency of electrokinetic energy conversion was experimentally investigated for various channel sizes. Potassium chloride, trimethylammonium formate, and tetrabutylammonium dihydrogen phosphate solutions with very different ionic mobilities at a concentration of 10−5 M were used as the working electrolytes. The efficiencies of electrokinetic energy conversion for 50 μm-wide nanochannels with heights of 200 nm, 500 nm, and 800 nm were obtained. We show that the efficiency of electrokinetic energy conversion behaves differently with respect to the ionic mobility depending on channel size. Experimental results showed that the electrolyte with lower ionic mobility performed better only when the channel size was larger than the Debye length (Channel height ≥ 0 (10λD)). Otherwise, the energy conversion efficiency was found to be independent of the ionic mobility of the working electrolyte.