(260w) How Ionic Valence and Concentration Affects the Electric Current Generation of in Nanochannel: A Study By Classical Density Function Theory

Authors: 
Hu, X., Tsinghua University
Kong, X., Tsinghua University
Lu, D., Key Lab of Industrial Biocatalysis, Ministry of Education, Tsinghua University
Liu, Z., Key Lab of Industrial Biocatalysis, Ministry of Education, Tsinghua University
Wu, J., University of California Riverside
The nanometer dimension intrinsically accounts for the dramatically different flow behavior and physicochemical prosperities of electrolytes, as compared to that in the conventional channel1-4. In this work, we applied classical density function theory (CDFT)5 and Navier-Stokes Equation to examine the effects of ion valences, concentration and size of channels on current density and efficiency upon fluid flow through nanochannel. A two dimensional nanochannel with 0.6 ~ 4.0 nm in height and surface potential of 0.5 V was set to evaluate the effects of 1- , 2- and 3-valence symmetry ions with concentration of 0.001~5 mol/L. It was shown that energy conversion efficiency was not linearly increased with respect to decrease in height or increase in ion concentration. Instead, an optimal current and energy conversion efficiency exists for given electrolytes. Effects of valence-asymmetry ions and radius-asymmetry ions were also examined respectively. The physical insights of above mentioned results were discussed in terms of charge density profile for co-ions and counter-ions. It was noted here that when we used diameter-asymmetric ion pair, both current and energy conversion efficiency were superior to those of symmetric ion pairs with the same valence. It was indicated that the asymmetric ion pairs, who have more charges opposite to surface charge and small size, can be used as working fluid to convert mechanical energy into electricity. The results presented by this work offer a molecular insight of electric power generation by force flow of fluid flow through nanochannels, which is helpful for the design of nanochannel and electrolyte and the determination of the process parameters for electricity generation.

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