Electroosmotic Drag of Water in Hydrated Potassium Perfluorosulfonated Polymer Membrane in External Electric Fields

Abstract

The electroosmotic drag and the corresponding mechanism of water molecules in hydrated potassium perfluorosulfonate electrolyte polymer membrane were studied using molecular dynamics simulations,and the relationship between the membrane structure and electroosmotic drag characteristics was analyzed.It is concluded that velocities of both H2O and K+ obey the Maxwell velocity distribution function without external electric field applied.If an appropriate electric field is applied,the velocities of H2O and K+ still obey the Maxwell velocity distribution in the direction perpendicular to the electric field,and obey the peak shifted Maxwell velocity distribution in the direction parallel to the electric field.The peak shifting velocities coincide with the average transport velocities of H2O and K+ induced by the applied electric field,and could be applied to evaluate the electroosmotic drag coefficient of water.The results also show that the average number of water molecules in the first coordination shell of K + is 4.04,and the average transport velocity of these water molecules is about 57% of that of K+.The electroosmotic drag coefficient contributed by these water molecules is about 77% of total the electroosmotic drag coefficient(2.97).