Nonequilibrium molecular dynamics simulations were performed
to
study the electrokinetic properties of five mainstream TIPxP water models (namely, TIP3P-FB, TIP3Pm, TIP4P-FB, TIP4P-Ew,
and TIP4P/2005) in NaCl aqueous solutions in the presence of a negatively
charged TiO2surface. The impact of solvent flexibility
and system geometry on the electro-osmotic (EO) mobility and flow
direction was systematically assessed and compared. We found that
lack of water flexibility decelerates the forward EO flow of aqueous
solutions at moderate (0.15 M) or high (0.30 M) NaCl concentrations,
in some special cases to such an extent that EO flow reversal occurs.
Zeta potential (ZP) values were then determined from the bulk EO mobilities
using the Helmholtz–Smoluchowski formula. The straight comparison
against available experimental data strongly suggests that water flexibility
improves the ZP determination of NaCl solutions adjacent to a realistic
TiO2surface under neutral pH conditions.