Water, not salt, causes most of the Seebeck effect of nonisothermal aqueous electrolytes

When two electrolyte-immersed electrodes have different temperatures, a voltage $\mathrm{\Delta }\psi$ can be measured between them. This electrolyte Seebeck effect is usually explained by cations and anions flowing differently in thermal gradients. However, our molecular dynamics simulations of aqueous electrolytes reveal a large temperature-dependent potential drop $\chi$ near blocking electrodes caused by water layering and orientation. The difference in surface potentials at hot and cold electrodes is more important to the Seebeck effect than ionic thermodiffusion, $\mathrm{\Delta }\psi \sim {\chi }_{\mathrm{h}\mathrm{o}\mathrm{t}}-{\chi }_{\mathrm{c}\mathrm{o}\mathrm{l}\mathrm{d}}$.