Water, Not Salt, Causes Most of the Seebeck Effect of Nonisothermal Aqueous Electrolytes

O Nickel and LJV Ahrens-Iwers and RH Meissner and M Janssen, PHYSICAL REVIEW LETTERS, 132, 186201 (2024).

DOI: 10.1103/PhysRevLett.132.186201

A temperature difference between two electrolyte-immersed electrodes often yields a voltage Delta yr between them. This electrolyte Seebeck effect is usually explained by cations and anions flowing differently in thermal gradients. However, using molecular simulations, we found almost the same Delta yr for cells filled with pure water as with aqueous alkali halides. Water layering and orientation near polarizable electrodes cause a large temperature-dependent potential drop X there. The difference in X of hot and cold electrodes captures most of the thermovoltage, Delta yr approximate to Xhot - Xcold.

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