  The electric field in an extended phase of a liquid electrolyte exposed to a
temperature gradient is attributed to different thermophoretic mobilities of
the ion species. As shown herein, such Soret-type ion thermodiffusion is not
required to induce thermoelectricity even in the simplest electrolyte if it is
confined between charged walls. The space charge of the electric double layer
leads to selective ion diffusion driven by a temperature-dependent
electrophoretic ion mobility, which -- for narrow channels -- may cause
thermo-voltages larger in magnitude than for the classical Soret equilibrium.
