We study Seebeck effect in liquid electrolytes, starting from its simple neutral analog\char22{}thermodiffusion (so-called Ludwig-Soret or Soret effect). It is observed that when two or more subsystems of mobile particles are subjected to the temperature gradient, various types of them respond to it differently. In the case when these fractions, with different mobility parameters (Soret coefficients), are oppositely charged (a case typical for electrolytes), the nonhomogeneous internal electric field is generated. The latter field prevents these fractions from space separation and determines the intensity of the appearing Seebeck effect.

We discuss the peculiarities of the Ohm law in dilute polyelectrolytes containing a relatively low concentration $n_{\odot }$ of multiply charged colloidal particles. It is demonstrated that in these conditions, the effective conductivity of polyelectrolyte is the linear function of $n_{\odot }$ . This happens due to the change of the electric field in the polyelectrolyte under the effect of colloidal particle polarization. The proposed theory explains the recent experimental findings and presents the alternative to mean spherical approximation which predicts the nonlinear I–V characteristics of dilute colloidal polyelectrolytes due to entropy changes.

We discuss the peculiarities of the structure of the interface between a metal and a stable colloidal dispersion of charged nanoparticles in an electrolyte. It is demonstrated that a quasi-2D ionic structure of elevated density arises in its vicinity due to the effect of electrostatic image forces. The stabilized colloidal particles, being electroneutral and spatially distributed objects in the bulk of the electrolyte and approaching the interface, are attracted to it. In their turn, the counterions forming their coat partially retract into the 2D-layer, which results in an acquisition by the colloidal particle of the effective charge $e{Z}^{*}\gg e$ and which, together with its mirror image, creates the electric dipole. The formed dipoles, possessing the moments directed perpendicularly to the interface, form the gas with repulsion between particles. The intensity of this repulsion, evidently, depends on the value of the effective charge $e{Z}^{*}$ acquired by the nanoparticle having lost a number of counterions. It can be related to the value of the excess osmotic pressure $P_{osm}$ measured in the experiment. On the other hand, this effective charge can be connected by means of the simple geometric consideration with the structural charge $eZ$ of the nanoparticle core being in the bulk of the electrolyte.

We discuss the peculiarities of the Seebeck effect in stabilized electrolytes containing the colloidal particles. Its unusual feature is the two stage character, with the linear increase of differential thermopower as the function of colloidal particles concentration $n_{\odot }$ during the first stage (“initial state”) and dramatic drop of it at small $n_{\odot }$ during the second one (“steady state”). We show that the properties of the initial state are governed by the thermo-diffusion flows of the mobile ions of the stabilizing electrolyte medium itself and how the colloidal particles participate in the formation of the electric field in the bulk of the suspension. In its turn, we attribute the specifics of the steady state thermoelectric effect the massive colloidal particles undergoing slow thermal diffusion and the break down of their electro-neutrality in the vicinity of electrodes.

The details of $ac$-conductivity measurements in a colloidal electrolyte cell with flat control gate electrodes are discussed. The use of impedance diagnostics in studies of transport phenomena in such systems requires caution in the definition of the thickness of the screening accumulation layers that appear along the metal-electrolyte interfaces. The value of this characteristic length ${\lambda }_0$ critically depends on the volume fraction ${\varphi }_{\odot }$ of colloidal particles in the bulk of the electrolyte. Accounting for the dependence ${\lambda }_0\left({\varphi }_{\odot }\right)$ makes it possible to consistently explain the large discrepancy in the available experimental data regarding the influence of the colloidal fraction on the effective conductivity of the colloidal suspension.

Impedance ac diagnostics is regularly used to study the transport phenomena in conducting systems of differrent dimensionalities. A common reason for using ac methods that are more complex than dc methods is the possibility to exclude the influence on the current-voltage (I−V) characteristic of contact phenomena accompanying dc measurements. In some cases (2d electron systems over helium) dc transport measurements are impossible. In weakly doped semiconductors (diluted electrolytes), the situation is less critical, but problems with the ohmic properties of the conducting contacts remain. The analysis of the details of the formalism that determines the reaction of a conducting medium to an external disturbance depends largely on the form of Ohm’s law for a conductor introduced into the impedance circuit. If there is a reason to define this law by the formula j = σΕ, where j, σ, E correspond to local values of current density, conductivity, and transport electric field, the structure of complex resistance ${\hat{Z}}_F(\omega )$ is considered as a force one. If there is a diffusion component in Ohm’s law then the structure of complex resistance ${\hat{Z}}_{\mu }(\omega )$ is considered as an electrochemical one. We describe a standard electrolytic capacitor in series RC with a step load in terms of force or complex electrochemical impedance. Comparison with experiment shows the electrochemical structure of the complex resistance.