In article was established the conditions for measuring thermal diffusion and thermoelectric effects in non-isothermal elements with composite electrodes of powdered iron and carbon in the alkaline electrolytes using electrochemical impedance spectroscopy. By the modeling of the impedance spectra of these systems has been established the most advantageous equivalent model scheme, which confirms that the external resistance has several components: the resistance of the electrolyte, the resistance of the capacity of the double electric layer and the resistance of thermal diffusion, which forms the dispersion of the capacity. By the calculations of the capacity and the dispersion of the capacity in the low- and high-frequency measurement range have been shown the effect of the concentration of composition components on the formation of the additional heat capacity, which creates the preconditions for realizing of the thermal electrical effects. Increasing of a concentration of the iron leads to the increase of the number of oxide (semiconductor) structures that increase the additional heat capacity. Such heat capacity induces electrical capacity and its dispersion. That is, it creates the preconditions for the occurrence of thermoelectric effects, especially Sore effects in the non-isothermal element. This work was realized due the projects of the Purpose Program for Basic Research of the Chemistry Department of NAS of Ukraine "Basic Research in Priority Areas of Chemistry" P - 1 - 17 DR 0117U000856 and "Strategy of creation of new heat-energy systems based on iron and its compounds, sulfur and oxygen" No. 0117U0008.
2. Rowe, D. M.. Thermoelectrics, an environmentally-friendly source of electrical power. Renewable energy. 1999. 16(1-4): 1251-1256.
3. Petit, C. J., Hwang, M. H., Lin, J. L. Thermal diffusion of dilute aqueous NH 4 Cl, Me 4 NCl, Et 4 NCl, n-Pr 4 NCl, andn-Bu 4 NCl solutions at 25° C. Journal of solution chemistry. 1988. 17(1): 1-13.
4. Malashetty, M. S., Gaikwad, S. N., Swamy, M. An analytical study of linear and non-linear double diffusive convection with Soret effect in couple stress liquids. International journal of thermal sciences. 2006. 45(9): 897-907.
5. Jokinen, M., Manzanares, J. A., Kontturi, K., & Murtomäki, L. Thermal potential of ion-exchange membranes and its application to thermoelectric power generation. Journal of Membrane Science. 2016. 499: 234-244.
6. Yella, A., Lee, H. W., Tsao, H. N., Yi, C., Chandiran, A. K., Nazeeruddin, M. K., ... & Grätzel, M. Porphyrin-sensitized solar cells with cobalt (II/III)–based redox electrolyte exceed 12 percent efficiency. Science. 2011. 334(6056): 629-634.
7. Burrows, B. Discharge behavior of redox thermogalvanic cells. Journal of The Electrochemical Society. 1976. 123(2): 154.
8. Ikeshoji, T. Thermoelectric conversion by thin-layer thermogalvanic cells with soluble redox couples. Bulletin of the Chemical Society of Japan. 1987. 60(4): 1505-1514.
9. Mua, Y., Quickenden, T. I. Power conversion efficiency, electrode separation, and overpotential in the ferricyanide/fer-rocyanide thermogalvanic cell. Journal of The Electrochemical Society. (1996). 143(8): 2558-2564.
10. Nuwayhid, R. Y., Moukalled, F., & Noueihed, N. On entropy generation in thermoelectric devices. Energy conversion and management. 2000. 41(9): 891-914.
11. Hu, R., Cola, B. A., Haram, N., Barisci, J. N., Lee, S., Stoughton, S., ... Gestos, A. ME d. Cruz, JP Ferraris, AA Zakhidov and RH Baughman. Nano Lett. 2010. 10: 838-846.
12. Tannhauser D.S. Conductivity in iron oxides. Journal of Physics and Chemistry of Solids. 1962. 23(1-2): 25-34.
13. Xu X., Li H., Zhang Q., Hu H., Zhao Z., Li J., Li J., Qiao Yu, Gogotsi Yu Self-Sensing, Ultralight, and Conductive 3D Graphene/Iron Oxide Aerogel Elastomer Deformable in a Magnetic Field. ACS Nano. 2015. 9(4): 3969-3977.
14. Trofimenko, N.E., Ullmann, H. Oxygen stoichiometry and mixed ionic-electronic conductivity of Sr1−aCeaFe1−bCobO3−x perovskite-type oxides. Journal of the European Ceramic Society. 2000. 20(9): 1241-1250.
15. Kravchenko, A. V., Pershina, K. D. Thermochemical and microstructural properties of the powdered iron– graphite–alumosilicate mixture. Ukrainian Chemistry Journal. 2017. 83(6): 117-124.
16. Sokirko, A. V. Theoretical study of thermogalvanic cells in steady state. Electrochimica acta. 1994. 39(4): 597-609.
17. De Bokx, P. K., Kock, A. J. H. M., Boellaard, E., Klop, W., Geus, J. W. The formation of filamentous carbon on iron and nickel catalysts: I. Thermodynamics. Journal of catalysis. 1985. 96(2): 454-467.
18. Erickson, K. J., Léonard, F., Stavila, V., Foster,M. E, Spataru, C. D., Jones, R. E., Foley, B. M., Hopkins, P. E., Allendorf, M. D, Talin, A. A. Thin Film Thermoelectric Metal–Organic Framework with High See-beck Coefficient and Low Thermal Conduc-tivity. Adv. Mater. (2015). 27: 3453–3459.
19. Mateeva, N., Niculescu, H., Schlenoff, J. B., Testardi, L. Correlation of Seebeck Coefficient and Electric Conductivity in Polyaniline and Polypyrrole. Journal of Applied Physics. 1998. 83: 3111 – 3119.
20. Kravchenko, A. V., & Pershina, K. D. Thermochemical and electrochemical description of the Fe-C catalytic system. Promising materials and processesin applied electrochemistry. 2017. 224-230.
21. Kravchenko, O. V., Pershina, K. D., Panteleymonov, R. A., & Potapenko, O. V. Electrochemical Properties of Powder Iron/Carbon System in Basic Solution. Materials Today: Proceedings. 2019. 6: 65-72.
22. Riabokin, O. L., Boichuk, A. V., & Pershina, K. D. Control of the State of Pri-mary Alkaline Zn–MnO2 Cells Using the Electrochemical Impedance Spectroscopy Method. Surface Engineering and Applied Electrochemistry. 2018. 54(6): 614-622.
23. Riabokin, O., Boichuk, O., Pershina, K. Assessment of mechanical damages in the primary Zn-MnO2 batteries by electrochem-ical impedance spectroscopy. Ukrainian Chemistry Journal. 2019. 85(8): 59-65.
24. Mulenko, S. A., Gorbachuk, N. T., & Stefan, N. Laser synthesis of nanometric iron oxide films with high Seebeck coefficient and high thermoelectric figure of mer-it. Lasers in Manufacturing and Materials Processing. 2014. 1(1-4): 21-35.
25. Regner, K. T., Majumdar, S., & Malen, J. A. Instrumentation of broadband frequency domain thermoreflectance for measuring thermal conductivity accumulation functions. Review of Scientific Instruments. 2013. 84(6): 064901.
26. Regner, K. T., Sellan, D. P., Su, Z., Amon, C. H., McGaughey, A. J., & Malen, J. A. Broadband phonon mean free path contributions to thermal conductivity meas-ured using frequency domain thermo-reflectance. Nature communications. 2013. 4(1): 1-7.
27. Koh, Y. K., Cahill, D. G. Frequency dependence of the thermal conductivity of semiconductor alloys. Physical Review B. 2007. 76(7): 075207.