• Energy Research

An important direction in the development of energy saving policy is harvesting and conversion into electricity of low-grade waste heat. The present paper is devoted to the improvement of the efficiency of thermo-electrochemical cells based on carbon fiber electrodes and potassium ferri-/ferrocyanide redox electrolyte. The influence of the carbon fiber electrode surface modification (magnetron deposition of silver and titanium or infiltration implantation of nanoscale titanium oxide) on the output power and parameters of the impedance equivalent scheme of a thermo-electrochemical cell has been studied. Two kinds of cell designs (a conventional electrochemical cell with a salt bridge and a coin cell-type body) were investigated. It was found that the nature of the surface modification of electrodes can change the internal resistance of the cell by three orders of magnitude. The dependence of the equivalent scheme parameters and output power density of the thermoelectric cell on the type of electrode materials was presented. It was observed that the maximum power for carbon fiber modified with titanium metal and titanium oxide was 25.2 mW/m2 and the efficiency was 1.37%.

Thermo-electrochemical cells (also known as thermocells, TECs) represent a promising technology for harvesting and exploiting low-grade waste heat (<100–150 °C) ubiquitous in the modern environment. Based on temperature-dependent redox reactions and ion diffusion, emerging liquid-state thermocells convert waste heat energy into electrical energy, generating power at low costs, with minimal material consumption and negligible carbon footprint. Recent developments in thermocell performances are reviewed in this article with specific focus on new redox couples, electrolyte optimisation towards enhancing power output and operating temperature regime and the use of carbon and other nanomaterials for producing electrodes with high surface area for increasing current density and device performance. The highest values of output power and cell potentials have been achieved for the redox ferri/ferrocyanide system and Co2+/3+, with great opportunities for further development in both aqueous and non-aqueous solvents. New thermoelectric applications in the field include wearable and portable electronic devices in the health and performance-monitoring sectors; using body heat as a continuous energy source, thermoelectrics are being employed for long-term, continuous powering of these devices. Energy storage in the form of micro supercapacitors and in lithium ion batteries is another emerging application. Current thermocells still face challenges of low power density, conversion efficiency and stability issues. For waste-heat conversion (WHC) to partially replace fossil fuels as an alternative energy source, power generation needs to be commercially viable and cost-effective. Achieving greater power density and operations at higher temperatures will require extensive research and significant developments in the field.

In this paper, the electrochemical and electrophysical properties of protonated potassium polytitanate synthesized at pH values varying from 3.11 to 8.88 depending on the magnitude of the polarization voltage and the magnitude of the measured signal were studied by the method of impedance spectroscopy. The values of effective conductivity, relaxation times, frequency dependences of the loss tangent, and dielectric permittivity are determined.

Abstract High-performance harvesting of waste heat energy and its conversion into electric energy via thermo-electrochemical cells is an essential strategy of renewable energy development. Even though there is a large amount of scientific research available, but due to expensive electrode materials and low efficiency, the thermo-electrochemical cells have not found practical application. Here we demonstrated thermo-electrochemical cell with nickel (Ni) hollow microspheres-based electrodes, provided the highest hypothetical Seebeck coefficient of 4.5 mV/K (for aqueous electrolyte based thermocells) until today and open-circuit voltage values of up to 0.2 V. High values of Seebeck coefficient provide the ability to collect low-temperature heat, and high output potential differences which allow to fabricate batteries for commercial power circuits for various microelectronic devices. This work also proposed a mechanism and science behind the electrode processes, which explains a extremely high values of the hypothetical Seebeck coefficient. This is the first time to use Ni hollow microsphere in thermo-electrochemical cell for heat harvesting and thermal energy conversion into electricity. Because of the low cost of Ni microspheres electrode-based developed thermo cells could be commercially feasible for harvesting low-quality thermal energy.

Low-grade waste heat harvesting and conversion into electric energy is an important way of renewable energy development and thermo-electrochemical cells are promising devices to solve this problem. In this paper, we report original data on the current density and maximum output power dependents on voltage of the thermos-cells with nickel hollow microspheres electrodes and different electrolyte concentration (from 0.1 to 3.0 mol/l)which exhibit excellent hypothetical Seebeck coefficient and accordingly high open-circuit voltage values at low source temperature. The composition, microstructure and morphology of the hollow nickel microspheres based electrodes are included here. Because of the low cost of nickel based thermo-cells could be commercially feasible for harvesting low-quality thermal energy, in this connection, the raw data of measurements of their properties are given here. The data is related to "High Seebeck coefficient thermo-electrochemical cell using nickel hollow microspheres electrodes", Burmistrov et al., Renewable Energy, 2020 [1].

The paper considers the electrochemical properties of potassium polytitanate synthesized at the values of pH varying from 3 to 8 in a wide temperature range from −26 to +80°C. The conductivity values and the activation energy were determined with the help of the method of impedance spectroscopy. The application of the obtained material used as a ceramic solid electrolyte in the energy storage units operating at low temperatures in the Far North is considered in the article.