Fuel cells

The concentrations of the main components of the (Li_0.62K_0.38)₂CO₃ melt have been evaluated by the thermodynamic modeling technique, and the Warburg coefficients of electroactive particles as a function of temperature and CO₂/O₂ gas mixture composition have been calculated. The same dependences of Warburg coefficient and charge transfer resistance were studied on Au cathode using coulostatic technique. It is shown that O₂ ions and O₂ molecules are the main electroactive species in the melt. Their relative concentration determines which reaction mechanism dominates.

Electrochemical activity of electrodes for electrolysis of water is investigated. As catalysts coating Ni-S-Co, suspension LaNi_2.5Co_2.4Al_0.1 or their combinations were applied. As electrolyte at test of electrodes 30% KOH or NaOH is used. Current density varied in a range from 10 to 600 мА/cm² at temperature 20-80°C. When the temperature increases from 20 to 80°C the current density on cathodes with composite LaNi2.5Co2.4Alo.i/Ni-S-Co catalyst increases 4 times at constant potential E = –1.10 V (rel. Hg/HgO). When the current density of more than 100 mA/cm² cathodes with all catalysts offered by us in this work have lower value of potential than the similar cathodes described in the scientific literature. In contrast to the cathodes, catalyst LaNi_2.5Co_2.4Al_0.1/Ni–S–Co does not render influence on electrochemical activity of the anode.

The phase composition, thermal coefficient of linear expansion and electrical conductivity of r_1.85Sr_0.15Ni_1-xCu_xO₄ (0.0; 0.1; 0.5; 0.9 и 1), Pr₂NiO₄ and Pr₂CuO₄ are investigated at air in the temperature range 100-1000°C.
The thermal coefficient of linear expansion are in range of ((11.2–16.6)·10^-6 deg_-1. The TCLE of some composition close to TCLE of solid electrolyte La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 (LSGM) и Ce_0.9Gd_0.1O_2-Δ (CGO). Pr_1.85Sr_0.15Ni_0.1Cu_0.9O₄ has the highest conductivity at temperatures above 350°C.

A high-temperature solid polymer electrolyte fuel cell using H 3 PO 4 -doped polybenzimidazole (PBI) as proton-exchange membrane has been developed and tested. The influences of temperature (in a range between 130 and 170°C), pressure (in a range between 1 and 3 bars) and air flow rate onto fuel cell performances have been studied. A maximum output power density of 200 mW·cm^-2 has been obtained. The existence of an optimum air flow rate (expressed in oxygen stoichiometric ratio) has been put into evidence. It allows an increase of the fuel cell voltage from 250 mV up to ca. 400 mV at 0.4 A·cm^-2. The results of the calculation of efficiency of PBI-based electrochemical power plant using the products of natural gas conversion as a fuel are presented.

The paper presents the performance of domestic PHOTON hydrogen-oxygen alkaline fuel cells. The issues of FC operation life is discussed, and reasons for reversible and irreversible voltage degradation are identified. The input of FC components into irreversible part of performance degradation is estimated.

By cyclic voltammetry and rotating disk electrode investigated the stability of the composite catalyst Pt/C–CNT from electrochemical action through multiple changes of the electrode potential from –150 to 1000 mV vs. silver chloride reference electrode. Investigated: the dynamics of the electrochemically active surface area of platinum and electrode in whole, change of amount of quinone groups, change in density of the kinetic current reduction of air oxygen on the surface of the catalyst. With the use of the method of differential thermal analysis studied the oxidation processes and the mechanisms of change of the physicochemical properties of the material under electrochemical action.

The thermal model of the power plant based on the solid oxide fuel cells (SOFC) fed with methane is developed. The power plant includes three heat-generating zones: a fuel-cell stack, a reactor of partial oxidation (RPO), and an afterburner. It is shown that temperature distribution along the battery depends on three factors: a methane consumption, a methane to air relation in the flow fed to the RPO, and a battery current. Results of modeling well correlate with the experimental data received on the power plant prototype with the SOFC stack consisted on 16 tubular cells.

The composites contained ultra low amounts of platinum, polymers and carbon nanotubes (SWCNTs) were investigated. The main goal were to elucidate the influence of the polymer functional groups nature on the structure and on electrocatalytic activity of the composites. The structure of the composite Platinum/sodium polystyrensulfonate (PSS)/SWCNTs/GC has been studied by TEM, HRSTEM, HAADF STEM and SAED methods. The loading of platinum was detected by ICP–AES. The electrochemical studies show high catalytic activity of the prepared composite in methanol oxidation reaction comparing to commercial catalyst Pt/C ETEK and other previously studied composites.

The oxygen reduction mechanisms on an oxide electrode are proposed. It was found, that in the temperature range 870–1020 K mechanism involving superoxide ions dominates, whereas in T < 870 К region the reaction mechanisms involving molecular oxygen apparently take place.

The results of the study of kinetics of oxygen reduction on the dense LaLi_0.1Co_0.1Fe_0.8O_3-d electrode in (Li_0.62K_0.38)₂CO₃ eutectic melt using coulostatic technique are reported. It was found, that the equivalent circuit that includes heterogeneous charge transfer step in series with heterogeneous chemical reaction most closely fits the kinetics of electrode processes.