Abstract
The paper presents the results of an investigation into thin single- and triple-layer ZrO2-Sc2O3-based electrolytes prepared using the tape-casting technique in combination with promising electrodes based on La2NiO4+δ and Ni-Ce0.8Sm0.2O2-δ materials. It is shown that pressing and joint sintering of single electrolyte layers allows multilayer structures to be obtained that are free of defects at the layer interface. Electrical conductivity measurements of a triple-layer electrolyte carried out in longitudinal and transverse directions with both direct and alternating current showed resistance of the interface between the layers on the total resistance of the electrolyte to be minimal. Long-term tests have shown that the greatest degradation in resistance over time occurs in the case of an electrolyte with a tetragonal structure. Symmetrical electrochemical cells with electrodes fabricated using a screen-printing method were examined by means of electrochemical impedance spectroscopy. The polarization resistance of the electrodes was 0.45 and 0.16 Ohm∙cm2 at 800 °C for the fuel and oxygen electrodes, respectively. The distribution of relaxation times method was applied for impedance data analysis. During tests of a single solid oxide fuel cell comprising a supporting triple-layer electrolyte having a thickness of 300 microns, a power density of about 160 mW/cm2 at 850 °C was obtained using wet hydrogen as fuel and air as an oxidizing gas.
Highlights
The application of high-temperature solid oxide electrochemical devices presents great opportunities for energy conversion; for example, the use of solid oxide fuel cells (SOFCs) for electricity production [1,2,3,4,5]
The studies were performed on three types of solid electrolyte: a single-layer electrolyte of the composition ZrO2 + 6 mol.% Sc2 O3 having a tetragonal structure, a single-layer electrolyte of the composition ZrO2 + 10 mol.% Sc2 O3 + 1 mol.% Y2 O3 with a cubic structure, as well as a triple-layer electrolyte with an internal c.Sc-stabilized ZrO2 (SSZ) layer and external t.SSZ layers
X-ray powder diffraction (XRD) analysis confirmed the absence of impurity phases for all materials under investigation, as well as the absence of chemical reactivity between the components of the used composites (Figure 1)
Summary
The application of high-temperature solid oxide electrochemical devices presents great opportunities for energy conversion; for example, the use of solid oxide fuel cells (SOFCs) for electricity production [1,2,3,4,5]. In conventional SOFCs, thick layers of Y-doped ZrO2 electrolyte (YSZ) are used as ionic-conducting materials. In this case, a considerable part of the produced energy is lost due to ohmic electrolyte resistance. Due to technological issues involved in the manufacture of such thin films, their formation should be carried out on a porous supporting substrate (cathode [9,10,11], anode [12,13,14], metal interconnector [15,16,17]) in order to ensure the mechanical strength of the cell For this reason, questions arise concerning the production technology of supporting
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