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Solid oxide fuel cells (SOFCs) are promising devices for electrical power generation from hydrogen or hydrocarbon fuels. The paper reports our study of CaO-SiO2-B2O3 material with composition 36 mol.% SiO2, 26 mol.% B2O3, and 38 mol.% CaO as a high-temperature sealant for SOFCs with an operating temperature of 850 °C. The material was studied as an alternative to presently existing commercial glass and glass-ceramics sealants for SOFCs with operating temperature of 850 °C. Many of these sealants have limited adhesion to the surface of Crofer 22APU steel, commonly used in these SOFCs. The present study included X-ray diffraction, dilatometric, thermal, and microstructural analysis The study has shown that the softening point of the CaO-SiO2-B2O3 glass is around 900 °C, allowing sealing of the SOFCs with this glass at convenient temperature of 925 °C. The CaO-SiO2-B2O3 glass sealant has shown excellent adhesion to the surface of Crofer 22APU steel; SEM images demonstrated evidences of chemical reaction and formation of strong interface on sealant–steel contact surface. Furthermore, the glass has shown a coefficient of thermal expansion about 8.4 × 10−6 1/K after sealing, making it thermomechanically compatible with the existing SOFC materials. [ABSTRACT FROM AUTHOR]

Increasing Sr and Ti concentrations in perovskite-type $$ {\left( {{\hbox{L}}{{\hbox{a}}_{0.{75} - x}}{\hbox{S}}{{\hbox{r}}_{0.{25} + x}}} \right)_{0.{95}}}{\hbox{M}}{{\hbox{n}}_{0.{5}}}{\hbox{C}}{{\hbox{r}}_{0.{5} - x}}{\hbox{T}}{{\hbox{i}}_x}{{\hbox{O}}_{{3} - }}_\delta \left( {x = 0 - 0.{5}} \right) $$ results in slightly higher thermal and chemical expansion, whereas the total conductivity activation energy tends to decrease. The average thermal expansion coefficients determined by controlled-atmosphere dilatometry vary in the range (10.8-14.5) × 10 K at 373-1,373 K, being almost independent of the oxygen partial pressure. Variations of the conductivity and Seebeck coefficient, studied in the oxygen pressure range 10-0.5 atm, suggest that the electronic transport under oxidizing and moderately reducing conditions is dominated by p-type charge carriers and occurs via a small-polaron mechanism. Contrary to the hole concentration changes, the hole mobility decreases with increasing x. The oxygen permeation fluxes through dense ceramic membranes are quite similar for all compositions due to very low level of oxygen nonstoichiometry and are strongly affected by the grain-boundary diffusion and surface exchange kinetics. The porous electrodes applied onto lanthanum gallate-based solid electrolyte exhibit a considerably better electrochemical performance compared to the apatite-type LaSiAlO electrolyte at atmospheric oxygen pressure, while Sr and Ti additions have no essential influence on the polarization resistance. In H-containing gases where the electronic transport in $$ {\left( {{\hbox{L}}{{\hbox{a}}_{0.{75} - x}}{\hbox{S}}{{\hbox{r}}_{0.{25} + x}}} \right)_{0.{95}}}{\hbox{M}}{{\hbox{n}}_{0.{5}}}{\hbox{C}}{{\hbox{r}}_{0.{5} - x}}{\hbox{T}}{{\hbox{i}}_x}{{\hbox{O}}_{{3} - }}_\delta $$ perovskites becomes low, co-doping deteriorates the anode performance, which can be however improved by infiltrating Ni and $$ {\hbox{Ce}}{{\hbox{O}}_{{\rm{2}} - }}_\delta $$v into the porous oxide electrode matrix. [ABSTRACT FROM AUTHOR]

The Sr0.75Y0.25Co0.5Mn0.5O3-y (SYCM) oxide with a cubic perovskite Structure was examined as a promising cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The electrical conductivity, thermal expansion coefficient (TEC), and reactivity with gadolinia-doped ceria (GDC) or yttria-stabilized zirconia (YSZ) were studied. Reflections from SrZrO3 (∼6 wt %) after heat-treatment of the SYCM:YSZ mixture at 900°C for 48 h and no reaction after heat-treatment with GDC were observed. In the low and intermediate temperature region (473-873 K), the TEC value is 13.3 ppm K-1 and most closely matches the common IT-SOFC electrolyte material GDC, but the TEC value increases to 19.6 ppm K-1 at 873-1073 K. The investigations of the electrochemical properties of the model SOFCs at 900°C with the SYCM cathode show that substituting the SYCM cathode for the standard (La,Sr)MnO3 cathode improves the cell performance. [ABSTRACT FROM AUTHOR]

Abstract: The performances of single cell solid oxide fuel cell (SOFC) stacks with Ni/8YSZ (8 mol% Y2O3 doped ZrO2) and Ni/10CGO (10 mol% Gd2O3 doped CeO2) anodes were compared with respect to sulfur poisoning (1–50 ppm) with H2/H2O/N2 fuel mixture at 850 °C. The mechanisms of the sulfur poisoning and regeneration of Ni/8YSZ and Ni/10CGO anodes at the triple phase boundaries are discussed. The effects of various parameters as H2S contamination cycles, H2S concentration, current density, H2O concentration and contamination durations were examined. A mechanism for the progress of the sulfur poisoning in the anode is proposed. It is shown that theoretically it is possible to calculate the nickel surface area accessible for the sulfur adsorption in the anode using H2S poisoning behavior for Ni/8YSZ anodes. The sulfur poisoning mechanisms of Ni/8YSZ and of Ni/10CGO anodes are proposed by taking into account the different oxidation mechanisms of H2 in the anodes considered in previous studies. The higher sulfur resistance of Ni/10CGO is explained with its high mixed ionic electronic conductivity as well as its ability to adsorb H2. Due to these properties CGO can continue electrochemical reactions even when nickel is covered with sulfur. [Copyright &y& Elsevier]

Herein, we reveal for the first time a comprehensive mechanism of poorly investigated electrochemical decomposition of CH 3 NH 3 PbI 3 using a set of microscopy techniques (optical, AFM, PL) and ToF-SIMS. We demonstrate that applied electric bias induces the oxidation of I - to I 2 , which remains trapped in the film in the form of polyiodides, and hence, the process can be conceivably reversed by reduction. On the contrary, reduction of organic methylammonium cation produces volatile products, which leave the film and thus make the degradation irreversible. Our results lead to a paradigm change when considering design principles for improving the stability of complex lead halide materials as those featuring organic cations rather than halide anions as the most electric field-sensitive components. Suppressing the electrochemical degradation of complex lead halides represents a crucial challenge, which should be addressed in order to bring the operational stability of perovskite photovoltaics to commercially interesting benchmarks.