Search

La0.3Ba0.7Zr0.5X0.3Y0.2 (X = Gd, Mn, Ce named as LaBaZrGdY, LaBaZrMnY, and LaBaZrCeY, respectively) SOFC electrolytes were prepared via novel organic and chemical auto-combustion methods, via spinach extract and oxalic acid as chelating agents.

The development of new chemically resistant anodes for protonic ceramic fuel cells (PCFCs) is urgently required to avoid the costly deep hydrogen purification method. Ba0.95Ca0.05Ce0.9Y0.1O3−δ (5CBCY), which is more chemically resistant than BaCaCe0.9Y0.1O3−δ, was here tested as a component of a composite NiO–5CBCY anode material. A preparation slurry comprising 5CBCY, NiO, graphite, and an organic medium was tape cast, sintered and subjected to thermal treatment in 10 vol.% H2 in Ar at 700 °C. Differential thermal analysis, thermogravimetry, quadrupole mass spectrometry, X-ray diffraction analysis, scanning electron microscopy, the AC four-probe method and electrochemical impedance spectroscopy were used for the investigation. The electrical conductivity of the Ni–5CBCY in H2–Ar at 700 °C was 1.1 S/cm. In the same gas atmosphere but with an additional 5 vol.% CO2, it was slightly lower, at 0.8 S/cm. The Ni–5CBCY cermet exhibited repeatable electrical conductivity values during Ni-to-NiO oxidation cycles and NiO-to-Ni reduction in the 5CBCY matrix, making it sufficient for preliminary testing in PCFCs.

The development of new chemically resistant anodes for protonic ceramic fuel cells (PCFCs) is urgently required to avoid the costly deep hydrogen purification method. Ba

International audience; Microstructural changes in grade 2 titanium generated by surface mechanical attrition treatment (SMAT) were studied using positron annihilation lifetime spectroscopy and complementary methods. A significant increase in the mean positron lifetime indicated many lattice defects introduced by SMAT. Two positron lifetime components were resolved in the positron lifetime spectra measured. The longer lifetime revealed the presence of vacancy clusters containing about 3 or 4 vacancies, while the shorter one was attributed to the annihilation of positrons trapped at dislocations. The changes of the positron lifetime indicated a decreasing dislocation density and the presence of a deeper layer with a higher concentration of vacancy clusters at the distance from the treated surface for which the microhardness approached the value for the strain-free matrix. Electrochemical impedance spectroscopy showed the positive effect of SMAT on the corrosion resistance of the titanium studied in a saline environment also after removal of the original oxide layer that was formed during the SMAT.

Thin films of lead sulfide (PbS) are being extensively used for the fabrication of optoelectronic devices for commercial and military applications. In the present work, PbS films were fabricated onto a soda lime glass substrate by using an electron beam (e-beam) evaporation technique at a substrate temperature of 300 °C. Samples were annealed in an open atmosphere at a temperature range of 200–450 °C for 2 h. The deposited films were characterized for structural, optical, and electrical properties. Structural properties of PbS have been studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and Rutherford backscattering spectrometry (RBS). The results of XRD showed that the PbS thin film was crystalline in nature at room temperature with cubic crystal structure (galena) and preferential (111) and orientation (022). The morphology of the thin films was studied by FESEM, which also showed uniform and continuous deposition without any peel-off and patches. EDS analysis was performed to confirm the presence of lead and sulfur in as-deposited and annealed films. The thickness of the PbS film was found to be 172 nm, which is slightly greater than the intended thickness of 150 nm, determined by RBS. Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) spectroscopy revealed the maximum transmittance of ~25% for as-deposited films, with an increase of 74% in annealed films. The band gap of PbS was found in the range of 2.12–2.78 eV for as-deposited and annealed films. Hall measurement confirmed the carriers are p-type in nature. Carrier concentration, mobility of the carriers, conductivity, and sheet resistance are directly determined by Hall-effect measurement. The as-deposited sample showed a conductivity of 5.45 × 10−4 S/m, which gradually reduced to 1.21 × 10−5 S/m due to the composite nature of films (lead sulfide along with lead oxide). Furthermore, the present work also reflects the control of properties by controlling the amount of PbO present in the PbS films which are suitable for various applications (such as IR sensors).

Comparative studies of the physicochemical and electrochemical properties of BaCe0.9Y0.1O3 and Ba0.95Ca0.05Ce0.9Y0.1O3 sintered ceramics are described. The orthorhombic (Pnma) space group was determined for both investigated samples within the temperature range 25–800 °C, using the X-ray diffraction method. A decrease in the cell volume of Ba0.95Ca0.05Ce0.9Y0.1O3 compared to that of BaCe0.9Y0.1O3 was observed within the investigated temperature range. It was found that the partial substitution of calcium for barium, resulting in Ba0.95Ca0.05Ce0.9Y0.1O3, caused an increase in specific free volume and global instability index compared to the original composition BaCe0.9Y0.1O3. Improvement of the chemical resistance of Ba0.95Ca0.05Ce0.9Y0.1O3 in a CO2 gas atmosphere was observed. It was found that Ba0.95Ca0.05Ce0.9Y0.1O3 exhibited a slightly lower level of electrical conductivity than BaCe0.9Y0.1O3 in air as well as in Ar H2 gas atmospheres. The greater chemical resistance of Ba0.95Ca0.05Ce0.9Y0.1O3 in a CO2 gas atmosphere enhances the suitability of the modified material as an electrolyte for fuel cells with proton-conducting ceramics. The electrochemical response of the interface (La0.60Sr0.40)0.95Co0.20Fe0.80O3−δ|Ba0.95Ca0.05Ce0.9Y0.1O3 was also investigated within the applied potential range from −0.05 to −0.5 V in SOFC mode as well as from 0.05 to 0.5 V in SOEC mode); it was found that the current reached a fairly stable value over time.

Ni–P and Ni–P–Re coatings with various concentrations of P and Re were obtained on copper substrate by the electroless deposition from succinate baths. The influence of certain bath parameters on the alloys composition and the deposition rate is presented, followed by the relation between these process parameters as well as the rhenium addition on the surface morphology, microstructure, phase composition and thermal stability of the deposited films. The conditions for the formation of uniform, smooth and compact alloy films on copper substrate were defined. On the basis of X-ray diffraction analysis it can be stated that the alloy containing less than 5.5 wt.% of phosphorus exhibits fully crystalline microstructure for both studied cases: Ni–P and Ni–P–Re alloys. Differential scanning calorimetry analysis performed for the Ni-based alloy layers with and without rhenium additive and the same level of phosphorus are provided, proving, that the addition of rhenium to the Ni–P coatings results in the increase of the crystallization temperature. The increase of the crystallization temperature from 411 °C to 434 °C was noted for NiP5.0 alloy, where the addition of Re was only of 3.7 wt.%.

Comparative studies were performed on variations in the ABO3 perovskite structure, chemical stability in a CO2-H2 gas atmosphere, and electrical conductivity measurements in air, hydrogen, and humidity-involving gas atmospheres of monophase orthorhombic Ba1−xSrxCe0.9Y0.1O3−δ samples, where 0 < x < 0.1. The substitution of strontium with barium resulting in Ba1−xSrxCe0.9Y0.1O3−δ led to an increase in the specific free volume and global instability index when compared to BaCe0.9Y0.1O3−δ. Reductions in the tolerance factor and cell volume were found with increases in the value of x in Ba1−xSrxCe0.9Y0.1O3−δ. Based on the thermogravimetric studies performed for Ba1−xSrxCe0.9Y0.1O3−δ, where 0 < x < 0.1, it was found that modified samples of this type exhibited superior chemical resistance in a CO2 gas atmosphere when compared to BaCe0.9Y0.1O3−δ. The application of broadband impedance spectroscopy enabled the determination of the bulk and grain boundary conductivity of Ba1−xSrxCe0.9Y0.1O3−δ samples within the temperature range 25–730 °C. It was found that Ba0.98Sr0.02Ce0.9Y0.1O3−δ exhibited a slightly higher grain interior and grain boundary conductivity when compared to BaCe0.9Y0.1O3−δ. The Ba0.95Sr0.05Ce0.9Y0.1O3−δ sample also exhibited improved electrical conductivity in hydrogen gas atmospheres or atmospheres involving humidity. The greater chemical resistance of Ba1−xSrxCe0.9Y0.1O3−δ, where x = 0.02 or 0.05, in a CO2 gas atmosphere is desirable for application in proton ceramic fuel cells supplied by rich hydrogen processing gases.

Silver is one of the most promising cathode materials for low temperature (300–500 °C) solid oxide fuel cells. The most important disadvantage of silver is its migration in the electric field. For better understanding of this phenomenon, an in situ observation of the migration mechanism was undertaken with the use of high-temperature microscopes. Scandia stabilised ceria doped zirconia CeScSZ electrolyte prepared from commercial powder was examined before and after silver migration experiments using scanning electron microscope. X-ray diffraction, broadband electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy. The silver electrodes for solid oxide fuel cells were prepared using magnetron sputtering. The described cells under polarisation were examined using a high-temperature low energy electron microscope. Reference cells and post-mortem cells were observed using a scanning electron microscope equipped with high temperature stage. Under polarisation, silver moved inside the electrolyte and along the surface towards the region between electrodes. The structures thus formed were similar to those previously described in the literature; however, direct observation of the deposit growth was unsuccessful. In situ scanning electron microscopy observations of the silver electrode at 650 °C revealed neither melting of the smallest silver particles nor movement of silver structures. Silver migration through the electrolyte caused a reduction in grain interior conductivity of the electrolyte, whereas its grain boundary conductivity remained unaffected.

The high efficiency of solid oxide fuel cells with La0.8Sr0.2MnO3−δ (LSM) cathodes working in the range of 800–1000 °C, rapidly decreases below 800 °C. The goal of this study is to improve the properties of LSM cathodes working in the range of 500–800 °C by the addition of YFe0.5Co0.5O3 (YFC). Monophasic YFC is synthesized and sintered at 950 °C. Composite cathodes are prepared on Ce0.8Sm0.2O1.9 electrolyte disks using pastes containing YFC and LSM powders mixed in 0:1, 1:19, and 1:1 weight ratios denoted LSM, LSM1, and LSM1, respectively. X-ray diffraction patterns of tested composites reveal the presence of pure perovskite phases in samples sintered at 950 °C and the presence of Sr4Fe4O11, YMnO3, and La0.775Sr0.225MnO3.047 phases in samples sintered at 1100 °C. Electrochemical impedance spectroscopy reveals that polarization resistance increases from LSM1, by LSM, to LSM2. Differences in polarization resistance increase with decreasing operating temperatures because activation energy rises in the same order and equals to 1.33, 1.34, and 1.58 eV for LSM1, LSM, and LSM2, respectively. The lower polarization resistance of LSM1 electrodes is caused by the lower resistance associated with the charge transfer process.

The lanthanum strontium cobalt ferrite (LSCF)-Ag composite cathode material was prepared in aqueous solution by new one-step method. In this method silver nanoparticles obtained by the reduction of [Ag(NH3)2]+ complex with sucrose were directly deposited onto the surface of LSCF powder. UV–Vis spectra of supernatant solution taken during synthesis showed the presence of a sharp excitation band near 397 nm attributed to the surface plasmon excitation of silver nanoparticles. Obtained composite powder was sintered to samaria doped ceria electrolyte in one step sintering procedure at 1000 °C. The presence of silver in LSCF cathode facilitates the oxygen reduction. The comparison of impedance spectra of LSCF-Ag cathodes with spectra reported in literature for similar LSCF cathodes shows that this effect is important at lower oxygen partial pressures. The analysis of the electrochemical impedance spectra recorded in the range 10−2–1010 Hz reveals that the second high frequency semicircle ascribed to the electrolyte grain boundary impedance is distorted due to process belonging to oxygen reduction reaction.

A proton-conducting membrane involving modified barium cerate BaCe0.9Y0.1O3 was obtained in the form of gas-tight ceramic tape. Monophase Ca0.05Ba0.95Ce0.9Y0.1O3 (5CBCY) powder and an organic medium consisting of polyvinyl butyral used as a binder, a plasticiser based on carboxylic acid esters, and a mixture of ethanol and methyl ethyl ketone were used to prepare slurry for the tape-casting process. Gas-tight ceramic tapes involving 5CBCY and sintered samples were tested as electrolytes in hydrogen–oxygen button solid oxide fuel cells within the temperature range 500–750 °C. Variations in OCV and ohmic resistance (Rs) were determined within this range. A considerable decrease in Rs value was recorded for 5CBCY tape compared to 5CBCY sintered samples. A series of symmetrical cells with 5CBCY electrolytes was analysed. The lowest ASR values for the investigated cells were found for a newly elaborated LSCF–5CBCY cathode as well as for a Ni–5CBCY anode. These electrode materials appear to be suitable for 5CBCY-electrolyte-supported solid oxide fuel cells.

Results on D. desulfuricans biofilm formation on austenitic-ferritic duplex (2205 DSS) and superaustenitic (904L) stainless steels are presented. Surface characterization including the structure, configuration and chemical composition of biofilms were carried out using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical impedance spectroscopy (EIS) measurements were used to monitor the attachment activity of bacteria on the steels' surface and to determine the effect of bacteria on passivity. It was proved that investigated steels are rapidly colonized by bacteria. The presence of biofilm caused significant ennoblement of 904L steel surface, while retarded the attainment of high passive state of 2205 DSS. XPS analysis revealed significant sulphidation of the biofilm and its layered structure. Accumulation of sulphides and hydroxides was proved in the outermost layer, while the increasing contents of disulphides, organometallic and C N bonds were detected in the internal part of the biofilm. Irreversible bondings between steel matrix and biofilm had also been observed.

NaCsZn 0.5 Mn 0.5 P 2 O 7 powders were prepared by solid state reaction method. The study of the powder structure was conducted by X-ray diffraction (XRD) in temperature range from room temperature (RT) to 700 K. Rietveld analysis of XRD patterns showed that obtained NaCsZn 0.5 Mn 0.5 P 2 O 7 is a mix of three phases: orthorhombic (s.g. Cmc 2 1 ) NaCsMnP 2 O 7 , monoclinic (s.g. P 2 1 /n) NaCsZnP 2 O 7 and monoclinic (s.g. P 2 1 /n) Cs 2 MnP 4 O 12 . In the temperature ranges (400–500) K and (500–600) K the anomalies of lattice parameters for the NaCsMnP 2 O 7 and Cs 2 MnP 4 O 12 phases respectively were found. The electrical properties of the sintered ceramics were investigated from RT to 700 K and in the frequency range 10–3 × 10 9 Hz. The anomalies of electrical conductivity, dielectric permittivity and dielectric losses in investigated temperature ranges in these ceramics were found. This phenomenon can be associated with disordering in the lattices of NaCsMnP 2 O 7 and Cs 2 MnP 4 O 12 compounds.

The paper presents recent advances in Poland in the field of high temperature fuel cells. The achievements in the materials development, manufacturing of advanced cells, new fabrication techniques, modified electrodes and electrolytes and applications are presented. The work of the Polish teams active in the field of solid oxide fuel cells (SOFC) and molten carbonate fuel cell (MCFC) is presented and discussed. The review is oriented towards presenting key achievements in the technology at the scale from microstructure up to a complete power system based on electrochemical fuel oxidation. National efforts are covering wide range of aspects both in the fundamental research and the applied research. The review present the areas of (i) novel materials for SOFC including ZrO2-based electrolytes, CeO2-based electrolytes, Bi2O3 based electrolytes and proton conducting electrolytes, (ii) cathode materials including thermal shock resistant composite cathode material and silver-containing composites, (iii) anode materials, (iv) metallic interconnects for SOFC, (v) novel fabrication techniques, (vi) pilot scale SOFC, including electrolyte supported SOFC (ES-SOFC) and anode supported SOFC (AS-SOFC), (vii) metallic supported SOFC (MS-SOFC), (viii) direct carbon SOFC (DC-SOFC), (ix) selected application of SOFC, (x) advances in MCFC and their applications, (xi) advances in numerical methods for simulation and optimization of electrochemical systems.

The gelcasting method was used to form gastight Ba0.95Ca0.05Ce0.9Y0.1O3 samples proposed for use as proton-conducting electrolytes in solid oxide fuel cells. Methylcellulose was used as an environmentally friendly shaping agent for Ba0.95Ca0.05Ce0.9Y0.1O3 powder in an ethanol solution. Samples of Ba0.95Ca0.05Ce0.9Y0.1O3 were also prepared from the same powder via traditional isostatic pressing, as a reference for cast samples, and sintered in the same conditions. Comparative studies of the physicochemical properties of Ba0.95Ca0.05Ce0.9Y0.1O3 electrolytes, formed by means of these two methods and then sintered at 1550 °C for 2.5 h, were presented and discussed. Using the X-ray diffraction method, only the pure orthorhombic phase of BaCe0.9Y0.1O3 was detected in the Ba0.95Ca0.05Ce0.9Y0.1O3 powder, as well as in the Ba0.95Ca0.05Ce0.9Y0.1O3 sintered pellets formed via both gelcasting (A) and isostatic pressing (B). Thermal effects occurring during heating of methylcellulose, as well as ceramic Ba0.95Ca0.05Ce0.9Y0.1O3 powder, dried cast samples obtained from the prepared slurry, and sintered Ba0.95Ca0.05Ce0.9Y0.1O3 samples, were examined by differential scanning calorimetry, differential thermal analysis, thermogravimetric analysis, and evolved gas analysis of volatile products using a quadrupole mass spectrometer. The measurements were performed within the temperature range of 20–1200 °C in air. Based on dilatometric tests, it was found that the Ba0.95Ca0.05Ce0.9Y0.1O3 cast samples exhibited slightly higher degree of sinterability than the 5CBCY samples obtained by isostatic pressing. In comparison with pressed pellets, higher values of total electrical conductivity in air or in a gas mixture of 5% H2 in Ar were also attained for Ba0.95Ca0.05Ce0.9Y0.1O3 cast samples. The Ba0.95Ca0.05Ce0.9Y0.1O3 samples were used to construct oxygen–hydrogen electrolytes for solid oxide fuel cells. The results of the electrochemical performance of solid oxide fuel cells with Ba0.95Ca0.05Ce0.9Y0.1O3 electrolytes were comparable to the data in the literature on BaCe0.9Y0.1O3 electrolytes. An electrochemical study of a Ba0.5Sr0.5Co0.8Fe0.2O3−δ|Ba0.95Ca0.05Ce0.9Y0.1O3 interface was also performed. Ba0.5Sr0.5Co0.8Fe0.2O3−δ appears to be a suitable cathode material for a Ba0.95Ca0.05Ce0.9Y0.1O3 electrolyte.

Composite cathodes contain Ba0.5Sr0.5Co0.8Fe0.2O3–δ and La0.6Sr0.4Co0.8Fe0.2O3–δ were tested in different configuration for achieving cathode of area specific resistance lower than Ba0.5Sr0.5Co0.8Fe0.2O3–δ and La0.6Sr0.4Co0.8Fe0.2O3–δ cathodes. Electrodes were screen printed on samaria-doped ceria electrolyte half-discs and tested in the three electrode setup by the electrochemical impedance spectroscopy. Microstructure was observed by scanning electron microscopy. The lowest area specific resistance 0.46 and 2.77 Ω cm−2 at 700 °C and 600 °C respectively revealed composite cathode contain Ba0.5Sr0.5Co0.8Fe0.2O3–δ and La0.6Sr0.4Co0.8Fe0.2O3–δ in 1:1 weight ratio. The area specific resistance of this cathode is characterized by the lowest activation energy among tested cathodes.

Results on biofilm formation and microbiologically influenced corrosion induced by pure D. desulfuricans strain on 2205 duplex stainless steel (DSS) are presented. Biofilm development stimulated by DSM642 standard strain was evaluated with reference to their metabolic activity and to the surface characterization including the structure and configuration of the biofilm. Electrochemical techniques (open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves) and X-ray photoelectron spectroscopy (XPS) were carried out to determine the effect of bacteria on the passivity and corrosion resistance of 2205 DSS. The electrochemical results showed that the DSS corrosion resistance was affected in the presence of DSM642 biofilm. This statement was based on the significant decrease in the charge transfer resistance (R1) obtained from EIS and the increase in the measured current densities obtained from potentiodynamic polarization curves. Although the breakdown potentials (Eb) were still high, SEM observations revealed micropits as well as signs of crevice attack on the steel surface. Significant sulphidation of the passive film affected the nature of cathodic behaviour of steel and helped to impede micropit growth. XPS analysis revealed the layered structure of the biofilm. Accumulation of sulphides and hydroxides was proved in the outermost layer, while the increasing contents of disulphides, organometallic and C N bonds were detected along the biofilm thickness in the XPS analysis.

The microstructure and phase composition of Ni-P and Ni-P-Re layers with medium phosphorus content of 8.8 and 8.2 wt. % of P, respectively, and 6.8 wt.% of Re electroless plated on copper substrate were studied. Both of the deposits showed amorphous X-ray profile, however, as it was expected, the presence of small (about 10 nm in size) nanocrystallites was observed in both kinds of plating under transmission electron microscope (TEM). The crystallization temperatures, measured in the range of 298–773 K, significantly increased with rhenium content as well as with increasing heating rate and differed by about 40 K. The activation energy calculated based on the Kissinger’s model in the case of Ni-8.2P-6.8Re plating was 217.7 kJ mol−1 and for Ni-8.8 P was 206.3 kJ mol−1. X-ray diffraction (XRD) measurements of the Ni-P deposits carried out after the heat treatment indicated the presence of the Ni and Ni3P phases, which was confirmed by electron diffraction and high resolution observations in TEM. XRD data concerning Ni-P-Re plating revealed the following phases: Ni, Ni3P, Ni0.21Re0.79, Ni5P2 and NiP, while TEM investigation confirmed the presence of Ni3P, NiP, Ni5P2 so far. Due to the very local information gathered from the TEM, this result needs further studies.

The corrosion resistance of the welds made of QE22, ZRE1, and WE43 rare-earth-metals-containing magnesium alloys was investigated in 0.5% NaCl solution saturated with Mg(OH)2 using the electrochemical methods: linear sweep voltammetry, small amplitude cyclic voltammetry, and electrochemical impedance spectroscopy. These tests elucidated how welding influences the susceptibility to corrosion of that class of magnesium alloys. For the sake of comparison AZ91 magnesium alloy was investigated too. All welds were obtained by tungsten inert-gas welding method. In the case of all investigated alloys welds showed corrosion resistance comparable to the base material. However, all rare-earth-metals-containing magnesium alloys show corrosion resistance inferior to AZ91 alloy. Significant differences in corrosion resistance evaluated by different electrochemical methods were observed.

The Sm0.5Sr0.5CoO3–δ–La0.6Sr0.4FeO3–δ 1:1 composite, obtained by sintering mixture of components, was tested as a prospective cathode material for the oxygen reduction reaction in solid oxide fuel cells. Catalytic activity of the prepared material was characterized using electrochemical impedance spectroscopy at 400, 450, 500, 550, 600, 650, and 700 °C in oxygen and oxygen-argon mixtures in half-cells with Sm0.2Ce0.8O1.9 as the electrolyte. Relatively low activation energies (65.2, 66.9, and 56.3 kJ mol−1 for PO2/P = 1.0, 0.1, and 0.01, respectively) for the reaction polarization resistance were observed. The specific surface area and the pore distribution were measured by N2 adsorption method. The non-localized density functional theory was used in the analysis of the porosity data. The activity of the prepared composite depended on the pore structure which, in turns, depends on the sintering temperature. The best results were obtained for the composite sintered at the temperature of 1000 °C, where significant decrease in porosity is observed. The series of 53 thermal cycles, consisting of heating to 750 °C and cooling to room temperature confirmed the stability of the composite.

The work presents results of the studies performed on electropolishing of pure niobium in a bath that contained: sulphuric acid, hydrofluoric acid, ethylene glycol and acetanilide. After the electropolishing, the specimens were subjected to anodic passivation in a 1moldm(-3) phosphoric acid solution at various voltages. The surface morphology, thickness, roughness and chemical composition of the resulting oxide layers were analysed. Thusly prepared niobium samples were additionally investigated in terms of their corrosion resistance in Ringer's solution. The electropolished niobium surface was determined to be smooth and lustrous. The anodisation led to the growth of barrier-like oxide layers, which were enriched in phosphorus species.

The behavior of a silver electrode contacting Ce0.8Sm0.2O1.9 (samaria-doped ceria or SDC) electrolyte under external cathodic polarization in the temperature range 350–700 °C was examined by means of long-term polarization experiments, scanning electron microscopy, and electrochemical impedance spectroscopy. A silver deposit is formed around the silver cathode via a surface migration mechanism without the occurrence of the gas-phase transport phenomenon during polarization. This results in an increase in both the electrode-electrolyte contact area and the triple-phase boundary length, which in turn causes decreases in charge transfer resistance and electrolyte resistance.

Reduction of oxygen at the silver point electrode|Gd0.2Ce0.8O1.9 interface was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Measurements were performed in the 500–700 °C temperature range, at the atmospheric pressure, in oxygen and in argon/oxygen atmospheres. The results of the experiments are consistent with the mechanism in which the oxygen reduction reaction proceeds through the non-electrochemical adsorption/dissociation step and a two-electron two-step electrochemical reaction with the transfer of the first electron as a rate-determining step. Slow diffusion of oxygen is confirmed by both electrochemical impedance spectroscopy and cyclic voltammetry techniques. New equivalent electrical circuit for the investigated interface is proposed.

Composite cathodes Ag-La0.6Sr0.4Co0.2Fe0.8O3-δ were obtained by two different procedures. In the first procedure porous La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) matrix was prepared by sintering the LSCF paste, the matrix was then saturated with AgNO3 solution and sintered again. Introduced silver crystalized in the form of 10 nm crystallites in the whole LSCF matrix. In the second procedure the paste of silver powder was deposited on the surface of electrolyte and dried. The layer of silver paste was then covered by a layer of the LSCF paste and sintered at 850°C. The following cells were tested: H2|Ni-Ce0.8Gd0.2O1.9|Ce0.8Sm0.2O1.9 LSCF|O2, H2|Ni-Ce0.8Gd0.2O1.9|Ce0.8Sm0.2O1.9|LSCF-Ag|O2 and H2|Ni-Ce0.8Gd0.2O1.9|Ce0.8Sm-O1.9|Ag|LSCF|O2. Introduction of silver interlayer between cathode and electrolyte increased output power by 18-28% whereas introduction of metallic silver into porous LSCF caused increase in power by 14-18%.

Composite cathodes for solid oxide fuel cells composed of metallic silver dispersed in ceramic (La0:8Sr0:2MnO3-σ) matrix were prepared on the surface of solid electrolyte by two-step procedure. First the matrix of controlled porosity was created by sintering mixture of La0:8Sr0:2MnO3-σ powder with the organic polymer beads then the matrix was saturated with AgNO3 solution and sintered again. Such obtained cathodes showed higher electrical conductivity and lower charge transfer resistance in oxygen reduction reaction in comparison to pure ceramic cathodes

The behavior of silver as the solid oxide fuel cell SOFC cathode material was investigated. Ag|Gd0.2Ce0.8O1.9 half cells were cathodically polarized at the temperatures between 300 and 700 °C at the potential of −0.5 V. Changes in the morphology and electronic states of the electrolyte surface on the cathodic side were examined by the Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy. Silver deposits arose around the point where electrodes contact the electrolyte. The negative polarization did not change electronic states of cerium and gadolinium in the electrolyte surface region. The mechanism of the silver migration is proposed.

Singly-doped and co-doped ceria powders with the formula Ce0.8M0.2O1.9 or Ce0.8M0.15Y0.05O1.9, M = Gd, Sm were synthesized using the spray pyrolysis method at 700 °C. X-ray diffraction analysis showed that all obtained powders were pure cubic CeO2-based solid solutions. Scanning and transmission electron microscopy were used to characterize the morphology of CeO2-based powders. It was found that the prepared powders were composed of fully spherical particles ranging in size from ∼0.1 to 1.3 μm. Additional heat treatment of these powders in the temperature range of 700–1000 °C resulted only in small increased particle size. The particles lost their spherical shape at temperatures above 1200 °C. A study of sintering activity of powders prepared in this way was also performed, using the dilatometric method. Finally, CeO2-based samples were sintered at 1500 °C in air for 2 h. The ionic conductivity of Ce0.8M0.2O1.9 and Ce0.8M0.15Y0.05O1.9 M = Gd, Sm sintered samples were studied by AC impedance spectroscopy. It was found that the partial substitution of Y3+ for Gd3+ resulted in increased ionic conductivity of Ce0.8M0.15Y0.05O1.9, M = Gd, Sm compared to Ce0.8M0.2O1.9, M = Gd, Sm. The possibility of using spherical CeO2-based powders for the preparation of screen-printable paste (to be used in turn for the deposition of gas-tight electrolyte films for anode-supported solid oxide fuel cells) was also investigated. The performance of single anode supported solid oxide fuel cells, involving singly doped ceria as Ce0.8Sm0.2O1.9 or Ce0.8Sm0.15Y0.05O1.9 as oxide electrolytes fueled with gaseous hydrogen, was presented and analyzed. The authors also pointed out that the co-doped ceria electrolytes Ce0.8Sm0.15Y0.05O1.9, M = Gd, Sm seem to be also promising oxide electrolytes for construction solid oxide fuel cells, which utilized solid carbon as fuel.

The direct carbon fuel cells with solid oxide electrolyte (DC-SOFC) and anodes deposited by inject printing (EM/DCIJP) were studied. The cells were fed with carbon fuel obtained by the direct RF plasma splitting of methane. Since the (EM/DCIJP)M/DCIJP technology allows easy modification of electrode material, the effect of Cu addition to the Ni–YSZ anode was investigated. The significant improvement of the cell performance with the new anode was observed.

Influence of the short time external polarization of silver electrode contacted Ce0.8Sm0.2O1.9 electrolyte was studied. Silver is moving along the Ce0.8Sm0.2O1.9 surface during the -0.5 V cathodic polarization at 600°C. It caused both the increase of the electrode - electrolyte contact area and the triple phase boundary length but also decrease of electrolyte and polarization resistances. Deposit of silver oxide was found at the place where the electrode polarized at the potential of 0.5 V contacted the electrolyte and around. The decrease of electrolyte and polarization resistance was smaller but more stable in this case. Composite cathodes were obtained on Ce0.8Sm0.2O1.9 electrolyte with the double step sintering procedure. Silver introduced into a La0.6Sr0.4Co0.8Fe0.2O3 cathode improved a performance of a La0.6Sr0:4Co0.8Fe0.2O3|Ce0.8Sm0.2O1.9|Ni cell by 33%.

This work presents the results of the investigations on electropolishing of the Ti–13Nb–13Zr titanium alloy. The electropolishing was conducted in the solution containing ammonium fluoride and sulfuric acid. The influence of electropolishing process parameters on the texture (AFM, SEM) and chemical composition (EDX, XPS) of the surface layer was established. The Ti–13Nb–13Zr alloy after the electropolishing is covered with a thin layer composed mainly of titanium, niobium and zirconium oxides. Electrochemical impedance spectroscopy in 5% NaCl solution was used for the determination of the corrosion resistance of the alloy. The application of the electropolishing increases the corrosion resistance of the Ti–13Nb–13Zr alloy significantly. The increase of the corrosion resistance of the alloy is connected with the smoothing of the surface and with the formation of Ti, Nb and Zr oxides layer on the surface.

Conversion coatings on the magnesium alloy AZ81 were prepared using the phosphate–permanganate baths differing in composition. The corrosion behavior of the coated and uncoated alloys has been investigated by electrochemical impedance spectroscopy (EIS) and linear polarization methods. The choice of proper electric equivalent circuit (EEC) is discussed. The effect of temperature, bath composition and time of conversion as well as etching in acids before application on the corrosion resistance of the coated alloy has been evaluated. The best corrosion resistance was obtained for the samples coated in the bath containing 25 g KMnO 4 , 150 g Na 2 HPO 4 and 50 ml H 3 PO 4 in 1 dcm 3 , applied at 80 °C. Differences in the morphology and composition of coated surfaces were investigated by the scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques and correlated with the corrosion resistance of the samples.

The Pechinni method (A) as well as hydrothermal treatment (B) of co-precipitated CeO2-based gels with NaOH solution were used to synthesise pure CeO2, and CeO2-based solid solutions with formula Ce1−xMxO2, Ce1−x(M0.5Ca0.5)xO2 M = Gd, Sm for 0.15

The oxygen electrode reaction at the interface gold∣yttria stabilized zirconia was investigate using microelectrodes by chronoamperometry and electrochemical impedance spectroscopy, with emphasis put on effect of prolonged polarization of the electrode. Two interesting phenomena were observed: (a) generally, the long-lasting negative polarization resulted in a slow monotonous decrease of the current flowing through the electrode, (b) the reaction mechanism was less complicated for the polarized then unpolarized electrodes, which resulted in a relatively simply equivalent circuit used for modelling the former ones. On the basis of the data obtained, the apparent exchange currents normalized vs. the three phase boundary length and Tafel slopes were determined. The methods of determining the three phase boundary length were discussed. The reconnaissance data obtained for the Pt microelectrode are also reported.

The reactions occurring at the electrodes of Pt|YSZ|Au cell fed with a mixture of CH4+air were investigated at 600–850∘C. The electrodes of this cell were made from Pt and Au wires, providing a small contact area between metal and YSZ (quasi-point electrodes). The dependences of the cell voltage on the composition of gas mixture and time were studied. A sequence of chemical and electrochemical reactions was proposed to explain the observed abrupt variation of the cell voltage from positive to negative values. Also the impedances of the Pt and Au electrodes were measured and analysed in order to justify the proposed mechanism of reactions.

The processes occurring at NiO and CoO monocrystalline electrodes in a basic Li+Na carbonate melt have been investigated at 923 K by electrochemical impedance spectroscopy (EIS). Four various equivalent circuits (two for the NiO electrode and two for the CoO electrode) were employed to examine the data obtained. These equivalent circuits consist of elements that represent the reduction–oxidation of oxygen entities dissolved in the melt, incorporation–extraction of Li + ions into/from the crystallographic network of either Ni or Co oxides and semicondutance properties of electrode materials. The effect of time elapsing since the electrode immersion on the behaviours of these elements was analysed to verify a reliability of the applied models.

The oxygen electrode reaction at a gold electrode in a molten 53 mol% Li 2 CO 3 +47 mol% Na 2 CO 3 eutectic has been studied at 923 and 1000 K by electrochemical impedance spectroscopy. The studies were generally performed in a basic melt, i.e. at the level of the CO 2 partial pressure corresponding to the thermal decomposition pressure of the carbonate ion. It was found that a semi-infinite diffusion controlled the rate of the electrode process and a modified Randles–Ershler model described the data obtained well. The dependence of the Warburg coefficient at the rest potential on the partial pressure of oxygen over the melt was analysed to verify an involvement of peroxide/oxide ions in the reduction/oxidation process at both the temperatures. Further analysis of the data allowed us to determine γ = D (O 2 2− ) 1/2 C *(O 2 2− )/ D (O 2− ) 1/2 C *(O 2− ), where C *(O 2 2− ) and C *(O 2− ) are the bulk concentrations of O 2 2− and O 2− ions and D (O 2 2− ) and D (O 2− ) are their respective diffusion coefficients. The C *(O 2 2− ) and C *(O 2− ) were also estimated. The conclusion about the reaction mechanism was corroborated by the effect of electrode potential on the Warburg coefficient.

The concept of mixed potential was used to explain phenomena observed during Ni oxidation in molten carbonates. The effect of acidity of (Li+Na) 2 CO 3 melt on the open-circuit potential characteristic of the electrode consisting of thin layer of Ni on Au was examined. These studies and scanning electron microscopy confirmed that spontaneous oxidation of Ni to NiO in basic molten carbonates proceeds through formation of an intermediate product.

To elucidate the mechanism of Li incorporation into NiO in molten carbonates, the open-circuit potential of the cell: O 2 +CO 2 (g) ∣ Ni or Co oxide (s) ∣ Li 2 CO 3 +Na 2 CO 3 (1) ∣ Au (s) ∣ O 2 +CO 2 (g) was examined for porous Li x Ni 1− x O (0≤ x ≤0.5), LiCoO 2 and Co 3 O 4 electrodes. These studies and X-ray diffraction examination of the samples before and after submersion in carbonate melt indicated that LiNiO 2 is formed in small amounts as an ultimate product of the reaction. Consequent extraction of Li + ions from LiNiO 2 formed this way occurs due to polarisation of the electrode by the electro-reduction of oxygen dissolved in molten carbonates and results in turn in partial decomposition of LiNiO 2 .