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In this work, the effect of nanocatalyst infiltration on the SOFC performance and electrode reaction characteristics was comprehensively investigated by the application of electrochemical impedance (EI) spectroscopy. The Ni-8 mol% yttria-stabilized zirconia (YSZ) anode-supported cell was fabricated using a YSZ electrolyte, and a mixed ionic electronic conductor (MIEC) La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF6428) cathode. The EI spectra were measured under various conditions (0.02 ≤ pO2,cat./atm ≤ 1; 0.2 ≤ pH2Oano./atm ≤ 0.6) in the temperature range of 600–800 °C. With the application of the equivalent circuit model (ECM) fitting using a transmission line model (TLM), the parameters (Rs,el, Rp,el, Cp,el, and QW) expressing the activation polarization of the cathode and anode were analyzed, and the chemical diffusion coefficients (), the reaction constant (k), and the effective length of the electrode reaction were calculated. A similar anode-supported cell was fabricated in which the LSCF6428 cathode was infiltrated by a monodispersed Sm0.5Sr0.5CoFe3−δ (SSC55) nanocatalyst using a sol–gel method. The cathode-infiltrated cell was measured under the same thermodynamic conditions. Each electrode was analyzed by using the TLM to evaluate the effect of the nanocatalyst on the SOFC performance and electrode reaction characteristics. With the application of nanocatalyst infiltration, the parameters (Rs,cat. and Rp,cat.) of the cathode were found to decrease by approximately one order and 40%, respectively. Similarly, Cp,cat. also fell by approximately one order of magnitude. From this investigation, it was confirmed that the diffusion of surface ions had a more significant contribution to conduction than the diffusion of bulk ions by the SSC55 nanocatalyst.

For achieving a sustainable energy future, energy consumption through renewable sources needs to be maximized and greenhouse emissions should be radically reduced. Automotive exhausts sharing the largest global NOX emissions must meet regulated standards by after-treatment systems (ATS) equipped with smart electronic feedback loops through on-board NOX monitoring. Herein, we demonstrate an efficient (Dy, W) co-doped Bi2O3-based electrochemical sensing architecture equipped with Ln2NiMnO6 double perovskite oxides (DPOs) as electrode materials for selective nitric oxides (NO) detection. The sensor configuration facilitates operation in a wide temperature range (325 °C–500 °C) with high sensitivity of 50 mV/decade, a response time below 60 sec. and detection abilities as low as 200 ppb. While investigating the impact of rare-Earth cations, a predominant Ni3+–O–Mn3+ interaction and acquisition of optimal eg 1 electron configuration of transition metal atoms in La2NiMnO6 was found responsible for improved electrocatalytic and redox chemical activity that substantiates the sensing behavior. The study carefully scrutinizes the sensing mechanism to abide by the mixed-potential model. Moreover, the durability assessed over a month of operation supported the applicability of presented sensing elements in on-board NOX monitoring systems.

A mixed-potential based sensor utilizing transition metal oxide (Ni, Co, Fe)-tin oxide nanocomposite sensing electrodes are fabricated for the first time and investigated for the gas sensing performance towards the highly toxic nitrogen dioxide. The nanocomposites are synthesized by solvo-combustion route and characterized for the physical, gas sensing and electrochemical properties in a temperature range of 600–700 ℃. The sensor equipped with Fe2O3-SnO2 (Fe:Sn = 2:1) nanocomposite sensing electrodes sintered at 1000 ℃ shows the maximum response of 60 mV towards 100 ppm NO2 with a relatively fast response and recovery dynamics at an operating temperature of 650 ℃. The sensor also shows a linear dependence of response over the logarithm of NO2 concentration with a sensitivity of ∼44 mV/decade. Additionally, the oxygen concentration dependence, cyclability and cross-sensitivity towards interfering gases are also investigated. Finally, the sensing mechanism and electrochemical activity of the sensing electrodes are studied using polarization curve measurement and electrochemical impedance spectroscopy.

The Influence of sintering temperature on the physical, electrochemical and sensing properties of α-Fe2O3-SnO2 nanocomposite sensing electrode for a mixed-potential type NOx sensor is investigated. The α-Fe2O3-SnO2 nanocomposite was synthesized by a solution combustion route and sintered at temperatures 900, 1000, 1100 and 1200 °C to form the sensing electrodes of a stabilized-zirconia based mixed-potential type NOx sensor. The influence of sintering temperatures on the physical properties was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption isotherm measurements. The gas sensing measurements were conducted at an operating temperature of 650 °C. A systematic increase in the response/recovery times was observed with an increase in the sintering temperature from 900 to 1200 °C. An optimum microstructure with a low surface area and large pore size leading to high electrochemical reactions at the interface and low heterogenous gas-phase decomposition of NO2 resulted in the maximum response magnitude (ΔV) and sensitivity for the electrode sintered at 1000 °C. Furthermore, the effect of sintering temperature on the electrochemical activity of the sensing electrode and its co-relation with the sensing properties was studied by dc polarization curve measurement. Moreover, the microstructure, sensing response, sensitivity, dynamics and O2 conc. dependence of the presented mixed-potential type NOx sensor is critically dependent upon the sintering temperature of the sensing electrodes.

High proton conductivity and chemical stability of electrolyte materials are the bottleneck challenges to be overcome for the practical feasibility of protonic ceramic fuel cells (PCFCs). Therefore, the fundamental electrochemical properties of electrolyte materials under cell operating conditions are critical. In this study, the partial conductivities, mobilities, and equilibrium constants of the electrolyte BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb1711) are determined by a DC four-probe conductivity measurement in the temperature range of 600–750 °C. The electrolyte acts as a proton conductor due to the dominant proton regime with a conductivity of 1.3 × 10−2 S cm−1 under an air atmosphere (3% H2O) at 600 °C, whereas mixed-ion conduction appears from 750 °C. The theoretical power densities were calculated from both oxygen ion and proton chemical potential gradient profiles based on the partial conductivities of the mobile charge carriers in the electrolyte. The results show a theoretical peak performance of around 5.28 W cm−2 for a 10 μm thick electrolyte at 600 °C without considering any electrode polarization. Most importantly, at this temperature, the peak performance of the BZCYYb1711 electrolyte is remarkable, about two times higher than that of conventional oxygen ion conductors, yttrium doped zirconia (YSZ) and gadolinium doped ceria (GDC), as an electrolyte for SOFCs. This indicates that the perovskite proton conductor BZCYYb1711 is an excellent candidate for a protonic fuel cell operated at intermediate temperatures (≤600 °C). Consequently, our work provides performance limits based on the transport properties of the electrolyte as a guideline for the further development of suitable electrode materials for PCFCs.

The thermodynamic activity of Li2O in Li0.23La0.61TiO3 (LLT) was measured by an electrochemical galvanic cell using YSZ as the reference electrode to determine the phase boundary of reaction of dif...

We have designed the solid-state electrochemical mixed potential type NiO and yttrium-stabilized zirconia (YSZ) composite based sensing electrode for selective detection of NOx at elevated temperatures. The planner NiO-YSZ composite sensing electrode could detect NOx even at 400 °C, with acceptable response/recovery rates. The change in emf values of the sensor varied linearly with NOx concentrations on a logarithmic scale in the range of 5–100 ppm. The response characteristic of the sensor was improved by modifying the surface with different vol% of pore former. As a result, obtained porous electrodes showed better response characteristics concerning speed and response owing to higher porosity. To improve response kinetics of porous NiO-YSZ electrode, NiO nanoparticles are infiltrated into an optimized NiO-YSZ sensing electrode surface by controlled urea/cation infiltration method. The experimental results demonstrated that NiO nanoparticles infiltrated NiO-YSZ sensor electrode reveal remarkably high emf response to NOx compared that of planar electrode, suggesting that NiO nanoparticles introduction can significantly enhance catalytic activity and electrochemical performance of NiO-YSZ electrode. Finally, the porosity effect of electrode subtracts (YSZ) with NOx gases response and recovery kinetics was examined under the optimum operating temperature at 400 °C. The sensing mechanism based on the mixed potential for the surface modified NiO-YSZ composite sensing electrode was discussed based on the obtained result of sensing characterizations.

This paper reports a systematic investigation of the radical scavenging behaviour of ceria with different morphological shapes inside Nafion membrane. All the ceria nanostructure is synthesized using a template-free hydrothermal route. Distinct crystal planes of CeO2 have different numbers of broken bonds and reaction sites having different surface energies. So, the preparation of CeO2 with various uncovered planes may enhance its scavenging activity. The crystal structure, morphology, and lattice structure are investigated using transmission electron microscopy (TEM), and x-ray diffraction (XRD). The results show that the radical scavenging efficiency of ceria strongly depends on the active surface plane, and decreases in the following order: nanorods > nanocube > nanosphere. Furthermore, the concentrations of surface oxygen vacancies and lattice cerium (III) are correlated with the morphology of the nanoparticles. This relationship clarifies the vital scavenging mechanism of CeO2 that mitigates degradation inside the polymer electrolyte membrane. This is because the inherent lattice strain on the active planes of nanosized ceria with different shapes affects their surficial reactions. The existence of prominent concentration of oxygen vacancy in the nanometric dimension of ceria leading to greater Ce3+ generation by exposed active phase CeO2 nanoparticles is key to achieve a durable hybrid Nafion membrane.

This work systematically investigates the oxygen nonstoichiometry, defect structure and mass/charge transport properties of Ba0.95La0.05FeO3−δ (BLF). Thermogravimetric measurement and coulometric titration were performed to determine change in oxygen nonstoichiometry (δ) with oxygen partial pressure ( P O 2 ) in 10−17 ≤ ( P O 2 /atm) ≤ 0.21 and 850 ≤ (T/°C)≤900 range. The δ− P O 2 −T plot showed “S-type” shape with a crossover plateau around δ ≈ 0.475. Defect modelling was used to explain the nonstoichiometry data and partial molar thermodynamic quantities for oxygen were determined. The DC 4-probe conductivity measurement was performed which showed a typical semiconductor-to-metal transition with temperature around the conductivity maxima at 450 °C. Electrical conductivity relaxation (ECR) measurement was performed to extract partial ionic conductivity, chemical diffusivity and surface exchange kinetics of oxygen ion by using Nernst-Einstein equation and Fick’s law. Isothermal chemical expansion was measured by dilatometry measurement in the range of 10−2 ≤ ( P O 2 /atm) ≤ 0.21 and 850 ≤ (T/°C) ≤ 950.

Because of a high global energy demand and challenging sustainability requirements, hydrogen has been promoted as a clean and green energy carrier allowing the potential replacement of nonrenewable fossil fuels. Hydrogen is a renewable energy carrier that does not contribute to CO2 emissions, and it holds the highest gravimetric energy density. It can be produced by the electrochemical splitting of water into hydrogen and oxygen molecules. Herein, we investigate the bifunctional activity of bimetallic oxide, sulfide, and selenide nanostructures in water electrolysis. Spinel-type, phase-pure NiCo2O4, NiCo2S4, and NiCo2Se4 with comparable morphological properties were synthesized by a hydrothermal method. The electrocatalytic characterization of NiCo2Se4 was found to demonstrate higher oxygen and hydrogen evolution reaction activities (245 mV and 122 mV @ 10 mA cm−2, respectively) compared to those of NiCo2O4 and NiCo2S4. Furthermore, a lab-scale water-splitting system was fabricated to examine the bifunctional properties of bimetallic nanostructures. A NiCo2Se4-based water-splitting system was found to require a cell voltage of 1.58 V, which is lower than that required by NiCo2S4 (1.64 V)- and NiCo2O4 (1.75 V)-based systems. In summary, this study explores bimetallic NiCo2Se4 as an efficient electroactive material that can be employed in various electrochemical energy systems.

High temperature co-electrolysis of steam and CO2 based on solid oxide electrolysis cell (SOEC) to produce syngas as a feedstock for the well-known Fischer-Tropsch process is the main aim of the present research. Here Ni-8YSZ/8YSZ/LSCF6428-GDC button cells have been fabricated and the effect of the different microstructural parameters like air electrode thicknesses, fuel electrode porosities, adhesion layer and thermodynamic parameters like gas composition, temperature, on the performance of SOEC has been investigated systematically. The SOEC with 10 μm air electrode thickness, functional layer, fuel electrode having 20 vol% PMMA content, addition of YSZ-GDC adhesion layer gives the better performance in overall results and the voltage obtained for this SOEC at current density of 0.8 A.cm−2 is ~1.25 V at 800°C in 49% N2, 5% H2, 23% CO2 and 23% H2O gas mixture at fuel electrode side. To identify the electrochemical processes occurring at the electrodes of SOEC, distribution function of relaxation time (DRT) analysis of the electrochemical impedance (EIS) data is carried out.

Decreasing the operating temperature leads to an issue of high polarization that results in slow electrode kinetics. Infiltration of multi-cation oxide nanoparticle catalyst layer over the cathode backbone can provide low activation energy in catalyzing several electrochemical processes. The adoption of cetrimonium bromide(CTAB)-amino acid (glycine) route can become an efficient route to infiltrate particle with proper stoichiometry due to three-dimensional network forming nature owing to the zwitterionic form of the amino acid. Herein, we report a novel route for the development of discrete Sm0.5Sr0.5CoO3-δ(SSC) nanoparticles on the cathode backbone. In particular, the full cell shows enhancement in electrochemical property with a power density of 1.57 W cm−2 at 700 °C and 100 h durability test under 1 A cm−2. These observations indicate that the selection of the CTAB-amino acid route for the infiltration process of SSC nanoparticle on the surface La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF6428) backbone is a significant step towards electrochemically viable SOFC performance improvement.

Despite several disadvantages with the electronic conduction of ceria, researchers report the high performance of ceria-based solid oxide fuel cells (SOFCs) at intermediate temperatures with advanced cathode materials. However, it appears the long-term stability of ceria-based SOFCs in the anode-supported cell configuration have still not been proved experimentally at practical operating conditions. In particular, the chemical expansion of ceria electrolytes can cause potentially irreversible failure of SOFCs under large P O 2 gradients. Hence, we investigate the degradation behavior of NiO-Nd0.1Ce0.9O2-δ anode-supported cells with Nd0.1Ce0.9O2-δ electrolyte in dynamic electrical modes, load trip (0.7–0 A cm−2), load cycle (0.2–0.12 A cm−2), and constant load operation (0.2 A cm−2), at 650 °C. We identify the specific degradation phenomenon of ceria-based cells by analyzing the electrochemical characteristics in post-mortem investigations after durability testing under various electrical load conditions. Additionally, we suggest a possible operation strategy to mitigate the performance degradation of cells under various electrical stresses through understanding of the main degradation mechanism.

The electrolyte is an important component in determining the performance of Fuel Cells. Especially, investigation of the conduction properties of electrolytes plays a key role in determining the performance of the electrolyte. The electrochemical properties of Yttrium stabilized zirconia (YSZ) were measured to allow the use of this material as an electrolyte for solid oxide fuel cells (SOFC) in the temperature range of 700-1000℃ and in 0.21 ≤ pO₂/atm ≤ 10 ?23 . A Hebb-Wagner polarization experimental cell was optimally manufactured; here we discuss typical problems associated with making cells. The partial conductivities due to electrons and holes for 8YSZ, which is known as a superior oxygen conductor, were obtained using I-V characteristics based on the Hebb-Wagner polarization method. Activation energies for holes and electrons are 3.99 ± 0.17 eV and 1.70 ± 0.06 eV respectively. Further, we calculated the oxygen ion conductivity with electron, hole, and total conductivity, which was obtained by DC four probe conductivity measurements. The oxygen ion conductivity was dependent on the temperature; the activation energy was 0.80 ± 0.10 eV. The electrolyte domain was determined from the top limit, bottom limit, and boundary (p=n) of the oxygen partial pressure. As a result, the electrolyte domain was widely presented in an extensive range of oxygen partial pressures and temperatures.

The impedance of Ni-YSZ cermet electrodes was investigated as a function of different partial pressure of hydrogen and water. The impedance spectra for the hydrogen/water reaction show two reactions by DRT analysis. Reaction at high-frequency region was assigned to transport of electrode – oxidation reaction within the electrode structure and the electrode / electrolyte interface. Whereas low frequency response is the adsorption of a gaseous H2O molecule from the gas phase onto the active electrode site. The data are analyzed using an equivalent circuit representing two parallel RC. The values of activation overpotential are separated under the fixed current load, which are well-fitted to the Butler-Volmer equation. Under the current load, the variation of exchange current density ( ) with pO2 indicated that the total reaction-rate is determined by charge transfer reaction at the high temperature.

This study focuses on mechanisms and symptoms of several simulated failure modes, which may have significant influences on the long-term durability and operational stability of intermediate temperature-solid oxide fuel cells (IT-SOFCs), including fuel/oxidation starvation by breakdown of fuel/air supply components and wet and dry cycling atmospheres. Anode-supported IT-SOFCs consisting of a Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF)-Nd 0.1 Ce 0.9 O 2-δ (NDC) composite cathode with an NDC electrolyte on a Ni-NDC anode substrate are fabricated via dry-pressings followed by the co-firing method. Comprehensive and systematic research based on the failure mode and effect analysis (FMEA) of anode-supported IT-SOFCs is conducted using various electrochemical and physiochemical analysis techniques to extend our understanding of the major mechanisms of performance deterioration under SOFC operating conditions. The fuel-starvation condition in the fuel-pump failure mode causes irreversible mechanical degradation of the electrolyte and cathode interface by the dimensional expansion of the anode support due to the oxidation of Ni metal to NiO. In contrast, the BSCF cathode shows poor stability under wet and dry cycling modes of cathode air due to the strong electroactivity of SrO with H 2 O. On the other hand, the air-depletion phenomena under air-pump failure mode results in the recovery of cell performance during the long-term operation without the visible microstructural transformation through the reduction of anode overvoltage.

In recent years, the environmental friendly solid oxide fuel cell (SOFC) has been considered as one of the most efficient power generation systems. During the SOFC operation, the over potential is mainly given by the cathodic oxygen reduction reaction. In this respect, the mechanism of oxygen reduction on the Electrode is important to reveal. Specially, employing ac-impedance spectroscopy which provides an exceptionally is powerful tool for separating the dynamics of several electrode processes with different relaxation times. The present work considers the oxygen reduction reaction on the porous mixed conducting La0.1Sr0.9Co0.8Fe0.2O3-δ (LSCF1982) electrode by using ac-impedance spectroscopy. Firstly, to attain a mixed conducting state of LSCF1982, the ac-impedance spectra measured at various temperatures and oxygen partial pressures were quantitatively analyses by employing the theoretical impedance model developed for oxygen reduction on the mixed conducting electrode. All the measured impedance spectra simply consisted of two depressed arcs which overlapped slightly over the whole T and pO2 ranges. The analysis of the ac-impedance spectra by employing discrete Fourier relaxation transformation (DFRT) allowed us to successfully differentiate the individual reaction steps. This indicates that the overall cathode reaction proceeds by the following two processes: charge transfer reaction and subsequent migration of oxygen vacancy. It is also shown, that the magnitude of the high frequency arc decreased significantly with increasing T, but it remained nearly constant regardless of pO2: In contrast, the low-frequency arc remained almost unchanged in magnitude irrespective of the value of T, while it was highly dependent on the value of pO2. From the experimental results that it is thus deduced that the high frequency arc is attributed to the charge transfer reaction at the TPBs, and the low-frequency arc is associated with diffusion of adsorbed oxygen atom along the electrode/gas interface. Figure 1 shows the steady-state current of the oxide anodes as a function of the electrode potential and aO,int. According to Wang and Nowick [1], the rate determining step determined to exchange current density value as a function of both temperature and oxygen partial pressure. i0 ∝pO2 n The n - value in a relation gives information about the type of species involved in the electrode reaction. The n values have 1 if the rate limiting step is diffusional process of molecular oxygen, 1/2 for dissociative adsorption and 1/4 for charge transfer process depending on the conditions for Langmuir adsorption isotherm. In this study for LSCF1982, the slopes of current exchange density were turned out to be 1/4 at 550 to 650oC. This indicated that the rate limiting step for the electrochemical oxygen reduction in this temperature range is the charge transfer process. In the present work, the oxygen reduction reaction on the porous LSCF1982 electrode was examined by means of analysis of the ac-impedance spectra and DC polarization. In addition, we’ll discuss the other technic like cathodic potentiostatic current transients and Gerisher impedance modeling. Reference [1] Da. Yu. Wang and A. S. Nowick, J. Electochem. Soc., 126, 1155 (1979) Acknowledgement This work was supported by Solid Oxide Fuel Cell of New & Renewable Energy R&D Program (20123010030010) under the Korea Ministry of Knowledge Economy (MIKE)

We report the electrochemical hydrogen charge/discharge properties of electrodes containing crystalline and amorphous FePO 4 as active material in KOH electrolyte. Crystalline and amorphous FePO 4 were synthesized by an alcohol-assisted precipitation method, and the powders obtained were characterized by X-ray diffraction. X-ray photoelectron spectroscopy is used to investigate the mechanism of hydrogen charge/discharge behavior of FePO 4 . The electrochemical hydrogen charge/discharge properties of electrodes containing crystalline and amorphous FePO 4 were investigated for potential application as negative electrodes in rechargeable hydrogen batteries. In galvanostatic discharge/charge mode at 25 °C, the crystalline FePO 4 showed a maximum discharge capacity of 109 mA h g −1 , while the amorphous FePO 4 showed a maximum discharge capacity of 81.4 mA h g −1 . The electrochemical kinetic properties, exchange current density, and proton diffusivity were calculated using linear polarization measurement and the potential-step method.

In this work, we studied the hydrogen storage properties of some La 0.1 Sr 0.9 Co 1− y Fe y O 3− δ perovskite oxides for the application in Ni–H batteries. Sr-doped La 0.1 Sr 0.9 FeO 3− δ (LSF), La 0.1 Sr 0.9 CoO 3− δ (LSC) and La 0.1 Sr 0.9 Co 0.8 Fe 0.2 O 3− δ (LSCF) oxides were synthesized by conventional solid state method and were selected as anode materials for Ni–H battery. Their electrochemical hydrogen charge/discharge properties of oxide electrodes were investigated and exchange current density and proton diffusivity were calculated using linear polarization measurement and the potential-step method, respectively. X-ray photoelectron spectroscopy (XPS) analysis was used to show the changes in oxidation states of transition metal ions during charging/discharging process. The proton diffusion rates for LSF, LSC and LSCF were 6.73 × 10 −17 , 1.45 × 10 −16 and 2.16 × 10 −16 cm 2 s −1 , respectively.

Undoped orthorthombic LaFeO 3 and monoclinic LaCoO 3 oxides were selected as an anode material for Ni–H battery due to their high electron conductivity by multivalent transition status of B-site cation. Both groups of oxides were prepared by a conventional solid-state reaction method, and their electrochemical charge/discharge properties were investigated. The electrochemical kinetic properties, exchange current density, and proton diffusivity were also extracted using linear polarization measurement and the potential-step method. X-ray photoelectron spectroscopy (XPS) analysis was used to measure the oxidation state of the transition metal in the specimens. A non-linear least-square fitting deconvoluted the peaks, suggesting that the valence state of Fe and Co in the sample was mainly +3. The hydrogen diffusion rate was also estimated using the potential-step method, giving 5.42×10 −16 and 5.72×10 −16 cm 2 s −1 for LaCoO 3 and LaFeO 3 , respectively which are an order of magnitude larger than that of Sr doped LaFeO 3 oxide electrodes.

The temperature dependence of the chemical diffusion coefficient and the surface exchange coefficient of LSCF1982 is successfully determined from the D.C. conductivity relaxation in the temperature range of 500 ≤ T/°C ≤ 700 and an oxygen partial pressure of 0.21 atm. The kinetic values of chemical diffusion coefficient ( D ˜ ) and surface exchange coefficient (k) are 1.85 × 10−5 cm2 s−1 and 2.42 × 10−4 cm s−1 at 650 °C, respectively. The electrochemical properties of La0.1Sr0.9Co0.8Fe0.2O3−δ (LSCF1982) as a cathode for ceria based IT-SOFC are successfully characterized by I–V performance measurement and electrochemical impedance spectroscopy (EIS) in terms of cathode microstructure effects by using microwave heat treatment. The cell with microwave heat-treated cathode shows the higher performance than conventional heat treated cathode. At 650 °C the open circuit potential (OCP) and maximum power density are respectively 0.753 V and 1.79 W cm−2 under 150 sccm of wet hydrogen and air gas flow conditions, and the ohmic and electrode area specific resistance (ASR) are 0.037 and 0.014 Ω cm2, respectively.

The real time detection of quantitative oxygen release from the cathode is performed by in-situ Gas Chromatography as a tool to not only determine the amount of oxygen release from a lithium-ion cell but also to address the safety concerns. This in-situ gas chromatography technique monitoring the gas evolution during electrochemical reaction presents opportunities to clearly understand the effect of surface modification and predict on the cathode stability. The oxide cathode, 0.5Li2MnO3∙0.5LiNi0.4Co0.2Mn0.4O2, surface modified by amorphous cobalt-phosphate nanoparticles (a-CoPO4) is prepared by a simple co-precipitation reaction followed by a mild heat treatment. The presence of a 40 nm thick a-CoPO4 coating layer wrapping the oxide powders is confirmed by electron microscopy. The electrochemical measurements reveal that the a-CoPO4 coated overlithiated layered oxide cathode shows better performances than the pristine counterpart. The enhanced performance of the surface modified oxide is attributed to the uniformly coated Co-P-O layer facilitating the suppression of O2 evolution and offering potential lithium host sites. Further, the formation of a stable SEI layer protecting electrolyte decomposition also contributes to enhanced stabilities with lesser voltage decay. The in-situ gas chromatography technique to study electrode safety offers opportunities to investigate the safety issues of a variety of nanostructured electrodes.

The chemical diffusivity and surface exchange constant of La 0.1 Sr 0.9 Co 0.8 Fe 0.2 O 3 − δ (LSCF1982) were successfully extracted by using the chemical expansion relaxation method, and the oxygen nonstoichiometry was determined by electrochemical coulometric titration as a function of oxygen partial pressure (pO 2 ) and temperature. The oxygen chemical diffusivity and surface exchange constants were 3.16 × 10 − 4 cm 2 /s and 6.31 × 10 − 3 cm/s at 1000 °C in air, respectively. These values and the activation energies for oxygen diffusion were in good agreement with our own previously reported values determined from the 4-probe D.C. conductivity relaxation method. The oxygen nonstoichiometry was increased with decreasing pO 2 and increasing temperature, due to the thermal and chemical release of lattice-site oxygen from the lattice sites. The oxygen self-diffusion coefficient and ionic conductivity were successfully extracted from the relation between the oxygen nonstoichiometry and the chemical diffusion coefficient, and are best expressed by the following equations: D O / cm 2 /s = ( 1.75 ± 0.05 ) × 10 − 4 exp − 0.68 ± 0.10 eV kT | pO 2 = 0.21 atm σ ion T / cm 2 /s K − 1 = ( 4.01 ± 0.02 ) × 10 5 exp − 0.65 ± 0.04 eV kT | pO 2 = 0.21 atm .

Pd76Ag24 nanoparticles with high purity and a face-centered cubic structure were prepared using a solvothermal method. The lattice parameter of the Pd77Ag23 nanopowders (space group 225Fm3m) was calculated to be a = 3.9382 A. The primary particle size was calculated to be 7.7 nm from the X-ray line width using the Scherrer formula, and the interplanar distances was estimated to be 2.272 and 2.000 A based on indexing on the (111) and (200) plane, respectively. These values are slightly larger than those of pure Pd and smaller than Ag in the (111) plane. The linear relationship of the hydrogen permeation flux with the square root of the hydrogen partial pressure gradient across a 0.26-mm-thick Pd/Ag-YSZ cermet membrane confirmed the major hydrogen transport through the Pd/Ag phase of cermet membranes. The Pd/Ag-YSZ cermet membranes showed significantly higher hydrogen permeation flux than the Pd-YSZ cermet membrane, even though the activation energy for the Pd/Ag alloy cermet membranes showed slightly higher values than that of the Pd cermet membranes. The hydrogen–oxygen dual flux through Pd/Ag-YSZ cermet membranes was confirmed by the maximum hydrogen production by combining the ability of hydrogen production from water with the function of hydrogen separation on composite membranes

In an effort to develop alternative anode materials based on mixed conducting ceramics capable of offering high mixed ionic–electronic conductivity, stability to redox cycles, and limited activity for carbon formation to Ni/YSZ cermets, CaMoO 3 ceramics for application as a solid oxide fuel cell (SOFC) anode material were synthesized as a function of temperature and oxygen partial pressure ( p O 2 ). CaMoO 3 perovskite-dominant powders were obtained by reducing the CaMoO 4 showing a structure of orthorhombic unit cells with the following lattice parameters: a = 5.45 A, b = 5.58 A, and c = 7.78 A. The equilibrium total conductivity of CaMoO 3 , measured by DC 4-probe method in 5% H 2 /balance N 2 condition ( p O 2 ≈ 10 −22 atm) at various temperatures, decreased with increasing temperature below 400 °C, indicating metallic properties with an activation energy of 0.028 eV. Between 400 °C and 600 °C, the equilibrium total conductivity slightly increased, and finally sharply decreased at 800 °C. The Mo metal precipitation during measurement was thermodynamically proved by the predominance diagram for CaMoO 3 . Finally, a fuel cell with CaMoO 3 anode exhibited poor performance with a maximum power density of only 14 mW/cm 2 at 900 °C, suggesting that further research is needed to enhance the ionic conductivity and thus improve the catalytic properties.

The proton conducting electrolyte cerium pyrophosphate was synthesized by digesting cerium oxide with 85% H3PO4. The crystal structure and phase stability of the material were analyzed by X-ray diffraction and thermogravimetric analysis/differential thermal analysis (TGA/DTA), and the microstructure was analyzed by scanning electron microscopy (SEM). The electric conductivity behavior of CeP2O7 sintered pellets was analyzed by electrochemical impedance spectroscopy (EIS) and modulus spectroscopy. The activation energies for migration (Eω) and dc conduction (Eσ) calculations indicates that the charge carriers responsible for conductivity and relaxation are same and the concentration of charge carries is independent of temperature. The variation of conductivity with temperature was studied in dry and humid atmosphere for the possible application as electrolyte in proton conducting ceramic electrolyte fuel cells (PCFCs) in the temperature range of 100–220 ◦ C, which showed that the conductivity of CeP2O7 was mainly due to the incorporation of water and the maximum conductivity was found to be 2.1 × 10 −4 Sc m −1 at 175 ◦ C and PH2O = 0.06 atm. The presence of water in CeP2O7 matrix increases the number of jump sites and facilitates the hopping of protons, leading to an increase in the conductivity.

The oxygen excess nonstoichiometry of La2NiO4 + δ is measured as a function of temperature and oxygen partial pressure (pO2) by coulometric titration method. A positive deviation from the ideal dilution solution behavior is exhibited, and the partial molar thermodynamic quantities of La2NiO4 + δ are calculated from the Gibbs–Helmholtz equation for regular solution by introducing the activity coefficient of the charge carriers. The activity coefficient of holes is successfully calculated by using the Joyce–Dixon approximation of the Fermi–Dirac integral. The effective mass of holes ( $$ m_{\text{h}}^{{*}} $$ ) is 1.27–1.29 times the rest mass (m h), which indicate the action of band-like conduction and allow the effect of the small degree of polaron hopping to be ignored. The activity coefficient of holes calculated against the oxygen nonstoichiometry clearly illustrates the early positive deviation of the activity coefficient of holes from unit, leading to $$ \gamma_{{{\text{h}}^{ \bullet }}} $$ ≈ 14 at δ ≈ 0.08, which is quite close to the literature value of $$ \gamma_{{{\text{h}}^{ \bullet }}} $$ ≈ 10 at δ ≈ 0.08. All the evaluated thermodynamic quantities are in good agreement with the experimental literature values.

The effect of metal-to-oxide grain boundary layer in \( {\text{Ni}} - {\text{BaCe}}_{{0.8}} {\text{Y}}_{{0.2}} {\text{O}}_{{3 - \delta }} \) (BCY) cermet membrane on hydrogen permeation was studied by applying the different size of oxide grain on Ni-BCY membranes. Two types of cermet membranes having different grain size of oxide were prepared by using different starting particle size of oxide powder. The hydrogen flux of coarse-oxide-grain membrane showed higher flux than that of small-oxide-grain membrane. It was understood that the negative potential at metal-to-oxide grain boundary, reference to the bulk oxide (\( \phi _{0} < \phi _{\infty } = 0 \)), was developed, and the accumulation of the effectively positively charged protons may occur at the grain boundary layer (space charge layer), which may result in providing highly conductive proton path by shifting the charge neutrality condition from \( {\left[ {OH^{ \bullet }_{O} } \right]} = {\left[ {Y^{/}_{{Ce}} } \right]} \) to \( {\left[ {OH^{ \bullet }_{O} } \right]} = n \).