The matrix material in a Molten Carbonate Fuel Cell, usually LiAlO2, has an important role in the ionic conduction, gas sealing and electrolyte retention. To avoid cracking, this material has been reinforced with various additives, mostly Al-based, which are subject to in situ lithiation. In this work, matrices were systematically synthesized through a fast and more environmentally friendly route and characterized, with two types of reinforcing agent, either Al powder or Al2O3 fibers, both with and without carbonates. Then, a comparative analysis was done, in terms of mechanical strength and porosity, on the effect of adding Al powder and Al2O3 fibers and their subsequent lithiation. This reaction was found to be quantitative after 50 h at 650 degrees C, and matrices with reinforcing agent and carbonates featured increased mechanical strength by a factor up to 2 compared to matrices with only reinforcing agent, reaching 0.61 kgf.mm 2. Al powder was also found to be better suited than Al2O3 fibers for addition in a matrix, also contributing to enhance the porosity, particularly after lithiation.

AISI 430 stainless steel is an attractive material to be used in the healthcare industry, particularly as a sensor due to its low cost, corrosion resistance, as well as being Ni-free. AISI 430 was evaluated in an artificial sweat solution with the presence of Escherichia coli, and Staphylococcus aureus. Surface microbial analyses did not reveal colonization of bacteria on metallic surfaces, even when bacteria adhesion was investigated in a Miieller-Hinton solution. However, by electrochemical techniques, the AISI 430 surfaces demonstrated clear signs of corrosion mainly in a sterile medium after two weeks of exposure.

Co-electrolysis of water and carbon dioxide in molten carbonates is nowadays a key issue in MCEC (molten carbonate electrolysis cell) and, reversely, for a better understanding of MCFC (molten carbonate fuel cell). The products of water and carbon dioxide reduction are the fuels that might be used in MCFC or other energy devices. The present study is dedicated to a thorough electrochemical investigation by voltammetric techniques (Cyclic Voltammetry CV or Linear Sweep Voltammetry LSV) at a Pt electrode of such fuels in Li2CO3-K2CO3 eutectic, under varied atmosphere conditions, including partial pressures of H2O, CO2, H2 and Ar at 650°C. The conditions of formation of soluble and/or adsorbed H2 and CO are established together with qualitative thermodynamics information on the redox systems involved. C is only detected in very specific conditions. Knowing that hydroxides, produced in the conditions of MCEC and MCFC, have a significant role on the operation of such devices, an electrochemical analysis (CV and impedance measurements) of the effect of added amounts of hydroxides is developed for the first time, showing the enhancement of oxidation currents and the progressive increase in electrolyte conductivity.

CO2 plays a major role in the molten carbonate fuel cell (MCFC) and its reverse process, the molten carbonate electrolysis cell (MCEC), because of the capability of the mentioned electrolyte to capture big amounts of this greenhouse gas. In particular, the co-electrolysis process together with water, would ideally yield syngas (H-2 + CO). The reduction of CO2 in such a case has been scarcely investigated in MCEC conditions. The present study is mainly focused on the online detection by Gas Chromatography (GC) of CO2 electrolysis product. Both thermodynamic predictions, including the chemical reactivity of CO and CH4, and experimental results on MCFC/MCEC performance and GC detection, allowed to prove that CO is produced electrochemically with a ratio depending on the electrolysis potential, deducing also the potentials that should be avoided to inhibit the formation of carbon. This first insight will be essential for analyzing the medium and long-term performance of MCECs. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Driven by the growing concern about the release of untreated emerging pollutants and the need for determining small amounts of these pollutants present in the environment, novel biosensors dedicated to molecular recognition are developed. We have designed biosensors using a novel class of grafted polymers, surface-attached hydrogel thin films, on conductive transducers as a biocompatible matrix for biomolecule immobilization. We showed that they can be dedicated to the molecular recognition of diclofenac (DCL). The immobilization of the aptamer onto surface-attached hydrogel thin films by covalent attachment provides a biodegradable shelter, providing the aptamer with excellent environments to preserve its active and functional structure while allowing the detection of DCL. The grafting of the aptamer is obtained using the formation of amide bonds via the activation of carboxylic acid groups of the poly(acrylic acid) hydrogel thin film. For improved sensitivity and higher stability of the sensor, a high density of the immobilized aptamer is enabled. The aptamer-modified electrode was then incubated with DCL solutions at different concentrations. The performances of the aptasensor were investigated by electrochemical impedance spectroscopy. The change in charge-transfer resistance was found to be linear with DCL concentration in the 30 pM to 1 μM range. The detection limit was calculated to be 0.02 nM. The improvement of the limit of detection can be mainly attributed to the three-dimensional environment of the hydrogel matrix which improves the grafting density of the aptamer and the affinity of the aptamer to DCL.

In order to reduce carbon dioxide emission, one solution is to convert into valuable chemicals or fuels, e.g. transforming CO2 into CO by electrochemical reduction. Thus, this greenhouse gas could be re-used in particular as syngas (CO + H2) by co-electrolysis of CO2/ H2O. High temperature electrolysis cells can be the best energetic devices to produce such syngas. In particular, molten carbonates are known to solubilize CO2 very significantly higher than other solvents. Therefore, it is compulsory to investigate and understand the mechanism of CO2 reduction in such media to consider its further use and valorisation. The present study is a critical approach aiming at elucidating the mechanisms for CO2 electroreduction, using an inert Pt electrode in the molten eutectic Li2CO3-K2CO3 (6238 mol%), at 650 ?C, under different partial pressures of CO2. Complementary electrochemical techniques, including sweep square-wave voltammetry and relaxation chronopotentiometry, were carried out. Their combination allowed us to evidence that the electroreduction of CO2 into CO is feasible in oxo-acidic conditions, involving a diffusionlimited quasi reversible system in a one electron-step. ? 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

As the capture and valorization of CO2 in molten carbonates is nowadays becoming a strategic energy topic, the need of accurate solubility measurements of such molecule is becoming compulsory. This study provides a new set of reliable CO2 solubility values, determined by a a carefully adapted manometric setup, in Li2CO3-K2CO3 (62:38 mol%), Li2CO3-Na2CO3 (52:48 mol%), Li2CO3-Na2CO3-K2CO3 (43.5:31.5:25.0 mol%) and Na2CO3-K2CO3 (56:44 mol%) carbonate eutectics in an overall range of temperatures from 450 to 850 degrees C. High solubility values are obtained for Li-K and Li-Na eutectics, respectively 1.7 x 10(-1) and 1.1 x 10(-1) mol atm(-1) 1(-)(1) at 650 degrees C. It is shown that CO2 solubility increases with the temperature for most of the eutectic mixtures. Another important trend is that the Li content significantly increases the solubility. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

This study is focused on the search of new electrolyte/cathode interface architecture for intermediate temperature solid oxide fuel cells (IT-SOFCs). India-doped zirconia (IDZ) thin multilayer with three different contents of indium oxide, allowing to pass from an ionic conductor (30 mol% of InO1.5) to an electronic one (80 mol% of InO1.5) are deposited by atomic layer deposition (ALD) technique on porous LSF cathode and dense substrates (Stainless steel, Si (100)) at 300 degrees C. The as-prepared thin layers are well crystallized without any subsequent annealing. Uniform, adherent and dense thin layers with high microstructural quality are obtained at low temperature 300 degrees C without post-deposition annealing. The deposit is perfectly followed the roughness of the porous substrate surface without penetrating into the pores. The study shows that the ionic conduction zone is even more extensive than in sintered pellets (55 mol% of InO1.5). The low normalized ionic resistance and activation energy confirm the good effect of the presence of composition gradient at the interface cathode/ electrolyte which favor the passage of charge carriers within the intermediate layers of IDZ. The values of the relaxation frequencies are situated between those corresponding to the grain boundaries and those of the bulks of an IDZ pellet. The electrochemical performances of IT-SOFC with IDZ are improved by decreasing the ohmic resistance losses and the polarization resistance associated with oxygen reduction reaction.

AISI 304L is used in Sudoscan(TM) technology (Impeto Medical Inc.) for the early diagnosis of small fiber neuropathy caused by type-2 diabetes or cystic fibrosis. In a recent paper, several substitute electrodes were analyzed, among which the biocompatible nickel-free AISI 430 appeared as an interesting material. In the present work, we compare in details the electrochemical behavior of AISI 430 with respect to the reference AISI 304L, using Electrochemical Impedance Spectroscopy (EIS) in mimetic electrolytic solutions of sweat. Apart of being cheaper than AISI 304L, AISI 430 has roughly similar characteristics but is slightly more sensitive to chloride ions concentration and, according to EIS and SEM analyses, forms a thicker, more homogeneous and protective oxide layer, which makes it a convenient electrode material.

In this work, La2NiO4+delta is used as cathode material for Intermediate temperature solid oxide fuel cells (IT-SOFC). Scanning electron microscopy, X-ray diffraction, and electrochemical impedance spectroscopy are used to investigate the effect of the presence of an ultrathin La(2)NiO4(+delta) layer (80 nm) deposited by dip-coating or sputtering at the interface YSZ/La2NiO4+delta. The thick porous cathode layer of La2NiO4+delta is deposited by screen-printing, and sintered at 1000 degrees C for 2 h or 1200 degrees C for 20 min in order to study the effect of sintering temperature on the electrochemical properties. The results show that the electrochemical performances of the cathode are influenced by the deposition technique. The best electrochemical properties are obtained with the use of the nano film interface layer deposited by sputtering. The introduction of ultrathin interface with nano grained between the cathode and electrolyte is a promising technique to reduce polarization resistance associated with oxygen reduction reaction (ORR) on the cathode. (c) 2018 Elsevier B.V. All rights reserved.

In the perovskite structures widely investigated and used as Solid Oxide Fuel Cells (SOFC) cathodes, oxygen reduction is mainly limited to the triple phase boundary (TPB), where oxygen (air), electrode and electrolyte are in contact. It is possible via the sol-gel modified Pechini method to: 1) control the material grain size, which can increase TPBs, 2) produce a homogenous material and 3) obtain a cathode material in a faster way compared with the solid state route. LaNi$_x$Co$_{1-x}$O$_3$ ($x = 0.3$, 0.5, 0.7) were synthesized by the modified Pechini method. The perovskite phase formation began at 350$^{\circ}$C and the presence of pure LaNi$_{0.7}$Co$_{0.3}$O$_3$ LaNi$_{0.5}$Co$_{0.5}$O$_3$ and LaNi$_{0.3}$Co$_{0.7}$O$_3$ structures was evidenced by High Temperature X-ray diffraction (HT-XRD) measurements. Scanning Electron Microscopy (SEM) micrographs showed that the microstructure evolves with the amount of cobalt from a coalesced to an open structure. Electrochemical impedance spectroscopy (EIS) on symmetrical cells LaNi$_x$Co$_{1-x}$O$_3$/YSZ (yttria-stabilized zirconia)/LaNi$_x$Co$_{1-x}$O$_3$ showed that the highest ASR (area specific resistance) is obtained with $x = 0.3$, whereas ASR values are similar for $x = 0.5$ and 0.7 at temperatures higher than 600$^{\circ}$C. At temperatures lower than 600$^{\circ}$C, ASR is the lowest for LaNi$_{0.5}$Co$_{0.5}$O$_3$, showing that this composition with intermediate porosity appears as a good choice for an intermediate-temperature solid oxide fuel cell (SOFC).

Improvement of the molten carbonate fuel cell electrolyte is a key parameter to increase the performance of such electrochemical generator. One of the main challenges is to enhance the global oxygen reduction at the state-of-the-art porous nickel cathode. In this study, the effect of adding 5 mol% of caesium in Li-K and Li-Na molten carbonate eutectics or 5 mol% of rubidium in Li-K melt was analysed with respect to the behaviour of nickel cathode towards oxygen reduction. Evolution of the open-circuit potential and electrochemical impedance spectroscopy measurements were carried out over time. In Li- K melt, both Cs and Rb additives induced an improved cathode behaviour: more rapid equilibration reaching more rapidly the equilibrium potential, and significantly lower total resistance (9 times less with Cs and 3 times less with Rb), in particular mass transport, with respect to the pristine electrolyte. Moreover, charge transfer resistance was significantly lower with Rb and nearly the same with Cs versus pristine Li-K. Both additions are significantly positive for enhancing oxygen reduction at the porous electrode, which seems to be particularly the case for Cs addition. However, addition of Cs to Li-Na did not show an important effect. Changing the composition of Li-K with the mentioned additives could be an important step towards a more performing MCFC, but more insight on oxygen reduction kinetics with Rb addition and single cell tests with both cases are compulsory. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

This study addresses the problem of the nickel cathode dissolution, decreasing the lifetime of molten carbonate fuel cells, by a protective coating of Nb2O5 processed by atomic layer deposition ALD onto the porous cathode substrate. Samples of different thicknesses were tested electrochemically in molten Li2CO3-K2CO3 eutectic at 650 degrees C during 230 h by means of chronopotentiometry and electrochemical impedance spectroscopy. A significant decrease in the stabilization time with respect to the oxygen reduction potential is observed with niobium coatings, which could indicate an electrocatalytic process favoured by the presence of Nb. The structure and morphology of the coated samples are characterised by XRD, SEM and XPS before and after the electrochemical tests. Mixed lithiated Ni and Nb oxides are likely to be formed at the cathode surface. Interestingly, this Nb-containing mixed oxide not only can protect Ni cathode but also maintains its good performance.. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Carbonate/oxide composites are very promising electrolyte materials in hybrid fuel cells which could operate at lower temperature than the usual Molten Carbonate Fuel Cells (MCFC) or Solid Oxide Fuel Cells (SOFC), presenting 0.1 S cm(-1) at 600 degrees C. This paper shows some significant and/or unexpected experimental data obtained by impedance spectroscopy, related to the impact of the carbonate/oxide ratios and the heating and cooling cycles in reducing atmospheres on the electrical behaviour of the composites. Based on this peculiar experimental behaviour, combined DFT calculations are selected for acquiring a deeper understanding of the transport mechanisms in such materials. A modelling strategy, in parallel with experimental results, is developed in the present paper. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Perovskite-type structures with the composition LaNixCo1−xO3 (x=0.3, 0.5, 0.7) were synthesized by a modified sol-gel method. Using transitional metal elements on the lanthanum base perovskites, properties could be tuned by doping the structure. Thermogravimetric analysis (TGA) evidenced a temperature of 350 °C as the start point of the perovskite-phase formation. Scanning electron microscopy (SEM) images showed the microstructure changes (grain size) of the cobalt-doped perovskite due to composition. In addition, it was shown that magnetic properties of the samples were dependent of cobalt content; experimental results pointed to the existence of disordered spins interactions, which were more evident with the decrease of cobalt content and the existence of ferromagnetic coupling among spins of the samples. These results showed the feasibility of producing a family of compounds with the desired properties, manipulating composition and therefore the microstructure.

Ceria-based composites are developed and considered as potential electrolytes for intermediate temperature hybrid fuel cell applications (IT-HFC). The structural properties of composite materials based on mixtures of gadolinia-doped ceria (GDC) and alkali chloride (LiCl-KCl) are analysed. The microstructure of the electrolyte is observed by scanning electron microscopy (SEM). High temperature and room-temperature X-ray diffraction allowed determining the precise structure of the composite and its regular and reversible evolution with the temperature. Finally, the electrical conductivity is determined by impedance spectroscopy and presented as a function of the electrolyte composition. The ageing behaviour after thermal cycling and at a constant temperature of 400°C shows that this material is very promising. After such conditions, conductivity of GDC/Li-K-Cl composite electrolyte is still close to 0.12 S.cm−1 at 400°C, which is more than the Li-K carbonate/GDC composite conductivity at 600°C under the same conditions.

In the world of alternative energy sources, the Molten Carbonate Fuel Cell (MCFC) is one of the promising technologies for the efficient conversion of hydrogen or hydrocarbons to power and heat. One of the main issues for optimizing this device is the control of the dissolution of the state-of-the-art porous nickel oxide cathode. A protective coating by more stable metal oxides seems to be one of the best solutions. In this paper, ultra-thin layers of TiO2 (50 nm), Co3O4 (50 nm) and CeO2 (20 nm) were deposited on porous nickel substrates, by a sequential CVD technique, known as Atomic Layer Deposition (ALD), producing high quality, homogeneous and conformal layers. The electrochemical behavior and morphological features of the three coated samples were compared in a Li2CO3-K2CO3 (62-38 mol%) eutectic melt under a standard cathode atmosphere (CO2/air 30:70 vol%) for 230 h. Finally, the respective advantages and drawbacks of Co3O4, TiO2 and CeO2 coatings are pointed out. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Cerium oxide based materials are versatile compounds in terms of properties and applications. This work analyses the production of thin layers, of less than 2 mu m thick of Gd-doped ceria (GDC) solid solution for high temperature electrochemical applications such as fuel cells and electrolyser cells. We focused on the synthesis of the deposit by cathodic electrodeposition by means of one unique chemical electrolytic bath to produce the doped compound. The resulting deposit is a single phase compound that presents a cubic structure being the expected composition Ce0.77Gd0.23O2-delta. The feasibility of a "one step deposition" (i.e. from one common solution bath) for Gd-doped ceria was demonstrated in the conditions presented in this paper. The presented results deal with the electrodeposition and the microstructural features of the produced materials, which were characterized by X-Ray Diffraction, Scanning Electron Microscopy (FE-SEM) coupled to EDX and Raman spectroscopy. (C) 2013 Elsevier Ltd. All rights reserved.