Electrochemical testing of an innovative dual membrane fuel cell design in reversible mode

Solid oxide fuel Cells (SOFC) are intrinsically reversible which makes them attractive for the development of reversible devices (rSOC). The main hurdles that have to be overcome are the higher degradation in electrolyzer (EL) mode and the slow and difficult switching form mode to mode. This work aims at the development and experimental validation of a concept for rSOC based on a new dual membrane fuel cell (dmFC) design which can overcome the existing problems of the classical SOFC. The kernel of the system is additional chamber - central membrane (CM) for water formation/evacuation in FC mode and injection in El mode. Its optimization in respect of microstructure and geometry in laboratory conditions is carried out on button cells. The electrochemical performance is evaluated based on volt-ampere characteristics (VACs) combined with impedance measurements in different working points. The influence of a catalyst in the water chamber is also examined. The VACs which give integral picture of the cell performance are in excellent agreement with the impedance studies which ensure deeper and quantitative information about the processes, including information about the rate limiting step. The results from the optimization of the water chamber show that the combination of design and material brings to important principle advantages in respect to the classical rSOC \u2013 better performance in electrolyzer mode combined with instantaneous switching

Impedance investigation of BaCe0.85Y0.15O3-delta properties for hydrogen conductor in fuel cells

International audienceThe influence of the sintering conditions on the electrochemical properties of the proton conducting electrolyte BaCe0.85Y0.15O3-delta (BCY15) and Ni - based BCY15 cermet anode for application in high temperature proton conducting fuel cell are investigated by electrochemical impedance spectroscopy. The results show that at lower sintering temperatures due to the formation of parasitic Y2O3 phase an increase of both the electrolyte and electrode resistances is observed. This effect is strongly reduced by enhancement of the sintering temperature. The obtained BCY15 conductivity (sigma = 2.5x10(-2) S/cm at 700 degrees C) is comparable with that of the best proton conducting materials, while the BCY15-Ni cermet (with ASR = 2.5 Omega cm(2) at 700 degrees C) needs further optimization. The results of impedance investigations of BCY15 as proton conducting electrolyte and cermet anode have been applied in development of innovative high temperature dual membrane fuel cell

Biomarkers for Severity of Spinal Cord Injury in the Cerebrospinal Fluid of Rats

One of the major challenges in management of spinal cord injury (SCI) is that the assessment of injury severity is often imprecise. Identification of reliable, easily quantifiable biomarkers that delineate the severity of the initial injury and that have prognostic value for the degree of functional recovery would significantly aid the clinician in the choice of potential treatments. To find such biomarkers we performed quantitative liquid chromatography-mass spectrometry (LC-MS/MS) analyses of cerebrospinal fluid (CSF) collected from rats 24 h after either a moderate or severe SCI. We identified a panel of 42 putative biomarkers of SCI, 10 of which represent potential biomarkers of SCI severity. Three of the candidate biomarkers, Ywhaz, Itih4, and Gpx3 were also validated by Western blot in a biological replicate of the injury. The putative biomarkers identified in this study may potentially be a valuable tool in the assessment of the extent of spinal cord damage

IDEAL-Cell, a High Temperature Innovative Dual mEmbrAne Fuel-Cell

IDEAL-Cell is a new concept of a high temperature fuel cell operating in the range 600-700\ub0C. It is based on the junction between the anode part of a PCFC and the cathode part of a SOFC through a mixed H+ and O2- conducting porous ceramic membrane. This concept, extensively described in the present paper, aims at avoiding all the severe pitfalls connected with the presence of water at the electrodes in both SOFC and PCFC concepts. Spark Plasma Sintering samples were designed specifically for proving the IDEAL-Cell concept. The first electrochemical results obtained at 600\ub0C under hydrogen on millimeter thick samples show that IDEAL-Cell behaves like a high temperature fuel cell. It is estimated that the overall efficiency of this new concept should greatly surpass that of standard SOFCs and PCFCs and that the material constraints, especially in the case of interconnect materials, should significantly decrease

Inductance correction in impedance study of solid oxide fuel cells

A procedure for evaluation and elimination of errors, caused by parasitic inductance and resistance in EIS studies of two solid oxide fuel cells (SOFC) materials: yttria stabilized zirconia (YSZ) electrolyte and lanthanum strontium manganite (LSM)/YSZ composite cathode is presented in this paper. It is shown that for these low impedance systems the parasitic inductance can affect not only the high frequencies but also the middle and low ones. The parasitic errors correction procedure increases significantly the reliability of the electrochemical impedance spectroscopy (EIS) results

Inductance correction in impedance studies of solid oxide fuel cells

A procedure for evaluation and elimination of errors, caused by parasitic inductance and resistance in EIS studies of two solid oxide fuel cells (SOFC) materials: yttria stabilized zirconia (YSZ) electrolyte and lanthanum strontium manganite (LSM)/YSZ composite cathode is presented in this paper. It is shown that for these low impedance systems the parasitic inductance can affect not only the high frequencies but also the middle and low ones. The parasitic errors correction procedure increases significantly the reliability of the electrochemical impedance spectroscopy (EIS) results

Differential impedance analysis for the study of the rate limiting step of electrodic process in sofc cathodes

The increasing demands for more efficient low temperature Solid Oxide Fuel Cells (SOFC) focused the investigations towards the development of systems with higher conductivities at lower temperatures. The cathode-electrolyte interface is of great importance for the operation of the device at lower temperatures. It is essential to develop high performance electrodes because at such temperatures the electrode reaction rate is slower. There are two main approaches for the description of the cathode reaction of mixed conducting porous electrodes. The classical approach follows the "three-phase boundary" concept, which allows the involvement of gas-phase species at the electrochemical interface, but in the same time needs an operation with one-dimensional interface among three phases. The limitations of the tpb concept are bypassed by break down of the electrode reaction into individual steps including charge-transfer across a two-dimensional interface as well as adsorption, solid state and gas diffusion. This approach is successfully applied in the impedance studies of cathode reaction of porous mixed conducting electrode, using equivalent circuit model description, where the non-charge transfer steps are treated as series of parallel combinations of charge-transfer elements. Although ensuring a good fit of measured with calculated data, in many cases this approach could be regarded as a formal description and not as a tool for elucidating the dominating mechanism of the complex process. Recently a non-charge transfer approach, known as ALS model was proposed for characterization of oxygen reduction on single phased porous mixed conducting oxide electrodes. It was found both theoretically and experimentally that the electrode polarization losses are associated mainly with the generation and transport of oxygen ions within the cathode material, while the actual interfacial charge-transfer is very fast provided the interface is not contaminated. Gas phase diffusion becomes dominant below 1 % oxygen in N2. In this work the electrochemistry of oxygen reduction on porous composite electrodes consisting of La(1-x)SrxMnO3-? (LSM) and Y-stabilised Zirconia (YSZ) has been analysed. Half cells consisting of YSZ electrolyte pellets and slurry coated cathodes were tested with a three electrodes configuration. The composite cathodes considered in this study have a fixed volume ratio LSM/YSZ equal to 1. Impedance measurements were analyzed by the technique of the Differential Impedance Analysis (DIA), which does not need a preliminary working hypothesis. The application of DIA gives information about the dominant phenomena, based on comparative study of the cathode behaviour of LSM and of composite materials. The analysis of the electrochemical data suggests that adsorption of oxygen or ionic transport could be the key phenomena in the cathodic process

Fuel cell e.g. mixed conduction membrane fuel cell, for producing electric energy for stationary applications, has channel whose cross section has minimum size larger than specific value so as to discharge from diaphragm to outside of cell

NOVELTY - The cell (1) has a porous central diaphragm (30) whose surfaces (32, 35) are in contact with an electrolyte (20) and a cathode (50). The electrolyte has material conducting M ions and the diaphragm has material conducting both M and N ions. Rectilinear channels (52) pass through the cathode and connected to the diaphragm and a free surface of the cathode. Minimum size of a cross-section of one of the channels is larger than 20 micrometers so as to enable a product i.e. water, from reaction of the ions to be discharged from the diaphragm to outside the cell through the channels. USE - Fuel cell e.g. mixed conduction membrane fuel cell, for producing electric energy for stationary applications. Can also be used for long term onboard applications e.g. car. ADVANTAGE - The minimum size of the cross-section of one of the channels is larger than 20 micrometers so as to enable the product resulting from reaction of the ions to be discharged from the diaphragm to outside the cell through the channels in an efficient manner, thus increasing power density of the fuel cell. The electrolyte and the central membrane are manufactured by using single operation e.g. sintering, so as to simplify manufacturing of the fuel cell and improve mechanical resistance and durability of the assembly