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

Preparation of transparent oxyapatite ceramics by combined use of freeze-drying and spark-plasma sintering

Lanthanum silicate oxyapatites, ion-conducting materials presenting a strong aversion against densification, have been obtained in the form of dense transparent ceramics, by combining the beneficial use of freeze-drying and spark plasma sintering methods

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

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

Multi-layer thin film electrolytes for application in High Temperature Ceramic Electrochemical Devices

Reducing thickness of the electrolyte is a key route to reduce ohmic losses in high temperature electrochemical devices and unlock operation at lower temperature. However the production of such a film through conventional ceramic process often requires a sintering step at high temperature – typically above 1200°C – not necessarily compatible with the shrinking behavior and the chemical properties of the supporting materials. This particularly holds true for metal supported cells when pre-manufactured substrates are used. Here we report about a multi-layer electrolyte architecture and its low temperature manufacturing route specifically design for metal supported cells. This consists in interlayers of porous yttria stabilized zirconia (YSZ) directly coated onto the functional electrode and fired at mild temperature – typically below 900°C – followed by a gas tight YSZ and Gadolinium doped Ceria (GDC) double layer deposited by electron beam physical vapor Deposition (EB-PVD). The architecture was implemented into metal supported cells with a size up to 90 mm x 100 mm. Cells were tested in Fuel Cell or Electrolysis operation for more than 1500 hours and 2000 hours respectively. The evolution of the interfaces was monitored by Electrochemical Impedance Spectroscopy, and the microstructure of the thin films was investigated by Scanning Electron Microscopy and Transmission Electron Microscopy. Most Actual status of development will be given and prospects and challenges will be discussed

Dual membrane fuel cell -impedance approach for proof of concept

International audienceThe dual membrane fuel cell (DMFC) is an innovative SOFC architecture in which an oxygen compartment (cathode and oxide ion conducting electrolyte) is combined with a hydrogen compartment (anode and proton conducting electrolyte) through a porous mixed conducting central membrane (CM) where the two types of ions react and produce water which is evacuated through the pores. This concept is proved on a model cell via sets of investigations based on D.C. testing and Impedance Spectroscopy. For optimization of the three DMFC compartments (oxygen, hydrogen and CM) with regard to materials and technological conditions for the deposition of the functional layers, impedance studies were carried out on symmetrical half cells. Special attention was given to some new experiments elucidating the processes of water formation and propagation through the central membrane

Gases permeability study in dual membrane fuel cell

International audienceGases permeability in a porous mixed (proton and oxide ion) conductive membrane, which is a component of a new high temperature dual membrane fuel cell design is investigated by specially designed testing system based on measurements of the gas flow [ml/min] and pressure P (mm H2O) when penetrating through porous media. A strong correlation expressed in increase of the permeability with the decrease of the gases molecular weight is registered. The water vapor permeability decreases with the temperature. This is in agreement with data from the literature which show that the viscosity of gases, including water vapor, increases with the temperature. The results obtained suggest optimal porosity in respect to permeability, mechanical stability and conductivity in the range of 35-40%. They confirm the need of optimization concerning not only the pores fraction, but also the pores geometry and distribution, as well as the central membrane geometry and the configuration of the cell. This approach can be applied also for optimization of the electrodes porosity (pores concentration, geometry, distribution etc), especially in cases when gas mixtures (including water vapor) are used or produced