Development of scientific bases of tailor-made design of functionally graded nanocomposite cathode materials for both IT-SOFCs and PC-SOFCs

The PROTON project aims to investigate new, promising double perovskite mixed ionic electronic conductors as air-side electrodes for proton-conducting solid-oxide fuel cells (PC-SOFC) and electrolyzer cells (PC-SOEC). These high temperature energy converters are potentially highly effective, and can offer a significant contribution to a cleaner energy production system. The proton conducting SOFC / SOECs are, however limited by a too high area specific resistance (ASR), arising first and formerly from overpotentials associated with the air-side oxygen red-ox reaction. The new layered Pr and Gd-based double perovskite materials offer new and improved possibilities for mixed oxide / electron- and possibly also protonic transport, which would theoretically be a significant improvement for the air-side electrode. Measurements of hydration and electrochemical performance of four tested materials so far show promising results. Characterization of polarization resistance as a function of temperature shows low ASR, and electric voltammetry performed on the three first materials shows that the materials have good reversibility, and that they can be able to operate both in fuel cell and electrolyzer modes.

Basic research studies on preparation routes of cathode materials, e.g. the double perovskites Pr1-yLayBaCo2-xFexO6-d, Gd1-yLayBaCo2-xFexO6-d in wide composition range will be performed. Precise analysis of the materials properties is necessary to avoid a trial and error approach. In the project we are going to investigate oxide compositions and their morphology using X-ray (XRD), scanning electron microscopy (SEM) and energy dispersive (EDA) analyses. Measurement of overall and oxide ion conductivity of these oxides using four-probe DC method and polarization technique, respectively, depending on temperature and oxygen partial pressure and determination of the electron and oxide ion transport parameters such as charge carrier mobilities, oxide ion diffus ion coefficients, activation energy etc. The oxygen nonstoichiometry of the electrode materials will be investigated as a function of temperature and oxygen partial pressure by means of thermogravimetric (TGA) and coulometric analyses along with their def ect structure. Calculation of oxide ion transport in the double perovskite using molecular dynamic simulation and comparison these results with those measured. Study of the crystal structure vs. temperature and oxygen partial pressure and determination of the oxides lattice thermal expansion using both X-ray and dilatometric analyses. Analysis of the oxide compositions and their morphology using XRD, SEM and EDX. Investigation of thermal and chemical compatibility of the prepared cathodes with the differe nt electrolytes. Preparation of binary combinations cathode/electrolyte and performance of test measurements such as polarization resistivity - Rp. The results from this approach will allow to find the best cathode materials and to prepare single cells of solid oxide fuel cell (SOFC) and proton conductive electrolyte fuel cell (PC-SOFCs) in order to check their performance such as power, open circuit voltage etc. in test measurements under real conditions.