Microfabrication of model Solid Oxide Fuel Cells for synchrotron-based operando studies

CATALINA JIMENEZ; MARIANO SANTAYA; JOHANNES FRISCH; LILIANA MOGNI; RONEN GOTTESMAN; ALEXANDER STEIGERT; MARCUS BÄR; MAURICIO ARCE; IVO RUDOLPH; REGAN WILKS

Dresden

Congreso; 21st International Symposium on Laser Precision Microfabrication 2020; 2020

Among the sustainable energy sources, solid oxide fuel cells (SOFC) is a key technology for decentralized power generation due to its high efficiency in converting electrical energy from chemical fuels[1]. Large commercialization still requires engineering new intermediate temperature SOFC (IT-SOFC) materials that support operation below 700°C and fuel flexibility to reduce costs and mitigate degradation phenomena. Strategies to address these problems include: replacing the conventional electronic conductor cathodes by mixed ionic-electronic conductors (MIEC) or nanostructured cathodes[1] and exchanging the currently employed anodes (Ni-cermets) by C tolerant MIEC ABO3-δ perovskites for direct use of lower hydrocarbons as fuels[2]. The MIEC Sr(Ti,Fe)O3-δ (STF) gained much attention as new electrode material for its capability of working at intermediate temperatures both as cathode and anode by tuning its stoichiometry [3, 4]. Ni-doped STF (STFN) exsolves Fe-Ni nanoparticles (NPs) in a reducing atmosphere. NP exsolution boosts the performance of these IT-SOFC anodes by enhancing the H2 dissociative adsorption, reducing the anode polarization resistance and improving C tolerance[3]. The underlying mechanisms and the reversibility of NP exsolution is a heavily debated topic, but if understood and controlled, it could be disruptive for SOFC technology[3, 6].For this work, in order to understand the exsolution process and gain device-level insights at the gas/solid interface, model SOFCs suitable for synchrotron operando ambient pressure X-ray photoelectron spectroscopy / electron-yield absorption spectroscopies (AP-XPS/XAS) and electrochemical impedance spectroscopy (EIS) at high temperature in oxidizing or reducing atmospheres were fabricated using various microfabrication techniques (Fig.1) [7]. These YSZ-electrolyte supported half-cells have 200 nm of non-stoichiometric STFN (or STF for reference) as working electrode deposited by pulsed laser deposition PLD, onto photolithographed Pt current collectors and a porous Pt counter electrode deposited by reactive sputtering. Here we present details of the cells fabrication process and some exemplary synchrotron based results. We discuss how dedicated synchrotron-based operando studies on model devices are extremely useful to study energy conversion processes that in turn, guide an application-oriented material (or device or component) optimization. Protocols for quality control are also critical upon each fabrication step of model devices to conduct experiments that result meaningful for the application.Fig.