Evaluating the regeneration capabilities and degradation mechanisms of electrocatalytically active Fe-Ni nanoparticles exsolved from Ni-doped Sr0.93(Ti0.3Fe0.7)O3-d electrodes by GIXRD

TOSCANI LUCIA; RONEN GOTTESMAN; LILIANA MOGNI; JIMÉNEZ CATALINA; GAMBA, NADIA; MARCUS BÄR; ARCE MAURICIO; MARIANO SANTAYA; DANIEL TÖBBENS

Darmstadt

Congreso; Materials Science and Engineering MSE Congress; 2022

Electrocatalytically active metallic nanoparticle (NP) exsolution from perovskite oxide electrodes boost solid oxide cell (SOC) performance [1]. This process can be triggered under reducing atmosphere and/or electrode polarization, and can be tuned by adjusting atmosphere composition, electrode potential and operating temperature [2]. Controlling the NP exsolution and reabsorption by these means opens a promising landscape for SOFC technology [3]. The reversibility capabilities after switching atmosphere or electrode polarization are still unclear and highly debated topics in the SOFC community. It is critical to understand the effect of the different variables that affect the exsolution/reabsorption process since these aggressive operation conditions can lead to degradation of cell performance.In this work we study in situ the NP exsolution and reabsorption process by combining GIXRD with electrochemical techniques on Sr0.93Ti0.3(Fe0.63Ni0.07)O3-d (STFN) thin model electrodes at the KMC-2 beamline of BESSY II Berlin synchrotron. This allowed us to detect phases produced on the surface while the material is exposed to redox atmospheres, high temperatures and electrode polarization. We were able to successfully detect and follow Ni-Fe NP exsolution and reincorporation into the perovskite lattice when switching atmospheres. We could establish that NP reabsorption is not total, since NiO prevails after the redox cycle. Furthermore, other secondary phases responsible for the cell degradation were detected, such as SrO, and a phase resulting from electrode and electrolyte reaction (SrTi0.2Zr0.8O3-d), which appears to be related with electrode polarization. Upon SOFC/SOEC electrode polarization, we observed significant changes on the surface species in reducing atmospheres. This information, together with the electrochemical performance obtained from electrochemical impedance spectroscopy, allowed us to better comprehend the material at operating conditions, assessing key information on how these variables affect NP exsolution and reabsorption processes, and propose degradation mechanisms.