Interface Problems in Solid Oxide Electrolysis Cells

Abstract

In this talk, I introduce topics, that I have been working on, in solid oxide electrolysis cells involving complicated interfacial structures and dynamics of interfaces. Then I will focus on my recent work on nickel (Ni) particle migration in electrodes consisting of Ni, yttria-stabilized zirconia (YSZ), and pores during the operation of oxygen-ion conducting solid oxide electrolysis cells (o-SOECs) and Faraday efficiency in proton-conducting solid oxide electrolysis cells (p-SOECs) under electrolysis operations. SOECs can have a significant impact on climate change over the next decade and beyond, in applications such as balancing renewable grid electricity via electrolytic fuel production. However, long-term performance degradation remains a key issue that may limit further implementation of O-SOECs, and the dependency of operation conditions on Faraday efficiency in P-SOECs has been under debate. In particular, in Ni/YSZ/pore electrode of O-SOEC, a phase-field model is proposed that employs the Ni-YSZ 3D microstructure as the initial condition and large-scale numerical simulation is implemented that predicts the directional Ni migration. The results are thus directly comparable to experimental observations. Quantitative predictions of the evolution of the Ni/YSZ/pore system's microstructures due to Ni particles' migration are studied through theoretical analysis and data analysis. In P-SOECs, an electrochemical model is proposed to study the dependency of Faraday efficiency on operation conditions for P-SOECs with yttrium-doped barium zirconates (BZY) and co-doping barium zirconate-cerate oxides with ytterbium and yttrium (BCZYYb) as electrolytes respectively. Our numerical predictions are verified by experimental results obtained in INL. An optimal structure of electrolyte is proposed to boost the Faraday efficiency in P-SOECs.