Importance of oxygen spillover for fuel oxidation on Ni/YSZ anodes in solid oxide fuel cells

Abstract

Using first principles simulations and the Monte Carlo method, the optimal structure of the triple-phase boundaries (TPB) of the Ni/Yttria-Stabilized Zirconia (YSZ) anode in solid oxide fuel cells (SOFCs) is determined. Based on the new TPB microstructures we reveal different reaction pathways for H₂ and CO oxidation. In contrast to what was believed in previous theoretical studies, we find that the O spillover from YSZ to Ni plays a vital role in electrochemical reactions. The H₂ oxidation reaction can proceed very rapidly, by means of both the H and O spillovers, whereas the CO oxidation can only proceed through the O spillover pathway. Further understanding of the roles of defects and dopants allows us to explain puzzling experimental observations and to predict ways to improve the catalytic performance of SOFCs.