Simultaneously improved reversibility and hydrogen production of solid oxide cells through infiltrating air electrode

Abstract

Among the various fuel cells, solid oxide cells (SOCs) are the unique type that can principally operate reversibly as either fuel cells to produce electricity or as an electrolyser to split water and produce green hydrogen (H₂). Nevertheless, the SOCs' reversibility presents enormous challenges that are manifested by the fast degradation through the cycling between fuel cell and electrolysis mode. While the La_0.8Sr_0.2MnO₃/yttria-stabilized zirconia (LSM/YSZ) air electrode possesses significant advantages in terms of high electrical conductivity and high thermal stability under fuel cell mode, the SOCs with the LSM/YSZ air electrode experience rapid performance degradation with catastrophic electrode delamination shortly after switching from fuel cell to electrolysis mode. To prevent such catastrophic delamination and enable the electrolysis H₂ production, a chemical solution with the designed chemistry of SrFe₂O_4−d was infiltrated into the LSM/YSZ air electrode. The infiltration immediately mitigates the catastrophic delamination, and the infiltrated cells exhibit significantly improved reversibility upon the electrochemical operation. Nanostructure examination reveals nanoscale cracks and second-phase nanograins formed in the air electrode from the baseline cell. By contrast, no delamination was observed at either the micron or the nanoscale for the infiltrated cell, which is attributed to the increased ion conductivity of the Fe-doped LSM mixed conductor induced by the significant interdiffusion between the LSM backbone and infiltrates. This study presents a viable method for preventing electrode delamination while enhancing the durability of H₂ production and power generation for reversible fuel cell/electrolysis cell operation. It further opens new research directions of modifying the electrochemical activity of the electrode of inherently functional cells through the infiltration of the solutions with different chemistry.