Reversal of chronic surface degradation of Sr(Ti,Fe)O3 perovskite-based fuel cell cathodes by surface acid/base engineering

The major barrier to commercialization of solid oxide fuel cells (SOFCs) is to overcome long-term surface degradation during operation. Sr/Co-based perovskite cathodes have been recognized to suffer from two major sources of degradation: inherent Sr segregation and extrinsic Cr-impurities at the surface, respectively. Here, we demonstrate the ability to simultaneously reverse both surface degradation modes in SrTi0.65Fe0.35O3-δ (STF35), a model high performance perovskite cathode, via surface acid/base engineering via infiltration. The acidic nature of Cr-infiltration is found to induce surface electron depletion, while enhancing Sr segregation to the surface, leading to ~40% drop in SOFC peak power. Subsequent infiltration of basic Ca-additives is demonstrated to not only neutralize these detrimental effects, but ultimately lead to 160% enhancement in peak power, thereby enabling Co-free operation. This approach holds great promise for extending the operating lives, more generally, of materials and devices for which the catalytic oxygen/solid interface reaction is central.