Sr-doped lanthanum manganite (LSM) is a widely used cathode material in solid oxide fuel cells (SOFC). Despite being a poor ion conductor, LSM electrodes can reduce oxygen via two pathways: a “3PB surface path” which includes surface diffusion of oxygen species and oxide ion incorporation at the three phase boundary (3PB), and a “bulk path” based on oxygen diffusion in LSM. In this work, the ki...