X-ray photoelectron spectroscopy analysis of (Ln1−xSrx)CoO3−δ (Ln: Pr, Nd and Sm)

► Sr and various lanthanide elements doped complex perovskites electrodes. ► Merged oxygen peaks of Ln1−xSrxCoO3−δ and generation of more oxygen vacancies on the surface of electrodes as a function of Sr and lanthanide concentration. ► Enhancement of the binding energy in Sr spectra by the substitution of Sr into the A-site of a perovskite. ► The partial existence of Co4+ to provide small polaron hopping by electrons, maintaining charge neutrality and providing electronic conduction.