*2.1. Preparation of Perovskite (La0.8Sr0.2Mn0.5Co0.5O3-*δ*. LSMCO)*

Stoichiometrically calculated amounts of lanthanum(III) nitrate hydrate (La(NO3)3·6H2O, 99.9%, Sigma Aldrich, St.Louis, MO, USA), strontium nitrate (Sr(NO3)2, 98%, Samchun), manganese(II) nitrate tetrahydrate (Mn(NO3)2·4H2O, 97%, Sigma Aldrich, St.Louis, MO, USA) and cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O, 97%, Samchun, Seoul, Korea) were used to prepare La0.8Sr0.2Mn0.5Co0.5O3-<sup>δ</sup> perovskites (LSMCO). The citric acid (HOC(COOH)(CH2COOH)2 and 99.5%, Samchun, Seoul, Korea) and ethylenediaminetetraacetic acid (EDTA, 99.5%, Sigma Aldrich, St. Louis, MO, USA) were used as the chelating agent. The obtained powder was calcined at 1273 K for 5 h.
