La0.6Sr0.4Co0.2Fe0.79M0.01O3-? (M = Ni, Pd) perovskites synthesized by Citrate-EDTA method: Oxygen vacancies effect on electrochemical properties

La0.6Sr0.4Co0.2Fe0.8O3-? (LSCF08), La0.6Sr0.4Co0.2Fe0.79Ni0.01O3-? (LSCF08-Ni) and La0.6Sr0.4Co0.2Fe0.79Pd0.01O3-? (LSCF08-Pd) perovskites were synthesized by Citrate-EDTA method, by using NiCl2 or PdCl2 as metal precursors, and their physicochemical properties were characterized by XRD, TGA, TPD and TPR. XRD data evidenced an expansion of the lattice parameters of LSCF08-Pd, while a contraction of the lattice occurred for LSCF08-Ni, with respect to the undoped LSCF, suggesting different oxygen vacancies content in the perovskite (confirmed by TGA) likely due to a different oxidation state of Ni and Pd species stabilized in the structure. TEM analyses performed over LSCF08-Pd revealed the presence of metallic Pd nanoparticles well dispersed in the matrix that accounts for the increased reducibility of the Co and Fe species with respect to LSCF08-Ni and undoped perovskite. AC impedance measurements that were carried out on symmetric cells consisting of LSCF-based materials deposited onto Ce0.8Gd0.2O2-? (GDC) electrolyte proved the enhanced electrochemical performances of Ni/Pd doped LSCF. The electrochemical characterization of LSCF08, LSCF08-Ni and LSCF08-Pd electrodes was completed by performing cyclic voltammetry experiments in the range of temperature 600-800 °C, varying the potential (U) between 0.3 V and -1 V, at scan rates in the range 1-50 mV s-1 and working under flow of 0.7 vol% O2 in He (30 ml/min).