Structural, Magnetic and Catalytic Properties of a New Vacancy Ordered Perovskite Type Barium Cobaltate BaCoO_2.67

Abstract

A new vacancy ordered, anion deficient perovskite modification with composition of BaCoO_2.67 (Ba₃ Co₃ O₈ □₁ ) has been prepared via a two-step heating process. Combined Rietveld analysis of neutron and X-ray powder diffraction data shows a novel ordering of oxygen vacancies not known before for barium cobaltates. A combination of neutron powder diffraction, magnetic measurements, and density functional theory (DFT) studies confirms G-type antiferromagnetic ordering. From impedance measurements, the electronic conductivity of the order of 10^-4 S cm^-1 is determined. Remarkably, the bifunctional catalytic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is found to be comparable to that of Ba_0.5 Sr_0.5 Co_0.8 Fe_0.2 O_3-y , confirming that charge-ordered anion deficient non-cubic perovskites can be highly efficient catalysts.