Structural, Magnetic and Catalytic Properties of a New Vacancy Ordered Perovskite Type Barium Cobaltate BaCoO2.67.

A new vacancy ordered, anion deficient perovskite modification with composition of BaCoO 2.67 (Ba 3 Co 3 O 8 □ 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.