Structural, magnetic and catalytic properties of a new vacancy ordered perovskite type barium cobaltate BaCoO_2.67

A new vacancy ordered, anion deficient perovskite modification with composition of BaCoO2.67(Ba3Co3O8􀀀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 Ba0.5Sr0.5Co0.8Fe0.2O3–y, confirming that charge-ordered anion deficient non-cubic perovskites can be highly efficient catalysts