Remarkable oxygen-evolution activity of a perovskite oxide from the Ca_2-xSr_xFe₂O_6-δ series

Herein in we report the unprecedented catalytic activity of an iron-based oxygen-deficient perovskite for the oxygen-evolution reaction (OER). The systematic trends in OER activity as a function of composition, defect-order, and electrical conductivity have been demonstrated, leading to a methodical increase in OER catalytic activity: Ca₂Fe₂O_6-δ2O_6-δ2Fe₂O_6-δ. Sr₂Fe₂O_6-δ also has the highest electrical conductivity and a unique type of defect-order. In conventional experiments using glassy carbon electrode, Sr₂Fe₂O_6-δ shows better OER activity than the current state of the art catalysts, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ and RuO₂. It also offers a high intrinsic electrical conductivity, which allows it to act as a catalyst without the need for glassy carbon electrode or carbon powder. Pure disks of this material exhibit an outstanding activity for OER, without any additives or need for electrode preparation. (copyright 2019 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)