Remarkable Oxygen‐Evolution Activity of Ca2‐xSrxFe2O6‐δ

The unprecedented catalytic activity of an iron‐based oxygen‐deficient perovskite for oxygen‐evolution reaction (OER) is reported, given the need for catalysts based on earth‐abundant elements. In addition, systematic trends in oxygen‐evolution activity as a function of composition, defect‐order and electrical conductivity have been demonstrated, leading to a methodical increase in OER catalytic activity: Ca2Fe2O6‐δ < CaSrFe2O6‐δ < Sr2Fe2O6‐δ. The latter material, which has the highest electrical conductivity and a unique type of defect‐order, exhibits the best OER activity. In conventional experiments using glassy carbon electrode, this compound shows superior OER activity compared to the current state of the art catalysts, Ba0.5Sr0.5Co0.8Fe0.2O3−δ and RuO2. It also offers an additional advantage, namely high intrinsic electrical conductivity, which allows Sr2Fe2O6‐δ to act as a catalyst without the need for glassy carbon electrode or carbon powder, that are frequently used for enhancing the charge transport in OER catalysts. Indeed, pure disks of this material exhibit an outstanding activity for OER, without any additives or need for electrode preparation.

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