Designed construction of hierarchical CoOOH@Co–FeOOH double-shelled arrays as superior water oxidation electrocatalyst

Hollow structures with multiple shells and complex compositions are especially attractive as highly active electrocatalysts towards oxygen evolution reaction (OER) due to their uniquely structural and compositional feature. In this work, hierarchical [email protected]–FeOOH double-shelled arrays (DSAs) are designed and fabricated through an etching/coprecipitation reaction followed by a simple electrooxidation reaction. The reaction between ZIF-67 and FeSO4 solution is of crucial importance in developing double-shelled structure and highly active material. The formed FeCo layer-double-hydroxide (LDH) not only functions as microreactor and protective layer to effectively prevent CoOOH from collapse, but also acts as precursor to deliver active Co–FeOOH. As expected, the as-prepared hierarchical [email protected]–FeOOH DSAs exhibit superior OER activity with a low overpotential of 224 ​mV and a small Tafel slope of 32 ​mV dec−1, far more outperforming RuO2 benchmark. The outstanding performance can be attributed to the remarkable electron transfer rate, robust structure, and abundant accessible active sites.