Activating CoOOH Porous Nanosheet Arrays by Partial Iron Substitution for Efficient Oxygen Evolution Reaction

Iron‐substituted CoOOH porous nanosheet arrays grown on carbon fiber cloth (denoted as FexCo1−xOOH PNSAs/CFC, 0≤x≤0.33) with 3D hierarchical structures are synthesized by in situ anodic oxidation of α‐Co(OH)2 NSAs/CFC in solution of 0.01 m (NH4)2Fe(SO4)2. X‐ray absorption fine spectra (XAFS) demonstrate that CoO6 octahedral structure in CoOOH can be partially substituted by FeO6 octahedrons during the transformation from α‐Co(OH)2 to FexCo1−xOOH, and this is confirmed for the first time in this study. The content of Fe in FexCo1−xOOH, no more than 1/3 of Co, can be controlled by adjusting the in situ anodic oxidation time. Fe0.33Co0.67OOH PNSAs/CFC shows superior OER electrocatalytic performance, with a low overpotential of 266 mV at 10 mA cm−2, small Tafel slope of 30 mV dec−1, and high durability. In situ anodic oxidation of α‐Co(OH)2 is developed to fabricate 3D FexCo1−xOOH porous nanosheet arrays for water oxidation. During the transformation from α‐Co(OH)2 to FexCo1−xOOH, the partial CoO6 octahedrons in CoOOH can be substituted by the unsaturated FeO6 octahedrons. The FexCo1−xOOH PNSAs/CFC exhibits the outstanding electrocatalytic performance for OER with low onset potential, small Tafel slope, and excellent durability.