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 Fex Co1-x OOH 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 )2 Fe(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 Fex Co1-x OOH, and this is confirmed for the first time in this study. The content of Fe in Fex Co1-x OOH, no more than 1/3 of Co, can be controlled by adjusting the in situ anodic oxidation time. Fe0.33 Co0.67 OOH 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.