Full Bulk‐Structure Reconstruction into Amorphorized Cobalt–Iron Oxyhydroxide Nanosheet Electrocatalysts for Greatly Improved Electrocatalytic Activity

Abstract The electrochemical oxidation is considered as an innovative chemical strategy to induce the structure reconstruction for the enhanced electrocatalytic performances. However, the structure reconstruction is limited to the shallow surface, not achieving full utilization of inner active components. Herein, the full bulk‐structure reconstruction into highly active amorphorized cobalt–iron oxyhydroxide nanosheets through the electrochemical oxidation of the cobalt–iron phosphide precatalyst is reported. As confirmed by ex situ X‐ray diffraction and photoelectron, Raman, and electron energy‐loss spectroscopies, the phosphorus species leached from the phosphide provide etching effect, promoting the oxidation of residual cobalt‐iron species for in‐depth bulk amorphorization. The unique core‐shell structure of amorphorized cobalt–iron oxyhydroxide nanosheets encapsulated by the carbon shell (denoted as Co 0.8 Fe 0.2 OOH @ C) is constructed to offer highly exposed abundant active sites and fast charge transfer capability. The excellence of the full structure reconstructed Co 0.8 Fe 0.2 OOH@C electrocatalysts is confirmed demonstrating greatly improved activity (low overpotentials of 254 and 292 mV at 10 and 100 mA cm −2 ) and long‐term durability (negligible activity decay for continuous operation of 15 days at 100 mA cm −2 ) for oxygen evolution reaction applications.