Regulating Reconstruction‐Engineered Active Sites of <scp>CoP</scp> Electrocatalyst by Br Ions During the Oxygen and Hydrogen Evolution Reaction

An in‐depth understanding of the catalyst surface evolution is crucial for precise control of active sites, yet this aspect has often been overlooked. This study reveals the spontaneous anion regulation mechanism of Br‐doped CoP electrocatalysts in the alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The introduction of Br modulates the electronic structure of the Co site, endowing Br‐CoP with a more metallic character. In addition, P ion leaching promotes the in situ reconstruction of Br‐CoOOH, which is the real active site for the OER reaction. Meanwhile, the HER situation is different. On the basis of P ion leaching, the leaching of Br ions promotes the formation of CoP‐Co(OH) 2 active species. In addition, Br doping enhances the adsorption of *H, showing excellent H adsorption free energy, thereby greatly improving the HER activity. Simultaneously, it also enhances the adsorption of OOH*, effectively facilitating the occurrence of OER reactions. Br‐CoP only needs 261 and 76 mV overpotential to drive the current density of 20 mA cm −2 and 10 mA −2 , which can be maintained unchanged for 100 h. This study provides new insights into anion doping strategies and catalyst reconstruction mechanisms.