Optimization sulfur doping of electronic structure with metal active center for defect-rich FeCo bimetallic hydroxyl oxide catalysts

Defect engineering is an effective method to tune electronic states, which can provide active sites for electrocatalytic reactions. Herein, a highly efficient sulfur-doped bimetallic hydroxyl oxide (FeCo/Vc-S) has been synthesized by a two-step hydrothermal reaction, which has the rich defective and amorphous phases. The low coordination number of Co in X-ray absorption fine structure (XAFS) analysis further confirms the Co center is the active center, while Fe plays a role in optimizing the electronic structure of active Co species. Meanwhile, abundant oxygen vacancies and metal defects are also found in the material, which greatly enhances the adsorption and desorption efficiency of × OOH. Moreover, density functional theory (DFT) shows that the addition of S atom alters the electron distribution of adjacent metal atoms, thus adjusting the electron distribution of the metal active site. These positive factors endow FeCo/Vc-S with excellent OER electrocatalytic performance, with an overpotential of only 255 mV and Tafel slope is 64.3 mV·dec⁻¹ at a current density of 10 mA cm⁻². This study provides a new route for the synthesis of bimetallic hydroxyl oxides, and also provides theoretical design for the identification of active centers and defection-rich catalysts.