Elevating the d‐Band Center of Six‐Coordinated Octahedrons in Co₉S₈ through Fe‐Incorporated Topochemical Deintercalation

Abstract Significant efforts have been dedicated to boosting the electrocatalytic activity of Co 9 S 8 for the oxygen evolution reaction (OER); however, with limited improvement in its intrinsic activity, which relies on careful band engineering. Fe possesses one less 3d electron and lower electronegativity than Co, suggesting a higher d‐band center when forming polyhedron with S anions. Here, to improve the intrinsic activity by elevating the d‐band center, the six‐coordinated octahedrons in Co 9 S 8 are redesigned utilizing an Fe‐incorporated topochemical deintercalation method. Through substituting partial Co octahedrons by Fe octahedrons with higher d‐band, the overall d‐band center is regulated to achieve optimized adsorption and thus superior OER activity. With a reduction of 95 mV on the overpotential (at 10 mA cm −2 ), this work sheds lights on the design of OER catalysts through polyhedron engineering using topochemical deintercalation.