Fe Coordination Environment Modulating Oxygen Evolution Reaction Properties of Cobalt Site

Co─Fe layered double hydroxide (LDH) has shown great performance for oxygen evolution reaction (OER), however, the effect of Fe in Co─Fe compounds as well as its mechanism for promoting OER are still of great challenge. Herein, Co─Fe bimetallic silicate hydroxides, with a similar structure of Co─Fe LDH and more advantages, are designed to address the issue about the performance-determining site (PDS). In designed Co─Fe bimetallic silicate hydroxides, two different coordinated Fe ions in cationic layers (Fe³⁺ (Oh)) and anionic layers (Fe³⁺ (Td)) are distinguished to achieve high-efficient OER catalysts, where introducing Al as heteroatom can shield the existence of Fe³⁺ (Td), creating a key contrast. It is found that different coordinated Fe ions modulate OER properties of cobalt sites into different directions: Fe³⁺ (Oh) immensely promotes the OER process on adjacent Co sites, while Fe³⁺ (Td) plays an opposite role. Taking advantage of the above effects, the overpotential has declined to 254 mV at 10 mA cm^-2, showing great progress in this field. The density functional theory (DFT) method identifies Co²⁺ as PDS and elucidates the related mechanisms with electronic structures. This work explores the mechanism of Co─Fe bimetallic effect promoting OER performance, providing a reference for the related controversy.