Mn doped CoFe layered double hydroxides lead to d-d orbital repulsion toward advanced electrocatalysts for oxygen evolution reaction

Currently, developing highly active and low-cost electrocatalytic materials for oxygen evolution reaction (OER) is an enormously grand challenge. Herein, we developed a novel and highly active Mn doped Co2Fe layer double hydroxide (LDH) electrocatalyst for OER. We discovered that these electrocatalytic materials can be directly grown on carbon papers to construct high-specific-surface-area electrode, which shows the lowest overpotential of 266 mV at 10 mA cm−2. Furthermore, after introducing Mn element, DFT + U calculation found that the ∗OOH of Fe-site on Co2Fe0.67Mn0.33 LDH could draw more electrons than Co2Fe LDH due to the electronegativity differences between Fe-site on Co2Fe0.67Mn0.33 LDH and Fe-site on Co2Fe LDH, which is reason that the energy level of Fe 3d (eg) was obviously downshifted by d-d repulsion of Mn 3d and Fe 3d in the neighboring sites of Co2Fe0.67Mn0.33 LDH after doped Mn element, which leads to reduce charge-transfer energy from O 2p to Fe 3d (eg) to promote oxygen evolution processes for OER. Meanwhile, the band gap is also decreased after doped Mn element in Co2Fe LDH due to the downshifted eg orbital energy of Fe 3d. This study gives a general avenue to design and developing efficiently active LDH electrocatalysts for OER in the future.