Inverse Spinel Cobalt–Iron Oxide and N‑Doped Graphene Composite as an Efficient and Durable Bifuctional Catalyst for Li–O₂ Batteries

Rational design of efficient bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts are critical for rechargeable Li–O₂ batteries. Here, we report inverse spinel Co­[Co,Fe]­O₄/nitrogen-doped graphene (NG) composite used as a promising catalyst for rechargeable Li–O₂ batteries. The cells with Co­[Co,Fe]­O₄/NG catalyst exhibit high initial capacity, remarkable cyclability, and good rate capability. Moreover, the overpotential of the Li–O₂ batteries is reduced significantly. The improved ORR/OER performances are attributed to the good property of Co­[Co,Fe]­O₄ with an inverse spinel structure toward ORR and the improved electronic conductivity of N-doped graphene. The density functional theory (DFT) calculation shows the rate limitation step for ORR on the inverse spinel surface is the growth of the Li₂O₂ cluster while the rate limitation step for the OER pathway is the oxidation of Li₂O₂. The inverse spinel surface in Co­[Co,Fe]­O₄/NG is more active than that of the normal spinel phases for the Li–O₂ battery reactions. This work not only provides a promising bifunctional catalyst for practical metal air batteries but also offers a general strategy to rationally design catalysts for various applications