Highly graphited carbon-coated FeTiO 3 nanosheets in situ derived from MXene: an efficient bifunctional catalyst for Zn-air batteries.

Developing high-efficiency and low-cost catalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is of great significance for the commercialization of rechargeable metal-air batteries. Herein, we demonstrated the construction of graphited carbon-coated FeTiO 3 (FeTiO 3 @C) via in situ annealing Ti 3 C 2 T x nanosheets in a rusted-reactor and its efficient bifunctional activity for rechargeable Zn-air batteries (RZABs). The electron-transport dynamics of FeTiO 3 @C can be improved by using highly conductive graphited carbon derived from Ti 3 C 2 T x . The FeTiO 3 @C catalyst annealed at 500 °C exhibits excellent OER and ORR activities. Specifically, FeTiO 3 @C shows a low overpotential of 323 mV at 10 mA cm -2 and a small Tafel slope of 53 mV dec -1 towards the alkaline OER. During the OER process, FeTiO 3 @C can be partially converted into highly active iron oxyhydroxide via in situ electrochemical reconstruction, which serves as the active species. After being assembled to RZABs, it shows an open-circuit potential of 1.33 V, a high trip efficiency of 63.4% and long-time cycling stability. This work can provide a new avenue for developing bifunctional electrocatalysts for RZABs used in portable devices.