Highly graphited carbon-coated FeTiO₃ 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 FeTiO₃ (FeTiO₃@C) via in situ annealing Ti₃C₂T_x nanosheets in a rusted-reactor and its efficient bifunctional activity for rechargeable Zn-air batteries (RZABs). The electron-transport dynamics of FeTiO₃@C can be improved by using highly conductive graphited carbon derived from Ti₃C₂T_x. The FeTiO₃@C catalyst annealed at 500 °C exhibits excellent OER and ORR activities. Specifically, FeTiO₃@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, FeTiO₃@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.