Vacancy Defect-Rich Perovskite SrTiO₃/Ti₃C₂ Heterostructures In Situ Derived from Ti₃C₂ MXenes with Exceptional Oxygen Catalytic Activity for Advanced Zn–Air Batteries

Abstract

The electrochemical performance enhancement for Zn–air batteries (ZABs) based on a perovskite SrTiO3 electrocatalyst is seriously obstructed by sluggish oxygen reduction and evolution reaction (ORR/OER) kinetics. Herein, we develop an in situ phase transformation strategy to synthesize Ti3C2@SrTiO3 MXene nanocomposites as a bifunctional electrocatalyst for ZABs. The Ti3C2@SrTiO3 heterostructures guarantee excellent structural stability and promote interfacial charge transfer to accelerate the electrocatalytic redox kinetics. Ti3C2 MXene not only promotes fast electronic/ionic transfer but also stably anchors SrTiO3 nanocubes without aggregation to provide abundant catalytic active sites and prominent structural stability. Advantageous oxygen vacancies introduced in SrTiO3 nanocrystals could effectively regulate the electronic structure of active sites, triggering higher intrinsic electrocatalytic activity. Furthermore, Ti vacancies in the MXene display an important synergetic effect to promote the electron transfer in Ti3C2@SrTiO3 heterostructures. Theory calculations reveal that abundant vacancy defects substantially strengthen the oxygen intermediates’ adsorption ability on the Ti3C2@SrTiO3 catalyst, essentially lowering the energy barrier for the ORR/OER process. As expected, the ZABs based on the Ti3C2@SrTiO3 catalyst exhibit exceptional electrochemical performance, an extraordinary open-circuit voltage of 1.44 V, and an essentially improved power density of 122 mW cm–2. The in situ transformation and defect modulation strategies provide enlightening clues to design a high-performance ZAB cathode catalyst.