A Potassium-Doped Perovskite-Based Nanocomposite as an Efficient Bifunctional Oxygen Electrocatalyst for Rechargeable Zn-Air Batteries.

Bifunctional oxygen electrocatalysts play a crucial role in the performance of rechargeable zinc-air batteries (ZABs), directly impacting key parameters such as capacity, round-trip efficiency, and durability. The ideal electrocatalysts for ZAB air electrodes must exhibit high catalytic activity for both oxygen reduction and oxygen evolution reactions in alkaline medium. This study presents a potassium-ion doping strategy to engineer the electron and defect structures of the perovskite oxide main phase, promoting phase separation to form a nanocomposite consisting of a perovskite phase and a secondary phase with an intergrowth structure. The resulting nanocomposite catalyst exhibits increased concentrations of Co and oxygen vacancies, enhanced hydrophilicity, and improved adsorption of oxygen intermediates. As a result, the catalyst with the optimized composition demonstrates exceptional bifunctional activity and superior durability, leading to extended cycling stability and improved energy conversion efficiency in ZABs. Notably, it achieves a 42% increase in power density compared to the potassium-free pristine catalyst, a reduced voltage gap (ΔE = 0.83 V), and an extended cycle life of over 250 h. This work introduces a novel design paradigm for advanced metal-air battery catalysts through potassium-promoted defect-engineered heterostructure manipulation of perovskite oxides.