High‐Performance Reversible Oxygen Reduction/Evolution Gas Diffusion Electrodes with Multivalent Cation Doped Core‐Shell Mn/Mn3O4 Catalysts

Abstract The development of precious‐metal‐free catalysts with bifunctional activities for both oxygen reduction and evolution reactions (ORR/OER) is crucial for the advancement of regenerative fuel cells and rechargeable metal−air batteries. Manganese oxides (MnO x ) have emerged as promising bifunctional catalysts. However, MnO x electrodes typically exhibit poor ORR/OER cycling stability owing to polarization‐induced MnO x redox reactions and phase transition. To address this issue, we developed metallic cation (i. e., Co 2+ , Ni 2+ , Cu 2+ , or Bi 3+ ) doped MnO x /carbon electrodes using potentiodynamic, potentiostatic and galvanostatic methods. Among the explored dopant cations Ni 2+ intercalated into MnO x under acidic conditions using a slow‐scan cyclic voltammetry method, significantly enhanced the ORR/OER activity and stability of MnO x . Alongside electrochemical doping, MnO x also underwent redox reactions leading to changes in Mn valence and phase transitions. The Ni‐incorporated MnO x gas diffusion electrode (GDE) demonstrated exceptional stability for over 120 accelerated OER and ORR cycles at ±10 mA cm −2 in 5 M KOH, surpassing the performance of the Pt/C−IrO 2 benchmark. Furthermore, it achieved OER current densities of approximately 22 mA cm −2 at 1.65 V RHE , which was twice as high as that of Pt/C−IrO 2 .