Boosting Oxygen Reduction Activity of Manganese Oxide Through Strain Effect Caused By Ion Insertion

Insights into the Electrochemical Behavior of Manganese Oxides as Catalysts for the Oxygen Reduction and Evolution Reactions: Monometallic Core-Shell Mn/Mn3 O4

Overcoming the sluggish electrode kinetics of both oxygen reduction and evolution reactions (ORR/OER) with non-precious metal electrocatalysts will accelerate the development of rechargeable metal-air batteries and regenerative fuel cells. The authors investigated the electrochemical behavior and ORR/OER catalytic activity of core-porous shell Mn/Mn₃ O₄ nanoparticles in comparison with other manganese dioxides (β- and γ-MnO₂ ), and benchmarked against Pt/C and Pt/C-IrO₂ . Under reversible operation in O₂ -saturated 5 M KOH at 22 °C, the early stage activity of core-shell Mn/Mn₃ O₄ shows two times higher ORR and OER current density compared to the other MnO₂ structures at 0.32 and 1.62 V versus RHE, respectively. It is revealed that Mn(III) oxidation to Mn(IV) is the primary cause of Mn/Mn₃ O₄ activity loss during ORR/OER potential cycling. To address it, an electrochemical activation method using Co(II) is proposed. By incorporating Co(II) into MnO_x , new active sites are introduced and the content of Mn(II) is increased, which can stabilize the Mn(III) sites through comproportionation with Mn(IV). The Co-incorporated Mn/Mn₃ O₄ has superior activity and durability. Furthermore, it also surpassed the activity of Pt/C-IrO₂ with similar durability. This study demonstrates that cost-effective ORR/OER catalysis is possible.

The synergistically enhanced activity and stability of layered manganese oxide via engineering of defects and K+ ions for oxygen electrocatalysis

Structural defects and interlayered ions are two classic architectures that regulate the electrochemical activity of layered manganese oxides. However, the synergistic effect of defects and interlayered ions and how it...