A Synergistic Catalytic Mechanism for Oxygen Evolution Reaction in Aprotic Li–O₂ Battery

The large polarization of a Li–O 2 battery is derived from oxygen evolution reaction (OER) processe. To achieve a long-life Li–O 2 battery with high round-trip efficiency, various catalysts have been extensively investigated for oxygen cathodes, especially for OER processes. Here, we designed an in situ growth of α-MnO 2 /RuO 2 composite on a graphene nanosheet with a carbon-embedded structure as the cathode electrode for a Li–O 2 battery. The synergistic catalytic effect between the α-MnO 2 and RuO 2 has significantly improved the OER kinetics. The fabricated Li–O 2 battery can deliver a high reversible capacity of 2895 mAh/g composite with a low charge overpotential of 0.25 V (0.34 V lower than bare RuO 2 cathode). The results revealed that more LiO 2 intermediates formed when α-MnO 2 was introduced into the RuO 2 electrode during the oxidation of Li 2 O 2 . The facilitation of the initial Li extraction was confirmed by density functional theory (DFT) calculations, which shows that the α-MnO 2 and RuO 2 interfaces can stabilize the primary Li ions and Li 2– x O 2 intermediates, respectively. Subsequently, Li 2– x O 2 would be easily oxidized to O 2 by RuO 2 catalyst. With the synergy between α-MnO 2 and RuO 2, the initial delithiation process and O 2 evolution are promoted simultaneously. By combining theoretic and experimental results, we proposed a synergistic catalytic mechanism for the OER processes.