▎ 摘　　要

Different forms of delta-MnO2 were constructed with their reduction sites anchored on non-support or other supports. Morphology, composition, and electrochemical properties of MnO2 and its hybrids were analyzed. Results revealed that MnO2/reduced graphene oxide (rGO) layered hybrid showed a higher BET surface area due to the synergistic effect on the introduction of rGO and the morphologic transformation of anchored MnO2. MnO2/rGO-2 exhibits a higher ratio of Mn3+: Mn4+ content, a better adsorption performance for O-2, and a lower charge-transfer resistance when respect to pristine delta-MnO2. Compared with other MnO2/rGO hybrids, porous MnO2/rGO-2 layered hybrid exhibits the best electrochemical property: a closer four-electron process (3.95), a more positive E ( onset ) (0.92 V vs RHE), and superior long-term durability (98.5% after 25,000 s). Especially, a mechanically reusable Mg-air battery with MnO2/rGO-2 cathode catalyst only exhibits a 5% decay for 264 h.