Enhanced electrocatalytic performance of NiOx@MnOx@graphene for oxygen reduction and evolution reactions

Oxygen electrodes for oxygen evolution reaction and oxygen reduction reaction were intensively investigated due to high overpotential required to drive the four-electron process. A NiOx@MnOx@G nanostructure supported homogenously on graphene nanosheets through an easy and scalable self-assembly method was studied. The NiOx@MnOx@G exhibited a nanostructured NiOx nanocrystalline with size around 2.3 nm and an amorphous MnOx with controllable thickness. The 25% NiOx@MnOx@G showed remarkable activity for oxygen reduction reaction with a 4-electron process, the half-wave potential was 50 mV, but the stability of 25% NiOx@MnOx@G was better than Pt/C-JM. NiOx@MnOx@G nanostructure exhibited significantly better activity for oxygen evolution reaction compared with MnOx, which can demonstrate that NiOx could tune the activity of surface amorphous MnOx and dramatically increased oxygen evolution reaction activity. NiOx@MnOx@G is demonstrated with superior oxygen catalysts performance for reversible oxygen evolution and oxygen reduction reaction, due to the synergistic effect of NiOx and amorphous MnOx.