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 nano sheets through an easy and scalable self-assembly method was studied. The NiOx@MnOx@G exhibited a nanostructured NiO nanocrystalline with size around 2.3 nm and an amorphous MnO 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@Mn0x0G nanostructure exhibited significantly better activity for oxygen evolution reaction compared with MnO,,, 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. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.