Graphene has attracted tremendous research efforts in the past decades and found broad applications in fields such as gas barriers, electronics, catalysis, etc. In particular, metal-free and heteroatom-doped graphene has attained much success in catalyzing oxygen reduction reactions (ORR) at similar reactivity yet much lower price as compared to the state-of-the-art catalyst platinum. However, due to the possible contamination of metal residue during the graphene oxide synthesis, whether the catalytic activity originates from the doped graphene or comes from the manganese residue is not clear. Due to the detection limit, conventional techniques such as TEM, XPS and XRD are hard to probe the existence of manganese at a concentration as low as a few hundred ppm. In this study, we found that the manganese residue is atomically distributed on the graphene surface in a structure analog to that of enzyme such as cytochrome P450 and porphyrin, where the single metal atom is bounded to ligands and acts as the active site for biologic reactions. The atomic-manganese-doped graphene possesses a much higher ORR catalytic activity than that of manganese oxide nanoparticles or nitrogen-doped graphene. This work not only differentiates the catalytic activity of diverse structures existing on graphene synthesized using conventional graphene oxide synthesis protocol, but may also have great implication on future development of biomimetic materials using graphene as a template.

Manganese deception on graphene

253rd National Meeting (2017)

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