(560cn) Transitional Metal Coordinated with N-Doped Carbon Nanofiber Integrated with Graphene for the Oxygen Evolution Reaction in Acid

Title: Transitional metal coordinated with N-doped carbon nanofiber integrated with graphene for the oxygen evolution reaction in acid

Author: Chaojun Lei, Lecheng Lei, Yang Hou*

[Chaojun Lei is reportor, Yang Hou is corresponding author]

Abstract: Proton exchange membrane (PEM) water electrolyzer requiring acidic electrolyte has been regarded as the most promising water splitting electrolyzer, however it is still limited due to the oxygen evolution reaction (OER) catalysts with both high activity and stability remain Ru-based and/or Ir-based noble-metal materials in acid medium. Developing high-peromance low cost electrocatalysts for OER in acid is crucial to realize large-scale water splitting to generate hydrogen energy. Inexpensive transitional metal (Fe, Co, Ni) materials are considered as ideal electrocatalysts to replace noble metal catalyst. To overcome the instability and understand the active sites of transitional metal materials under harsh acid electrolyte for OER is of great significance. In this study, we used graphite flake as substrate to load polyamine via electrochemical deposition and then made polyamine to coordinate with transitional metal by impregnation and pyrolysis. The prepared transitional metal-nitrogen coordinated carbon-based electrocatalysts delivered an impressive OER activity. Beyond OER performance, we also consider the role of transitional metal in this carbon-based material. The role is that the content of transitional metal adjusted by the impregnation concentration has significant impact in OER. The transitional metal dispersed in carbon-based material as transitional metal-nitrogen coordinated sites rather than particles showed the best OER performance. Moreover, the pyrolysis temperature also affects performance that the catalysts carbonized under 900℃ showed the best OER performance. As a typical example, the active site (FeN₄) was detected by X-ray photoemission spectroscopy (XPS), X-ray absorption near edge structure (XANES), Extended X-ray absorption fine structure (EXAFS) and KSCN poisoning experiment. The transitional metal coordinated with nitrogen was harder than transitional metal oxides to dissolve in acidic electrolyte, exhibiting remarkable stability. Thus, this study opens a new road to rational design and synthesis of highly efficient transition-metal/nitrogen-doped carbon catalysts and identifies the active sites.