▎ 摘　　要

Development of inexpensive and efficient oxygen evolution reaction (OER) catalysts in acidic environment is very challenging, but it is important for practical proton exchange membrane water electrolyzers. A molecular iron-nitrogen coordinated carbon nanofiber is developed, which is supported on an electrochemically exfoliated graphene (FeN4/NF/EG) electrocatalyst through carbonizing the precursor composed of iron ions absorbed on polyaniline-electrodeposited EG. Benefitting from the unique 3D structure, the FeN4/NF/EG hybrid exhibits a low overpotential of approximate to 294 mV at 10 mA cm(-2) for the OER in acidic electrolyte, which is much lower than that of commercial Ir/C catalysts (320 mV) as well as all previously reported acid transitional metal-derived OER electrocatalysts. X-ray absorption spectroscopy coupled with a designed poisoning experiment reveals that the molecular Fe-N-4 species are identified as active centers for the OER in acid. The first-principles-based calculations verify that the Fe-N-4-doped carbon structure is capable of reducing the potential barriers and boosting the electrocatalytic OER activity in acid.