O-hetero-Fe-N3.6 active sites in ZIF-derived carbon nanotubes for the electrocatalytic oxygen evolution reaction

In order to clarify competitive reactions between lattice oxygen oxidation mechanism (LOM) with lower energy barrier and conventional adsorbate evolution mechanism (AEM), O-hetero-Fe-N3.6 active site was built in ZIF-derived carbon nanotubes to transform traditional AEM mechanism on iron-unsaturated active site into LOM mechanism during electrocatalytic oxygen evolution reaction (OER). In-situ attenuated total reflectance infrared (ATR-FTIR) and X-ray absorption fine structure results confirmed the formation of Fe-O bonds and a Fe-N3.6 structure, indicating that O-hetero-Fe-N3.6 active sites were built. A key intermediate O* was detected on ATR-FTIR, which suggests that OER proceeded via LOM mechanism. The alkaline OER activity and stability are enhanced on the O-hetero-Fe-N3.6 active sites to accelerate rate-determining step of water oxidation. The ZIF-derived carbon nanotubes expose more O-hetero-Fe-N3.6 active sites to facilitate electron and mass transfer during electrocatalytic OER. The Fe-NC catalyst exhibits excellent OER activity with an overpotential of 235 mV at 10 mA cm−2 and Tafel slope of 98 mV dec−1 in 1 M KOH.