Catalytic reaction on FeN4/C site of nitrogen functionalized carbon nanotubes as cathode catalyst for hydrogen fuel cells

•For the first time, a whole electrocatalytic reaction cycle involving ORR and WFR on the FeN4/C site is investigated.•O2 molecule can be adsorbed and partially reduced on FeN4/C site without any activation energy barrier.•The partially reduced O2 can react with H+ and e− through a direct pathway and form water molecules without energy barrier.•Through an indirect pathway, there is an activation energy barrier of 0–0.16 eV for the formation of H2O.•This work may help to understand experimental results on ORR activity over FeN4/CNT catalysts.

We utilized first-principles spin-polarized density functional theory (DFT) calculations to study the electrocatalytic reaction steps on FeN4/C site of carbon nanotubes. O2 molecule can be adsorbed and partially reduced on FeN4/C site without any activation energy barrier. The partially reduced O2 further reacts with H+ and e− through a direct pathway (DPW) and form two water molecules without any activation energy barrier. Through an indirect pathway (IDPW), there is an activation energy barrier of ~ 0.15 eV for the formation of the first H2O molecule. The formation of the second H2O molecule through IDPW does not have any activation energy barrier.

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