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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