Recent experimental reports proposed that pyridinic-type sites on the open-edges of carbon nanotubes (CNTs) may contribute to the high catalytic activity for oxygen reduction reaction (ORR) on nitrogen-doped CNTs (N-CNTs). Herein, we performed first-principles spin-polarized density functional theory (DFT) calculations to examine the catalytic steps for ORR and water formation reaction (WFR) on the open-edges of N-CNTs. For half N doping on the open-edge of CNTs (HN-CNTs), O2 can be adsorbed and partially reduced on the C-N bridge site. There is no energy barrier for the ORR step. The subsequent WFR between reduced O2 and H+ needs to overcome an energy barrier of 0.30~0.54 eV for the formation of two water molecules, that complete an electrocatalytic reaction cycle on the cathode catalyst for hydrogen fuel cells (HFCs). For full N doping on the open-edge of CNTs (FN-CNTs), O2 can be reduced and dissociated on the N-N bridge site. There is an energy barrier of 0.57 eV during the ORR. Then, the WFR steps can be finished without energy barrier. The rate-limiting steps for the full electrocatalytic reactions on the N-CNTs as cathode catalyst for HFCs are determined.

Catalytic reactions on the open-edge sites of nitrogen-doped carbon nanotubes as cathode catalyst for hydrogen fuel cells

247th National Meeting (2014)

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