Influence of the reaction temperature on the oxygen reduction reaction on nitrogen-doped carbon nanotube catalysts

• N-doped carbon nanotubes prepared by CVD method with iron as growth catalyst.
• Influence of iron on the oxygen reduction reaction activity accessed by the RRD electrode.
• Influence of the temperature on the ORR activity and stability.
• Comparison of the ORR stability between N-CNT and Pt/C catalysts.

Nitrogen-doped carbon nanotubes (N-CNT) were synthesized at 700 °C via the chemical vapour deposition (CVD) method and were used as catalysts in the oxygen reduction reaction (ORR) in 0.1 M KOH. The activity toward the ORR and the stability of these N-CNTs in alkaline solution were studied as a function of the reaction temperature and of the chemical treatment applied to the catalyst. The kinetic analysis of these catalysts was also carried out and compared to the ORR performance of the commercial Pt/C Vulcan XC72 catalyst. N-CNT-700BW catalyst without any chemical treatment after the CVD synthesis, possesses a half-wave potential E1/2 of approximately 0.82 V vs. RHE, 50 mV lower than the E1/2 value of Pt/C catalyst and a specific current density Jk at 0.9 V = 5.46 mA/mg at T = 25 °C. Removal of the major part of the iron growth catalyst by a chemical treatment resulted in a strongly decreased but still measurable activity. The activation energy of the N-CNT-based catalyst was calculated and is around 38 kJ mol−1 at an ORR overpotential of 300 mV. Increasing the temperature of the electrolyte up to 75 °C leads to a positive shift of the half-wave potential of the reaction as well as an increase of the H2O2 escape. The long-term stability test has also been conducted and indicates a good stability of the activity of the N-CNT-based catalysts under operation in alkaline media.

Figure optionsDownload high-quality image (326 K)Download as PowerPoint slide