Temperature controlled surface chemistry of nitrogen-doped mesoporous carbon and its influence on Pt ORR activity

• The nitrogen content of amorphous nanostructured carbon was varied by heating at different temperatures.
• Nitrogen content and graphiticity are reciprocal to each other.
• Microstructure was crucial in determining the effect of nitrogen defects on size and dispersion of platinum nanoparticles.
• High nitrogen content and small Pt size resulted in enhanced catalyst–support interaction.
• We provide a way to tailor nitrogen-doped carbon for high Pt oxygen reduction reaction activity.

In this work, the influence of surface nitrogen on the dispersion and oxygen reduction reaction (ORR) activity of Pt nanoparticles (NPs) supported on nitrogen-doped mesoporous carbon (NMC) was investigated. The NMCs were synthesized from a modified SBA-15 template to impart a disordered pore structure. The nitrogen content was thermally controlled by heating the NMCs to 800, 1000, 1200, or 1400 °C. X-ray diffraction and Raman spectroscopy showed that the nitrogen content and the graphiticity of NMC were inversely coupled. Pt NPs dispersion worsened with a decrease in nitrogen content or increase in the graphiticity. The highest ORR mass activity was obtained for Pt supported on NMC treated at 1000 °C. However, the highest ORR specific activity was obtained for Pt supported on NMC treated at 1400 °C. The results of this work show that both the nitrogen content and the carbon graphiticity can be tailored to yield Pt ORR catalysts with excellent dispersion and high ORR activity.

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