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<p>The chemical states of Fe, Co, and Ni catalyst particles during single-walled carbon nanotube (SWCNT) growth under conventional chemical vapor deposition (CVD) conditions, using ethanol and C<sub>2</sub>H<sub>2</sub> as feedstock gases, were investigated through in situ X-ray absorption fine structure (XAFS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). In situ XAFS analysis of Fe/Al<sub>2</sub>O<sub>3</sub>, Co/Al<sub>2</sub>O<sub>3</sub>, and Ni/Al<sub>2</sub>O<sub>3</sub> samples showed that Fe and Co catalysts were partially carbonized during SWCNT growth with both ethanol and C<sub>2</sub>H<sub>2</sub> feedstock gases, whereas Ni catalysts remained predominantly metallic. XRD and TEM analyses indicated that SWCNTs were grown from Fe<sub>3</sub>C particles and that the surface of Co catalysts underwent carbonization during SWCNT growth under conventional growth CVD conditions. The findings showed that the degrees of carbonization of Fe and Ni catalysts correlated with their bulk carbon solubility. However, the carbonization of Co catalysts significantly exceeded the level predicted by bulk carbon solubility. This deviation is likely attributable to nanosized effects, as suggested by previous quantum chemical molecular dynamics simulations.</p>

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In situ XAFS study on the chemical states of transition-metal nanoparticle catalysts during single-walled carbon nanotube growth under conventional CVD conditions

  • 期刊论文

  • 发表日期：

    2025年6月2日

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  • Shinya Mizuno,
  • Jumpei Horiuchi,
  • Kamal Prasad Sharma,
  • Takahiro Saida,
  • Takahiro Maruyama

摘要

The chemical states of Fe, Co, and Ni catalyst particles during single-walled carbon nanotube (SWCNT) growth under conventional chemical vapor deposition (CVD) conditions, using ethanol and C2H2 as feedstock gases, were investigated through in situ X-ray absorption fine structure (XAFS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). In situ XAFS analysis of Fe/Al2O3, Co/Al2O3, and Ni/Al2O3 samples showed that Fe and Co catalysts were partially carbonized during SWCNT growth with both ethanol and C2H2 feedstock gases, whereas Ni catalysts remained predominantly metallic. XRD and TEM analyses indicated that SWCNTs were grown from Fe3C particles and that the surface of Co catalysts underwent carbonization during SWCNT growth under conventional growth CVD conditions. The findings showed that the degrees of carbonization of Fe and Ni catalysts correlated with their bulk carbon solubility. However, the carbonization of Co catalysts significantly exceeded the level predicted by bulk carbon solubility. This deviation is likely attributable to nanosized effects, as suggested by previous quantum chemical molecular dynamics simulations.