Breakdown of diameter selectivity in a reductive hydrogenation reaction of single-walled carbon nanotubes

TL;DR

This study investigates how the diameter of single-walled carbon nanotubes influences their reductive hydrogenation, revealing unexpected diameter-dependent selectivity and yield variations linked to alkali metal intercalation efficiency.

Contribution

It demonstrates that diameter selectivity in reductive hydrogenation is more complex than simple curvature effects, highlighting the role of alkali dopant accessibility.

Findings

Yield decreases in small-diameter tubes due to limited dopant access.

Lower diameter selectivity occurs above a critical diameter.

Reaction yield and selectivity strongly depend on nanotube diameter.

Abstract

Reductive hydrogenation was applied to two types of single-walled carbon nanotubes with different diameter range. Alkali metal intercalation, followed by reaction with methanol, led to hydrogenated products. Both yield and selectivity of this reaction showed strong dependence on diameter, contrary to expectation based on simple curvature effects. The observed yield, as detected by thermogravimetry-mass spectroscopy and 1H-NMR, is drastically reduced in small-diameter tubes where the alkali dopant does not reach the inside of the bundles. Wide range optical transmission measurements were employed to determine the selectivity and indicate that besides higher yield, lower diameter selectivity occurs above a critical diameter.