Long-Alkyl-Chain Phosphonium Surfactant Molecular Wrapping to Block Oxygen Impurities in n-Type Carbon Nanotubes for Thermoelectric Applications

Abstract

In several electronics applications, the instability of components containing n-type carbon nanotubes (CNTs) to atmospheric oxidation in harsh environments or high temperatures is a significant concern. Here, we reported that a dense molecular wrapping of n-type CNTs with phosphonium salts reduced the exposed CNT surface by 79% and suppressed the electrophilic reaction of oxygen on the CNT surface. After aging at 353 K for 28 days, 89% of its initial thermoelectric power factor was retained (290.3 μW m–1 K–2). This opens new avenues for the use of n-type materials in high-temperature electronics.

Prolonging the n-type conduction of thermoelectric carbon nanotubes exposed to warm air by mixing hydrated water into the adsorbed dopant layers composed of Li+-receptor molecules

“…17 Furthermore, in CNT samples with characteristically small specific surface areas (<100 m 2 g −1 ), an adsorbed molecular layer consisting of a phosphonium salt surfactant has been suggested to block water molecules and oxygen molecules (at 353 K) from directly contacting doping sites, stabilizing the delocalized negative charge of the CNT. 18 For high-temperature applications, investigating how the size, charge density, and hydrophilicity/hydrophobicity of the dopant shell covering the negatively charged doping sites affect the n-type conduction lifetime and developing facile techniques to improve the oxygen shielding function of the dopant shell and the oxygen permeability of the matrix would provide valuable insights.…”