A facile approach towards sulfonate functionalization of multi-walled carbon nanotubes as Pd catalyst support for ethylene glycol electro-oxidation

Functional sulfonic acid groups were covalently grafted onto the surface of multi-walled carbon nanotubes (MWNTS) via a facile route from sulfuric acid and acetic anhydride under mild conditions. The resulting sulfonated MWNTS (S-MWNTS) were further deposited with Pd nanoparticles (S-MWNTS/Pd) as catalysts for ethylene glycol electro-oxidation. Structural characterizations revealed that homogeneously dispersed Pd nanoparticles with an average size of 4.5 nm were loaded on the S-MWNTS supports. It was found that S-MWNTS/Pd catalysts exhibited better electrocatalytic activity and long-term stability than the unsulfonated counterparts. In contrast to the common sulfonication approaches, our strategy could make the functionalization process more easily and effectively, in this way resulting in small size and uniform dispersion of Pd nanoparticles loaded onto the nanotube surfaces. All these demonstrate that it is a simple and efficient approach towards sulfonate-assisted surface functionalization.