Carbon-shell-encapsulated gold–palladium nanoreactors for highly efficient 5-hydroxymethylfurfural oxidation: Confinement and alloy effects study

Abstract

Encapsulating noble metal nanoparticles in carbon nanoshells is an emerging and efficient way to enhance the activity and stability of noble metal species. A novel type of hollow rod-shaped carbon-shell-encapsulated gold–palladium (AuPd) alloy nanoreactor (AumPdn@CT) was designed and constructed. The Au2Pd1@C800 nanoreactor afforded a satisfactory 2,5-furandicarboxylic acid (FDCA) yield of 99.9 % from 5-hydroxymethylfurfural (HMF) oxidation using O2 as the oxidant in water. Remarkably, carbon-shell-encapsulated only 1.0 wt% AuPd alloy could offer an outstanding FDCA formation rate of 2003.6 mmol·g−1·h−1. Mechanistic studies demonstrated that the generated confinement and AuPd alloy species not only improved the adsorption capacity of the HMF substrate and the key intermediate 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), but also facilitated the adsorption and activation of molecular oxygen to generate oxygen active species of superoxide radicals. Constructing a carbon shell around AuPd alloy active sites provided effective physical protection for the metal core, thus enhancing the catalyst stability and reusability.