Promoting role of bismuth and antimony on Pt catalysts for the selective oxidation of glycerol to dihydroxyacetone

The group 15 metals, bismuth and antimony, play important roles in promoting noble-metal-catalyzed oxidation reactions toward high value-added chemicals. Herein, we report that the selective oxidation of glycerol to 1,3-dihydroxyacetone (DHA) catalyzed by Pt supported on N-doped carbon nanotubes (Pt/NCNT) can be significantly promoted in the presence of Bi or Sb in reaction solution. This catalyst system showed not only comparable even better performance to the Pt/NCNT with pre-loaded Bi, but also the greatly simplified catalyst preparation. It was found that the Bi-promoted Pt/NCNT underwent dynamic surface reconstruction through leaching and adsorption of Bi adatoms, due to the formation of glyceric acid. By characterizing the adsorption of Bi on Pt catalyst with high-resolution transmission electron microscopy, CO-stripping, horizontal attenuated total reflection infrared spectroscopy and X-ray photoelectron spectroscopy, it has been ascertained that Bi preferentially deposits on the step sites of Pt, and then blocks the terrace sites to promote the Pt catalyst mainly through a geometrical effect, which facilitates the activation and transformation of the secondary hydroxyl group of glycerol through the chelation between substrate and Pt-Bi sites.