Pt NPs immobilized on core–shell magnetite microparticles: novel and highly efficient catalysts for the selective aerobic oxidation of ethanol and glycerol in water

Abstract

Three core–shell structures were prepared with pyrrole, glucose, and tetraethyl orthosilicate (TEOS), respectively, encasing magnetic Fe₃O₄ microparticles, through three different “green” approaches without any toxic solvents. Pt nanoparticles (NPs) were immobilized onto these supports with NaBH₄ as the reducing agent. The as-prepared catalysts were characterized thoroughly by TEM, VSM, XRD, FT-IR, ICP, and XPS. As expected, the shells remarkably affected the distribution of Pt NPs and catalytic activity. Pt NPs dispersed evenly on the surface of Fe₃O₄@PPy and Fe₃O₄@C, which were much better than Fe₃O₄@SiO₂. Most attractively, the prepared catalysts exhibited better kinetics, higher activity and stability than Pt/Fe₃O₄ and Pt/C for selective oxidation of ethanol to acetic acid and glycerol to glyceric acid with molecular oxygen in water. Among them, the catalyst with a shell of polypyrrole (PPy) showed the best catalytic property, affording yields of 88% and 55%, respectively. Moreover, it could be recovered facilely from the reaction mixture and recycled four times without any significant loss in activity.