Synthesis of Pt/PEI–MWCNT composite materials on polyethyleneimine-functionalized MWNTs as supports

Graphical abstract: Schematic diagram for (a) the preparation of Pt/MWCNT functionalized with PEI and (b) TEM of Pt/PEI–MWCNT. Highlights: ► We prepared Pt/PEI/MWCNT where MWCNT was first functionalized by PEI (polyethyleneimine) followed by Pt deposit onto it. ► PEI functionalization provided high density homogeneous functional groups on MWCNT's sidewall. ► Cationic PEI leads to homogeneous dispersion in solutions such as water and organic solvents. ► Pt/PEI/MWCNT catalyst exhibits excellent electrocatalytic activity compared to that of Pt/MWCNT catalyst obtained with polyvinylpyrrolidine (PVP). -- Abstract: Composite materials with highly dispersed platinum (Pt) nanoparticles on multiwalled carbon nanotubes (MWCNTs), functionalized with polyethyleneimine (PEI) by a noncovalent method were prepared. The PEI-functionalization provided high density homogeneous functional groups on the MWCNTs' sidewalls for binding Pt nanoparticles. Cationic PEI leads to homogeneous dispersion in solutions such as water and organic solvents. The effects of a reducing agent on the Pt nanoparticles that form on the surfaces of the MWCNT were studied by varying the molar ratio of NaOH to H2PtCl6. These composite materials were characterized with transmission electron micrograph (TEM), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The Pt/PEI–MWCNT catalyst exhibits excellent electrocatalytic activity and compared with Pt/PVP–MWCNT catalysts obtained with polyvinylpyrrolidone (PVP). Finally, the cyclic voltammogram of methanol electrooxidation for Pt/PEI–MWCNT shows better tolerance to CO and methanol oxidation to CO2 than of Pt/PVP–MWCNT.