Polymer end-group mediated synthesis of well-defined catalytically active platinum nanoparticles

Abstract

Simple, short polyethyleneglycol (PEG) chains were found to mediate the synthesis of well-defined 7–8nm cubic and truncated cubic platinum (Pt) particles that required only mild ligand removal conditions to yield highly active catalysts for the oxygen reduction reaction (ORR). FTIR analyses showed that only the hydroxyl end groups of the PEG chains associate with the platinum particles, which oxidize readily to form carbonyl groups with weaker interactions with the platinum surface. ORR analysis showed a mass activity of 50 μA μg−1 for the PEG synthesized Pt nanoparticles (NPs), as compared to a mass activity of 45 μA μg−1 for platinum black. The half-wave potentials of PEG Pt NPs and Pt black were found to be 427 mV and 529 mV, respectively, showing a high catalytic activity of PEG Pt NPs towards ORR. Well-defined particles were also produced from amine-terminated PEG, but as the amines could not be removed by simple acid washing, the ORR activity was greatly diminished. Since short low molecular weight PEG was found to control particle nucleation and growth predominantly through its end groups, this work demonstrates that PEG is a versatile scaffold from which to screen a wide variety of functional moieties, including biomolecules, as templates for complex nanoparticle synthesis.