Hydrolysis-induced immobilization of Pt(acac)2 on polyimide-based carbon nanofiber mat and formation of Pt nanoparticles

Abstract

Electrospun polyimide (PI)-based carbon nanofibers have recently garnered much interest due to their high conductivity and high mechanical strength. Promising applications include electrodes for supercapacitors, filters, sensors, and fuel cells. Here, we demonstrate that Pt nanoparticles can be loaded on the surface of PI nanofibers via an immobilization process induced by hydrolysis. The uniform distribution and sizes of Pt nanoparticles were controlled further by carbonization. Pt(acac)₂ dissolved in acetone was impregnated on the hydrolyzed PI nanofibers. Pt ions were localized exclusively on the surface of PI nanofibers by precise control of the hydrolysis process. Our X-ray photoelectron spectroscopy results show that Pt ions in Pt(acac)₂ molecules (40%) are immobilized on the hydrolyzed PI surface while some of them (60%) bind to O in the carboxylic group to form a PtO structure, and then are fully decomposed into Pt nanoparticles during carbonization. Using density functional calculations, we show that the binding of Pt(acac)₂ on hydrolyzed PI is strong with a binding energy of −4.3 eV, which originates mostly from Pt–O binding and π-stacking between (acac) and PAA, confirming experimental observations of robust formation of Pt nanoparticles on hydrolyzed PI. The cyclic voltammetric test demonstrates that our robust carbon nanofiber mat can be utilized for fuel cell electrodes.