Synthesis and characterization of conductive polyimide/carbon composites with Pt surface deposits

Abstract

The preparation of free-standing polyimide/carbon (PI/Carbon) substrates and the electrochemical deposition of Pt to produce PI/Carbon/Pt electrodes are demonstrated to provide thermally stable and conductive PI composites. The conductivity of polyimide (PI)/Carbon composites is evaluated as a function of composition of a binary solvent involving DMSO (dimethyl sulfoxide) and highly volatile acetone, which enhances carbon dispersion (PI/Carbon) in the polymer precursor. The solution conditions have been optimized to provide the highest conductivity for the lowest relative carbon loading. The deposition of Pt metal on PI/Carbon composite electrodes is demonstrated using cyclic voltammetry. The conductivity of the PI/Carbon composite is sufficient that the metal precursor PtCl 4 2− is fully reduced and deposited without the need for additional chemical reduction processes. Thermal gravimetric analysis (TGA) shows that the thermal stability of PI is maintained with carbon incorporation and platinum deposition. Scanning electron microscopy (SEM) analysis shows that carbon aggregation at the PI surface is minimized and that Pt deposits are well dispersed. X-ray photoelectron spectroscopy (XPS) results indicate that the electrochemical reduction of PtCl 4 2− produces metallic Pt deposits on the PI/Carbon composite. Four-point probe measurements are utilized to assess the conductivity of the materials and highlight the influence of C and Pt on the electronic properties of modified PI. Finally, the electrochemical reactivity of PI/Carbon/Pt composite is examined using the redox properties for ferricyanide and the catalytic oxidation of methanol in acidic solution. The electrochemical experiments demonstrate that the free-standing PI/Carbon composites are sufficiently conductive to observe the electrodeposition of Pt metal that is stable and reactive on the organic substrate.