In-Situ Reduction of Au, Pd, and Pt Metal Precursors in Polyaniline: Electrochemistry of Variable Metal Content Polymer/Metal Composites in Alkaline Solution

The controlled electrochemical uptake and reduction of metal precursors, AuCl4−, PdCl42−, and PtCl42− in polyaniline (PANI) is used in the synthesis of variable metal content composites. The potential and current associated with the initial electrochemical deposition of each metal precursor into pristine PANI is unique when compared to subsequent reduction in the composite materials. Deposition into the polymer and at existing deposits is resolved in the voltammetry for the reduction of Au and Pd in PANI. In contrast, distinct processes for Pt reduction into the polymer and at existing metal deposits are not resolved. After the initial reduction of the Pt precursor, the peak current continues to shift to more positive potential and diminishes as a function of increasing metal content. The PANI/metal composites are characterized using FTIR spectroscopy, thermal gravimetric analysis, and conductivity measurements to evaluate the interactions between the metal and polymer, the total metal content, and the electronic properties of the composites. The Au, Pd, and Pt metals deposited in PANI are evaluated using surface specific electrochemical reactions including the formation/reduction of metal oxide and the catalytic oxidation of n-propanol in alkaline solutions (pH ≈ 14). Furthermore, the electrochemical studies demonstrate that the oxidation/reduction of the polymer directly influences the polarization and reactivity of the metal surface in the organic matrix. The results confirm that PANI/metal composite materials containing Au, Pt, and Pd remain conductive in alkaline environments thereby expanding their use outside traditional acid solutions.

127