Reduction of PtCl62- and PtCl42- in polyaniline: Catalytic oxidation of methanol at morphologically different composites

The synthesis of polyaniline/platinum composites (PANI/Pt) has been achieved using the controlled electrochemical reduction of PtCl62- and PtCl42-. The formation of the PANI/Pt composite is initiated by the uptake and reduction of either PtCl62- or PtCl42- into a priori electrochemically deposited PANI film. The electrochemical reduction of PtCl62- and PtCl42- produces morphologically different composite materials. In the case of PtCl62-, a uniform dispersion of spherical Pt particles with diameters ranging between 200 nm and 1 μm occurs. A more coalesced Pt deposition encapsulates PANI filaments when PtCl42- is reduced using identical electrochemical parameters. Reduction of either platinum species results in an electron deficient polymer with reduced proton doping. The catalytic oxidation of methanol is enhanced after Pt reduction in comparison to pure PANI for both composites. However, the highest degree of methanol oxidation is obtained using PANI/Pt electrodes produced electrochemically using PtCl42-. The morphology of the Pt deposit and higher intrinsic electron density of the polymer result in an enhanced response relative to the composite produced with PtCl62-.