Dispersed platinum and tin polyaniline film electrodes for the anodes of the direct methanol fuel cell

To develop better and cheaper electrocatalysts for the oxidation of methanol in direct methanol fuel cells, several combinations of a conductive polymer polyaniline (PANI) and dispersed metal particles such as Pt and Sn were examined. The anodic current for the methanol oxidation (i _MeOH) showing the electrocatalytic activity of Pt particles was remarkably enhanced when the particles were dispersed on PANI films that should provide higher surface areas for the dispersed particles. The activity strongly depended on the morphology and the electric conductivity of the PANI films electropolymerized in five different acid solutions: H₂SO₄, HNO₃, HClO₄, HBF₄, and HCl. The highest activity was achieved using the dispersed Pt particle on PANI film electropolymerized from H₂SO₄ polymerizing solution. In order to reduce the dispersed amount of the expensive Pt particles, other metal particles were pre-dispersed on the PANI film prepared from the H₂SO₄ polymerizing solution, and then Pt particles were dispersed on the film. Among the pre-dispersed metal particles attempted here (Sn, Cu, Cr, Ni, In, Co, Sb, Bi, Pb, and Mn), the highest activity was obtained with Sn particles. When the ratio of dispersed Pt to Sn particles ranges from 32:68 to 100:0, i _MeOH is higher than that measured with the dispersed Pt particle on PANI films without the Sn particles. This means that the dispersed amount of the Pt particles could be reduced by utilizing dispersed Sn particles.