Semiconductivity Variance of Polypyrrole(PPy) Films in HCl Aqueous Solution

Metals, as sheets, are potential candidates for bipolar plate materials of proton exchange membrane fuel cell (PEMFC). However, metal oxide formation and metal dissolution under operating conditions of PEMFC cause considerable power degradation, which can be solved by coating metallic plates with corrosion resistant and electrically conducting layers. Conductive polymer coatings have potential for application in PEMFC. In this study, polpyrrole films doped with short-chain SO₄ ^2- and long-chain dodecylsulfate (DS^-), respectively, were prepared on Pt, and the semiconducting behavior of the polymers during exposure to 0.01 M HCl solution was examined in the potential range of -800 mV to 600 mV vs. SCE by Mott-Scottky curves. The PPy(SO₄ ^2-) films exhibit p-type semiconducting behavior in the potential region above 100 mV vs. SCE and n-type semiconducting behavior below this potential. The PPy(DS) films behave like a p-type semiconductor at the potentials higher than 150 mV vs. SCE and lower than -400 mV vs. SCE, while in the potential range from -400 mV to 150 mV vs. SCE, the n-type semiconductor is observed, but not so marked.