Raman characterization of pseudocapacitive behavior of polypyrrole on nanoporous gold.

The practical applications of high-capacitance polypyrrole (PPy) as an active material for electrochemical supercapacitors are mainly limited by their poor cycling stability. By utilizing nanoporous gold enhanced Raman scattering of PPy, we investigated ex situ and in situ the structural origins of the low electrochemical stability of PPy. This study provided direct evidence that the stability degradation of PPy is caused by the irreversible transition between oxidation and reduction states of PPy, which is associated with the permanent deformation of PPy molecular chains subjected to applied potentials.