X-ray photoelectron spectroscopy (XPS) as a useful tool to characterize polyaniline doped by 12-tungstosilicic, 12-tungstophosphoric and 12-molybdophosphoric acids

X-ray photoelectron spectra of polyaniline (PANI) doped by molybdophosphoric, tungstophosphoric and tungstosilicic acids were measured and discussed. Three different nitrogen species (imine, amine and protonated) were distinguished, and their proportions were determined. The N(1s) binding energies of the protonated species varied within a 400.5–402.5 eV range, while the imine and amine species showed constant values of the electron binding energies. Protonation of PANI was manifested both in N(1s) and O(1s) spectra. Even a small protonation by water molecules was recognized in X-ray photoelectron spectroscopy (XPS). Differences in acidic strength of the heteropolyacids were noticed. The thermal treatment (catalytic activation) converted the surface H2O into OH. Catalytic conversion of ethanol resulted in a strong deprotonation of all the samples.