In Fig. 1, the peaks at 1164 cm−1 and 1588 cm−1 are due to the structure of quinone, which is an important factor of the electrical conductance. Excellent electrical conductance ensures the effectiveness of the electrolyzing method. The 1495 cm−1 peak is due to the benzene form. The ratio of the peak intensity of 1588 cm−1 and 1495 cm−1 gives the oxidation extent of the molecular chain (Genies et al., 1990). In Fig. 1, it can be seen that the intensities of these two peaks are almost the same, so it can be concluded that the polyaniline does have a good structure and is expected to have good electrical conductance.
In Fig. 2 and Fig. 3, the peaks between 800 cm−1 and 1300 cm−1 assigned to the Sdouble bond; length as m-dashO bond or S–O bond are the characteristic peaks, their shapes and relative intensities suggested that in the film, the structure of the SO42−/TiO2 solid superacid remains stable even when many other components exist. According to the literature, before TiO2 was impregnated with SO42−, the vibration peak of Ti–O was at 650 cm−1(Yang et al., 2003). After impregnating with SO42−, this peak shifted to a lower frequency, 618 cm−1, as illustrated in Fig. 2 and Fig. 3.
The acid strength of the SO42−/TiO2 determined by the Hammett flow indicator method is shown in Table 1. From Table 1, the acid strength of SO42−/TiO2 was estimated to be: −13.75 < H0 < −11.99.