Improving the photocatalytic activity of polyaniline and a porphyrin via oxidation to obtain a salt and a charge-transfer complex

Environmental problems caused by organic dyes have led to the development of efficient methods for their treatment. Photocatalytic degradation has proved to be a viable technique to decompose these pollutants into less dangerous compounds. In this study, the photocatalytic activity of a polyaniline salt and a porphyrin was improved by preparing a hybrid of both components, i.e., a polyaniline-sulfate- 5,10,15,20-tetrakis(4-hydroxy phenyl)-21H,23H porphine salt (PANI-H2SO4-TKHP). This salt was synthesized by a chemical oxidative polymerization pathway and used as a photocatalyst for the degradation of RhB dye. The formation of this salt was confirmed by FT-IR, XRD and UV-vis spectroscopy. Oxidation of aniline in the presence of TKHP by ammonium persulfate results in the formation of both the polyaniline salt (PANI-H2SO4-TKHP) and a charge-transfer complex between PANI and TKHP via p-p stacking. PANI-H2SO4-TKHP was observed in a nanotube morphology (which was confirmed by SEM and TEM) with a reasonably good yield (88 wt%), conductivity (1.2 ohm1 cm1) and thermal stability (200 1C). The photocatalytic performance of PANI-H2SO4-TKHP was compared with its individual components of PANI-H2SO4 and TKHP under visible light irradiation. PANI-H2SO4-TKHP exhibited an effective photocatalytic activity (78% dye degradation), and a plausible mechanism for photocatalytic degradation was proposed in terms of the HOMO and LUMO levels of the components.