Photocatalytic degradation of P-Cresol using TiO2/ZnO hybrid surface capped with polyaniline.

This study evaluated the photocatalytic activity of polyaniline (PANI)-capped titanium dioxide and zinc oxide (TiO2/ZnO) hybrid, for the degradation of P-Cresol. The hybrid was synthesized by precipitating ZnO on the surface of commercial TiO2. An "in situ" chemical oxidative polymerization method was used to prepare the PANI capped hybrid (TiO2/ZnO/PANI). The photocatalysts were characterized by powder X-ray diffraction (XRD), a Brunauer Emmett Teller (BET) analyzer, Fourier-transform infrared (FTIR) and photoluminescence spectroscopies, high resolution-transmission electron microscopy (HR-TEM) and thermogravimetric analysis (TGA). During photodegradation under ultraviolet (UV) irradiation, ZnO, TiO2, TiO2/ZnO hybrid and TiO2/ZnO/PANI composite had P-Cresol removal of 43%, 50%, 61% and 99%, respectively. The higher activity of the TiO2/ZnO hybrid as compared to TiO2 and ZnO was attributed to a reduced electron-hole pair recombination. The recombination was further significantly reduced upon introduction of PANI; hence, the highest activity observed with TiO2/ZnO/PANI. The initial reaction rate constant for TiO2/ZnO/PANI (0.9679 min-1) was more than twice compared to that for TiO2/ZnO hybrid (0.1259 min-1). A synergistic effect between PANI and TiO2/ZnO resulted in a highly efficient charge separation caused by the transfer of photogenerated holes from the hybrid to highest occupied molecular orbitals (HOMO) of PANI. The best TiO2/ZnO/PANI (PANI to TiO2/ZnO) ratio observed was 0.5:2 for the photodegradation of P-Cresol. Total organic carbon (TOC) analysis indicated a 97.4% mineralization of P-Cresol with PANI/TiO2/ZnO.