Structure controlled enhanced photocatalytic activity of polyaniline (PANI)

Here authors report the preparation of polyaniline (PANI) with crystalline structures in the form of Emeraldine salt (ES) following a simple wet chemical route by chemical oxidative polymerization method. Crystalline PANI is used for various applications such as photocatalysis, solar cells, supercapacitors, electromagnetic shielding, and anticorrosive protection. Enhanced crystallinity with modulated band structure is highly desirable for the effective use of this functional material. Hence, we attempted to synthesize polyaniline with enhanced crystallinity by controlling various process parameters. As process parameters, the molarity of HCl viz. 0.1M, 0.5M, 1.0M, 2.0M, and 6.0M; and precipitation (polymerization) temperature viz. 25 °C (room temperature, RT) and 0 °C (using ice) were investigated to synthesize PANI with maximum crystallinity to find optimum synthesis conditions. The structure of the polyanilines was investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) ultraviolet-visible (UV-vis) spectroscopy, differential scanning calorimetry (DSC) and zeta potential. Analyzing experimental data in addition to percent crystallinity, bond structure, particle morphology and optical band gap were studied. Finally, photocatalytic activity was investigated using Rh B dye. PANI synthesized using 2.0 M HCl and polymerization temperature 25 °C showed maximum photocatalytic activity which is attributed to its highest percent crystallinity with maximum I_Q to I_B ratio and largest band gap.