Investigation of solar-induced photoelectrochemical water splitting and photocatalytic dye removal activities of camphor sulfonic acid doped polyaniline -WO3- MWCNT ternary nanocomposite

Abstract

The camphor sulfonic acid doped polyaniline-WO3-multiwall carbon nanotube (CSA PANI-WO3-CNT) ternary nanocomposite was synthesized during in-situ oxidative polymerization and characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), and Energy-dispersive X-ray spectroscopy (EDS). The application of CSA PANI-WO3-CNT ternary nanocomposite was investigated as the photocatalyst in the degradation of methylene blue dye (MB) and as the noble metal-free photoanode in photoelectrochemical water splitting under solar light irradiation. The degradation percentage of MB dye after 60 min illumination by CSA PANI-WO3-CNT ternary nanocomposite reached 91.40% which was higher than that of pure WO3 (43.45%), pure CSA PANI (48.4%) and CSA PANI-WO3 binary nanocomposite (85.15%). The photocurrent density of indium tin oxide (ITO)/CSA PANI-WO3-CNT photoanode obtained 0.81 mA/cm2 at 1.23 V vs. reversible hydrogen electrode under illumination which was 1.27, 2.13, and 4.26 times higher than that of the ITO/CSA PANI-WO3 (0.64 mA/cm2), ITO/pure CSA PANI (0.38 mA/cm2), and ITO/pure WO3 (0.19 mA/cm2). Also, the applied bias photon-to-current efficiency (ABPE) of ITO/CSA PANI-WO3-CNT was obtained 0.11% which showed two-fold, four-fold, and five-fold enhancements compared to the ITO/CSA PANI-WO3, ITO/CSA PANI, and ITO/WO3, respectively. The electrochemical impedance spectroscopy, as well as the Mott-Schottky results, confirmed the better photoelectrocatalytic activity of ITO/CSA PANI-WO3-CNT in comparison with ITO/WO3, ITO/CSA PANI, and ITO/CSA PANI-WO3. The observed improvement in the photocatalytic and photoelectrocatalytic performances of WO3 in the presence of CSA PANI is due to the formation of type -II heterojunction between WO3 and CSA PANI which allows the separation of charge carriers easier and faster. On the other hand, MWCNT addition to the CSA PANI-WO3 nanocomposite provided the conducting substrate for efficient interfacial charge separation as well as transferring.