Investigating the Behaviour of Polyaniline-Iron Oxide (III) Nanocomposite on Titanium Substrate as a Photoanode for Photoelectrochemical Cathodic Protection of Mild Steel

In this study, camphor sulfonic acid doped polyaniline (CSA PANi) and its nanocomposite with α-Fe2O3 nanoparticles were synthesized using in situ oxidative polymerization and were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM). The paste was prepared from synthesized compounds and applied to the pre-treated titanium substrates (sanded and etched) by Dr. Blade method and used as the photoanode for photoelectrochemical cathodic protection of mild steel. The Mott-Schottky analysis was performed to study the type of semiconductor compounds as well as the density of charge carriers. The performance of the prepared photoanodes in the photoelectrochemical cathodic protection of mild steel was studied using electrochemical impedance spectroscopy (EIS) and Tafel polarization. The results showed that the corrosion potential (Ecorr) of mild steel decreased from -706 mV in the case without photoanode connection to -842 mV in the case of connection to Ti / CSA PANI-Fe photoanode under light irradiation, indicating the flux of produced electrons from the photoanode to the surface of mild steel and its cathodic protection. The EIS results also showed that the charge transfer resistance (Rct) for Ti / CSA PANI-Fe was 578.6 Ωcm2 which is less compared to Ti / α-Fe2O3 (874.9 Ωcm2 ) and Ti / CSA PANi (693.4 Ωcm2 ), confirming the low recombination rate of electrons and holes and more flux of electrons to the surface of mild steel and the proper performance of Ti / CSA PANI-Fe photoanode in photoelectrochemical cathodic protection.