Multi-walled carbon nanotubes decorated polyaniline- α-Fe2O3 nanocomposite as an efficient photoanode for photoelectrochemical water splitting and photoelectrochemical cathodic protection of mild steel

Abstract

In this research, polyaniline nanocomposites with iron (III) oxide and multi-walled carbon nanotubes (PANi-Fe and PANi-Fe-CNT) were synthesized and successfully characterized by various techniques such as X ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, Field emission scanning electron microscopy (FESEM), and X-ray energy dispersive spectroscopy (EDS). The photoelectrochemical (PEC) performance of PANi, α-Fe2O3 nanoparticles, PANi-Fe and PANi-Fe-CNT on indium tin oxide (ITO) substrate was evaluated by linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in the dark and under simulated sunlight (100 mW/cm2). The results showed that ITO/PANi-Fe-CNT photoanode had higher photocurrent density (1.05 mA/cm2), more significant applied bias photo-to-current efficiency percentage (0.16%), and smaller charge transfer resistance (1008 Ωcm2) than other photoanodes under light irradiation. To study the photoelectrochemical cathodic protection (PEC cathodic protection) properties, the pastes were prepared from synthesized compounds and doctor-bladed on the pre-treated titanium (Ti) substrates and used as the photoanodes for the protection of mild steel. The performance of the as-prepared photoanodes in photoelectrochemical cathodic protection of mild steel was investigated using electrochemical impedance spectroscopy (EIS) and Tafel polarization. The corrosion potential (Ecorr) of mild steel decreased from −706 mV (without connection to the photoanode) to −864 mV in the state of connection to Ti/PANi-Fe-CNT photoanode under light irradiation, which indicated its cathodic protection.