Synergetic effect of graphene and Co(OH)2 as cocatalysts of TiO2 nanotubes for enhanced photogenerated cathodic protection

Abstract

A layer of graphene (GR) particles was successfully deposited at the interface between Co(OH)2 nanoparticles and TiO2 nanotubes, aiming to improve the photoelectrochemical performance of the large-bandgap semiconductor TiO2. The obtained Co(OH)2/GR/TiO2 was extensively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectra and photoluminescence (PL) emission spectra. Electrochemical impedance spectra, photogenerated potential-time (E-t), photocurrent density-time (i-t) and i-E curves and open circuit potential (OCP) curves were measured to investigate the photoelectrochemical activities and photogenerated cathodic protection properties. The results revealed that Co(OH)2/GR/TiO2 exhibits excellent photoelectrochemical and photogenerated cathodic performance due to synergistic effect between Co(OH)2 and graphene. Co(OH)2 and graphene co-modified TiO2 photoanode could provide an effective protection for 304 stainless steel (304SS) in 3.5 wt% NaCl solution for 12 h, which would be promising for future practical applications in the field of marine corrosion protection.