Carbon quantum dots/Ag sensitized TiO2 nanotube film for applications in photocathodic protection

Abstract In order to obtain a TiO 2 composite film with improved photoelectrochemical properties, a TiO 2 nanotube array (NTA) film was constructed on a Ti substrate via anodization, then Ag nanoparticles (NPs) and carbon quantum dots (CQDs) were successively deposited on the TiO 2 NTA film by pulse current deposition and hydrothermal treatment, respectively. After the sensitization by CQDs and Ag NPs, the light absorption of the TiO 2 composite film was extended to the visible region. Under white light irradiation, the photocurrent density of the composite film in a 0.5 M Na 2 SO 4 solution reached 110 μA cm −2 , much higher than that (60 μA cm −2 ) of the single TiO 2 film. The CQDs/Ag/TiO 2 composite film as a photoanode showed an improved photocathodic protection effect, which made the potential of the coupled 403 stainless steel (403SS) in the 0.5 M NaCl solution drop by 400 mV relative to its corrosion potential.