ZnFeAl-layered double hydroxides/TiO2 composites as photoanodes for photocathodic protection of 304 stainless steel

Abstract

A series of ZnFeAl-layered double hydroxides/TiO₂ (ZnFeAl-LDHs/TiO₂) composites are synthesized by a combined anodization and hydrothermal method. The structure, surface morphology, photo absorption and photocathodic protection properties of these samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) and electrochemical tests. The unique structure of the ZnFeAl-LDHs reduces the charge carriers recombination, and the visible photoresponse property increase the light harvesting. The XPS study reveals that the electrons in the ZnFeAl-LDHs travel to TiO₂, and the ZnFeAl-LDHs/TiO₂ composites generate and transfer more electrons to 304 stainless steel (304SS), and exhibits a better photocathodic protection performance than pure TiO₂. In addition, after intermittent visible-light illumination for four days, the photoanode still exhibits good stability and durability.