Preparation of tungsten-modified hematite-based photoconductors for photoelectrochemical cathodic protection of stainless steel

Cathodic protection by using photocatalysts, a new method of metal protection, is known as photoelectrochemical cathodic protection. In this study, at first, hematite nanotubes were prepared by electrochemical anodizing method; and then, using chemical bath deposition method at different times, tungsten trioxide particles were created on the surface of hematite nanotubes. Electron microscopy images confirmed the formation of regular hematite nanotubes on the surface; so by increasing the deposition time, the nanotubes diameter reduced from 40 nm to about 36 nm. The results of XRD, EDX and EDX-Mapping showed the presence of tungsten particles and their uniform distribution on the surface of the nanotubes. In order to study the photoelectrochemical properties of the samples, as photoanode in the photoelectrochemical protection of 403 stainless steel, chronoamprometry, open circuit potential and Tafel methods were used. The results showed that the coated (modified) samples had better performance than the uncoated ones (bare nanotubes), and of all prepared samples, sample T3 (with a deposition time of three hours) has the best performance. Also, the calculation of electron half-life in the samples using OCP tests showed that this value for H, T1, T2 and T3 samples is 0.92, 1.96, 2.12 and 1.99 seconds, respectively.