Photocathodic Protection of Cobalt Doped ZnO Nanorod Arrays for 316 Stainless Steel and Q235 Carbon Steel in 3.5 wt.% NaCl Solution

Abstract

In this work, cobalt-doped ZnO nanorod arrays with anticorrosion function were successfully prepared on fluorine-doped tin oxide (FTO) substrates by a simple aqueous solution method. The XRD patterns and the energy-dispersive X-ray spectroscopy (EDX) analysis indicate the doped Co2+ were successfully incorporated into the ZnO crystal lattice. The photocurrent density and open circuit potential (OCP) results indicate the photocathodic protection performance for 316 stainless steel (316 SS) and Q235 carbon steel in a 3.5 wt.% NaCl solution under a Xe lamp with a power of 300 W was enhanced with the increase of cobalt concentration, and the photoanode with a 15% Co/Zn ratio had the optimal photocathodic protection effect. The mechanism of enhancement may be result from the narrowed band gap, the lower recombination rate of the photogenerated electron-hole pairs, the intermediate impurity level, and the split of the hypo-outer shell of cobalt ions.