Indium oxide thin film as potential photoanodes for corrosion protection of stainless steel under visible light

This paper reports the photoelectrochemical cathodic protection of 304 stainless steel by In2O3 thin-film under visible-light. The films were fabricated with In2O3 powders, synthesized by both sol–gel (In2O3-sg) and solid-state (In2O3-ss) processes. The photo-induced open circuit potential and the photo-to-current efficiency measurements suggested that In2O3 could be a promising candidate material for photoelectrochemical cathodic protection of metallic alloys under visible light. Moreover, the polarization curve experimental results indicated that In2O3-sg thin-film can mitigate the corrosion potential of 304 stainless steel to much more negative values with a higher photocurrent density than the In2O3-ss film under visible-light illumination. All the results demonstrated that the In2O3-sg thin-film provides a better photoelectrochemical cathodic protection for 304 stainless steel than In2O3-ss thin-film under visible-light illumination. The higher photoelectrochemical efficiency is possibly due to the uniform thin films produced with the smaller particle size of In2O3-sg, which facilitates the transfer of the photo-induced electrons from bulk to the surface and suppresses the charge recombination of the electrons and holes.