Graphitic carbon nitride homojunction films for photocathodic protection of 316 stainless steel and Q235 carbon steel

Abstract

Constructing homojunction of the same semiconductors is another new effective method to promote charge separation and thus to improve the photocathodic protection performance. In this work, we prepared graphic carbon nitride (g-C3N4) homojunction films on Indium tin oxide (ITO) substrate by simultaneously calcining mixture precursors containing melamine and thiourea of different proportions. Photocurrent density and open circuit potential (OCP) results indicate the photocathodic protection performance for 316 stainless steel (316 SS) and Q235 carbon steel in 3.5 wt% NaCl solution under 300 W Xe lamp enhanced with the combination of different g-C3N4 photoanode films, and g-C3N4 film with 40% thiourea/melamine weight ratio has the optimal photocathodic protection effect. The mechanism of enhancement may be result from the narrowed band gap and the small difference potentials between n-n homojunctions which promote the separation of photogenerated electron-holes, and improve the photon-to-electron conversion efficiency.