Enhanced photoelectrochemical cathodic protection performance of the C3N4@In2O3 nanocomposite with quasi-shell–core structure under visible light

Carbon nitride@Indium oxide (C 3 N 4 @In 2 O 3 ) composite with quasi-shell–core structure was successfully prepared in this work. The photoinduced open circuit potential and current density results show that the C 3 N 4 @In 2 O 3 composite with quasi-shell–core structure could provide the optimal photoelectrochemical cathodic protection capability for 304 stainless steel under visible light when the adding amount of C 3 N 4 in the C 3 N 4 @In 2 O 3 composite is 3   wt%. The light absorption capability of the C 3 N 4 @In 2 O 3 composite was enhanced due to the synergistic effect of heterojunction structure. According to the HRTEM images, photoinduced Volt–Ampere characteristic curves and electrochemical impedance spectra, the ultrathin coating layer of C 3 N 4 on the surface of In 2 O 3 helps to form a heterojunction electric field at the interface between C 3 N 4 and In 2 O 3 , which enhances the separation efficiency of the photogenerated electron–hole pairs. Excessive C 3 N 4 will decline the photoelectrochemical cathodic protection of this composite due to the lower intrinsic electronic mobility and the lower photoelectric conversion property of C 3 N 4 .