Epitaxial heterostructure of CdIn2S4/WO3 with the tunable built-in field for efficient photocathodic protection of 304SS and Q235

Photocathodic protection (PCP) can convert solar energy into protecting marine metallic structures from corrosion. However, the serious photocarrier recombination in the photoanode has hindered the development of the PCP technique. This study reported a feasible approach to construct the heterojunction with a tunable built-in electric field by epitaxially growing CdIn2S4(CIS) on the surface of WO3. The light absorbance, carrier separation, and transportation were found to be strongly dependent on the built-in field, and it would enable not only protection of the 304SS but also retard the corrosion of more vulnerable Q235. Accordingly, the OCP of coupled photoelectrode shifted to -950 and -880 mVAg/AgCl for 304SS and Q235, and their photocurrent density also reached 100 and 170 μA/cm2, respectively. Notably, the PCP performance of anti-corrosion on the 304SS and Q235 was visualized by microscopy, further proving the effectiveness of the photoanode. The underlying mechanisms and different protection capabilities were discussed in detail.