Indium oxide nanoflakes/cerium oxide nanoclusters composites for improving sustained photocathodic protection under light and darkness

The hazards of metal corrosion and the shortcomings of photoelectric cathodic protection pose a major challenge to metal protection under dark conditions. Thus, In2O3 nanoflakes/CeO2 nanoclusters composites were prepared and their photocathodic protection (PCP) performance for 304 SS was studied in 3.5 wt% NaCl solution under light and darkness, respectively. Under illumination, the self-corrosion potential of 304 SS coupled with In2O3/CeO2 decreased by 180 mV, and the corresponding current density was 2.13 and 170 times higher than that of In2O3 and CeO2, respectively. In the darkness, In2O3/CeO2 remained current density of 10 μA cm−2 and protect 304 SS for 4.7 h. The enhanced PCP performance can be contributed to the introduction of the In2O3/CeO2 heterojunction, which extends the light absorption range, facilitates the transfer and separation of the photocarriers, resulting in more effective electron aggregation on 304 SS. Furthermore, the oxidation-reduction of Ce4+/Ce3+ with charge storage is response for the dark state protection performance of In2O3/CeO2 heterojunction. The photogenerated electrons are stored by a reduction reaction of Ce4+/Ce3+ under illumination, while in the dark state these stored electrons will release through the oxidation reaction of Ce3+/Ce4+. This work would be a reference for the application in metal corrosion protection under dark conditions.