Solar energy protects steels against corrosion: Advancing Sn doped hematite as photoanode

Abstract Photoelectrochemical cathodic protection (PECP) provides a sustainable and attractive approach for protecting metals. However, the wide bandgap of the photoanodes leads to low utilization of solar energy that inhibits further development of PECP. Herein, the narrow bandgap of α-Fe2O3 is found with PECP capacity, and a significant increase in the open circuit potential and photocurrent density is observed after Sn doping. Under illumination, the OCP of 304 stainless steel (304SS) coupled with α-Fe2O3/0.5 mM Sn shifts to −640 mVAg/AgCl, which is 460 mV more negative than the corrosion potential of 304SS, and 100 mV negative than the OCP of α-Fe2O3. The photocurrent density improves to 37 μA/cm2, which is 3.7 times higher than the α-Fe2O3. Further electrochemical impedance investigations reveal that the enhanced PECP performance can be attributed to the increased carrier density, the negative shift of the flat band potential, and the suppressed photocarrier recombination. We believe that our study on α-Fe2O3 and doping strategy provide an insight to improve PECP effectively.