Fabrication of a novel TiO2/Mn-CdS photoanode and its photocathodic protection performance and mechanism for Q235 carbon steel

Photocathodic protection (PCP) provides a sustainable strategy for corrosion control, but conventional TiO 2 /CdS photoanodes remain limited by inefficient interfacial charge transfer and CdS photocorrosion. Herein, TiO 2 /Mn-CdS composite photoanodes were fabricated via anodic oxidation combined with the successive ionic layer adsorption and reaction (SILAR) method for the photocathodic protection of Q235 carbon steel (Q235 CS). The optimized photoanode, prepared using a 0.04 M Mn precursor solution (denoted as TiO 2 /Mn-CdS-0.04), exhibited a photocurrent density of 1590 μA·cm −2 . When coupled with Q235 CS, it induced a cathodic shift of the open-circuit potential to −1.30 V (vs. SCE) under visible-light irradiation. During a 24-day stability test, the photocurrent density remained above 1000 μA·cm −2 and the coupled potential remained approximately −0.95 V (vs. SCE). First-principles calculations indicated that Mn-induced electronic states facilitated carrier separation and interfacial charge transfer, suggesting that Mn incorporation promotes cascade charge transfer within the composite photoanode. This study demonstrates the potential of TiO 2 /Mn-CdS as a non-noble-metal photoanode for durable photocathodic protection of Q235 CS.